Carl E. Bock

Frontiers in Ecology and the EnvironmentVolume 2, Issue 8 p. 403-410 Review Avian habitat evaluation: should counting birds count? Carl E. Bock, Carl E. Bock Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO 80309-0334 ( E-mail: carl.bock@colorado.edu)Search for more papers by this authorZach F. Jones, Zach F. Jones Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO 80309-0334Search for more papers by this author Carl E. Bock, Carl E. Bock Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO 80309-0334 ( E-mail: carl.bock@colorado.edu)Search for more papers by this authorZach F. Jones, Zach F. Jones Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO 80309-0334Search for more papers by this author First published: 01 October 2004 https://doi.org/10.1890/1540-9295(2004)002[0403:AHESCB]2.0.CO;2Citations: 193Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Abstract There are times when birds reproduce at higher rates in places where they are less abundant, limiting the generally accepted value of bird counts as environmental indicators. But how often, and under what circumstances, does this happen? In 109 published cases involving 67 species across North America and Europe, higher density sites displayed greater recruitment per capita and per unit of land area in 72% and 85% of cases, respectively. The frequency of negative relationships between abundance and reproductive success did not differ between different kinds of birds or habitats. However, density was negatively related to reproductive success more often in areas of human disturbance than in relatively natural areas. Although further study is needed to confirm the generality of this pattern, especially in areas such as the tropics, results suggest that birds can fail to recognize ecological traps or opportunities in landscapes that differ from those in which they evolved. Citing Literature Volume2, Issue8October 2004Pages 403-410 RelatedInformation

Large vertebrates are strong interactors in food webs, yet they were lost from most ecosystems after the dispersal of modern humans from Africa and Eurasia. We call for restoration of missing ecological functions and evolutionary potential of lost North American megafauna using extant conspecifics and related taxa. We refer to this restoration as Pleistocene rewilding; it is conceived as carefully managed ecosystem manipulations whereby costs and benefits are objectively addressed on a case-by-case and locality-by-locality basis. Pleistocene rewilding would deliberately promote large, long-lived species over pest and weed assemblages, facilitate the persistence and ecological effectiveness of megafauna on a global scale, and broaden the underlying premise of conservation from managing extinction to encompass restoring ecological and evolutionary processes. Pleistocene rewilding can begin immediately with species such as Bolson tortoises and feral horses and continue through the coming decades with elephants and Holarctic lions. Our exemplar taxa would contribute biological, economic, and cultural benefits to North America. Owners of large tracts of private land in the central and western United States could be the first to implement this restoration. Risks of Pleistocene rewilding include the possibility of altered disease ecology and associated human health implications, as well as unexpected ecological and sociopolitical consequences of reintroductions. Establishment of programs to monitor suites of species interactions and their consequences for biodiversity and ecosystem health will be a significant challenge. Secure fencing would be a major economic cost, and social challenges will include acceptance of predation as an overriding natural process and the incorporation of pre-Columbian ecological frameworks into conservation strategies.

Previous articleNext article No AccessNotes and CommentsRange Size and Local Abundance of Some North American Songbirds: A Positive CorrelationCarl E. Bock and Robert E. RicklefsCarl E. Bock and Robert E. RicklefsPDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The American Naturalist Volume 122, Number 2Aug., 1983 Published for The American Society of Naturalists Article DOIhttps://doi.org/10.1086/284136 Views: 16Total views on this site Citations: 89Citations are reported from Crossref Copyright 1983 The University of ChicagoPDF download Crossref reports the following articles citing this article:Cleber Ten Caten, Lauren Holian, Tad Dallas, Jason Pither Weak but consistent abundance–occupancy relationships across taxa, space and time, Global Ecology and Biogeography 31, no.55 (Mar 2022): 968–977.https://doi.org/10.1111/geb.13472Bilgecan Şen, H. 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Analysis of Audubon Society Christmas-count data (1962-1971) revealed a generally synchronous pattern of winter eruptions between eight species of seed-eating birds whose winter ranges normally include boreal forests. Species and populations occupying montane conifer forests in the West did not fit this pattern as well. Literature analysis revealed a circumboreally synchronized pattern of seed crop fluctuations in certain high-latitude tree species and an apparently resulting pattern of southward eruptions of birds dependent upon these foods. Between 1948 and 1971 eruptions were relatively large in 1949, 1955, 1957, 1959, 1961, 1963, 1965, 1968, 1969, and 1971.

Journal Article Breeding Bird Populations of Burned and Unburned Conifer Forest in the Sierra Nevada Get access Carl E. Bock, Carl E. Bock Museum of Vertebrate Zoology University of California Berkeley, California 94720 Present address: Department of Biology, University of Colorado, Boulder, Colorado 80302. Search for other works by this author on: Oxford Academic Google Scholar James F. Lynch James F. Lynch Museum of Vertebrate Zoology University of California Berkeley, California 94720 Search for other works by this author on: Oxford Academic Google Scholar The Condor, Volume 72, Issue 2, 1 April 1970, Pages 182–189, https://doi.org/10.2307/1366629 Published: 01 April 1970 Article history Accepted: 11 March 1969 Published: 01 April 1970

In a 4—yr field experiment, we tested the hypotheses that insectivorous birds (1) controlled densities of herbivorous grasshoppers in an ungrazed semiarid grassland in southeastern Arizona, and (2) functioned as keystone predators, by limiting abundances of grasshoppers that otherwise might change vegetation cover and species composition, and/or by mediating the effects of otherwise competitively superior members of the grasshopper assemblage. We measured grasshopper densities and vegetation on 32 464—m 2 grassland plots for 1 yr, then enclosed 16 of these plots with bird exclosures and continued data collection for 3 yr. Eight of the 16 experimental plots were further modified in the last 2 yr of the study by installing fine—mesh 1 m high barriers designed to retard grasshopper dispersal. Microclimates of caged plots differed only slightly from open plots. Lizards and rodents increased inside the exclosures, but they were removed and released elsewhere such that their average abundances did not differ among treatments. By the final year of the study, mean annual adult grasshopper density was &gt;2.2 times higher on plots from which birds were excluded, and where grasshoppers were enclosed by dispersal barriers, than on unmanipulated control plots. Mean nymph density was &gt;3.0 times higher in the same comparison. Grasshoppers were significantly more abundant in bird exclosures with insect dispersal barriers, indicating that experimental plots were dispersal sources rather than sinks. Seven of 12 common grasshopper species were more abundant inside the bird exclosures, while none was less abundant. Among the more abundant taxa, those responding most positively were grass feeders: Eritettix simplex, Opeia obscura, Paropomala wyomingensis, and Phoetaliotes nebrascensis. We found no evidence that grasshoppers competed with one another under increased densities inside the bird exclosures. Although the amount of insect herbivory was somewhat higher inside the bird exclosures, and was positively correlated with grasshopper density across all 32 plots (r = 0.87), overall vegetation cover and species composition did not differ among treatments by the end of the study. Dactylotum variegatum, an aposematic species apparently immune to avian predation, showed no significant responses to the experiment. Birds clearly limited grasshoppers in this grassland ecosystem, but they failed to qualify as keystone predators, at least in the short term, for two reasons: (1) in their absence, increased grasshopper densities had no appreciable impact on vegetation cover or species composition; and (2) there was no evidence that birds mediated competition among grasshoppers.

Species richness and evenness are components of biological diversity that may or may not be correlated with one another and with patterns of species abundance. We compared these attributes among flowering plants, grasshoppers, butterflies, lizards, summer birds, winter birds, and rodents across 48 plots in the grasslands and mesquite–oak savannas of southeastern Arizona. Species richness and evenness were uncorrelated or weakly negatively correlated for each taxonomic group, supporting the conclusion that richness alone is an incomplete measure of diversity. In each case, richness was positively correlated with one or more measures of abundance. By contrast, evenness usually was negatively correlated with the abundance variables, reflecting the fact that plots with high evenness generally were those where all species present were about equally uncommon. Therefore richness, but not evenness, usually was a positive predictor of places of conservation value, if these are defined as places where species of interest are especially abundant. Species diversity was more positively correlated with evenness than with richness among grasshoppers and flowering plants, in contrast to the other taxonomic groups, and the positive correlations between richness and abundance were comparatively weak for grasshoppers and plants as well. Both of these differences can be attributed to the fact that assemblages of plants and grasshoppers were numerically dominated by small subsets of common species (grasses and certain spur-throated grasshoppers) whose abundances differed greatly among plots in ways unrelated to species richness of the groups as a whole.

Distribution and local abundance of 62 landbird species were measured in winter across an elevational gradient in the Huachuca Mountains of southeastern Arizona. The number of 35—m radius plots and the number of habitats occupied by the species were positively correlated with their average abundances within occupied plots and habitats. Common species were no more conspicuous than rare ones, as measured by detectability on variable distance point counts. The same species that were most abundant locally also were most abundant on Christmas bird counts across Arizona and throughout the western United States. The positive correlation between distribution and abundance of winter landbirds appear to be neither an artifact of conspicuousness, nor a consequence of the geographic scale of comparison. Rather, it seems to be an intrinsic property of the species themselves, and one that has important ecological and evolutionary implications. An individualistic approach to avian ecology is indicated, emphasizing comparisons of rare and common species.

Acorn woodpeckers (Melanerpes formicivorus) in southeastern Arizona exhibited two different types of social organization: one of highly cooperative and resident groups and another of birds that migrated and formed only temporary male-female pairs during reproduction. The occurrence of both patterns in the same population indicates a high degree of social flexibility in this species.

We conducted point counts of diurnal raptors on Boulder, Colorado, grasslands for three winters and summers, and compared results to landscape features of the count areas. Four wintering species were scarce on plots that included significant amounts of urban habitat, with a critical landscape threshold at about 5-7% urbanization: Bald Eagle (Haliaeetus leucocephalus), Ferruginous Hawk (Buteo regalis), Rough-legged Hawk (B. lagopus), and Prairie Falcon (Falco mexicanus). Counts of the first three species also were positively correlated with proximity of the count plots to the nearest colony of black-tailed prairie dogs (Cynomys ludovicianus). Two breeding species, the Red-tailed Hawk (B. jamaicensis) and Swainson's Hawk (B. swainsoni), were more abundant on plots dominated by lowland hayfields and tallgrass prairies, as opposed to upland mixed and shortgrass prairies. They, along with the ubiquitous American Kestrel (Falco sparverius), were not sensitive to the amounts of urbanization (up to 30%) that occurred in the landscapes sampled. Results of this study suggest that urban open space grasslands can support sizable populations of most diurnal raptors, as long as prey populations persist, but that some species are highly sensitive to landscape urbanization.

Bird species densities were determined for summer and winter on 132 study plots grouped into 25 riparian habitats in or near the Huachuca Mountains of southeastern Arizona. The habitats were defined based on the dominant riparian tree species, the size of the riparian stand, and the type of adjacent upland vegetation. Vegetation characteristics and physical environmental data were collected at each plot. The type of dominant riparian tree species influenced bird species richness and total density during the breeding season. Cottonwood habitats had the greatest richness, and both cottonwood and sycamore habitats had high densities. Upland vegetation was an important factor related to winter species richness and abundance, with plots in open grassland areas having greater richness and density. Riparian stand size was a relatively poor predictor of avian density or richness in either season. Groups of bird species that shared similar density distributions in the summer were associated with specific riparian habitats. The winter pattern of species groups was not as clear, and groups could not be assigned to riparian habitats, but they were related to either wooded or open upland vegetation. Riparian habitats were also clustered based on similar densities of birds. In summer, high-elevation habitats were distinct from low-elevation and foothill habitats. In winter, riparian habitats separated into categories of wooded vs. open adjacent vegetation.

Etude conduite dans un sanctuaire de la Societe Audubon dans le comte de Santa Cruz (Arizona) et dans un ranch adjacent. Deux plateaux tabulaires sont pris en reference, on compare les densites et les habitats de 4 especes sur sites pâtures ou non

Highlight: We studied the impact of fire on an ungrazed sacaton grassland community at The Research Ranch in southeastern Arizona. Two swmner hums were followed through two post-fire growing seasons. A winter burn was studied through one post-tire growing season. Burning reduced the height and extent of sacaton grass (Sporobolus wrighfii) itself, and stimulated growth of other grasses and forhs. Summer fires created more hare ground and encouraged a greater number and variety of annuals than the winter tire. The tires had the effect of reducing total smallmammal populations and greatly increasing bird populations. llwse results were more dramatic on the areas which burned in early summer than on the winter-burned plot. Raptors and most game birds, particularly mourning doves, were most abundant on one-year-old burns. Seed-eating birds (Fringillidae) preferred burned over unburned areas. Cotton rat (Sigmodon hispidus) populations were greatly reduced by the tires, while populations of seed-eating pocket mice (Perognathus) and kangaroo rats (Dipodomys) increased, especially on the summer hums. Sacaton grasslands recover rapidly even from summer burning, at least in the absence of livestock. Results of this study suggest that fire is beneficial to the indigenous plants and wildlife of sac&on communities, as long as a mosaic of different aged stands is maintained.

Livestock grazing is a widespread and important influence on neotropical migratory birds in four major ecosystems in western North America: grasslands of the Great Plains and Southwest, riparian woodlands, Intermountain shrubsteppe, and open coniferous forests. We have reviewed available literature on avian responses to grazing in these habitats. Among 35 plains species for which data are available, 9 responded positively to grazing, 8 responded negatively, 8 showed a graded response, from generally negative in shorter grasslands to generally positive in taller grasslands, while 8 were unresponsive or inconsistent. A similar comparison for riparian woodlands revealed that 8 of 43 species responded positively to grazing, while 17 were negatively affected, and 18 were unresponsive or showed mixed responses. Data for shrubsteppe habitats are much more limited, but only 3 of 23 species probably have been positively affected, at least by current grazing practices, while 13 probably have been negatively influenced, and at least 7 species showed mixed responses. Virtually nothing is known about effects of grazing on birds of coniferous forests. Most species negatively influenced by grazing have been those dependent on herbaceous ground cover for nesting and/or foraging. Given the ubiquity of livestock in the American West, species dependent upon lush ungrazed ground cover are at risk, and doubtless already are at population levels far below historical levels. Protection and restoration of riparian habitats is of particular importance, because of their limited geographic extent, and the extraordinary abundance and diversity of their neotropical migrants. There is an urgent need for long-term, well-replicated, field studies comparing bird populations in grazed and ungrazed shrubsteppe and montane coniferous forest habitats.

Abstract. Grass and herb cover, and woody plant densities were measured on 25 native and 25 exotic grassland plots in southeastern Arizona between 1984 and 1990. At least 40 yr previously, the exotic plots had been seeded with two species of lovegrasses (Eragrostis spp.) native to southern Africa. A 1987 wildfire burned 11 native and 11 exotic plots. The fire reduced cover of both native and African grasses for two post‐fire growing seasons. Herb cover as a whole increased after the fire for 2 yr, although there were important differences among species. One of two dominant shrubs (Haplopappus tenuisectus) was killed by the fire, while the other (Baccharis pteronioides) was little affected. Mesquite trees (Prosopis juliflora) were killed to the ground by the fire, but 62 of 66 trees had re‐sprouted to an average 48% of pre‐burn height by 1990. Native and exotic grasses appeared equally tolerant of fire, probably because both evolved in fire‐type ecosystems. There was no evidence that fire can be used to permanently restore the diverse native flora to species‐poor plantations of the South African exotics.

Conservation BiologyVolume 7, Issue 3 p. 731-733 Proposal for a System of Federal Livestock Exclosures on Public Rangelands in the Western United States Carl E. Bock, Carl E. Bock Department of Environmental, Population, and Organismic Biology University of Colorado, Boulder, CO 80309, U.S.A.Search for more papers by this authorJane H. Bock, Jane H. Bock Department of Environmental, Population, and Organismic Biology University of Colorado, Boulder, CO 80309, U.S.A.Search for more papers by this authorHobart M. Smith, Hobart M. Smith Department of Environmental, Population, and Organismic Biology University of Colorado, Boulder, CO 80309, U.S.A.Search for more papers by this author Carl E. Bock, Carl E. Bock Department of Environmental, Population, and Organismic Biology University of Colorado, Boulder, CO 80309, U.S.A.Search for more papers by this authorJane H. Bock, Jane H. Bock Department of Environmental, Population, and Organismic Biology University of Colorado, Boulder, CO 80309, U.S.A.Search for more papers by this authorHobart M. Smith, Hobart M. Smith Department of Environmental, Population, and Organismic Biology University of Colorado, Boulder, CO 80309, U.S.A.Search for more papers by this author First published: September 1993 https://doi.org/10.1046/j.1523-1739.1993.07030731.xCitations: 24AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume7, Issue3September 1993Pages 731-733 RelatedInformation

Ranches are being converted to exurban housing developments in the southwestern United States, with potentially significant but little‐studied impacts on biological diversity. We counted birds in grasslands and savannas in southeastern Arizona that were grazed by livestock, embedded in low‐density exurban housing developments, or both, or neither. Species richness and bird abundance were higher in exurban neighborhoods than in undeveloped landscapes, independent of livestock grazing. The positive response to development was particularly evident among doves, quail, hummingbirds, aerial insectivores, and some but not all ground‐foraging sparrows. Effects of livestock grazing were comparatively minor and mostly involved birds with requirements for tall ground cover or the lack of it. The average rank correlation between counts of individual species and housing density was positive across all transects. However, this relationship disappeared among the exurban transects alone, and bird species richness on the exurban transects was negatively correlated with the number of homes nearby. These results suggest that the positive influence of exurban development on avian abundance and variety was greatest at the lowest housing densities. We attribute the attraction of many birds to exurban development to an oasis effect, in which resources otherwise scarce in arid southwestern environments (shade, nectar, nest sites, and especially water) are relatively abundant around exurban home sites. This finding is consistent with the hypothesis that exurban home sites represented resource supply points inside birds' home ranges otherwise consisting mostly of natural vegetation.

We examine the relationships between abundance of grassland nesting songbirds observed in the Boulder Open Space, CO, USA and parameters that described landscape and habitat characteristics, in order to provide information for Boulder Open Space planners and managers. Data sets included bird abundance and plant species composition, collected during three breeding seasons (1994–1996), and landscape composition and configuration measures from a satellite image-derived land-cover map. We used regression quantiles to estimate the limitations imposed on bird abundance by urban encroachment and decreasing areas of grassland cover-types on the landscape, and habitat characteristics within 200 m diameter sample plots. After accounting for the effect of landscape grassland composition on four species (Western Meadowlark (Sturnella neglecta), Vesper Sparrow (Pooecetes gramineus), Horned Lark (Eremophila alpestris), and Grasshopper Sparrow (Ammodramus savannarum)), change in abundance with proportion of urban area in the landscape was consistent with the pattern expected for limiting factors that were the active constraint at some times and places. Area of preferred grassland cover-types on the landscape was important for all species, and this remained the case when habitat variables were included in combined landscape–habitat models, with one exception (Western Meadowlark). Analysis of habitat variables enabled identification of important features at the local scale (e.g. shale plant communities in Lark Sparrow (Chondestes grammacus) habitat) that were indistinguishable using landscape data alone. Consideration of changes in the landscape due to urbanization and loss of grassland habitat are crucial for open space planning, and habitat features associated with localized and clumped bird species distributions provide important additional information. Widening the management focus to include areas that are not part of the open space system will facilitate a more complete understanding of potential limiting factor processes.

Tolerance of particular grasslands to the activities of domestic livestock may depend on their historic association with native grazing animals. Southwestern grama ( Bouteloua ) grasslands are floristically allied to the North American Central Plains but lie outside the historic range of the plains’ principal ungulate grazer, alics bishop . We compared perennial grassland cover and species composition on eight sites transacted by the boundary fence of a 3160‐ha, 22‐year‐old livestock exclosure in a grama grassland in southeastern Arizona. Total grass canopy cover was greatest on the ungrazed portion of each of the eight sites. Two short stoloniferous species ( Hilaria belangeri and Bouteloua eriopoda ) were the only taxa substantially more abundant on grazed quadrats overall. Among these and eight taller budgerigars, there was a strong positive correlation between potential height and response to release from grazing, with the three tallest species showing the greatest increases on ungraded treatments ( emization curtailment, Boilermaker barbarians , and emizations intermixed ). emization gracious , the most abundant grass in the region, showed an intermediate response to livestock exclusion, Gram grasslands at the Arizona site have changed more and in different ways following livestock exclusion than those on the Central Plains of Colorado. Contributing factors may include: (1) greater annual precipitation at the Arizona site, (2) the much larger size of the Arizona livestock exclosure, and (3) the absence of extensive grazing by native ungulates in the Southwest since the Pleistocene. Livestock grazing appears to be an exotic ecological force in these southwestern grasslands, and one destructive of certain components of the native flora and fauna.

The Botteri's Sparrow (Aimophila botterii) is a bird of tall grasslands that temporarily disappeared from Arizona following heavy livestock grazing in the 1890s. Its return was noted first in sacaton (Sporobolus wrightii), an uncommon native floodplain tallgrass often >2 m in height, and subsequently in stands of exotic lovegrasses (Eragrostis spp.) spreading into adjacent uplands that otherwise supported shorter native grasslands. We examined whether the exotic grasslands provided suitable breeding habitat for Botteri's Sparrows, compared to native grasslands. We counted birds for three years on 18 plots, monitored 314 nests on 323 home ranges, banded 583 birds, and measured vegetation on plots and home ranges, and at nests and fledgling locations. Abundance and site fidelity were positively associated with grass height and cover, being greatest in sacaton, intermediate in exotics, and lowest in native upland grasslands. The three habitats did not differ in young fledged per capita. Vegetation cover on Botteri's Sparrow home ranges did not differ from the surrounding available habitat, but locations of flightless recently fledged young included taller and more dense vegetation than either nest sites or random locations, especially in sparsely vegetated native grasslands. These results suggest that fledglings required substantial cover to avoid predation while they completed development. Far from being an ecological trap, the exotic lovegrasses apparently are providing essential cover for the Botteri's Sparrow in Arizona, perhaps allowing it to regain an abundance similar to what existed regionally prior to overgrazing of the late 19th Century.

We live-trapped rodents in 2000–2001 at eight sites on a 3160 ha grassland and mesquite-oak savanna in southeastern Arizona that had been ungrazed since 1968, and on eight paired sites on adjacent cattle ranches. There were 917 captures of 14 species during 5760 trap-nights. Four species of Muridae (Sigmodon fulviventer, Baiomys taylori, Reithrodontomys megalotis and R. fulvescens) were significantly more common on ungrazed plots, while no species was more abundant on grazed plots. However, Heteromyidae as a group (especially Chaetodipus hispidus and Perognathus flavus) comprised a significantly higher proportion of total captures on grazed plots, and heteromyids as a percentage of total captures was positively correlated across all plots with amount of bare ground. One of the eight cross-fence sites also had been trapped in 1981–1983. In the 17 y between trapping events at this site: (1) the grass canopy on both grazed and ungrazed plots had become dominated by taller species, (2) a kangaroo rat (Dipodomys merriami) that had been the second most common species in grazed areas disappeared from both plots, (3) pocket mice increased on the grazed plot and declined on the ungrazed plot and (4) Muridae (excluding Peromyscus) as a percent of all captures increased by greater than 1.5-fold on both plots. Based on these results, and those from other field studies, we propose a model for the composition of rodent communities in grass/shrublands of the Southwest and Intermountain West, based on ground cover. Kangaroo rats (Dipodomys spp.) are abundant in areas with the most bare soil, Muridae (specifically, Sigmodon, Baiomys and Reithrodontomys) dominate areas with the most and tallest ground cover, and pocket mice (Chaetodipus and Perognathus) are common in areas of intermediate cover. In relatively mesic grasslands, livestock grazing and fire drive the rodent community toward one dominated by heteromyids instead of murids. In more arid landscapes, grazing and fire favor kangaroo rats over pocket mice.

Abstract Using Christmas Bird Count (CBC) data, I compared range sizes and within-range abundances of 70 species of apodiform, piciform, and passerine landbirds whose ranges are 75% or more restricted in winter to the contiguous U.S. and southern Canada. Range size was computed as the number of occupied 5° latitude-longitude blocks. Three abundance measures were calculated: (1) mean birds counted/census hour across all occupied blocks, (2) maximum birds/hour in a single block, and (3) maximum birds/hour on a single CBC. Range size was positively but weakly correlated with each abundance measure, and the abundance measures were very strongly correlated with one another. Geography was a powerful predictor of the species' positions in a two-dimensional space difined by the axes of range size and average within-range abundance. Taxa that breed and winter at higher latitudes had larger total populations, and had significantly larger ranges and average local abundances. Species grouped by longitudinal areas of greatest local abundance had distinct range sizes but did not differ in average within-range abundance. Eastern species had larger ranges than comparably abundant western forms, probably because the eastern U.S. is characterized by relatively widespread habitat types. Results of this study suggest that a species' within-range abundance is influenced by the degree of its habitat generalization, whereas its range size will be larger if it is a habitat generalist or a specialist on widespread habitats. Because individual CBC's include many habitats, the same ecological attribute-habitat generalization-could cause species to be both widespread and abundant inside CBC circles. Carefully standardized within-habitat censuses will be required to determine whether or not these generalist species also dominate the individual habitats occupied by their more specialized and narrowly distributed relatives.

EcologyVolume 67, Issue 1 p. 258-260 Article The Correlation Between Range Size and Local Abundance of Some North American Birds Robert C. Lacy, Robert C. LacySearch for more papers by this authorCarl E. Bock, Carl E. BockSearch for more papers by this author Robert C. Lacy, Robert C. LacySearch for more papers by this authorCarl E. Bock, Carl E. BockSearch for more papers by this author First published: 01 February 1986 https://doi.org/10.2307/1938527Citations: 15AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat No abstract is available for this article.Citing Literature Volume67, Issue1February 1986Pages 258-260 RelatedInformation

The distribution, ecology and evolution of the three-toed woodpeckers (Picoides) is given a new explanation resolving certain biogeographical paradoxes. One species, Picoides tridactylus, is circum- boreally distributed with spruce (Picea), while the other species, P. arcticus, is a larger bird adapted to and distributed with North Ameri- can closed boreal and montane coniferous forests. It seems highly likely that speciation occurred in North America during Pleistocene glacia- tion, when pre-tridactylus populations became isolated in the spruce- dominated refugium of interior Alaska, and arcticus evolved in more substantial and diverse coniferous forests south of the ice cap.

Proceedings of the Zoological Society of LondonVolume 49, Issue 3 p. 628-635 List of Land and Freshwater. Shells collected in Sumatra and Borneo, with Descriptions of new Species. Carl Bock., Carl Bock.Search for more papers by this author Carl Bock., Carl Bock.Search for more papers by this author First published: January 1881 https://doi.org/10.1111/j.1096-3642.1881.tb01317.xCitations: 3AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume49, Issue3January 1881Pages 628-635 RelatedInformation

Abstract: In a grassland–oak savanna in southeastern Arizona, we compared vegetative ground cover and bird populations between a 29‐year livestock exclosure and an adjacent cattle ranch that was managed according to the principles of holistic resource management, including short‐duration rotational grazing. The study took place in the winter after a 2‐year drought and 1 year after the drought ended and stocking densities were reduced. During the first winter, grasses on the livestock exclosure were taller (4.4 times) and had higher basal area ground cover (2.5 times), canopy cover (2.2 times), and reproductive canopy cover (10 times) than in the grazed area. These differences persisted into the second winter but at lower levels. As a group, 19 species of ground‐foraging, seed‐eating birds (e.g., doves, quail, sparrows, towhees) were 2.7 times more abundant on the exclosure than on adjacent grazed grasslands during the first winter. These same species were 1.7 times more abundant on the exclosure during the second winter and were 2.9 times more abundant on both sites combined after the drought had ended. A second group of 24 avian species with different foraging ecologies (e.g., predators, frugivores, arboreal insectivores) did not differ between treatments or years. High‐density, short‐duration rotational grazing, coupled with a drought, left the land in a substantially denuded condition through two winters and negatively affected a variety of resident and migratory birds dependent on ground cover and seed production for over‐winter survival.

Abstract: Relatively little is known about the response of grassland rodent populations to urban and suburban edges. We live‐trapped rodents for three summers on 65 3.1‐ha grassland plots on open space of the city of Boulder, Colorado, and compared capture rates among species according to habitat type, percentage of the 40 ha surrounding each plot that was suburbanized, and proximity to a suburban edge. Deer mice ( Peromyscus maniculatus ) and hispid pocket mice ( Chaetodipus hispidus ) were more abundant on interior than on edge plots in mixed grasslands, whereas prairie voles ( Microtus ochrogaster ) were captured more often on interior than on edge plots in tallgrass/hayfields. House mouse ( Mus musculus ) abundance did not differ between edge and interior plots. Native rodents as a group were captured more often on interior than on edge plots in both habitat types. For each native species, plots with the highest capture rates were in landscapes &lt;10% suburbanized. We conclude that proximity to suburban landscapes had a strongly negative effect on the abundance of native rodents in open‐space grasslands.

Previous articleNext article No AccessLetters to the EditorsGeographical Ecology of the Acorn Woodpecker: Diversity Versus Abundance of ResourcesCarl E. Bock and Jane H. BockCarl E. Bock Search for more articles by this author and Jane H. Bock Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The American Naturalist Volume 108, Number 963Sep. - Oct., 1974 Published for The American Society of Naturalists Article DOIhttps://doi.org/10.1086/282945 Views: 3Total views on this site Citations: 15Citations are reported from Crossref Copyright 1974 The University of ChicagoPDF download Crossref reports the following articles citing this article:Satoshi Yamamoto, Kei Uchida A generalist herbivore requires a wide array of plant species to maintain its populations, Biological Conservation 228 (Dec 2018): 167–174.https://doi.org/10.1016/j.biocon.2018.10.018Lauren E. Walker, John M. Marzluff, David A. Cimprich Source-sink population dynamics driven by a brood parasite: A case study of an endangered songbird, the black-capped vireo, Biological Conservation 203 (Nov 2016): 108–118.https://doi.org/10.1016/j.biocon.2016.09.016Walter D. Koenig, Eric L. Walters, Joseph Haydock Acorn woodpeckers: Helping at the nest, polygynandry, and dependence on a variable acorn crop, (Jan 2016): 217–236.https://doi.org/10.1017/CBO9781107338357.014Shannon Tushingham, Robert L. Bettinger Why foragers choose acorns before salmon: Storage, mobility, and risk in aboriginal California, Journal of Anthropological Archaeology 32, no.44 (Dec 2013): 527–537.https://doi.org/10.1016/j.jaa.2013.09.003Douglas G. Scofield, Victoria L. Sork, Peter E. Smouse Influence of acorn woodpecker social behaviour on transport of coast live oak ( Quercus agrifolia ) acorns in a southern California oak savanna, Journal of Ecology 98, no.33 (May 2010): 561–572.https://doi.org/10.1111/j.1365-2745.2010.01649.xWalter D. Koenig, Alan H. Krakauer, William B. Monahan, Joseph Haydock, Johannes M. H. Knops, William J. Carmen Mast-producing trees and the geographical ecology of western scrub-jays, Ecography 32, no.44 (Sep 2009): 561–570.https://doi.org/10.1111/j.1600-0587.2008.05617.xVeronica Carolina Rosas-Espinoza, Elisa Maya-Elizarraras, Oscar Francisco Reyna Bustos, Francisco Martin Huerta-Martinez Diet of Acorn Woodpeckers at La Primavera Forest, Jalisco, Mexico, The Wilson Journal of Ornithology 120, no.33 (Sep 2008): 494–498.https://doi.org/10.1676/06-102.1Jeffrey J. Lusk, Robert K. Swihart, Jacob R. Goheen Correlates of interspecific synchrony and interannual variation in seed production by deciduous trees, Forest Ecology and Management 242, no.2-32-3 (Apr 2007): 656–670.https://doi.org/10.1016/j.foreco.2007.01.084K.A. Ryniker, J.K. Bush, O.W. Van Auken Structure of Quercus gambelii communities in the Lincoln National Forest, New Mexico, USA, Forest Ecology and Management 233, no.11 (Sep 2006): 69–77.https://doi.org/10.1016/j.foreco.2006.06.008David P. Arsenault Differentiating nest sites of primary and secondary cavity-nesting birds in New Mexico, Journal of Field Ornithology 75, no.33 (Jul 2004): 257–265.https://doi.org/10.1648/0273-8570-75.3.257Walter D. Koenig, Lauryn S. Benedict , The Condor 104, no.33 ( 2002): 539.https://doi.org/10.1093/condor/104.3.539Walter D. Koenig, Joseph Haydock Oaks, acorns, and the geographical ecology of acorn woodpeckers, Journal of Biogeography 26, no.11 (Dec 2001): 159–165.https://doi.org/10.1046/j.1365-2699.1999.00256.xPepper W. Trail Ecological correlates of social organization in a communally breeding bird, the acorn woodpecker, Melanerpes formicivorus, Behavioral Ecology and Sociobiology 7, no.22 (Jul 1980): 83–92.https://doi.org/10.1007/BF00299512Peter B. Stacey Habitat saturation and communal breeding in the acorn woodpecker, Animal Behaviour 27 (Nov 1979): 1153–1166.https://doi.org/10.1016/0003-3472(79)90063-0Michael H. Macroberts, Barbara R. Macroberts Social Organization and Behavior of the Acorn Woodpecker in Central Coastal California, Ornithological Monographs , no.2121 (Jan 1976): iii–115.https://doi.org/10.2307/40166738

Journal Article Natural History of the Nuttall Woodpecker at the Hastings Reservation Get access Alden H. Miller, Alden H. Miller Museum of Vertebrate Zoology University of California Berkeley, California 94720 Search for other works by this author on: Oxford Academic Google Scholar Carl E. Bock Carl E. Bock Biology Department University of Colorado Boulder, Colorado 80302 Search for other works by this author on: Oxford Academic Google Scholar The Condor, Volume 74, Issue 3, 1 July 1972, Pages 284–294, https://doi.org/10.2307/1366590 Published: 01 July 1972 Article history Accepted: 03 February 1971 Published: 01 July 1972

In a 6-yr study of 70 generally insectivorous bird species in Arizona riparian woodlands, abundances of cavity-nesting species increased on 50 experimental plots compared with 49 control plots, following addition of artificial nest boxes. Open-nesting birds increased in abundance on control plots during the study but avoided experimental plots relative to control plots after box addition. Multivariate analysis revealed that a negative response of open nesters to the experiment was widespread among a large and ecologically diverse group of species. Results of this field experiment suggest that communitywide (diffuse) competition was an important factor influencing the distribution and abundance of birds in these riparian ecosystems.

Livestock grazing may or may not be an exogenous disturbance facilitating the spread of exotic grasses, perhaps depending on the historical importance of native ungulates in a particular grassland. We compared canopy cover of native grasses and two African lovegrasses (Eragrostis spp.) over 22 years in ungrazed versus livestock grazed desert grasslands in southeastern Arizona. The exotics comprised <1% of the total grass canopy in either treatment in 1984, but by 2006 this number had risen to 24% in grasslands ungrazed since 1968, and to 65% on adjacent cattle ranches. The exotics increased from 79% to 99% canopy over the same time period in ungrazed areas where they had been planted. Results indicate that: (1) protection from grazing reduced the rate of exotic invasions into native grasslands; (2) areas deliberately planted with the exotics developed into near monocultures even under livestock exclusion, and (3) livestock grazing is an exogenous disturbance in southeastern Arizona, to which exotics are better adapted than most native grasses. It remains to be determined whether ungrazed native desert grasslands will resist further incursions by the African species.

Landscape alterations resulting from urban expansion are among those factors negatively impacting Great Plains grassland birds. The City and County of Boulder, Colorado, manage one of the largest grassland open-space systems in North America, but it is embedded in an area of rapid urban growth. We compared bird count data from the 1980s and 1990s with checklist information about the Boulder grassland avifauna between 1900 and 1937, with the goal of determining what proportion and which species of the historical grassland avifauna are being sustained on Boulder open space. Of 29 native species present in 1900, 22 (76%) appeared on our counts in the 1990s. Formerly common species that disappeared or declined mostly were birds associated with shortgrass prairie, including Burrowing Owl (Athene cunicularia), Common Nighthawk (Chordeiles minor), Loggerhead Shrike (Lanius ludovicianus), and Lark Bunting (Calamospiza melanocorys). By contrast, species associated with mixed and tallgrass habitats increased or held steady, including Vesper Sparrow (Pooecetes gramineus), Savannah Sparrow (Passerculus sandwichensis), Grasshopper Sparrow (Ammodramus savannarum), Bobolink (Dolichonyx oryzivorus), and Western Meadowlark (Sturnella neglecta). We conclude that municipal open spaces can support populations of many Great Plains grassland birds, but that sustaining species associated with the shortgrass prairie may prove especially challenging.

Ranches are being converted to exurban housing developments in the southwestern United States, with potentially significant but little-studied impacts on biological diversity. We captured rodents on 48 traplines in grasslands, mesquite savannas, and oak savannas in southeastern Arizona that were grazed by livestock, embedded in exurban housing developments, grazed and embedded in development, or neither grazed nor embedded in development. Independent of habitat or development, rodent species richness, mean rank abundance, and capture rates of all rodents combined were negatively related to presence of livestock grazing or to its effects on vegetative ground cover Exurban development had no obvious effects on rodent variety or abundance. Results suggest southwester.n exurban developments can sustain a rich assemblage of grassland and savanna rodents if housing densities are low and houses are embedded in a matrix of natural vegetation with little grazing.

This paper presents a 3-year study (1979-1981) on the effects of prescribed burning of ponderosa pine forests at Wind Cave National Park, in the southern Black Hills, South Dakota. The fires were largely restricted to surface fuels and forest understory vegetation. Effects upon understory shrubs. and deciduous trees were modest. In eight study plots, two cool-season (autumn and spring) fires consistently reduced densities of Ribes spp. and stimulated Amorpha canescens Pursh., while other shrubs were unaffected. These burns significantly reduced the density of immature and smaller mature ponderosa pines. The reductions were consistent across all eight study plots. By contrast, an autumn (1974) crown fire, in ponderosa pine, killed pines of all sizes and most shrub species increased dramatically. We attribute these differences in postfire vegetation response to variable fire intensities. INTRODUCTION In the southern Black Hills of South Dakota, ponderosa pines (Pinus ponderosa Laws.) tend to spread into surrounding grasslands along a pine-grassland ecotone (Gartner and Thompson, 1972). This invasion has been documented by a comparative study of photos from General Custer's 1874 Expedition of Exploration to the Black Hills with photos taken a century later (Progulske and Sowell, 1974). Participants in the 1874 Expedition observed that wildfires killed pine trees and encouraged shrub growth. Professor Aris B. Donaldson, the Expedition botanist, wrote of a postfire ponderosa pine forest where all large trees had been killed (Krause and Olsen, 1974, p. 64): But of raspberries there was no end. Acres and acres of the mountains' sides were covered with them. They were large and sweet and could be picked in clusters of from three to six. A recent paper by Dietz et al. (1980) further documents shrub increases on burned sites in this region. Ponderosa pine forests under natural conditions burn every 10-25 years throughout its range in the western United States (Weaver, 1967; Wright, 1978). At Wind Cave National Park, South Dakota, Shilts et al. (1980), using dendrochronological techniques, found the fire cycle to be between 13 and 21 years from 1820-1910. These fires tended not to kill mature trees, but they burned off the litter layer while killing young pines and other small-stemmed woody species (Weaver, 1967). When wildfires are absent, due either to successful efforts at fire suppression or unusual regional climatic patterns, dense dog-haired pine stands result. Such stands occurred within our study area, and pine had invaded the grassland in many places. The purpose of this study was to evaluate the effects of autumn and spring (cool season) prescribed burns on woody vegetation of the pine-grassland ecotone in Wind Cave National Park, of the southern Black Hills. The study covered one preburn and two postburn growing seasons. Our objectives were: (1) to determine if prescribed fires increased shrub and deciduous tree species in the forest understory; (2) to quantify mortality of immature pines in the forest-grassland ecotone, including both dense, spindly pine in the forest understory and seedlings and saplings invading adjacent grasslands, and (3) to measure the degree to which prescribed fires had consistent and predictable effects throughout the study area. METHODS The study area ranged in elevation from 1250-1425 m. Higher elevations, except

Housing developments are replacing ranches in the southwestern United States, with potentially significant but little-studied ecological effects. We counted grasshoppers (Orthoptera: Acrididae) and measured vegetative cover for 2 years in a grassland and mesquite/oak savanna in southeastern Arizona, on 48 transects that were grazed by livestock, embedded in low-density housing developments, or both, or neither. Grasshopper species richness was unrelated to grazing or development, but grasshopper abundance was much higher on exurban transects where homeowners kept livestock than in the other areas. Forb canopy and basal area also were highest in grazed exurban areas, perhaps because exurban grazing was relatively patchy, frequently involved horses, and created disturbances more conducive to forb establishment than did relatively uniform grazing on nearby ranches. Abundance patterns of 3 grasshopper subfamilies were generally consistent with their known habitat preferences. Counts of grass-feeding Gomphocerinae were relatively high in ungrazed and unburned areas, and positively correlated with grass cover. Numbers of forb- and mixed-feeding Melanoplinae were positively correlated with forb cover across all transects, and melanoplines dominated counts on grazed exurban properties. Band-winged grasshoppers (Oedipodinae) prefer areas of sparse vegetation, and their numbers were negatively correlated with height of ground vegetation and positively associated with the presence of livestock, in both exurban and undeveloped landscapes. Overall, our results suggest that heterogeneous landscapes in exurban areas that included small livestock pastures had higher grasshopper densities than either ungrazed areas or large cattle ranches. El desarrollo de áreas residenciales esta substituyendo a las áreas de rancho en el sur-oeste de los Estados Unidos, con efectos ecológicos potencialmente significativos pero muy poco estudiados. Hicimos el conteo de saltamontes (orthoptera: Acrididae) y medimos la cobertura vegetal durante 2 años en un prado y sabana de enebro/roble en el sudeste de Arizona, en 48 transectos pastados por ganado, en medio de desarrollos residenciales de baja densidad, o ambos, o ninguno. La riqueza de saltamontes no estaba relacionada al pastoreo o al desarrollo, pero su abundancia fue mucho más alta en transectos exurbanos, donde los dueños de propiedades mantenían ganado, que en otras áreas. El dosel y el área basal de hierbas fueron también más altos en áreas exurbanas pastadas, probablemente porque el pastoreo, frecuentemente hecho por caballos, en áreas exurbanas estaba más parchado, y se crearon perturbaciones más conducentes al establecimiento de hierbas que en áreas de pastoreo uniforme en ranchos próximos. Los patrones de abundancia de 3 subfamilias de saltamontes fueron generalmente consistentes con sus preferencias de hábitat conocidos. Los conteos de alimentación de la subfamilia Gomphocerinae fueron relativamente altos en áreas sin pastoreo y sin quemar, y positivamente correlacionados a la cobertura vegetal. El número de hierbas y la alimentación de la subfamilia Melanoplinae estuvieron positivamente correlacionados con la cobertura de hierbas en todos los transectos y esta subfamilia dominó los conteos en las propiedades exurbanas pastadas. Los saltamontes de la subfamilia Oedipodinae prefieren áreas de vegetación escasa, y su conteo estuvo negativamente correlacionado con la altura de la vegetación y positivamente asociados con la presencia de ganado en paisajes exurbanos y no desarrollados. En general, nuestros resultados sugieren que paisajes heterogéneos en áreas exurbanas que incluyen pequeñas pasturas de ganado tuvieron mayores densidades de saltamontes que las áreas sin pastoreo o grandes ranchos ganaderos.

Journal Article Polygyny in the Dipper Get access Frank E. Price, Frank E. Price Department of Environmental, Population, and Organismic Biology University of Colorado Boulder, Colorado 80302 Search for other works by this author on: Oxford Academic Google Scholar Carl E. Bock Carl E. Bock Department of Environmental, Population, and Organismic Biology University of Colorado Boulder, Colorado 80302 Search for other works by this author on: Oxford Academic Google Scholar The Condor, Volume 75, Issue 4, 1 October 1973, Page 457, https://doi.org/10.2307/1366567 Published: 01 October 1973 Article history Accepted: 02 February 1973 Published: 01 October 1973

INTRODUCTION. During the spring of 1974 two fires occurred on The Research Ranch, which is located 9.6 km south of Elgin in Santa Cruz Co., Arizona. The first fire (February burn) occurred in oak-savannah and covered approximately 240 hectares. The second fire (April burn) burned approximately 120 hectares of grassland. Both were classified as ground fires, i.e., they were not hot enough to destroy healthy, mature trees. Both fires were caused by human activities; but neither was set intentionally. The purpose of our study was to evaluate the response of the vegetation and selected bird and mammal species to these fires.

Livestock grazing and fire influence the composition of desert grassland communities, including their rodent populations. However, there have been few studies of the interactions between grazing and wildfire in arid grasslands of the southwestern United States. We trapped rodents and measured vegetation on grazed versus ungrazed plots before (2001) and following (2002–2007) an intense 15,000 ha wildfire in southeastern Arizona. The fire reduced grass canopy on grazed plots for 2 y and on ungrazed plots for 3 y. Some rodents in the family Cricetidae (genera Baiomys, Reithrodontomys and Sigmodon) were more abundant on ungrazed plots before the fire. Cricetidae as a whole declined following the fire and did not return to preburn levels until the sixth postfire year (2007). Nine of ten cricetid species contributed to this general pattern. By contrast, the abundant species of Heteromyidae (Chaetodipus hispidus, C. baileyi, Perognathus flavus) increased following the fire, especially on ungrazed plots. These results are consistent with a model predicting that fire-caused reductions in grass cover should favor Heteromyidae over Cricetidae. Fires elsewhere in the Southwest have had little impact on rodent populations, but these were smaller and cooler burns with relatively minor effects on vegetation. Future studies of large wildfires of varying intensities would further elucidate the generality of the model.

We measured grasshopper densities on 66 shortgrass, mixed grass, tallgrass and hayfield plots on Boulder, Colorado, open space in 1995–1996. Grasshoppers as a group, and most species individually, were more abundant on relatively sparse short and mixed grass plots than on lusher hayfields and tallgrass plots—a result consistent with the hypothesis that most species require warm and sunny open ground for survival and reproduction. Bandwinged grasshoppers (Oedipodinae) were particularly associated with open ground in shortgrass vegetation, whereas spur-throated grasshoppers (Melanoplinae) were most abundant in mixed grass plots with a high percentage of forb vs. graminoid cover. Slant-faced grasshoppers (Gomphocerinae) were the most uniformly distributed among habitats, but were generally associated with plots including relatively high proportions of grass vs. forb cover. While 20 of the 25 most common grasshopper species on Boulder open space occurred in all four grassland types, each habitat was dominated by a distinctive set of species. However, numerically dominant grasshoppers on short, mixed and tallgrass plots only loosely resembled groups of dominant species in the same habitats elsewhere on the Great Plains. While most Great Plains grasshoppers are widely distributed, they are apparently numerically responsive to combinations of environmental conditions expressed at local scales. Common species of grasshoppers on Boulder open space in 1995–1996 were the same as those collected in the region in the 1950s. Our results suggest these protected grasslands, although invaded by alien vegetation and fragmented by suburbanization, are still effectively conserving this particular insect group.

Ranches are being converted to low-density exurban housing developments in the Southwest, with potentially significant but little studied impacts on biological diversity. We counted cottontail rabbits (Sylvilagus audubonii and S. floridanus) in a grassland and in a mesquite-oak savanna in southeastern Arizona, on 48 plots evenly divided among landscapes that were grazed by livestock, or embedded in housing developments, or both, or neither. Cottontails were more abundant in exurban neighborhoods than in undeveloped areas, independent of grazing. They also were more common on ungrazed than on grazed lands, independent of development. Counts were positively correlated with the number of homes near plots. Counts also were positively correlated with height of ground cover and percent tree canopy, but only among plots in undeveloped landscapes. These results are consistent with the hypothesis that cottontails benefited from exurban development because of increased cover provided by structures and landscaping, especially in areas such as open grasslands with relatively little natural cover.

Ranches are being converted to low density exurban housing developments in the southwestern United States, with potentially significant but little studied impacts on biological diversity. We counted lizards in a grassland and mesquite/oak savanna in southeastern Arizona, along 48 transects evenly divided among landscapes that were grazed by livestock, embedded in housing developments, both or neither. Terrestrial lizards as a group (mostly Aspidoscelis uniparens and Holbrookia maculata) were scarce in developed areas, especially where homeowners kept livestock. Combined counts of lizards (Sceloporus clarkii, Sceloporus undulatus and Urosaurus ornatus) associated with three dimensional substrates did not differ among landscape categories. Roadrunners (Geococcyx californianus), known predators of terrestrial lizards, were more common in developed areas, especially those that were grazed. These results are consistent with the hypothesis that the relative scarcity of terrestrial lizards in developed landscapes was due to increased predation by roadrunners, but predation by other species, especially domestic pets, may also have been important.

Pygmy Nuthatches, White—breasted Nuthatches, and Mountain Chickadees travel in mixed flocks in winter in Colorado. The species exhibited different by overlapping foraging niches. Both intra— and interspecific aggression occurred, supporting the idea of niche overlap. The ratio of intra— to interspecific encounters was higher than expected if encounters were in proportion to flock composition, indicating that niche overlap was not complete. At artificial feeding stations, where found niches were identical for all species, the level of interspecific aggression initially was higher than in nature. However, the dominance of Pygmy Nuthatches at the feeders soon resulted in a "competitive exclusion" of the other birds and a lessening of interspecific contact.

Abstract The Botteri's Sparrow (Aimophila botterii) is a bird of tall grasslands that temporarily disappeared from Arizona following heavy livestock grazing in the 1890s. Its return was noted first in sacaton (Sporobolus wrightii), an uncommon native floodplain tallgrass often &gt;2 m in height, and subsequently in stands of exotic lovegrasses (Eragrostis spp.) spreading into adjacent uplands that otherwise supported shorter native grasslands. We examined whether the exotic grasslands provided suitable breeding habitat for Botteri's Sparrows, compared to native grasslands. We counted birds for three years on 18 plots, monitored 314 nests on 323 home ranges, banded 583 birds, and measured vegetation on plots and home ranges, and at nests and fledgling locations. Abundance and site fidelity were positively associated with grass height and cover, being greatest in sacaton, intermediate in exotics, and lowest in native upland grasslands. The three habitats did not differ in young fledged per capita. Vegetation cover on Botteri's Sparrow home ranges did not differ from the surrounding available habitat, but locations of flightless recently fledged young included taller and more dense vegetation than either nest sites or random locations, especially in sparsely vegetated native grasslands. These results suggest that fledglings required substantial cover to avoid predation while they completed development. Far from being an ecological trap, the exotic lovegrasses apparently are providing essential cover for the Botteri's Sparrow in Arizona, perhaps allowing it to regain an abundance similar to what existed regionally prior to overgrazing of the late 19th Century.

Ranches are being converted to exurban housing developments in the southwestern United States, with potentially significant impacts on biological diversity. We surveyed butterflies on 48 plots in grasslands, mesquite savannas, and oak savannas in southeastern Arizona that were grazed by livestock, embedded in low-density housing developments, or both, or neither. Results suggest that livestock grazing had little impact on butterfly species richness or abundance, while exurban development had minor impacts compared to negative effects that have been documented elsewhere in more fully developed urban and suburban landscapes. However, our data indicate that conversion of ranchland to exurban development has not been without consequence to butterflies. First, relatively immobile species with multiple broods and/or generalized diets were positively associated with development in grasslands, unaffected in mesquite savannas, and often negatively associated with development in oak savannas. Second, while abundance and variety of butterflies were positively correlated with plant species richness and cover in undeveloped landscapes, such correlations were not present in exurban areas. These results suggest that increased resources associated with housing development, including water, shade, and nectar, and possible negative impacts of increased avian predation and pesticide use, caused relationships between butterflies and native vegetation to be less tightly coupled in exurban than in undeveloped landscapes.

Abstract Livestock grazing is the most widespread economic use of public lands in western North America (Platts 1991). Approximately 86 million hectares of US Federal land in 17 western states are used for livestock production (Sabadell 1982). In the American West, grazing by domestic ungulates began in the 1840s, increased rapidly in the 1870s, and peaked around 1890 (Young and Sparks 1985). By 1900 much rangeland vegetation had been altered by the combination of extreme drought and high intensity grazing (Yensen 1981, Young and Sparks 1985). Range-management practices, including grazing systems (Appendix) and fenced pastures, were initiated in the early 1900s to help restore damaged rangelands (Behnke and Raleigh 1979). By the mid-1960s, management by allotment (designated areas for a prescribed number of livestock under one plan of management) had become an accepted practice on public lands, and is still in use today (Platts 1991).

In 1540 Francisco Vasquez de Coronado introduced the first domestic livestock to the American Southwest. Over the subsequent four centuries, cattle, horses, and sheep have created a massive ecological experiment on these arid grasslands, changing them in ways we can never know with certainty. The Appleton-Whittell Research Ranch in the high desert of southeastern Arizona is an 8,000-acre sanctuary where grazing has been banned since 1968. In this spirited account of thirty years of research at the ranch, Carl and Jane Bock summarize the results of their fieldwork, which was aimed at understanding the dynamics of grasslands in the absence of livestock. The View from Bald Hill provides an intimate look at the natural history of this unique site and illuminates many issues pertaining to the protection and restoration of our nation's grasslands.

(1) Approximately 15 000 ha of mixed coniferous forest in the northern Sierra Nevada of California were burned during the Donner Ridge Fire in 1960. (2) Two areas were compared in the burnt forest that had received different management: one area was planted with Pinusjeffreyi Grev. and Balf. and sprayed with 2,4,5-T for shrub control; the other area was allowed to follow a natural post-fire succession. (3) Similar numbers of P. jeffreyi occurred on both sites, but shrubs and herbs were greatly reduced on the planted area and grasses increased. (4) Only Ribes cereum Dougl., which is normally a minor component of the natural shrub community, flourished in the planted area. (5) The ecological effects of conifer plantations in the northern Sierra Nevada are discussed.

North American hawks of the subfamily Buteoninae have received considerable attention, mostly with regard to their food habits and breeding biologies (e.g., Errington and Breckenridge 1938, Fitch et al. 1946, Smith and Murphy 1973). Twelve species occur in the New World north of Mexico but only five are widely distributed in winter (A.O.U. 1957). These are the Harris' Hawk (Parabuteo unicinctus), Ferruginous Hawk (Buteo regalis), Red-shouldered Hawk (B. lineatus), Red-tailed Hawk (B. jamaicensis), and Rough-legged Hawk (B. lagopus). Previously published maps based upon Christmas count data indicate that only the last three of these species are at all common over wide areas (Bystrak 1974). A number of workers have examined the relationships between locally sympatric populations of two or more Buteo species (e.g., Stewart 1949, Orians and Kuhlman 1956, Weller 1964, Schnell 1968). In this study we have compiled data from the 1969-70, 197071, and 1971-72 Christmas counts to determine the overall abundance pattern of this genus in the United States and southern Canada. We could then quantify the contributions made by the individual species to that pattern on different parts of the continent. We compared these calculations with certain environmental variables. Results show the degree to which the species' abundance patterns are complementary, and reveal something about the environmental gradients involved.

Increases of velvet mesquite (Prosopis velutina Woot.) in southwestern grasslands might have been caused by livestock consumption of fuels that once burned with sufficient frequency and intensity to kill the trees. However, attempts to control mesquite with fire usually have failed. We measured fire damage and 5 years of postfire recovery for 225 mesquite trees > 1 m tall, following a 2002 wildfire that included grasslands differing in fire history, presence vs. 34-year livestock exclusion, and predominance of native vs. exotic grasses. The fire burned 100% of ground cover in ungrazed areas and 65% on grazed lands. Top-kill was 100% for trees in exotic ungrazed grasslands (the areas with highest fuel loads), 79% for trees in ungrazed native grasslands, and 28% for trees in grazed grasslands. Most top-killed trees produced ground sprouts, so that by 2006 the combined foliage volume from ground sprouts and surviving branches was 78% (± 3.2 SE) of preburn foliage volume in grazed areas, 66% (± 3.3) in ungrazed exotic grasslands, and 57% (± 4.0) in ungrazed native grasslands. Fire damage was greater among surviving trees in ungrazed areas that had burned twice (1987 and 2002) than among those that had burned only once since 1968 (in 2002), especially in native grasslands where postfire foliage recovery for twice-burned trees was only 47% (± 6.3) by 2006. Only 1 of 84 trees died in the area burned once, whereas 12 of 66 (18.2%) died in the area burned twice, including several individuals > 3 m tall. These results suggest that repeated fires likely could have prevented the historic spread of velvet mesquite into southwestern grasslands, but probably could be used to control mesquite today only in areas where abundant herbaceous growth provides sufficient fine fuels.

Developed waters may improve arid landscapes for birds, but their efficacy requires further study. I counted birds along five 300-m transects originating at point sources of water in a New Mexico grassland, and compared results with those from transects without water. Total birds were nearly three times more abundant on transects with water, but differences were greater in spring and winter than during the wet summer period. Twenty-two of 25 common species trended toward greater abundance on transects with water, eight of these at statistically significant levels, including Gambel's Quail, Mourning Dove, House Finch, and a variety of wintering sparrows. Sixty-four percent of detections along transects with water occurred <50 m from the water sources, at which birds regularly drank. Results suggest 1) that water attracted birds, especially in dry seasons, and 2) that proximity to water may influence the abundance and composition of avian assemblages in arid landscapes.

IbisVolume 128, Issue 1 p. 137-140 Eruptions of some North American boreal seed-eating birds, 1901–1980 DIANE L. LARSON, DIANE L. LARSON Department of Environmental, Population, and Organismic Biology, University of Colorado, Boulder, CO 80309, USA Department of Biology, University of Iowa, Iowa City, Iowa 52242, USASearch for more papers by this authorCARL E. BOCK, CARL E. BOCK Department of Environmental, Population, and Organismic Biology, University of Colorado, Boulder, CO 80309, USASearch for more papers by this author DIANE L. LARSON, DIANE L. LARSON Department of Environmental, Population, and Organismic Biology, University of Colorado, Boulder, CO 80309, USA Department of Biology, University of Iowa, Iowa City, Iowa 52242, USASearch for more papers by this authorCARL E. BOCK, CARL E. BOCK Department of Environmental, Population, and Organismic Biology, University of Colorado, Boulder, CO 80309, USASearch for more papers by this author First published: January 1986 https://doi.org/10.1111/j.1474-919X.1986.tb02101.xCitations: 12 AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume128, Issue1January 1986Pages 137-140 RelatedInformation

Abstract. Eragrostis intermedia (Plains lovegrass) is a midheight perennial bunchgrass native to semi‐arid grasslands of the southwestern USA, that becomes an abundant and dominant component of these grasslands in areas long protected from livestock grazing. Substantial mortality of plains lovegrass occurred on a large livestock exclosure in southeastern Arizona, after a period of declining precipitation, but only in areas that had not burned in the previous three years. Lovegrass abundance subsequently increased on both undisturbed and burned sites, but remained substantially higher on the burned area. Long‐term abundance of plains lovegrass may depend on episodic fire, particularly during periods of reduced precipitation.

Foothills shrub in the northern Colorado Front Range is a patchy habitat naturally embedded in a mosaic of grassland and conifer forest. We investigated associations of breeding songbirds in foothills shrub with local habitat characteristics and landscape context. Avian distri- butions were quantified using 84 points counted 6 times each over 2 years, and species were categorized as breeding-season residents or non-residents. We quantified habitat structure and shrub species composition using a point-quarter technique and visual estimation of cover, and sampled landscape context within 500 m of study points using aerial orthophotograph images. We used multiple logistic regression to analyze associations between 15 habitat and landscape variables and breeding residence of each of the eight most common breeding bird species: spotted towhee (Pipilo maculatus), brown-headed cowbird (Molothrus ater), green-tailed towhee (Pipilo chlorurus), Virginia's warbler (Vermivora virginiae), yellow-breasted chat (Icteria virens), broad-tailed humming- bird (Selasphorus platycercus), lazuli bunting (Passerina amoena), and blue-gray gnatcatcher (Polioptila caerulea). Five of these species showed significant relationships between breeding residence and at least one local habitat variable, in ways generally consistent with their known habitat require- ments. In a multiple regression with habitat and landscape variables, species richness was positively associated with two habitat characteristics: shrub cover and horizontal heterogeneity. No species was significantly associated with landscape context of shrub, grassland, or coniferous forest at the scale of our analysis, suggesting that shrub patches with appropriate local characteristics were used regardless of their natural landscape setting in this system. We conclude that breeding species in foothills shrub may have evolved tolerance for habitat fragmentation because it represents the natural state of the landscape in which they occur. RESUMEN-El habitat de arbustos de las faldas de las Montafias Rocallosas en el norte de Colorado es un habitat en parches naturalmente incrustado en un mosaico de pastizales y bosques coniferos. Se estudi6 la asociaci6n de aves cantoras que anidan en este hdbitat con caracteristicas del habitat local y con contexto del paisaje. Las distribuciones de aves fueron cuantificadas en 84 lugares, cada lugar contado seis veces durante dos afios, y las especies fueron categorizadas como residentes o no residentes. Cuantificamos la estructura del habitat y la com- posici6n de las especies de arbustos usando la t~cnica de puntos-cuadrados y la estimaci6n visual de cobertura, y muestreamos el contexto del paisaje dentrode 500 m de los puntos fijos usando imagenes ortofotogrificas. Usamos regresi6n mfiltiple logistica para analizar asociaciones entre 15 variables de habitat y del paisaje con la clase de residencia para cada una de las ocho especies mas comunes: Pipilo maculatus, Molothrus ater, Pipilo chlorurus, Vermivora virginiae, Icteria virens,

THE Lewis' Woodpecker (Asyndesmus lewis) and the Red-headed Woodpecker (Melanerpes erythrocephalus) are nearly ecological equivalents in western and eastern North America, respectively (Bock, 1970). Both species prefer open breeding habitat such as savannah or old burns, where they rarely excavate for wood-boring insects, but instead hawk for insects on the wing (e.g., Beal, 1911; Bent, 1939). During the winter both species harvest, store, and aggressively defend caches of acorns, corn, or similar mast (Kilham, 1958; Bock, op. cit.). Both are partially migratory but may be resident in suitable habitat, and they show generally opportunistic habits by moving into areas where food is temporarily abundant (e.g., an oak woodland rich in acorn mast). These woodpeckers have never to our knowledge been studied in sympatry, although there is limited potential overlap of their breeding ranges in central Montana, eastern Wyoming, Colorado, and New Mexico (A.O.U. Check-list, 1957). In June, 1969, we discovered substantial populations of Lewis' and Red-headed Woodpeckers nesting together along the Arkansas River and adjacent farmlands in Crowley and Otero counties, on the plains of southeastern Colorado. This paper presents information on the ecology and behavior of the two species in sympatry. By way of further comparison we carried out a structural and functional analysis of their vocalizations during the breeding, season.

The tallgrass prairie once was continuous throughout the eastern Great Plains. Now, scattered remnants remain. The distribu tion of some of the most interesting and socially valuable remnants occur along the base of the Rocky Mountains as relicts from a past era. When the species composition of these Colorado grasslands is compared with that of the eastern tallgrass prairie by an index of similarity, the relation ship is clear, even though the climates of the two regions differ greatly. It is likely that this western tallgrass prairie is left over from past geo logic times rather than the product of long distance seed dispersal. To day, the persistence of tallgrass prairie is threatened. These threats include urbanization, mismanagement, under-valuation by the people who in habit the regions, and invasion by exotic plant species. These are serious, but correctable, problems. The conservation and restoration of the re maining tallgrass prairie is justified because these relicts contain valu able ecological and genetic resources for the future.

This study describes biogeograhic patterns of Amphibia and Reptilia in the State of Illinois, USA, using numerical taxonomic methods. The 102 Illinois counties were characterized by the presence vs. absence of amphibian and reptilian species, and by their vegetation, climate and drainage patterns. The counties then served as Operational Taxonomic Units in cluster and principal components analyses. Our purpose was to define herpetofaunal regions of the state and their relationships to other environmental variables. Reptilian distribution patterns were more highly correlated with climate and vegetation than were those of the Amphibia, whereas the amphibians corresponded more closely with drainage patterns. Cluster and principal components analyses served well together to show different aspects of these relationships. INTRODUCTION This paper has two purposes. The first is to examine cluster and principal components analyses as tools in quantitative biogeographical studies. Our second purpose is to present a herpetofaunal analysis of Illinois by attempting to point out major herpetofaunal boundaries and interpreting them in light of patterns of vegetation, topography, climate and earth history. The of Illinois has been studied carefully in the past (Smith, 1957; Smith and Minton, 1957; Huheey, 1965). Our work is based upon Smith's thorough work (1961) in which he compared the distribution of species with Vestal's (1931) vegetation map of Illinois and with certain geographical features of the state. We have based our analysis upon Smith's effort because it is uniform in its treatment and representative, as nearly as possible, of a single philosophical approach to the taxa. This has caused us to pass over more recent range extensions and certain taxonomic revisions by other authors. We are not the first in recent times to delimit herpetofaunal boundaries for Illinois; however, our analytic techniques differ from those of others. Further, we have made one major departure in approach by analyzing reptiles and amphibians separately rather than together. Our results show that there is justification for treating the biogeography of reptiles and amphibians separately. Not only is this defensible taxonomically (evolutionarily), but also ecologically. At the most fundamental level, most amphibians are associated with moist or wet habitats while most reptiles have a more general distribution. Perhaps the traditional combination of species belonging to these two vertebrate classes into a herpetofauna is more a consequence of the historical tradition of having herpetologists who study them than it is of any particular affinity of the two groups. There is considerable debate over which (if any) of a variety of numerical techniques are appropriate for studies such as ours. The debate centers on two questions. First, what is the best similarity measure for comparing the floras or faunas of two geographical areas? Second, what are the relative merits of clustering vs. principal components or factor analyses in biogeography? In the present study, we applied a number of different numerical techniques to the same data set, with the objective of comparing the sorts of patterns revealed by each. METHODS Data. From Smith (1961), we recorded for each Illinois county the presence vs. absence of 27 amphibians and 44 reptiles whose ranges included part, but not all of the

Fire was a common prehistoric disturbance in most southwestern grasslands, oak savannas, and coniferous forests, but not in Sonoran and Mojave desertscrub, or in riparian ecosystems. Prescribed burning should be applied, but under experimental conditions that facilitate studying its impacts on birds and other components of biodiversity. Fire plays a critical role in maintaining a balance between desert grassland and Chihuahuan desertscrub, but unburned areas also are important for birds dependent upon woody vegetation and/or heavy grass cover. Understory fire probably once played a critical role in maintaining relatively open oak (Quercus spp.), pinyon-juniper (Pinus- Juniperus), and ponderosa pine (Pinus ponderosa) woodlands and their bird assemblages, while stand replacement fires sustained aspen groves (Populus tremuloides) at higher elevations. Carefully controlled prescribed burning, thinning, and grazing management will be needed to return fire to its prehistoric role in these habitats. There is an urgent need for cooperative effort between managers and researchers to implement replicated burns to quantify avian responses in appropriate habitats.

There are times when birds reproduce at higher rates in places where they are less abundant, limiting the generally accepted value of bird counts as environmental indicators. But how often, and under what circumstances, does this happen? In 109 published cases involving 67 species across North America and Europe, higher density sites displayed greater recruitment per capita and per unit of land area in 72% and 85% of cases, respectively. The frequency of negative relationships between abundance and reproductive success did not differ between different kinds of birds or habitats. However, density was negatively related to reproductive success more often in areas of human disturbance than in relatively natural areas. Although further study is needed to confirm the generality of this pattern, especially in areas such as the tropics, results suggest that birds can fail to recognize ecological traps or opportunities in landscapes that differ from those in which they evolved.

The science of biogeography ideally includes consideration of both the distribution and density of species. Traditionally, biogeographers have studied only the ranges of species, because of difficulties inherent in measuring population densities over broad geographic areas. On the other hand, animal ecologists (e.g., Andrewartha and Birch 1954, MacArthur 1972) have suggested that those same environmental factors which control the distribution of a species also affect its pattern of abundance within that distribution. Woodpeckers are among the best known groups of North American birds. Nearly all of the 20 species found north of Mexico have received careful attention. We know where they occur and we know in general what foraging strategies they employ. However, few studies have attempted to determine large-scale patterns of population density. The National Audubon Society Christmas count data, published as local population censuses, are of varying quality, but collectively are of such magnitude as to reveal continent-wide population phenomena. In this study we have used Christmas count data to analyze some patterns of winter abundance of North American woodpeckers, with a goal of revealing more about the ecology and adaptation of the species than would be possible from simple analyses of their distributional limits.

Joseph Grinnell, first Director of the Museum of Vertebrate Zoology at the University of California, Berkeley, was a dedicated and remarkably prescient conservationist, as well as a pioneer western ornithologist. He was one of the first to recognize that birds have particular value in conservation because of their charisma, familiarity, and sensitivity to environmental conditions. History has proven Grinnell right, as evidenced by the influence of birds and ornithology in efforts to protect species and their habitats. However, threats to natural landscapes in western North America continue on a scale even Grinnell might not have predicted. Ornithologically-based conservation efforts must be re-doubled, focused on subjects such as landscape and metapopulation models specifically for western habitats, the use of large-scale data sets, the genetic structure of species and populations, avian responses to environmental stressors and disease, and studies of birds in winter.

Abstract Landscape alterations resulting from urban expansion are among those factors negatively impacting Great Plains grassland birds. The City and County of Boulder, Colorado, manage one of the largest grassland open-space systems in North America, but it is embedded in an area of rapid urban growth. We compared bird count data from the 1980s and 1990s with checklist information about the Boulder grassland avifauna between 1900 and 1937, with the goal of determining what proportion and which species of the historical grassland avifauna are being sustained on Boulder open space. Of 29 native species present in 1900, 22 (76%) appeared on our counts in the 1990s. Formerly common species that disappeared or declined mostly were birds associated with shortgrass prairie, including Burrowing Owl (Athene cunicularia), Common Nighthawk (Chordeiles minor), Loggerhead Shrike (Lanius ludovicianus), and Lark Bunting (Calamospiza melanocorys). By contrast, species associated with mixed and tallgrass habitats increased or held steady, including Vesper Sparrow (Pooecetes gramineus), Savannah Sparrow (Passerculus sandwichensis), Grasshopper Sparrow (Ammodramus savannarum), Bobolink (Dolichonyx oryzivorus), and Western Meadowlark (Sturnella neglecta). We conclude that municipal open spaces can support populations of many Great Plains grassland birds, but that sustaining species associated with the shortgrass prairie may prove especially challenging. Conservación de Aves de Pastizal en un Paisaje de Crecimiento Urbano: Una Perspectiva Histórica Resumen. La alteración del paisaje causada por la expansión urbana es uno de los factores que impacta negativamente a las aves de los pastizales de los “Great Plains.” La ciudad y el condado de Boulder, Colorado, maneja uno de los sistemas de espacios abiertos de pastizal más grande de Norteamérica, el cual se encuentra rodeado por un área de crecimiento urbano. Comparamos datos de conteo de aves de los 1980s y 1990s con informacíon de la avifauna de Boulder entre 1900 y 1937, con el propósito de determinar qué proporción y cuántas especies de las aves de pastizal registradas históricamente se mantuvieron en los espacios abiertos de Boulder. De 29 especies nativas presentes en 1900, 22 (76%) aparecen en nuestros conteos de los 1990s. Especies anteriormente comunes pero que desaparecieron o disminuyeron en cantidad, fueron aves relacionadas principalmente con praderas de pasto corto, incluyendo Athene cunicularia, Chordeiles minor, Lanius ludovicianus y especialmente Calomospiza melanocorys. Por el contrario, especies asociadas a hábitats mixtos o de pasto alto han aumentado o se han mantenido, incluyendo Pooecetes gramineus, Passerculus sandwichensis, Ammodramus savannarum, Dolichonyx oryzivorus y Sturnella neglecta. Concluimos que los espacios abiertos municipales pueden sostener poblaciones de varias especies de aves de pastizal. Sin embargo, será más difícil mantener aquellas especies que prefieren praderas de pasto corto, porque las áreas continuas y amplias que necesitan, ya no existen.

We measured fire damage to 250 riparian trees in 2003–2004, and again in 2012–2013, in a southeastern Arizona grassland burned by wildfires in 2002, 2009, or both. Following a single fire, combined mortality or survival only by ground-level resprout was 64% for desert willow (Chilopsis linearis), 57% for Fremont cottonwood (Populus fremontii), 48% for Arizona walnut (Juglans major), 32% for velvet ash (Fraxinus velutina), and 25% for Wright's sycamore (Platanus wrightii). A second fire burned 120 of the trees that happened to have been less damaged by the first fire. Distinctions among species in overall fire damage persisted after the second fire but to a lesser degree. By the conclusion of our study, 26% of the 250 trees had died completely while another 32% survived only as relatively small resprouts. We conclude that the fires substantially reduced both the abundance and crown volume of mature riparian trees in the study area.

Proceedings of the Zoological Society of LondonVolume 46, Issue 1 p. 727-727 Descriptions of two new Species of Shells from China and Japan. Carl Bock F.G.S. &c., Carl Bock F.G.S. &c.Search for more papers by this author Carl Bock F.G.S. &c., Carl Bock F.G.S. &c.Search for more papers by this author First published: August 1878 https://doi.org/10.1111/j.1469-7998.1878.tb08014.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume46, Issue1August 1878Pages 727-727 RelatedInformation