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At least 1,477 records · Page 82Linked to original sources
USGS2000

A dynamic landscape model for fish in the Everglades and its application to restoration

A model (ALFISH) for fish functional groups in freshwater marshes of the greater Everglades area of southern Florida has been developed. Its main objective is to assess the spatial pattern of fish densities through time across freshwater marshes. This model has the capability of providing a dynamic measure of the spatially-explicit food resources available to wading birds. ALFISH simulates two functional groups, large and small fish, where the larger ones can prey on the small fish type. Both functional groups are size-structured. The marsh landscape is modeled as 500×500 m spatial cells on a grid across southern Florida. A hydrology model predicts water levels in the spatial cells on 5-day time steps. Fish populations spread across the marsh during flooded conditions and either retreat into refugia (alligator ponds), move to other spatial cells, or die if their cell dries out. ALFISH has been applied to the evaluation of alternative water regulation scenarios under the Central and South Florida Comprehensive Project Review Study. The objective of this Review Study is to compare alternative methods for restoring historical ecological conditions in southern Florida. ALFISH has provided information on which plans are most are likely to increase fish biomass and its availability to wading bird populations.

Ecological Modelling↗
USGS2011

Microanatomy of passerine hard-cornified tissues: Beak and claw structure of the black-capped chickadee (Poecile atricapillus)

The microanatomy of healthy beaks and claws in passerine birds has not been well described in the literature, despite the importance of these structures in avian life. Histological processing of hard‐cornified tissues is notoriously challenging and only a few reports on effective techniques have been published. An emerging epizootic of beak deformities among wild birds in Alaska and the Pacific Northwest region of North America recently highlighted the need for additional baseline information about avian hard‐cornified structures. In this study, we examine the beak and claw of the Black‐capped Chickadee ( Poecile atricapillus ), a common North American passerine that is affected by what has been described as “avian keratin disorder.” We use light and scanning electron microscopy and high‐magnification radiography to document the healthy microanatomy of these tissues and identify features of functional importance. We also describe detailed methods for histological processing of avian hard‐cornified structures and discuss the utility of special stains. Results from this study will assist in future research on the functional anatomy and pathology of hard‐cornified structures and will provide a necessary reference for ongoing investigations of avian keratin disorder in Black‐capped Chickadees and other wild passerine species.

Journal of Morphology↗
USGS2024

Counting the chorus: A bioacoustic indicator of population density

Passive acoustic monitoring has grown in utility for tracking wildlife populations, although challenges remain when using acoustic detections to monitor population size and density. Distance sampling is considered the ‘gold standard’ for estimating animal densities but has several important limitations, especially for rare, cryptic, and high-density species. Here, we test the performance of a simple, quickly derived bioacoustic indicator for monitoring population density: call density—the proportion of recording samples containing vocalizations. Over three years, we collected synchronized bioacoustic and point-transect distance sampling data for eight forest bird species native to the Island of Hawai‘i, including four endangered species, across diverse ecosystems ranging from subalpine dry woodland to montane rainforest. The species studied exhibit varied population structures, from gregarious flocks to small, territorial family groups. Our results revealed significant, strong correlations between call density and distance sampling-based animal density estimates for all species, demonstrating that call density is a reliable indicator of animal density that can be used independently or in combination with traditional monitoring methods. Our analysis uses a fixed amount of manual validation of machine learning classifier output examples, without requiring prohibitively high classifier performance, and is robust to variation in vocal activity rates across time and space, making it both adaptable and scalable. This approach could enhance passive acoustic monitoring by providing a more sensitive population health indicator than commonly used detection/nondetection methods, facilitating prompt conservation and management decisions, particularly for species that are difficult to monitor with distance sampling.

Hawaii↗
USGS2018

Fitness consequences of interspecific nesting associations among cavity-nesting birds

Interspecific aggregations of prey may provide benefits by mitigating predation risk, but they can also create costs if they increase competition for resources or are more easily detectable by predators. Variation in predation risk and resource availability may influence the occurrence and fitness effects of aggregating in nature. Yet tests of such possibilities are lacking. Cavity-nesting birds provide an interesting test case. They compete aggressively for resources and experience low nest predation rates, which might predict dispersion, but across 19 years of study we found that they commonly aggregate by sharing nest trees. Tree sharing was more common when aspen were more abundant and was somewhat more common in years with higher nest predation risk. Nest success was higher in shared trees when nest predation risk was higher than average. Ultimately, the costs and benefits of aggregating (nest tree sharing) varied across years, and we outline hypotheses for future studies.

The American Naturalist↗
USGS2004

Comparative dynamics of small mammal populations in treefall gaps and surrounding understorey within Amazonian rainforest

Variation in food resource availability can have profound effects on habitat selection and dynamics of populations. Previous studies reported higher food resource availability and fruit removal in treefall gaps than in the understorey. Therefore, gaps have been considered 'keystone habitat' for Neotropical frugivore birds. Here we test if this prediction would also hold for terrestrial small mammals. In the Amazon, we quantified food resource availability in eleven treefall gaps and paired understorey habitats and used feeding experiments to test if two common terrestrial rodents ( Oryzomys megacephalus and Proechimys spp.) would perceive differences between habitats. We live-trapped small mammals in eleven gaps and understorey sites for two years, and compared abundance, fitness components (survival and per capita recruitment) and dispersal of these two rodent species across gaps and understorey and seasons (rainy and dry). Our data indicated no differences in resource availability and consumption rate between habitats. Treefall gaps may represent a sink habitat for Oryzomys where individuals had lower fitness, apparently because of habitat-specific ant predation on early life stages, than in the understorey, the source habitat. Conversely, gaps may be source habitat for Proechimys where individuals had higher fitness, than in the understorey, the sink habitat. Our results suggest the presence of source-sink dynamics in a tropical gap-understorey landscape, where two rodent species perceive habitats differently. This may be a mechanism for their coexistence in a heterogeneous and species-diverse system.

World Biosphere Park Manu↗
USGS2011

Global seabird responses to forage fish depletion - One-third for the birds

Determining the form of key predator-prey relationships is critical for understanding marine ecosystem dynamics. Using a comprehensive global database, we quantified the effect of fluctuations in food abundance on seabird breeding success. We identified a threshold in prey (fish and krill, termed “forage fish”) abundance below which seabirds experience consistently reduced and more variable productivity. This response was common to all seven ecosystems and 14 bird species examined within the Atlantic, Pacific, and Southern Oceans. The threshold approximated one-third of the maximum prey biomass observed in long-term studies. This provides an indicator of the minimal forage fish biomass needed to sustain seabird productivity over the long term.

Science↗
USGS2000

Ecological correlates of mate fidelity in two Arctic-breeding sandpipers

Monogamous birds exhibit considerable interspecific variation in rates of mate fidelity between years, but the reasons for this variation are still poorly understood. In a 4-year study carried out in western Alaska, mate-fidelity rates in Semipalmated Sandpipers ( Calidris pusilla ; mate fidelity was 47% among pairs where at least one mate returned and 94% among pairs where both mates returned) were substantially higher than in Western Sandpipers ( Calidris mauri ; 25 and 67%, respectively), despite the similar breeding biology of these sibling species. Divorce was not a response to nesting failure in Western Sandpipers, and mate change had no effect on the reproductive performance of either species. Nor were mate-fidelity rates related to differential rates of breeding dispersal, because the species did not differ in site fidelity. Reunited pairs and males that changed mates showed strong site tenacity, while females that changed mates moved farther. Differences in local survival rates or habitat are also unlikely to explain mate fidelity, since the two species did not differ in local survival rates, ϕ (Western Sandpipers: ϕ –hat = 0.57 ± 0.05 (mean ± SE), Semipalmated Sandpipers: ϕ –hat = 0.66 ± 0.06), and they bred in the same area, sometimes using the same nest cups. Although we were able to reject the above explanations, it was not possible to determine whether mate retention was lower in Western Sandpipers than in Semipalmated Sandpipers because of interspecific differences in mating tactics, time constraints imposed by migration distance, or a combination of these factors. Western Sandpipers exhibited greater sexual size dimorphism, but also migrated for shorter distances and tended to nest earlier and more asynchronously than Semipalmated Sandpipers. Finally, we show that conventional methods underestimate divorce rates, and interspecific comparisons may be biased if breeding-dispersal and recapture rates are not considered.

Alaska↗
USGS2010

Epizootic of beak deformities among wild birds in Alaska: An emerging disease in North America?

The sudden appearance of a large cluster of animals with gross abnormalities may signal a significant change in an ecosystem. We describe an unusual concentration of beak deformities that appear to have arisen rapidly within Alaska and now extend southward along the Pacific Coast. In Alaska we have documented 2,160 Black-capped Chickadees ( Poecile atricapillus ) and 435 individuals of 29 other species of birds, primarily during the past decade, with grossly overgrown and often crossed beaks. The annual prevalence of beak abnormalities among adult Black-capped Chickadees in south-central Alaska varied from 3.6% to 9.7% and averaged 6.5 ± 0.5% between 1999 and 2008. Only 0.05 ± 0.05% of nestlings and 0.3 ± 0.2% of juveniles <6 months old had abnormal beaks, which suggests that this is either a latent developmental or an acquired condition. We documented 80 cases in which a Black-capped Chickadee captured with an apparently normal beak was subsequently recaptured with a beak abnormality and 8 cases in which a beak deformity was no longer detectable upon recapture. Necropsy and histopathology of a sample of affected individuals provided no conclusive evidence of the etiology of this condition. Deformities appear to affect primarily the keratin layer of the beak and may result from abnormally rapid growth of the rhamphotheca. Some affected birds also exhibited lesions in other keratinized tissues of the skin, legs, feet, claws, and feathers, which may represent a systemic disorder or secondary conditions. Additional studies are currently underway to determine diagnostic signs and the underlying cause of this avian keratin disorder.

Alaska↗
USGS2015

Morphological divergence in a continental adaptive radiation: South American ovenbirds of the genus Cinclodes

Cinclodes is an ecologically diverse genus of South American passerine birds and represents a case of continental adaptive radiation along multiple axes. We investigated morphological diversification in Cinclodes using a comprehensive set of morphometric measurements of study skins. Principal component analysis identified 2 primary axes of morphological variation: one describing body size and a second capturing differences in wing-tip shape and toe length. Phylogenetic analyses of the first principal component suggest an early divergence of Cinclodes into 2 main clades characterized by large and small body sizes. We suggest that 2 morphological outliers within these main clades ( C. antarcticus and C. palliatus ) may be cases of island gigantism and that a third ( C. patagonicus ) may reflect ecological character displacement. Despite its ecological and physiological diversity, the genus Cinclodes does not appear to show morphological diversity beyond what is typical of other avian genera.

The Auk↗
USGS2005

Foraging location and site fidelity of the Double-crested Cormorant on Oneida Lake, New York

We studied the foraging behavior of the Double-crested Cormorant (Phalacrocorax auritus) on Oneida Lake, New York, by monitoring the activities of 27 radio-tagged birds in July and August of 1999 and 2000. A total of 224 locations were obtained of cormorants actively diving, and presumed foraging, at the time of detection. A geographic information system was used to examine foraging distances from the nesting island, the water depth and type of substrate at preferred foraging sites, and to estimate kernel home ranges for analysis of individual foraging site fidelity. An explanatory model was developed to determine parameters affecting the distance to cormorant foraging sites. The mean distance to foraging locations of tagged cormorants from the colony site was 2,920 m (SE ?? 180 m, max = 14,190 m), and 52% of the locations were within 2,000 m of the nesting island. No cormorant was observed making daily foraging trips to outside water bodies. Mean foraging distance was greater during morning than in the afternoon, and there was a significant effect of the time of day on distance. There was no significant effect of sex date, a seasonal measure on distance to foraging location. Individual cormorants exhibited fidelity to specific foraging sites. Most cormorants foraged in close proximity to the nesting island much of the time, while those detected further from the island tended to return repeatedly to the same locations. Ninety percent of the foraging locations were in water depths ???7.5 m, and most were in water 2.5-5 m deep. Compositional analysis of habitat use revealed a preference for these depths, along with substrates of cobble with rubble, and silt with clay.

Waterbirds↗
USGS1949

Wildlife effects of DDT dust used for tick control on a Texas prairie

The effect of DDT dust on wildlife was studied at Camp Bullis, Bexar County, Texas, in the summer of 1947. Studies were made on a 206.6 acre plot that was treated with DDT for experimental control of the Lone Star tick ( Amblyomma americanum ). A dust consisting of one part of DDT to nine parts of pyrophyllite was applied at an average rate of 4.4 pounds of DDT per acre. The limits of DDT concentration that affected wildlife cannot be stated exactly because of a heavy rain that fell near the end of the dusting, and because of irregularity in DDT deposition. Since absolute uniformity of dusting could not be expected in any large scale DDT application, the effects observed in these trials were probably fairly representative. However, continued dry weather would have permitted longer exposure to DDT, possibly with more severe effects than those found in this study. The vegetation of the experimental area was roughly 70 percent ungrazed tall-grass prairie and 30 percent trees and shrubs. Ground and bush feeding birds were severely affected. Cardinals, lark sparrows, field sparrows, Bewick's wrens, Carolina wrens, Kentucky warblers, yellow-breasted chats, blue grosbeaks, and painted buntings were nearly or entirely eliminated from the treated area. Birds affected, but less drastically reduced in numbers, were yellow-billed cuckoo, black and white warbler, yellow-throated vireo, and white-eyed vireo. Birds found dead in the DDT area were 9 cardinals, 2 painted buntings, 2 lark sparrows, 1 yellow-breasted chat, and 1 white-eyed vireo. Bird mortality had begun by the day after dusting and was largely over by the end of the fifth day. Census of deer in DDT and check areas before and after treatment showed no reduction in deer numbers and no diminution in use of the DDT area. No deer or fawns were found dead or affected. Box-trapping of raccoons in DDT and check areas before and after treatment showed no effects that could be attributed to DDT. Limited observations on armadillos, striped skunks, and rabbits gave no indication of pronounced damage to these forms. No mammals of any kind were found dead or affected in or near the DDT area. Four rough green snakes and one Texan spiny lizard were found dead in the DDT area. Mortality was probably high among insectivorous reptiles.

Texas↗
USGS2014

Mercury in fishes from Wrangell-St. Elias National Park and Preserve, Alaska

In this study, mercury (Hg) concentrations were examined in fishes from Wrangell-St. Elias National Park and Preserve, Alaska, the largest and one of the most remote units in the national park system. The goals of the study were to (1) examine the distribution of Hg in select lakes of Wrangell-St. Elias National Park and Preserve; (2) evaluate the differences in Hg concentrations among fish species and with fish age and size; and (3) assess the potential ecological risks of Hg to park fishes, wildlife, and human consumers by comparing Hg concentrations to a series of risk benchmarks. Total Hg concentrations ranged from 17.9 to 616.4 nanograms per gram wet weight (ng/g ww), with a mean (± standard error) of 180.0 ±17.9 across the 83 individuals sampled. Without accounting for the effects of size, Hg concentrations varied by a factor of 10.9 across sites and species. After accounting for the effects of size, Hg concentrations were even more variable, differing by a factor of as much as 13.2 within a single species sampled from two lakes. Such inter-site variation suggests that site characteristics play an important role in determining fish Hg concentrations and that more intensive sampling may be necessary to adequately characterize Hg contamination in the park. Size-normalized Hg concentrations also differed among three species sampled from Tanada Lake, and Hg concentrations were strongly correlated with age. Furthermore, potential risks to park fish, wildlife, and human users were variable across lakes and species. Although no fish from two of the lakes studied (Grizzly Lake and Summit Lake) had Hg concentrations exceeding any of the benchmarks used, concentrations in Copper Lake and Tanada Lake exceeded conservative benchmarks for bird (90 ng/g ww in whole-body) and human (150 ng/g ww in muscle) consumption. In Tanada Lake, concentrations in most fishes also exceeded benchmarks for risk to moderate- and low-sensitivity avian consumers (180 and 270 ng/g ww in whole-body, respectively), as well as the concentration at which Alaska State guidelines suggest at-risk groups limit fish consumption to 3 meals per week (320 ng/g). However, the relationship between Hg concentrations and fish size in Tanada Lake suggests that consumption of smaller-sized fishes could reduce Hg exposure in human consumers.

Alaska↗
USGS1993

Detailed study of irrigation drainage in and near wildlife management areas, west-central Nevada, 1987-90; Part B, Effect on biota in Stillwater and Fernley Wildlife Management Areas and other nearby wetlands

A water-quality reconnaissance study during 1986-87 found high concentrations of several potentially toxic elements in water, bottom sediment, and biota in and near Stillwater Wildlife Management Area (WMA). This study prompted the U.S. Department of the Interior to initiate a more detailed study to determine the hydrogeochemical processes that control water quality in the Stillwater WMA, and other nearby wetlands, and the resulting effects on biota, especially migratory birds. Present wetland size is about 10% of historical size; the dissolved- solids load in the water in these now-isolated wetlands has increased only moderately, but the dissolved-solids concentration has increased more than seven-fold. Wetland vegetation has diminished and species composition in flow water has shifted to predominant salt-tolerant species in many areas. Decreased vegetative cover for nesting is implicated in declining waterfowl production. Decreases in numbers or virtual absence of several wildlife species are attributed to degraded water quality. Results of toxicity tests indicate that water in some drains and wetland areas is acutely toxic to some fish and invertebrates. Toxicity is attributed to the combined presence of arsenic, boron, lithium, and molybdenum. Biological pathways are involved in the transport of mercury and selenium from agricultural drains to wetlands. Hatch success of both artificially incubated and field-reared duck eggs was greater than/= 90 percent; no teratogenesis was observed. Mercury in muscle tissue of waterfowl harvested from Carson Lake in October 1987 exceeded the human health criterion six-fold.

Water-Resources Investigations Report↗
USGS1960

Lake Erie walleyes--again on the upswing?

SUMMARY The effect of DDT dust on wildlife was studied at Camp Bullis, Bexar County, Texas, in the summer of 1947. Studies were made on a 206.6 acre plot that was treated with DDT for experimental control of the Lone Star tick (Amblyomrna americanum). A dust consisting of one part of DDT to nine parts of pyrophyllite was applied at an average rate of 4.4 pounds of DDT per acre. The limits of DDT concentration that affected wildlife cannot be stated exactly because of a heavy rain that fell near the end of the dusting, and because of irregularity in DDT deposition. Since absolute uniformity of dusting could not be expected in any large scale DDT application, the effects observed in these trials were probably fairly representative. However, continued dry weather would have permitted longer exposure to DDT, possibly with more severe effects than those found in this study. The vegetation of the experimental area was roughly 70 percent ungrazed tall-grass prairie and 30 percent trees and shrubs. Ground and bush feeding birds were severely affected. Cardinals, lark sparrows, field sparrows, Bewick's wrens, Carolina wrens, Kentucky warblers, yellow-breasted chats, blue grosbeaks, and painted buntings were nearly or entirely eliminated from the treated area. Birds affected, but less drastically reduced in numbers, were yellow-billed cuckoo, black and white warbler, yellow-throated vireo, and white-eyed vireo. Birds found dead in the DDT area were 9 cardinals, 2 painted buntings, 2 lark sparrows, 1 yellow-breasted chat, and 1 white-eyed vireo. Bird mortality had begun by the day after dusting and was largely over by the end of the fifth day. Census of deer in DDT and check areas before and after treatment showed no reduction in deer numbers and no diminution in use of the DDT area. No deer or fawns were found dead or affected. Box-trapping of raccoons in DDT and check areas before and after treatment showed no effects that could be attributed to DDT. Limited observations on armadillos, striped skunks, and rabbits gave no indication of pronounced damage to these forms. No mammals of any kind were found dead or affected in or near the DDT area. Four rough green snakes and one Texan spiny lizard were found dead in the DDT area. Mortality was probably high among insectivorous reptiles.

Ohio Conservation Bulletin↗
USGS2007

Winter behavior and ecology of the Alder Flycatcher (Empidonax alnorum) in Peru

The winter ecology and behavior of Alder Flycatchers (Empidonax alnorum) were studied along the Manu, a white-water meander river in Manu National Park, Madre de Dios, Peru during October and November, 1993 to 1997. The birds occupied territories in primary-succession habitats on growing point bars. They were most common in mixed stands of Tessaria integrifolia (Asteraceae) and Gynerium sagittatum (Gramineaceae) interspersed with bare sand areas. The uneven height of the Tessaria canopy, which resulted in openings in the vegetation large enough for the birds to flycatch, was an important habitat feature. Birds obtained insects, which formed about 96% of the diet, by aerial hawking (91%), perch gleaning (6%), and hover gleaning (3%). They also fed on fruit. Territory sizes ranged from 0.04 to 0.25 ha. Of nine territories that we observed closely, six were occupied by two birds each, two by one bird each, and one by three birds. Every territory had one dominant individual who was primarily responsible for territory defense; the other birds were associates. Vocalizations given included the fee-bee-o song, a two-syllable song, and the pit note, which are also given on the breeding grounds. A series of pits given increasingly rapidly signaled a territorial interaction. In aggressive encounters, the birds (1) interacted vocally, remaining on their territories and counter calling or exchanging agitated calls; (2) moved toward a common territorial boundary and engaged in a vocal duel; or (3) the dominant chased intruders out of the territory. Chases were most common when a wave of new birds entered the area. Dominant birds, which sang the full song, were probably adult males. Immature males do not sing a full song, and females are not known to sing in nature. Associate individuals were likely females or young males.

Ornitologia Neotropical↗
USGS1991

Effects of resighting errors on capture-resight estimates for neck-banded Canada geese

Biologists who study neck-banded Canada Geese (Branta canadensis) have used capture and resighting histories to estimate annual resighting rates, survival rates and the number of marked birds in the population. Resighting errors were associated with 9.4% ( n = 155) of the birds from a sample of Canada Geese neckbanded in the Mississippi flyway, 1974-1987, and constituted 3.0% ( n = 208) of the resightings. Resighting errors significantly reduced estimated resighting rates and significantly increased estimated numbers of marked geese in the sample. Estimates of survival rates were not significantly affected by resighting errors. Recommendations are offered for using neck-band characters that may reduce resighting errors.

Wisconsin↗
USGS2007

Winter behavior and ecology of the Alder Flycatcher (Empidonax alnorum) in Peru

The winter ecology and behavior of Alder Flycatchers (Empidonax alnorum) were studied along the Manu, a white-water meander river in Manu National Park, Madre de Dios, Peru?? during October and November, 1993 to 1997. The birds occupied territories in primary-succession habitats on growing point bars. They were most common in mixed stands of Tessaria integrifolia (Asteraceae) and Gynerium sagittatum (Gramineaceae) interspersed with bare sand areas. The uneven height of the Tessaria canopy, which resulted in openings in the vegetation large enough for the birds to flycatch, was an important habitat feature. Birds obtained insects, which formed about 96% of the diet, by aerial hawking (91%), perch gleaning (6%), and hover gleaning (3%). They also fed on fruit. Territory sizes ranged from 0.04 to 0.25 ha. Of nine territories that we observed closely, six were occupied by two birds each, two by one bird each, and one by three birds. Every territory had one dominant individual who was primarily responsible for territory defense; the other birds were associates. Vocalizations given included the fee-bee-o song, a two-syllable song, nd the pit note, which are also given on the breeding grounds. A series of pits given increasingly rapidly signaled a territorial interaction. In aggressive encounters, the birds (1) interacted vocally, remaining on their territories and counter calling or exchanging agitated calls; (2) moved toward a common territorial boundary and engaged in a vocal duel; or (3) the dominant chased intruders out of the territory. Chases were most common when a wave of new birds entered the area. Dominant birds, which sang the full song, were probably adult males. Immature males do not sing a full song, and females are not known to sing in nature. Associate individuals were likely females or young males. ?? The Neotropical Ornithological Society.

Ornitologia Neotropical↗
USGS2013

Vascular plant and vertebrate species richness in national parks of the eastern United States

Given the estimates that species diversity is diminishing at 50-100 times the normal rate, it is critical that we be able to evaluate changes in species richness in order to make informed decisions for conserving species diversity. In this study, we examined the potential of vascular plant species richness to be used as a surrogate for vertebrate species richness in the classes of amphibians, reptiles, birds, and mammals. Vascular plants, as primary producers, represent the biotic starting point for ecological community structure and are the logical place to start for understanding vertebrate species associations. We used data collected by the United States (US) National Park Service (NPS) on species presence within parks in the eastern US to estimate simple linear regressions between plant species richness and vertebrate richness. Because environmental factors may also influence species diversity, we performed simple linear regressions of species richness versus natural logarithm of park area, park latitude, mean annual precipitation, mean annual temperature, and human population density surrounding the parks. We then combined plant species richness and environmental variables in multiple regressions to determine the variables that remained as significant predictors of vertebrate species richness. As expected, we detected significant relationships between plant species richness and amphibian, bird, and mammal species richness. In some cases, plant species richness was predicted by park area alone. Species richness of mammals was only related to plant species richness. Reptile species richness, on the other hand, was related to plant species richness, park latitude and annual precipitation, while amphibian species richness was related to park latitude, park area, and plant species richness. Thus, plant species richness predicted species richness of different vertebrate groups to varying degrees and should not be used exclusively as a surrogate for vertebrate species richness. Plant species richness should be included with other variables such as area and climate when considering strategies to manage and conserve species in US National Parks. It is not always appropriate to draw conclusions about analyses of taxonomic surrogates from one area to another. Two patterns evident from the linear regressions were the increase in species richness with the increase of park area and with increase of vascular plant species richness. To test whether there were differences in these patterns among networks, we used analysis of covariance (ANCOVA). Differences among networks were detected only in bird species richness versus plant species richness and for all taxa except mammals for vertebrate species richness versus park area. Some of these results may be due to small sample size among networks, and therefore, low statistical power. Other factors that could have contributed to these results were differences in average park area and habitat heterogeneity among networks, latitudinal gradients, low variation in mean annual precipitation, and different use of vegetation by migratory species. Based on these results we recommend that management of biodiversity be approached from local and site specific criteria rather than applying management directives derived from other regions of the US. It is also recommended that analyses similar to those presented here be conducted for all national parks, once data become available for all networks in the US, to gain a better understanding of how vascular plant species richness, area, and vertebrate species richness are related in the US.

Natural Resource Technical Report NPS/NCR/NCRO/NRT↗