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Finite population sampling theory is useful in estimating total population size (abundance) from abundance estimates of each sampled unit (quadrat). We develop estimators that allow correlated quadrat abundance estimates, even for quadrats in different sampling strata. Correlated quadrat abundance estimates based on mark-recapture or distance sampling methods occur when data are pooled across quadrats to estimate, for example, capture probability parameters or sighting functions. When only minimal information is available from each quadrat, pooling of data across quadrats may be necessary to efficiently estimate capture probabilities or sighting functions. We further include information from a quadrat-based auxiliary...
The Mexican spotted owl (Strix occidentalis lucida) is a threatened subspecies whose recovery depends, in part, on both an understanding of its habitat requirements and the protection of its habitat. Therefore, we evaluated habitat composition and configuration around owl sites in the Tularosa Mountains, New Mexico, using a vegetation map derived from Landsat Thematic Mapper (TM) digital imagery and digital elevation models. Owls occupied sites with more mature mixed-conifer and mature pine and less pinyon-juniper than random sites. No difference existed in the amount of young forest between owl and random sites. After correcting for the area of the vegetation classes within owl territories, no difference existed...
No intensive studies have been conducted on the migration habitat requirements of whooping cranes (Grus americana). Consequently, we characterized habitats used by cross-fostered whooping cranes during the 1986 and 1987 autumn migration in the San Luis Valley (SLV), Colorado. Water depths 0.05) in distances flown from 1 activity site to the next. Distances flown from roost sites to feeding sites were greater (P = 0.0002, P = 0.0004, morning and evening, respectively) than distances flown from feeding sites to loafing areas. Whooping cranes appeared to minimize daily movements by flying to a nearby feeding area and later returning to the roost complex to loaf, or by using loafing sites located nearer feeding sites...
Recent energy development has resulted in rapid and large-scale changes to western shrub-steppe ecosystems without a complete understanding of its potential impacts on wildlife populations. We modeled winter habitat use by female greater sage-grouse (Centrocercus urophasianus) in the Powder River Basin (PRB) of Wyoming and Montana, USA, to 1) identify landscape features that influenced sage-grouse habitat selection, 2) assess the scale at which selection occurred, 3) spatially depict winter habitat quality in a Geographic Information System, and 4) assess the effect of coal-bed natural gas (CBNG) development on winter habitat selection. We developed a model of winter habitat selection based on 435 aerial relocations...
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Identifying environmental parameters that influence probability of nest predation is important for developing and implementing effective management strategies for species of conservation concern. We estimated daily nest survival for a migratory population of burrowing owls (Athene cunicularia) breeding in black-tailed prairie dog (Cynomys ludovicianus) colonies in Wyoming, USA. We compared estimates based on 3 common approaches: apparent nesting success, Mayfield estimates, and a model-based logistic-exposure approach. We also examined whether 8 intrinsic and extrinsic factors affected daily nest survival in burrowing owls. Positive biases in apparent nest survival were low (36%), probably because prior knowledge...
Determining population size and long-term trends in population size for species of high concern is a priority of international, national, and regional conservation plans. Long-billed curlews (Numenius americanus) are a species of special concern in North America due to apparent declines in their population. Because long-billed curlews are not adequately monitored by existing programs, we undertook a 2-year study with the goals of 1) determining present long-billed curlew distribution and breeding population size in the United States and 2) providing recommendations for a long-term long-billed curlew monitoring protocol. We selected a stratified random sample of survey routes in 16 western states for sampling in...
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Mule deer (Odocoileus hemionus) fawn:doe (f:d) ratios in December have declined by 0.015 fawns/doe/year from 1972 through 1995 in Colorado, USA. To determine whether lower pregnancy or fetal production was the cause of low December f:d ratios, we estimated mule deer pregnancy rates in the Poudre River drainage during January 1998 and pregnancy and fetal rates on the Uncompahgre Plateau during February 1999. Twenty-seven (93.1%) of 29 yearling and adult does in the Poudre River drainage were detected pregnant with pregnancy-specific protein-B (PSPB). This proportion did not differ (P > 0.2) from the proportion of yearling and adult does that were pregnant when collected by various methods in previous studies in Colorado....
We estimated electrocution rates for raptors and common ravens (Corvus corax) for the Moon Lake Electrical Association in northeastern Utah and northwestern Colorado, USA. From July 2001 to May 2003, we conducted mortality searches at randomly selected distribution line segments and poles within 3 regions, but rate estimates (0.0036–0.0112 deaths/pole/yr) may have been biased by the effects of scavengers and by long sampling intervals (≥3 months), which prevented us from determining the cause of death for most birds because of advanced decay. In 2002–2003, we conducted carcass removal experiments in the Rangely Oil Field (ROF) in northwestern Colorado to estimate scavenging effects, and in 2003–2004, we...
We responded to the claim by Greenwald et al. (2005) that the management recommendations for the northern goshawk in the Southwestern United States (MRNG; Reynolds et al. 1992), a food web-based conservation plan that incorporated both northern goshawk (Accipiter gentilis) and multiple prey habitats, may be inadequate to protect goshawks. Greenwald et al. (2005) based this claim on their review of 12 telemetry studies of goshawk habitat selection and 5 nontelemetry studies of the effects of vegetation structure at the home range scale on goshawk nest occupancy and reproduction that appeared after the 1992 publication of the MRNG. Greenwald et al. (2005) summarized their review as showing that 1) goshawks were habitat...
Black-tailed prairie dog (Cynomys ludovicianus) colonies are important to many vertebrate populations in the shortgrass prairie ecosystem. Because it is often desirable to assess black-tailed prairie dog populations, and indirect methods generally are more economical than direct counts, we tested whether aboveground counts of black-tailed prairie dogs were related to burrow entrance densities. Higher densities of burrow entrances have been assumed to reflect higher prairie dog densities. We determined if maximum aboveground counts of black-tailed prairie dogs differed temporally in morning and evening in southwestern Kansas, compared maximum aboveground count data with burrow entrance densities, and evaluated the...
Prairie dog (Cynomys spp.) populations have been reduced by 98% compared to historical levels because of widespread poisoning, habitat loss, recreational shooting, and outbreaks of sylvatic plague (Yersinia pestis). Our objectives were to identify habitat correlates of Gunnison's prairie dog (C. gunnisoni) colonies and to develop a predictive logistic regression model to identify potential reintroduction sites for this species. During 2000 and 2001, we examined habitat features at 50 Gunnison's prairie dog colonies and 50 paired random sites in northern Arizona, USA. When compared to random sites, Gunnison's prairie dog colonies had deeper soils, less variability in slope, and less rock ground cover. Our results...
map background search result map search result map Factors Affecting Daily Nest Survival of Burrowing Owls Within Black-Tailed Prairie Dog Colonies Estimating population size with correlated sampling unit estimates Long-Term Trends in Mule Deer Pregnancy and Fetal Rates in Colorado Estimating population size with correlated sampling unit estimates Factors Affecting Daily Nest Survival of Burrowing Owls Within Black-Tailed Prairie Dog Colonies Long-Term Trends in Mule Deer Pregnancy and Fetal Rates in Colorado