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Wildlife managers in northwestern Colorado have had difficulty accurately estimating numbers of subadult male elk (Cervus elaphus) by sampling winter population densities and sex ratios. We investigated emigration and survival of telemetered 2-year-old male elk in a trophy hunting area in a northwestern Colorado Game Management Unit (GMU) to evaluate management strategies. We hypothesized that skewed numbers of males resulted from high subadult mortality or dispersal of subadult males. We used telemetered elk and Kaplan-Meier staggered entry methods to estimate emigration probability of 0.56 and 0.33 in 1995 and 1996, respectively. Maximum distances moved by emigrants from their capture point averaged 87 km (median...
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This data product consists of a database of population change and abundance estimates for North American birds, estimated from North American Breeding Bird Survey (BBS) data. Data are presented for 548 species of birds in 4 spreadsheets containing trend estimates and annual indices for 2 time periods. Estimates are derived for each species using the 1 of 4 alternative models, and a cross-validation model selection procedure was used to select the best model for each species.
We surveyed a discrete population of Mountain Plovers (Charadrius montanus) in South Park, Park County, Colorado, to determine the size and relative contribution of this geographically isolated area to the global population of plovers. First, we mapped potential plover habitat within South Park based on landform and vegetation descriptors. Second, we identified occupied habitat using observations from a systematic inventory of potential habitat from 1995-1999 and from a study of breeding biology from 2000-2002. Third, we estimated breeding densities within a framework designed specifically for distance sampling. We mapped 82750 ha of potential habitat. We recorded 2516 plover locations from which we estimated 29...
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With the decline of many lekking species, the need to develop a rigorous population estimation technique is critical for successful conservation and management. We employed mark?resight methods to estimate population size for 2 lekking species: greater sage-grouse (Centrocercus urophasianus) and Gunnison sage-grouse (Centrocercus minimus). We evaluated 2 different estimators: Bowden's estimator and the mixed logit-normal mark?resight model. We captured and marked 75 greater sage-grouse. We counted marked and unmarked birds as they attended 15 known leks. We used 36 and 37 marked Gunnison sage-grouse to estimate population size in 2003 and 2004, respectively. We observed marked and unmarked Gunnison sage-grouse daily...
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This data product consists of a database of population change and abundance estimates for North American birds, estimated from North American Breeding Bird Survey (BBS) data. Data are presented for 548 species of birds in 4 spreadsheets containing trend estimates and annual indices for 2 time periods. Estimates are derived for each species using the 1 of 4 alternative models, and a cross-validation model selection procedure was used to select the best model for each species. Metadata for the BBS data used to produce these estimates is available from a USGS ftp site (ftp://ftpext.usgs.gov/pub/er/md/laurel/BBS/DataFiles/). Metadata associated with this data product provides information specific to the analysis results.
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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Values for predicted probabilities of avian species occupancy were determined using colonization-extinction models (MacKenzie and others, 2003) as implemented in R (Version 3.4.4; https://www.r-project.org/) via the ‘colext’ function of the Unmarked package (Version 0.12-0; Fiske and Chandler 2011). Performance of a null model (without covariates) and 153 additional models that assessed the effects of geographic coordinates and habitat context covariates were evaluated using Akaike information criteria (AIC; Burnham and Anderson, 2002). When more than one model had substantial support, their respective model weights were used to spatially predict occupancy relative to covariate influence. Predictive model covariates...
    map background search result map search result map Population Estimation Techniques for Lekking Species Predicted Avian Species Occupancy, Area of Sustainable Forest Habitat, and Area of Occupied Habitat within the Mississippi Alluvial Valley Bird Conservation Region Population Estimation Techniques for Lekking Species Predicted Avian Species Occupancy, Area of Sustainable Forest Habitat, and Area of Occupied Habitat within the Mississippi Alluvial Valley Bird Conservation Region