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To investigate whether Northern Goshawk textit(Accipiter gentilis) reproduction is food-limited, we evaluated the reproductive output from 401 goshawk breeding opportunities on the Kaibab Plateau, Arizona during 1999-2002. Concurrently, we estimated densities of 10 goshawk prey species (seven birds, three mammals) using distance sampling. We then assessed the relationship between goshawk productivity (number of fledglings produced) and prey density within and among years by relating the contribution of individual prey species and total prey density to goshawk productivity. We also estimated the proportion of total diet and biomass for each species that contributed ?3% of all prey items. Total prey density was highly...
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...
Density estimates of four mammal species in the upper subalpine and alpine zones of the Sierra Nevada range, 2008 - 2012. The estimates were derived from variable distance data collected 3-4 per year along each of 21 transects (10 km in length). The transects were randomly selected from a pool of 53 potential routes. Nine transects were sampled in 2008, 12 were sampled in 2009, 19 were sampled in 2010, 21 were sampled in 2011, and 17 were sampled in 2012. All counts were done in July and August each year. Replicate samples within a given year were done within 2-8 days of each other. All counts were done by single observers. The spreadsheet has six worksheets, including three with density estimates for each species...
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The dataset contains 6 columns of data collected during line transect surveys (Line) that evaluated bait cartridge efficacy for Brown Treesnake control on Guam. Two-person teams recorded all bait cartridges observed while walking the center line of transects in the Habitat Management Unit (HMU). Perpendicular distance (DIST (m)) to cartridges from center line was measured to the nearest 0.005 meters.
Density estimates of four mammal species in the upper subalpine and alpine zones of the Sierra Nevada range, 2008 - 2012. The estimates were derived from variable distance data collected 3-4 times per year at point count stations randomly located along line transects. There were 21 transects (10 km in length) that had been randomly selected from a pool of 53 potential routes, with 10 point count stations along each transect (minimum of 200 m spacing between stations). 45 stations were sampled in 2008 (5 stations on each of 9 transects), 60 stations were sampled in 2009 (5 stations on each of 12 transects),190 stations were sampled in 2010 (10 stations on each of 19 transects), 210 stations were sampled in 2011 (10...
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Since 2017, U.S. Geological Survey, Western Ecological Research Center (USGS WERC) partnered with California State Parks to continue long-term, annual at-sea surveys to estimate at-sea abundance and juvenile (i.e. hatch-year) productivity of Marbled Murrelets (Brachyramphus marmoratus) in U.S. Fish and Wildlife Service Conservation Zone 6 (central California: San Francisco Bay to Monterey Bay). Marbled Murrelets have been listed as Endangered by the State of California and Threatened by the U.S. Fish and Wildlife Service since 1992. Marbled Murrelets have been surveyed at sea off central California since 1995 (Becker et al. 1997), and standardized surveys to estimate abundance and productivity have been conducted...
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...
Effective wildlife conservation strategies require an understanding of how fluctuating environmental conditions affect sensitive life stages. As part of a long-term study, we examined post-fledging and post-independence survival of 89 radio-marked juvenile Northern Goshawks (Accipiter gentilis) produced from 48 nests in northern Arizona, USA, during 1998-2001. Information-theoretic methods were used to examine within- and among-year variation in survival relative to environmental (prey abundance, weather), territory (hatching date, brood size), and individual (gender, body mass) sources of variation. The results support age- and cohort-specific differences in survival that were best explained by behaviors occurring...
    map background search result map search result map Annual Marbled Murrelet Abundance and Productivity Surveys Off Central California (Zone 6), 1999-2021 (ver. 4.0, May 2022) Failed Brown Treesnake bait cartridges from an aerially application in Guam, 2018 Failed Brown Treesnake bait cartridges from an aerially application in Guam, 2018