Comparative Diets of Nesting Golden Eagles in the Columbia Basin Between 2007–2013 and the Late 1970s

Watson, James; Davies, R. W.

doi:10.1898/nwn13-31.1

Cited by 11 publications

(17 citation statements)

References 18 publications

(13 reference statements)

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“…Watson and Davies (2015) found evidence for a dietary shift away from sciurids and phasianids (family Phasianidae) and toward coyote pups (Canis latrans) and deer fawns (Odocoileus sp.). This dietary shift coincided with decreased populations of Townsend's ground squirrel (Urocitellus townsendii townsendii), Washington ground squirrel (Urocitellus washingtoni), and both species of jackrabbit, which was consistent with conversion of shrubsteppe habitat to agriculture.…”

Section: Resultsmentioning

confidence: 97%

“…The Cold Deserts ecoregion includes the sagebrush steppe ecosystems of high elevation intermountain basins and plateaus from northern New Mexico to eastern Washington. In the Columbia Plateau of Washington, yellow-bellied marmots (Marmota flaviventris) were the primary prey of nesting Golden Eagles, both by frequency in the diet and biomass (Knight and Erickson 1978, Marr and Knight 1983, Watson and Davies 2015. The number of land-cover types within a 2-km radius of Golden Eagle nest sites was not associated with the number of prey species or prey items, suggesting greater habitat diversity at this scale did not increase dietary breadth (Marr and Knight 1983).…”

Section: Resultsmentioning

confidence: 99%

“…In the Columbia Plateau of eastern Oregon (Cold Deserts ecoregion), Watson and Davies (2015) compared Golden Eagle diets determined between 2007 and 2013 to those reported for a study conducted 30 yr earlier in the same area (Marr and Knight 1983). Watson and Davies (2015) found evidence for a dietary shift away from sciurids and phasianids (family Phasianidae) and toward coyote pups (Canis latrans) and deer fawns (Odocoileus sp.).…”

Section: Resultsmentioning

confidence: 99%

“…Remains of large ungulates at nests were classified as carrion, but the biomass consumed from carrion was unknown (Marr and Knight 1983). Analysis of prey remains and regurgitated pellets collected at nests underestimated total prey biomass compared to direct observation, but the two methods did not differ significantly with regard to percent biomass (Collopy 1983a) or percent frequency (Watson and Davies 2015). More prey species were detected by camera observations than by identification of prey remains (Longshore et al 2017).…”

Section: Methodsmentioning

confidence: 99%

“…We did not use prey biomass data, although this approach has been used to assess dietary energetics and the relative importance of larger prey species (Connolly et al 1976, Lockhart 1976, Knight and Erickson 1978, Smith and Murphy 1979, U.S.D.I. 1979, Bloom and Hawks 1982, Collopy 1983a, MacLaren et al 1988, Phillips et al 1990, Hunt et al 1995, Collins and Latta 2009, Losee et al 2014, Watson and Davies 2015, Preston et al 2017.…”

Section: Methodsmentioning

confidence: 99%

See 4 more Smart Citations

Spatial and Temporal Patterns in Golden Eagle Diets in the Western United States, with Implications for Conservation Planning

Bedrosian

Watson

Steenhof³

et al. 2017

Journal of Raptor Research

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Section: Resultsmentioning

confidence: 97%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 3 more Smart Citations

Spatial and Temporal Patterns in Golden Eagle Diets in the Western United States, with Implications for Conservation Planning

Bedrosian

Watson

Steenhof³

et al. 2017

Journal of Raptor Research

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Eagle visitation rates to carrion in a winter scavenging guild

et al. 2019

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Understanding the behavioral ecology of species of conservation concern can help to inform better management. During winters 2011 through 2017, we placed camera traps at stations baited with carrion to investigate characteristics of winter scavenging by golden eagles (Aquila chrysaetos) and bald eagles (Haliaeetus leucocephalus) in eastern Washington and Oregon, USA. Our objectives were to better understand exposure risk of individual eagles to lead contaminants and evaluate factors that affect eagle visitation to carrion to inform measures that reduce lead exposure. We studied photo sequences from 108 traps (truex¯ = 2,725 ± 306 [SE] images/trap) and used plumage and physical characteristics to track visitation of 183 individual golden eagles and 90 bald eagles at deer (Odocoileus spp.) carrion until it was totally consumed. At least 1 eagle visited 76% of traps (truex¯ = 2.5 ± 0.3 unique eagles/trap). On average, an eagle visited a trap 3.4 ± 0.2 times (range = 1–19 visits) over 1.9 ± 0.1 days (range = 1–9 days). We used general linear mixed models to identify influences on number of eagle visits and pooled visit duration. Individual golden eagles visited carrion about 25% more often and 50% longer than bald eagles, and individual juvenile eagles visited carrion more often and longer than immature and adult eagles. On average, an eagle made an additional visit to carrion for every golden eagle that came to the same trap. Eagles spent less time at offal (truex¯ = 26.2 ± 6.4 min) than at a whole carcass (truex¯ = 92.9 ± 7.5 min), and understory vegetation immediately surrounding carrion was associated with a 30% reduction in visitation time. In the Pacific Northwest during winter, adult and juvenile golden eagles, by virtue of their abundance and visitation to carrion compared to the immature age class and bald eagles of all ages, have the highest potential for exposure to anthropogenic effects from carrion visitation. Concealment of offal piles in vegetation may reduce, but not eliminate, eagle use because of competing scavengers that expose carrion locations. We found no evidence that carrion proximity to nearest known nests, topography, or snow cover affect visitation by eagles. Thus, short of using alternative ammunition to lead, we recommend burial or removal of offal from hunter‐killed ungulates. © 2019 The Wildlife Society.

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Evidence for Depressed Reproduction of Golden Eagles in Washington

et al. 2020

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Beginning in 1977 the Washington Department of Fish and Wildlife conducted annual surveys to determine statewide golden eagle (Aquila chrysaetos) occupancy and productivity. Current interest in the regional and national status of the species prompted our investigation to determine utility of historical data in assessing trends in reproduction, and to test efficacy of a sampling protocol that surveyed randomly selected territories and also accounted for detection probability. We found evidence indicating poor reproduction from 38 annual surveys conducted at 301 known territories statewide between 1977 and 2014. At 256 territories in eastern Washington, USA, apparent occupancy was low (truex¯ = 50.9%) and nesting success declined by 22%. All reproductive parameters were higher than at 45 territories in western Washington. We tested efficacy of a sampling protocol in 2013 and 2014 by surveying 108 randomly selected eastern territories. Probability of detecting eagles for these years from ground (x-3.8pt̂= 89%) was greater than from air (x-3.7pt̂= 66%). Our estimate of territory occupancy, corrected by probability of detection, was lower in 2013 (x-3.8pt̂= 56.7%, 95% CI = 46.3–66.7%) than in 2014 (x-3.8pt̂= 73.7%, 95% CI = 64.8–81.7%), as was the estimated number of breeding pairs (2013: x-3.8pt̂= 158, 95% CI = 151–164; 2014: x-3.8pt̂= 187, 95% CI = 182–192). Higher productivity (young/occupied territory) in 2013 (x-3.8pt̂= 0.59, 95% CI = 0.40–0.82) than in 2014 (x-3.8pt̂= 0.41, 95% CI = 0.27–0.59) and lower proportions of ≥1 immature eagle among nesting pairs in 2013 (16%) than in 2014 (31%), suggested higher immature pairing among sampled pairs contributed to inter‐year differences in these reproductive parameters. Current and historical evidence for depressed golden eagle nesting in Washington is consistent with documented effects from habitat conversion, prey declines, lead contamination, and wind power development. We recommend future surveys in eastern Washington adhere to the random sampling protocol and conduct surveys at regular intervals to allow for trend analysis of reproductive parameters to better monitor golden eagle status. Surveys in western Washington, conducted exclusively from ground at all nests, will improve detection and cost efficiency. © 2020 The Wildlife Society.

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Comparative Diets of Nesting Golden Eagles in the Columbia Basin Between 2007–2013 and the Late 1970s

Cited by 11 publications

References 18 publications

Spatial and Temporal Patterns in Golden Eagle Diets in the Western United States, with Implications for Conservation Planning

Spatial and Temporal Patterns in Golden Eagle Diets in the Western United States, with Implications for Conservation Planning

Eagle visitation rates to carrion in a winter scavenging guild

Evidence for Depressed Reproduction of Golden Eagles in Washington

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