Spatial patterns in occupancy and reproduction of Golden Eagles during drought: Prospects for conservation in changing environments

Wiens, J. David; Kolar, Patrick S.; Hunt, W. Grainger; Hunt, T. L.; Fuller, Mark R.; Bell, Douglas A.

doi:10.1650/condor-17-96.1

Cited by 8 publications

(22 citation statements)

References 52 publications

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“…To address redundancies, we used a hierarchical selection algorithm [45] to thin spatially clustered nest locations into one nest site based on: 1) the most recent observation of a nest with the highest level of nest status (e.g., In-Use > Occupied); and 2) imposing a 3-km threshold (thinning) distance between nests based on typical nearest-neighbor distances and core-use area size [12, 52]. Restricting nest sites included in our data set to those >3-km apart reduced over-representation of intensively surveyed areas where golden eagle territories were very closely spaced (e.g., Central California Coast Ranges; [29] and the Snake River canyon in southwestern Idaho; [53]).…”

Section: Methodsmentioning

confidence: 99%

“…Data describing golden eagle breeding sites in the western U.S. are routinely collected by land management agencies, researchers, and energy developers during the course of project planning. These data are often collected opportunistically (i.e., without a formal sampling design; but see [28, 29]), limiting their application in presence-absence analysis designs. Presence-only (or presence-available) species distribution models (SDMs), however, have become powerful and popular tools for evaluating species-environment relationships (e.g., [30]).…”

Section: Introductionmentioning

confidence: 99%

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Modeling spatial variation in density of golden eagle nest sites in the western United States

et al. 2019

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In order to contribute to conservation planning efforts for golden eagles (Aquila chrysaetos) in the western U.S., we developed nest site models using >6,500 nest site locations throughout a >3,483,000 km2 area of the western U.S. We developed models for twelve discrete modeling regions, and estimated relative density of nest sites for each region. Cross-validation showed that, in general, models accurately estimated relative nest site densities within regions and sub-regions. Areas estimated to have the highest densities of breeding golden eagles had from 132–2,660 times greater densities compared to the lowest density areas. Observed nest site densities were very similar to those reported from published studies. Large extents of each modeling region consisted of low predicted nest site density, while a small percentage of each modeling region contained disproportionately high nest site density. For example, we estimated that areas with relative nest density values <0.3 represented from 62.8–97.8% ( = 82.5%) of each modeling area, and those areas contained from 14.7–30.0% ( = 22.1%) of the nest sites. In contrast, areas with relative nest density values >0.5 represented from 1.0–12.8% ( = 6.3%) of modeling areas, and those areas contained from 47.7–66.9% ( = 57.3%) of the nest sites. Our findings have direct application to: 1) large-scale conservation planning efforts, 2) risk analyses for land-use proposals such as recreational trails or wind power development, and 3) identifying mitigation areas to offset the impacts of human disturbance.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Modeling spatial variation in density of golden eagle nest sites in the western United States

et al. 2019

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“…In Washington, productivity at successful territories did not decline over time and nest success increased with rates of occupancy, which lends support to the conclusion that specific territories may be sustaining core reproduction for the population as was surmised in eagle populations in Idaho and Scotland (Hipkiss et al 2014, Kochert et al 2018). Such territories may provide comparatively more prey and would be the most important candidates to protect in the population (Sergio and Newton 2003, Peery and Gutiérrez 2013, Wiens et al 2018). Protection may be hampered by significant fire events that are increasing in frequency and intensity, such as occurred in eastern Washington in 2014 and 2015 and consumed as many as 45 golden eagle territories (J. W. Watson, WDFW, unpublished data).…”

Section: Discussionmentioning

confidence: 99%

“…Fire has the potential for long‐term consequences on golden eagle nesting habitat, prey abundance, and long‐term reproduction (Kochert et al 1999). Other future effects on golden eagle reproduction from climate change may include increased weather severity that affects prey populations prior to eagle nesting, and hotter temperatures during nesting that reduce nest success and brood survival (Steenhof et al 1997, Wiens et al 2018, Kochert et al 2019).…”

Section: Discussionmentioning

confidence: 99%

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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“…Broad-scale survey designs are needed to identify possible population-level responses of rare and highly mobile raptor species to site-level changes in landscape conditions and to inform future management decisions. In this sense, monitoring and survey protocols that are standardized across temporal and spatial scales are essential in establishing linkages between small-scale, short-term conservation efforts and long-term population trajectories (Hewitt et al, 2007;Pavlacky et al, 2017;Wiens et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Golden Eagle Occupancy Surveys and Monitoring Strategy in Coastal Southern California, United States

Wiens

Bloom²,

Madden

et al. 2022

Front. Ecol. Evol.

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Golden eagles (Aquila chrysaetos) are of increasing conservation concern in western North America. Effective conservation measures for this wide-ranging, federally protected raptor species require monitoring frameworks that accommodate strong inference on the status of breeding populations across vast landscapes. We used a broad-scale sampling design to identify relationships between landscape conditions, detection rates, and site occupancy by territorial pairs of golden eagles in coastal southern California, United States. In 2016 and 2017, we surveyed 175 territory-sized sample sites (13.9-km2 randomly selected grid cells) up to four times each year and detected a pair of eagles at least once in 22 (12.6%) sites. The probability of detecting pairs of eagles varied substantially between years and declined with increasing amounts of forest cover at survey sites, which obscured observations of eagles during ground-based surveys. After accounting for variable detection, the mean estimate of expected site occupancy by eagle pairs was 0.156 (SE = 0.081). Site-level estimates of occupancy were greatest (>0.30) at sample sites with more rugged terrain conditions, <20% human development, and lower amounts of scrubland vegetation cover. The proportion of a sample site with open grassland or forest cover was not strongly correlated with occupancy. We estimated that approximately 16% of the 5,338-km2 sampling frame was used by resident pairs of golden eagles, corresponding to a sparsely distributed population of about 60 pairs (95% CI = 19 – 151 pairs). Our study provided baseline data for future surveys of golden eagles along with a widely applicable monitoring framework for identifying spatial conservation priorities in urbanizing landscapes.

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Spatial patterns in occupancy and reproduction of Golden Eagles during drought: Prospects for conservation in changing environments

Cited by 8 publications

References 52 publications

Modeling spatial variation in density of golden eagle nest sites in the western United States

Modeling spatial variation in density of golden eagle nest sites in the western United States

Evidence for Depressed Reproduction of Golden Eagles in Washington

Golden Eagle Occupancy Surveys and Monitoring Strategy in Coastal Southern California, United States

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