Depredation of Sea Otter Pups by Bald Eagles at Amchitka Island, Alaska

Sherrod, Steve K.; Estes, James A.; White, Clayton M.

doi:10.2307/1379491

Cited by 44 publications

(58 citation statements)

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“…A sample of 43 Ontario nests had from 1 to 3 eggs, but averaged 2.05 eggs (Peck and James, 1983). In Alaska, 57 nests had from 1 to 4 eggs and averaged 2.31 (Sherrod, White, and Williamson, 1976), suggesting that a higher average clutch size may be typical of northern populations. However, it would appear that only infrequently (up to three percent of the active nests, based on various studies) are three young ("triplets") ever fledged from nests, and four fledged young are very rare indeed.…”

Section: Breeding Biologymentioning

confidence: 94%

“…American coots (Fulica americana) were the most important bird species, representing 19 percent of the total biomass, and similarly were the most common prey at one Washington study site but not at another fairly nearby site, emphasizing the opportunistic feeding tendencies of bald eagles (Fielder, 1982). Sherrod, White, and Williamson (1976) estimated that on Amchitka Island, Alaska, the biomass of foods brought to nests averaged 14 percent fish, 49 percent birds, 36 percent mammals, and a trace of invertebrates (octopus and amphipods). They judged that the birds may be able to carry prey as large as baby sea otters (or about 1,850 grams), at least for short distances, and once an adult emperor goose (Chen canagica) (which weigh an average of about 2,800 grams) was observed to be killed and carried to a sea stack.…”

Section: Foods and Foragingmentioning

confidence: 97%

“…Iris pale yellowish gray; cere grayish; bill brownish horn; tarsi and toes clear lemon. Sherrod, White, and Williamson (1976) suggested that four age classes can be recognized in the field, including first-year ("brown" stage) juveniles, second-and third-year combined age classes ("mottled" stage), presumed fourth-year subadults ("eye-stripe" stage, those with some brown still present on the tail and on the head, especially behind the eyes), and adults, presumably at least five years old. These correspond approximately to the four stages listed above.…”

Section: Descriptionmentioning

confidence: 99%

“…About 30-35 percent of normally reproducing wild eagle populations probably consists of juveniles and subadults, whereas the incidence of such immature-plumaged birds during periods of reproductive decline may average less than 25 percent (Sherrod, White, and Williamson, 1976). Furthermore, even in an area of excellent eagle habitat with an abundance of nests, an apparently substantial portion of the adult population may be nonbreeders.…”

Section: Social Behaviormentioning

confidence: 99%

“…In coastal Alaska and the Aleutian Islands where no trees are available, nesting commonly occurs on isolated or connected sea stacks, peninsular ridges, islets, hillsides, and the like (Sherrod, White, and Williamson, 1976), all of which variably provide height and isolation, especially from mammalian predators such as arctic foxes (Alopex lagopus) and red foxes (Vulpes fulva).…”

Section: Breeding Biologymentioning

confidence: 99%

See 4 more Smart Citations

Hawks, eagles, & falcons of North America: biology and natural history

1991

Choice Reviews Online

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Section: Breeding Biologymentioning

confidence: 94%

Section: Foods and Foragingmentioning

confidence: 97%

Section: Descriptionmentioning

confidence: 99%

Section: Social Behaviormentioning

confidence: 99%

Section: Breeding Biologymentioning

confidence: 99%

See 3 more Smart Citations

Hawks, eagles, & falcons of North America: biology and natural history

1991

Choice Reviews Online

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Location‐specific factors influence patterns and effects of subsistence sea otter harvest in Southeast Alaska

et al. 2019

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To better understand the spatial context of population dynamics of sea otters (Enhydra lutris) in Southeast Alaska (SEAK), we investigated the spatial and temporal patterns of subsistence sea otter harvest and assessed the effect of harvest on population growth. U.S. federal law permits subsistence harvest of sea otters and sale of clothing and handicrafts made by coastal Alaska Natives. Hunters are required to self‐report these harvests along with information on date, location, age class, and sex. Using harvest data collected from 1988 to 2015, we developed a spatially explicit, age‐structured, density‐dependent population simulation model to explore the potential impacts of harvest on sea otter population dynamics. We examined patterns of harvest and simulation model results at two spatial scales: the SEAK stock and three smaller subregions that vary in sea otter occupation time and carrying capacity: Sitka Sound, Keku Strait, and the Maurelle Islands. Annual sea otter harvest in SEAK increased from 55 animals in 1988 to a reported maximum of 1449 animals in 2013. Estimated mean annual harvest rate was 2.8% at the SEAK stock scale, but ranged from 0% to 39.3% across the three focal subregions described above. Across all subregions (n = 55), annual sea otter harvest rate was strongly influenced by time since recolonization, sea otter population density, and proximity to communities with sea otter hunters. The simulation model predicted population trends and per capita harvest rates similar to those estimated from aerial survey data, providing a reasonable approximation of population dynamics. Results of the simulation model suggested that current harvest levels can reduce population size at both the SEAK and subregional scales. Variation in harvest impacts was a function of subregion‐specific factors, including time since recolonization and population status with respect to carrying capacity. We found that subsistence harvest and its population effects were scale‐ and location‐dependent, indicating that higher spatial and temporal resolution of sea otter population and hunting data could help address emerging sea otter management and conservation concerns in this region.

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Productivity, diets, and environmental contaminants in nesting bald eagles from the aleutian archipelago

Anthony

Miles

Estes

et al. 1999

Enviro Toxic and Chemistry

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Abstract-We studied productivity, diets, and environmental contaminants in nesting bald eagles from the western Aleutian Islands, Alaska, USA, during the summers of 1993 and 1994. Productivity on Adak, Tanaga, and Amchitka Islands ranged from 0.88 to 1.24 young produced per occupied site and was comparable to that of healthy populations in the lower 48 United States. However, productivity on Kiska Island was depressed, averaging 0.67 young per occupied site. The lower reproductive success on Kiska was associated with elevated levels of dichlorodiphenyldichloroethylene and other organochlorine pesticides. Many of the organochlorine pesticides were elevated in bald eagle eggs from the four islands, but concentrations of these contaminants and Hg were significantly higher in eggs from Kiska Island than in eggs from the other islands. In contrast, polychlorinated biphenyl concentrations were higher in eggs from Adak, Amchitka, and Kiska (where military facilities have been installed) than in those from Tanaga (which has had little military activity). The most likely source of these contaminants in bald eagles was from their diets, which were variable spatially and temporally. Fish made up most (56%) of the eagles' diet on Adak and Tanaga Islands, followed by birds (25%) and mammals (19%). In contrast, birds comprised the majority (60%) of bald eagle diets on Amchitka and Kiska Islands, followed by mammals (30%) and fish (10%). The high proportion of seabirds in the diet of eagles from Kiska Island could be the major source of organochlorine and Hg contamination. Elevated concentrations of organochlorines in bald eagle eggs from the Aleutian Archipelago was surprising, because of the distance to agricultural areas. The results indicate that these contaminants can be transported long distances and affect wildlife populations in remote and pristine areas. We also discuss potential sources and transport mechanisms of these contaminants to the Aleutian Islands.

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Depredation of Sea Otter Pups by Bald Eagles at Amchitka Island, Alaska

Cited by 44 publications

References 0 publications

Hawks, eagles, & falcons of North America: biology and natural history

Hawks, eagles, & falcons of North America: biology and natural history

Location‐specific factors influence patterns and effects of subsistence sea otter harvest in Southeast Alaska

Productivity, diets, and environmental contaminants in nesting bald eagles from the aleutian archipelago

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