Geology topics

Research about Yukon–Kuskokwim Delta

Source-linked reports with geographic coverage including Yukon–Kuskokwim Delta.

4 recordsLinked to original sources

USGS2017

Development of microsatellite loci exhibiting reverse ascertainment bias and a sexing marker for use in Emperor Geese (Chen canagica)

The Alaskan population of Emperor Geese ( Chen canagica ) nests on the Yukon–Kuskokwim Delta in western Alaska. Numbers of Emperor Geese in Alaska declined from the 1960s to the mid-1980s and since then, their numbers have slowly increased. Low statistical power of microsatellite loci developed in other waterfowl species and used in previous studies of Emperor Geese are unable to confidently assign individual identity. Microsatellite loci for Emperor Goose were therefore developed using shotgun amplification and next-generation sequencing technology. Forty-one microsatellite loci were screened and 14 were found to be polymorphic in Emperor Geese. Only six markers – a combination of four novel loci and two loci developed in other waterfowl species – are needed to identify an individual from among the Alaskan Emperor Goose population. Genetic markers for identifying sex in Emperor Geese were also developed. The 14 novel variable loci and 15 monomorphic loci were screened for polymorphism in four other Arctic-nesting goose species, Black Brant ( Branta bernicla nigricans ), Greater White-fronted ( Anser albifrons ), Canada ( B. canadensis ) and Cackling ( B. hutchinsii ) Goose. Emperor Goose exhibited the smallest average number of alleles (3.3) and the lowest expected heterozygosity (0.467). Greater White-fronted Geese exhibited the highest average number of alleles (4.7) and Cackling Geese the highest expected heterozygosity (0.599). Six of the monomorphic loci were variable and able to be characterised in the other goose species assayed, a predicted outcome of reverse ascertainment bias. These findings fail to support the hypothesis of ascertainment bias due to selection of microsatellite markers.

Alaska↗

USGS2017

Shorebirds adjust spring arrival schedules with variable environmental conditions: Four decades of assessment on the Yukon–Kuskokwim Delta, Alaska

Arctic summers are brief, and there has been strong selection for migratory birds to arrive in Arctic nesting areas as early as possible to time breeding with peak food availability and complete reproduction. The timing of emergence of nesting habitat in spring is, however, extremely variable in the Arctic, and few long-term studies have examined the ability of avian migrants to track spring conditions to assure optimal nesting. Such studies require long-term migration monitoring under variable spring habitat conditions. These conditions were met during our long-term (1977–2008) study of the timing of arrival of shorebirds to their nesting grounds on the central Yukon–Kuskokwim (Y-K) Delta, in western Alaska. Over this period, the timing of arrival on the nesting grounds of 12 species of shorebirds varied significantly, with the Black-bellied Plover (Pluvialis squatarola) generally arriving first (mean arrival of 4 May), the Red Phalarope (Phalaropus fulicarius) usually arriving last (mean arrival of 20 May). The Western Sandpiper (Calidris mauri), Dunlin (Calidris alpina), and Red-necked Phalarope (Phalaropus lobatus), the most common breeding shorebird species we studied, all arrived about the same time each year (7–9 May). From year to year, first arrival of all species varied significantly by more than 2 weeks, but there was no long-term trend in arrival times over the length of our study. Shorebird arrival was highly correlated with the timing of the break-up of ice on the Kashunuk River, which in turn was correlated with decreasing snow cover and increasing ambient temperature. The date of break-up of river ice also varied by year but did not advance significantly during our study. After arriving on the breeding grounds, Arctic-nesting shorebirds rely on local food resources, which on the Y-K Delta they achieve by timing their arrival to coincide with availability of snow-free habitat. Temperatures along the terminal portions of the spring migration route were significantly correlated with both conditions on the breeding ground and the timing of shorebirds’ arrival there, which suggests that shorebirds may use environmental cues during spring migration to regulate its pace. Ours is one of the few multi-decadal studies to evaluate the responses of a suite of migrant species to annual variation in conditions in their Arctic breeding habitat. Shorebirds’ adaptations to variable conditions on the Y-K Delta are probably rooted in frequent changes to the landscape since the last glacial maximum. Such inherent flexibility may serve them well under future scenarios associated with a changing climate.

Alaska↗

USGS1999

Concentrations of selenium, mercury, and lead in blood of emperor geese in western Alaska

We found up to 10 ppm wet weight of selenium in blood samples collected from emperor geese ( Chen canagica ) on their breeding grounds on the Yukon‐Kuskokwim Delta in western Alaska, USA. Incubating adult females captured in late May through mid‐June 1997 had significantly higher concentrations of selenium in their blood (mean = 5.60 ppm) than adult females captured during wing molt in late July 1996 (mean = 2.78 ppm). Females that nested early or were in good body condition had higher concentrations of selenium in their blood than did other nesting females. Blood samples from 4 of 29 goslings had detectable levels of selenium (mean = 0.14 ppm). Our findings suggest that emperor geese are exposed to more selenium in the marine environment of their wintering and staging areas on the Alaska Peninsula than on the breeding grounds. The highest concentration of mercury found in the blood of emperor geese was 0.24 ppm. One bird had a blood lead concentration of 0.67 ppm, but 82% had no detectable lead in their blood, suggesting that lead exposure from the ingestion of lead shot poses little threat for emperor geese in western Alaska, contrary to findings reported for sympatric spectacled eiders ( Somateria fischeri ).

Alaska↗

USGS1991

Seasonal patterns of prey availability and the foraging behavior of arctic foxes ( Alopex lagopus ) in a waterfowl nesting area

The foraging behavior of arctic foxes was observed in a waterfowl nesting area on the Yukon–Kuskokwim Delta of Alaska in 1985–1986. Observations were made during peak fox activity from two towers, 3 m high, located in different community types. Data were collected continuously for individual foxes on specific activities, the community in which activities occurred, and the type of food obtained. After migratory birds started nesting in the area, the food potentially available to foxes changed from microtines, old caches, and carrion to include eggs and birds. This change was reflected in the foraging behavior of the foxes as they switched to predation on eggs. After nesting began, the search success rate of foxes increased (from <30% to >50%) and search duration decreased (mean 19.7 s before nest initiation versus mean 9.4 s in mid-incubation) as the rate of food acquisition increased. Over 80% of the eggs taken by foxes were cached rather than eaten immediately, which extended the availability of this temporally limited resource to foxes. Eggs were the primary prey of arctic foxes during the nesting stages in both years, even though microtine populations were high in one year (1985) and low in the other (1986).

Alaska↗