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Brood rearing ecology of King Eiders on the North Slope of Alaska.

Article Excerpt
Declines in the North American population of King Eiders (Somateria spectabilis) have increased interest in the status and ecology of this species (Dickson et al. 1997, Gratto-Trevor et al. 1998, Suydam et al. 2000). King Eiders are circumpolar breeders that nest primarily along the margins of freshwater ponds and lakes on the arctic tundra (Suydam 2000). King Eider females leave the nest after hatch with their brood and move over land among tundra ponds (Bergman et al. 1977). Some waterfowl studies hypothesize that distance traveled over land may reduce duckling survival by increasing risk of mortality due to predation or exposure (Rotella and Ratti 1992, Seymore and Jackson 1996), while other studies suggest a positive correlation (Yerkes 2000, Mehl and Alisauskas 2007) or no effect (Wayland and McNicol 1994, Dzus and Clark 1997).

Estimates of duckling survival for waterfowl species suggest that survival rates are lower from hatching to fledging than during later life stages, and variation in survival is linked to recruitment (Mendenhall and Milne 1985, Johnson et al. 1992). Duckling mortality has been attributed to predation, adverse weather, starvation, and disease (Johnson et al. 1992). Identifying mortality at different life history stages is important for developing conservation plans for King Eiders. We examined survival of King Eider ducklings on the North Slope of Alaska and examined survival in relation to distance traveled over land.

METHODS

Study Area.--We trapped female King Eiders on nests in 2002 and 2003 at the Kuparuk oil field (70[degrees] 20' N, 149[degrees] 45' W) between the Colville and Kuparuk rivers on the North Slope of Alaska. The site was characterized by numerous thaw lakes, ponds, and basins (Anderson et al. 1999).

Capture and Telemetry.--We searched accessible areas in the Kuparuk oil field for nesting King Eiders during each summer, 2002 and 2003. We candled and floated eggs from nests to assess incubation stage and estimate hatch date (Weller 1956). We monitored nests at least once per week.

We captured hens on nests about 1 week prior to hatch using hand-carried mist nets (Bacon and Evrard 1990) or bow-net traps (Sayler 1962). We originally planned to trap 20 randomly selected hens each year but, due to low nest success we attempted to trap any female still on a nest 1 week prior to predicted hatch date. We captured 12 females in 2002, clipped feathers on their upper back between their wings, and attached 8-g VHF transmitters (Telonics Inc., Mesa, AZ, USA) to the area using epoxy. We attached 10-g VHF anchor transmitters using a suture technique (Pietz et al. 1995) to 12 hens in 2003 to reduce transmitter loss. We checked nests daily after capture to document departure of broods. We did not flush hens from nests during these checks. We checked nests for number of hatched eggs when females...

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