Stuart M. Slattery

Distribution and Habitat Use of Ross's and Lesser Snow Geese During Late Brood Rearing

Abstract We assessed spatial distribution and habitat use by Rosss and lesser snow geese (Chen rossii and C. caerulescens caerulescens) during late brood rearing to begin understanding goose–habitat interactions and monitoring key habitats around a rapidly growing nesting colony located at Karrak Lake, Nunavut, Canada. We conducted aerial surveys to count geese and georeference locations, then used Landsat Thematic Mapper satellite imagery to identify habitats associated with each flock. We observed 435 and 407 flocks and 36,287 and 32,745 birds in 1994 and 1995, respectively. Birds were somewhat uniformly distributed over the 5,000-km2 study area, with larger aggregations occurring closer to the coast, about 70 km from the colony. We assessed habitat use using Bonferroni intervals at both the flock and individual scales. At the flock level, birds avoided lichen–heath, used other terrestrial habitats as available, and selected freshwater. At the individual level, geese selected lowland habitats: wet sedge meadow, hummock graminoid tundra, and freshwater, which accounted for about 70% of the birds observed, and avoided upland habitats. Selection of lowland habitats is likely due to greater availability of food and easier predator avoidance compared to drier upland areas. Because most geese in our study used freshwater habitats, our results demonstrate that assessment of carrying capacity, at least in the central Arctic, must be expanded beyond the coastal salt marshes traditionally considered by researchers and managers as primary brood-rearing habitat for mid-continent light geese.

Identifying carry-over effects of wintering area on reproductive parameters in White-winged Scoters: An isotopic approach

ABSTRACT Events during one stage of the annual life cycle of migratory birds can have lasting (i.e. carry-over) effects that influence demographic parameters in subsequent seasons. We studied migratory connectivity and potential carry-over effects in a declining population of sea ducks. We measured stable isotope values of carbon (δ13C) and nitrogen (δ15N) in head feathers to assign breeding White-winged Scoters (Melanitta fusca; hereafter scoters) to either Atlantic or Pacific winter populations. The discriminant function for δ13C and δ15N correctly classified 93% of scoters sampled from these 2 winter areas. We then applied this classification scheme to head feathers of females breeding at Redberry Lake, Saskatchewan, and Cardinal Lake, Northwest Territories, to stratify each breeding population by winter provenance. We evaluated carry-over effects associated with winter location of females breeding in Saskatchewan by testing for differences in (1) nesting phenology, (2) clutch size, (3) mid-incubation body mass, (4) nest success, and (5) concentrations of trace elements contaminants of cadmium (Cd), mercury (Hg), selenium (Se), and lead (Pb) in blood, between strata of putative winter origin. Breeding females from the Atlantic coast had later dates of nest initiation, greater mid-incubation body mass, and also had higher concentrations of Cd (one year only), Pb, and Se, relative to birds from the Pacific. Neither nest initiation date nor mid-incubation body mass, however, were related to contaminant concentrations in blood. We found no differences in clutch size or nest success between putative winter strata. Our study detected carry-over effects in the Saskatchewan population that merit further attention.

Cross-Seasonal Association Between Winter Trophic Status and Breeding Ground Selenium Levels in Boreal White-Winged Scoters

The effect of cross-seasonal interactions on reproduction and fitness in migratory species is of increasing interest to ecologists, particularly because of the conservation implications of habitat change. Variation in contaminant levels that can affect reproduction in migratory species may reflect differing exposure across seasons. We examined the relationship between concentrations of liver selenium, a known teratogen, and winter trophic level in breeding White-winged Scoters ( Melanitta fusca) using claw δ15N values as an index of winter trophic level. Claw δ15N was a significant predictor of variation in breeding ground selenium levels (r = 0.32), and liver selenium increased by approximately 12 ± 5 SE μg·g-1 with one trophic level increase in δ15N (Δ3‰). This relationship demonstrates that contaminant exposure from wintering or staging areas can result in higher levels in birds on breeding grounds, where some contaminants are more likely to have impacts.