Changes in abundance and spatial distribution of geese molting near Teshekpuk Lake, Alaska: interspecific competition or ecological change?
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Goose populations molting in the Teshekpuk Lake Special Area of the National Petroleum Reserve—Alaska have changed in size and distribution over the past 30 years. Black brant (Branta bernicla nigricans) are relatively stable in numbers but are shifting from large, inland lakes to salt marshes. Concurrently, populations of greater white-fronted geese (Anser albifrons frontalis) have increased seven fold. Populations of Canada geese (Branta canadensis and/or B. hutchinsii) are stable with little indication of distributional shifts. The lesser snow goose (Anser caerulescens caerulescens) population is proportionally small, but increasing rapidly. Coastline erosion of the Beaufort Sea has altered tundra habitats by allowing saltwater intrusion, which has resulted in shifts in composition of forage plant species. We propose two alternative hypotheses for the observed shift in black brant distribution. Ecological change may have altered optimal foraging habitats for molting birds, or alternatively, interspecific competition between black brant and greater white-fronted geese may be excluding black brant from preferred habitats. Regardless of the causative mechanism, the observed shifts in species distributions are an important consideration for future resource planning.
KeywordsAlaska Black brant Canada geese Greater white-fronted geese Habitat change Interspecific competition Molting Snow geese Teshekpuk Lake
Funding for this project was provided by the US Fish and Wildlife Service (Region 7, Alaska) and US Geological Survey, Alaska Science Center. R. Oates provided logistic and administrative support. C. Markon assisted with habitat stratification classifications. B. Jones developed the Aster image figure. This paper benefited from the reviews of D. Nigro, J. Fischer, and M.W. Weller as well as several anonymous reviewers.
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