Glaucous Gull Predation of Goslings on the Yukon-Kuskokwim Delta, Alaska

• Published in: The Condor
• Main Authors: Bowman, Timothy D., Stehn, Robert A., Scribner, Kim T.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Oxford University Press (OUP) 2004
• Subjects: Animal Science and Zoology; Ecology, Evolution, Behavior and Systematics; Yukon; Canada; The ''Y''; Branta canadensis; Canada Goose; Glaucous Gull; Kuskokwim; Larus hyperboreus; Alaska
• Online Access: http://dx.doi.org/10.1093/condor/106.2.288; http://academic.oup.com/condor/article-pdf/106/2/288/29711379/condor0288.pdf

Abstract Glaucous Gulls (Larus hyperboreus) nesting on the Yukon-Kuskokwim (Y-K) Delta frequently prey on juvenile waterfowl. We collected 434 Glaucous Gulls from late June to early August 1994 to examine diet. Identification of undigested prey tissue, based on DNA microsatellite loci, showed three species of goslings in gull stomachs: Emperor Goose (Chen canagica), White-fronted Goose (Anser albifrons), and Cackling Canada Goose (Branta canadensis minima). Gulls that nested inland and were collected >1.6 km from the coast accounted for approximately 70% of the total gull predation on Emperor and Canada Geese, and 96% on White-fronted Geese. Our stratified sample of gull stomachs and aerial survey estimates of population size and distribution of gulls and juvenile geese enabled extrapolation of species-specific predation rates to the entire Y-K Delta. We estimated that a minimum of 21 000 Emperor Goose, 34 000 Canada Goose, and 16 000 White- fronted Goose goslings were consumed by 12 600 Glaucous Gulls during the brood-rearing period on the Y-K Delta in 1994. Minimum estimated take by gulls represented 33% of Cackling Canada Goose, 47% of Emperor Goose, and 39% of White-fronted Goose eggs estimated to have hatched in the same area as gull collections. Gulls selected the three species of geese approximately in proportion to their abundance. Although gull predation caused significant gosling mortality, its role in regulating goose populations on Y-K Delta remains unresolved. Depredación de Pichones de Gansos por Gaviotas Larus hyperboreus en el Delta del Yukon-Kuskokwim, Alaska Resumen. Las gaviotas Larus hyperboreus que nidifican en el delta del Yukon-Kuskokwim (Y-K) depredan aves acuáticas juveniles con frecuencia. Para examinar su dieta, colectamos 434 gaviotas de esta especie entre finales de junio y principios de agosto de 1994. Identificamos los tejidos de presas no digeridos con base en loci de ADN microsatelital y encontramos pichones de tres especies de gansos (Chen canagica, Anser albifrons y Branta ...