A quantitative approach to identifying predators from nest remains

• Published in: Journal of field ornithology 2004, Vol.75 (1), p.40-48
• Main Authors: Anthony, R. Michael, Grand, James B, Fondell, Thomas F, Manly, Bryan F. J
• Format: Article
• Language: English
• Subjects: Alaska; artificial egg; Bald Eagle; Branta canadensis; brown bear; camera; CONTENTS; Dusky Canada Goose; eagles; earthquakes; eggs; feeding behavior; geese; Haliaeetus leucocephalus; mixture-model analysis; nest predation; nesting; nests; predation; predators; probability; Ursus arctos
• ISSN: 0273-8570; 1557-9263
• DOI: 10.1648/0273-8570-75.1.40

Nesting success of Dusky Canada Geese (Branta canadensis occidentalis) has declined greatly since a major earthquake affected southern Alaska in 1964. To identify nest predators, we collected predation data at goose nests and photographs of predators at natural nests containing artificial eggs in 1997–2000. To document feeding behavior by nest predators, we compiled the evidence from destroyed nests with known predators on our study site and from previous studies. We constructed a profile for each predator group and compared the evidence from 895 nests with unknown predators to our predator profiles using mixture-model analysis. This analysis indicated that 72% of destroyed nests were depredated by Bald Eagles and 13% by brown bears, and also yielded the probability that each nest was correctly assigned to a predator group based on model fit. Model testing using simulations indicated that the proportion estimated for eagle predation was unbiased and the proportion for bear predation was slightly overestimated. This approach may have application whenever there are adequate data on nests destroyed by known predators and predators exhibit different feeding behavior at nests.