Predation is the primary causeof nest mortality for most passerines, but observations of real-time nest defense are rare. We quantified nest-defense behaviors from video of 48 visits by snakes to 34 nests of grassland passerines; 37 visits resulted in predation. When adult birds encountered snakes (33 visits), 76 percentof the encounters resulted in nest defense. In almost half of the encounters, birds physically struck snakes, primarily by pecking. Nest defense rarely appeared to alter snake behavior; seven nests defended aggressively and two nests defended nonaggressively were partially depredated, whereas six nests defended each way were depredated completely. There is much potential for studying nest-defense behavior using video recordings of both real and simulated encounters.
Keywords: grassland birds; nest defense; nest predation; snakes; video
Chapter. 6151 words. Illustrated.
Subjects: Zoology and Animal Sciences
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