Patterns of sentinel behavior at the nest in the cooperatively breeding American crow (Corvus brachyrhynchos)

Sentinel activity within the cooperatively breeding American crow ( Corvus brachyrhynchos) is well documented during foraging but sentinel nest-guarding in this species has received little attention. Nest sentinel activity was studied in an established population of American crows in Ithaca, NY. This study suggests temporal changes and family size affect sentinel and feeding contributions. There was more sentinel effort later in nesting when young are worth more protection. A nest sentinel's coordination of guarding the nest in the breeding female's absence was most pronounced during the final stages of nesting. Both breeders and helpers contribute to feeding and sentinel activity, but the presence of more helpers significantly increases the time that a nest is guarded by a sentinel. Helper contributions to sentinel activity and feeding varied by age with significantly more two-year olds than yearlings contributing to both activities.