Nest Defense by Male Red-Winged Blackbirds (Agelaius phoeniceus) Improves Survival of Broods They Provision

Abstract

ABSTRACT I observed male Red-winged Blackbirds (Agelaius phoeniceus) defend and provision nests, and I documented survival of pair-fed and female-fed broods to determine whether male parental behavior affects nestling survival and nest success. Broods provisioned by both males and females (n = 208) had significantly higher daily survival and were significantly more likely to produce fledglings than those fed only by females (n = 268). Examination of male responses to a crow model during incubation (n = 114) showed that males were more aggressive towards the simulated predator at nests they would later provision than at nests fed only by females. These results show that male provisioning is associated with more aggressive nest defense and increased nestling and nest survival, and suggest that parental behavior of male Red-winged Blackbirds is both plastic and adaptive.