Antipredator Behavior of Adult and Nestling Red-winged Blackbirds (Agelaius phoeniceus)

Red-winged Blackbirds (Agelaius phoeniceus) experience high rates of nest predation and are therefore expected to exhibit adaptations to reduce the risk of eavesdropping by predators. We used a simulated predator and observations of adult and nestling behavior to test predictions of the predator eavesdropping hypothesis. Females (n = 42) delayed their feeding visits significantly longer and took significantly longer to complete their round trips when a plastic American crow (Corvus brachyrhynchos) was 20 m from their nests than when a black wood block was at the same location, but time spent off territory foraging did not differ significantly. Nestlings (n - 35 broods) begged appropriately (in response to a female at the nest) significantly less and at significantly lower intensity when the plastic crow was 20 m from their nests than when the wood block was at the same location, but the crow had no significant effect on the amount or intensity of inappropriate (no female present) begging. These and other results demonstrate that adult and nestling Red-winged Blackbirds have evolved adaptations to reduce nest predation.