Nest defense in Blackbirds Turdus merula: effect of predator distance and parental sex

Abstract

We tested the dynamic risk assessment hypothesis: whether Blackbirds adjust their nest defense according to distance of the predator, Black-billed Magpie Pica pica, from their nest. Intensity of mobbing reaction was highest for near magpie dummy in both parents, although males showed higher overall intensity of mobbing behavior than females.

When magpie dummy was situated far from the nest, Blackbirds preferred hiding in vegetation to active mobbing. Both parents used "chink" calls to near magpie more than to far magpie dummy, while the "seee" calls were used mostly to far magpie dummy.

Keywords

• Nest defense
• Blackbird
• Turdus merula
• predator distance
• Magpie
• Pica pica
• dynamic risk assessment