To flee or wait and see? Response of incubating white-browed scrubwrens to information about danger

Abstract Animals suffer elevated predation risk during reproduction, with nesting parents having to decide whether to flee from nearby predators for their own safety or to stay and thus avoid betraying the nest's location to protect offspring. Gaining information about the source of danger is therefore crucial. From inside a nest, it might be difficult to gather relevant information visually and so acoustic signals and cues become particularly important. However, there has been little investigation of the response of nesting parents to acoustic information about different predation risks. We used a playback experiment to test how incubating female white-browed scrubwrens, Sericornis frontalis—which build extremely cryptic, dome-shaped nests close to the ground—respond to aerial alarm calls (warning of airborne predators), mobbing alarm calls (warning of stationary predators on or above the ground), the footstep sounds of a nest predator on the ground, and control calls of a harmless parrot. We found that incubating scrubwrens responded more to the “danger” treatments compared with the control but, contrary to expectation, rarely fled in response to any of the predatory threats. However, birds looked around more actively (more saccades) after mobbing calls compared with the other playbacks, perhaps because mobbing calls do not indicate the specific location of danger and so additional information gathering is valuable. Incubating scrubwrens can therefore recognize potential danger by sounds, but evaluated risk from within the nest rather than immediately fleeing, suggesting that they prioritize nest crypsis over other anti-predator strategies.