ALARM CALLING BY INDIVIDUAL WILLOW TITS, PARUS-MONTANUS

Alarm responses of wild-captured individual willow tits to model sparrowhawks, Accipiter nisus, flying over a test chamber were studied. Tits did not usually give alarm calls if the apparent predator was passing nearby (at a height of 10 m), while over half of the individuals responded by alarm calling for a more distant predator (40 m). This suggests that alarm calling involves a risk to the caller. Second, there was individual variation in the responses, with older males giving the call more frequently than females or young males. The greater responsiveness of adult males may indicate that different individuals in a flock gain different benefits by warning the others. The tendency to give alarm calls increased over the autumn, which could be related to the establishment of cohesive flocks at the time. © 1990 The Association for the Study of Animal Behaviour.