Contexts and possible functions of alarm calling in the willow tit, parus montanus; The principle of 'better safe than sorry'

The primary alarm call in the willow tit consists of a series of high-pitched, short zi (zee)-notes, A large variety of birds Eying overhead may evoke alarm calls in the willow tit, many of which are quite harmless to the species. Also many types of 'disturbances' in the forest may elicit alarm calls, including sudden appearance of humans. Alarm calling seems to be an altruistic event since the caller puts itself into a dangerous situation by attracting the predator's attention, while leaving time for associates to take relevant precautions. For an evolutionary selection of alarm calling the cost involved must somehow be outweighed by factor(s) beneficial to the caller. Among several hypotheses trying to explain possible functions of alarm calls, warning of kin and mates seems most likely with regard to tits. The relevance of the 'food resource usurpation-hypothesis' needs further study under natural conditions. The high proportion of 'false' alarms is remarkable. A strategy of 'better safe than sorry' seems to be advantageous, because the time left for appropriate precautions in case of a real attack is so marginal that it pays in the long run to react to any possible threat even if it turns out to be harmless.