Communicative Behavior in Breeding Ospreys (Pandion haliaetus): Description and Relationship of Signals to Life History

Abstract

.--The Osprey (Pandion haliaetus), although studied extensively, is relatively un- known with respect to its behavior, especially communication. We conducted a two-year study on a resident Osprey population in Corsica, and describe the communicative behavior of this species. The behavioral repertoire of Ospreys included 11 visual displays (resting, upright, alarm low and high, solicitation low and high, defense, protection, nest protecting, attack, and sky dance) and eight acoustic signals (alarm, solicitation low, high and very high, guard, excited, screaming, and copulation calls). The meaning of each of the displays and calls was inferred from the analysis of behavioral sequences. The communication system of the Osprey consisted of sexual behaviors (between partners), such as solicitation and sky dance, and agonistic behaviors (between breeders and nonbreeders), such as nest-protecting and defense postures. We also analyzed Osprey relationships with other species (including man), and found that there was a gradation within alarm displays and alarm calls according to stimulus distance. In the last section, we try to account for several peculiarities of Osprey behaviors, namely their complexity, the behavioral sexual dimorphism, and the importance of motivational displays. We suggest that all these characters may be related to the life-history traits shown by this species: semicoloniality, breeding strategy, and predation risk (on eggs and chicks).