Détail de la notice
Titre du Document
Colonial breeding and nest defence in Montagu's harrier (Circus pygargus)
Auteur(s)
ARROYO Beatriz ; MOUGEOT Francois ; BRETAGNOLLE Vincent
Résumé
We assessed whether colonial breeding allows individuals to decrease their investment in predator defence, by presenting decoys of owls, foxes and crows to Montagu's harrier, Circus pygargus. Decoy detection increased with colony size, as did the number of individuals mobbing the decoy. The number of mobbers was greater for predators potentially risky for the adults (owl or fox) than for non-dangerous predators (crow). Recruits (breeding neighbours, fledglings and non-breeders) were present a lower percentage of the time, and attacked and alarm called less frequently than tested individuals. Nevertheless, the overall attack rate on the predator increased with the number of mobbers. When the size of the mobbing group increased, individuals were more likely to attack predators that represented a risk for adults, but did so less intensively and with a lower frequency of close dives. Thus, coloniality decreased the individual costs of defence in terms of risk taken, whilst enhancing defence efficacy. Birds alarm called more intensively when presented with dangerous predators than with the crow. The number of recruits significantly increased with increasing alarm rate of the tested individuals, even when taking colony size into account. Furthermore, the alarm rate of the tested birds also had a significant effect on the proportion of recruits that engaged in attacks against dangerous predators but not against the crow. The higher recruitment and attack rates for dangerous predator
Editeur
Springer; Springer
Identifiant
ISSN : 0340-5443 CODEN : BESOD6
Source
Behavioral ecology and sociobiology (Print) A. 2001, vol. 50, n° 2, pp. 109-115 [bibl. : 53 ref.]
Langue
Anglais
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