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La Tour du Valat

Institut de recherche pour la conservation des zones humides méditerranéennes

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Titre :	Local survival, natal dispersal, and recruitment in Little Egrets Egretta garzetta
Auteurs :	Heinz Hafner, Auteur ; Yves Kayser, Auteur ; V. Boy, Auteur ; M. Fasola, Auteur ; A. C. Julliard, Auteur ; R. Pradel, Auteur ; F. Cezilly, Auteur
Type de document :	Article
Dans :	Journal of Avian Biology (29(3) SEP 1998)
Article en page(s) :	216-227
Langues:	Anglais
Résumé :	Survival rates, natal dispersal, and age at first breeding of Little Egrets Egretta garzetta breeding in the Camargue (southern France) were estimated using individually marked birds observed in nesting colonies from 1987 to 1995. Survival and probability of resighting were estimated separately, using capture-mark-recapture models. Annual survival rates of adult breeding birds were constant (71.4%) during the study period, whereas the survival rates of yearlings showed marked variations between years, ranging from 6.54% to 55.19%. Rank in the brood at fledging had no effect on subsequent first-year or adult survival. There was no evidence for an effect of winter severity or trophic conditions at fledging on first-year survival during the study period. Age and time (study year), but not rank in the brood, had a significant interactive effect on resighting rates. A higher proportion of philopatric individuals was observed among birds first observed breeding at age one, compared to individuals observed breeding for the first time at an older age. Little Egrets that settled in colonies other than the natal one, dispersed at fairly even distances, with only a slight tendency to stay close to their natal colony. There was no influence of rank in the brood on the degree of philopatry. Direct observations and estimates from demographic models revealed that a substantial proportion of birds started breeding at age one, with large variations between years. This pattern of recruitment contrasts markedly with previous records for Ciconiiforms.

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