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Résumé :
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Capsule Creches formed early in the season lasted longer than those formed later, but a longer creching period did not appear to confer higher chick survival. Aims To investigate the ecological factors influencing the benefit to parents of creching behaviour by measuring chick survival. Methods Mark-recapture was used to model apparent daily survival of 505 chicks during the creching period in three different creches. We contrasted models with different tipping points to assess possible differences across creches in chick survival during the first week and in the moment at which chick departures began. Results We did not find a clear difference across creches on daily chick survival during the first stages of the creche. By modelling chick apparent survival as a linear function of time we showed that the latest formed creche dispersed more rapidly. Conclusions The two creches formed early in the season lasted longer than the one formed later but chicks did not appear to have a higher survival over the first week of creching. We suggest that a longer period at the creche should result in a higher survival in the period soon after fledging because chicks leave the creche 4-7 days older than other chicks. Furthermore, early creches are synchronous with those of other species breeding in the same area, thus perhaps diluting predation. We discuss the limitations of our analysis and the possible implications for the community of waterbirds breeding at our study site.
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