MEPS 180:267-273 (1999) - doi:10.3354/meps180267
Recruitment of Audouin's gull to the Ebro Delta colony at metapopulation level in the western Mediterranean
Daniel Oro1,2,*, Roger Pradel1
ABSTRACT: Few studies have been carried out on movements among local populations of long-lived birds due to the difficulty of marking and following individuals in different populations within a metapopulation for the long term. An extensive long-term ringing programme carried out in most of the local breeding populations (i.e. colonies) within the western Mediterranean metapopulation of Audouin's gull allowed us to assess the probability of a gull being recruited into the Ebro Delta colony according to the colony of birth. The studied metapopulation includes 93% of total world population of breeding pairs. Resights of 1302 ringed breeders during 1 breeding season at the Ebro Delta were used to model the probability of recruiting as a function of distance from the natal colony. A negative binomial distribution accounting for overdispersion was fitted in the framework of generalized linear models. Distance explained 97% of the difference among colonies which themselves accounted for 67% of the total deviance. Recruitment probability decreased exponentially with distance from the Ebro Delta colony, despite the high movement capabilities of the species during the breeding and non-breeding seasons. However, dispersal was recorded even from the most distant colony at 655 km from the Ebro Delta, although at a very low rate. Results agree with the prediction of several theoretical models of animal movement that distance is one of the most important determinants of dispersal and colonization rates within metapopulations.
KEY WORDS: Audouin's gull · Recruitment · Metapopulation · Distance · Colony growth · Population dynamics
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