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Résumé :
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Philopatry, especially natal philopatry, can vary noticeably even in related species. Ringing of nestlings and native juveniles on the Courish Spit revealed that in some species (Barred Warbler Sylvia nisoria, Willow Warbler Phylloscopus trochilus, Chaffinch Fringilla coelebs) the bulk of yearlings returns to breed at their natal site, whereas in other species (Lesser Whitethroat Sylvia curruca, Scarlet Rosefinch Carpodacus erythrinus) only an insignificant number of individuals appear to return. Specific differences in level of natal philopatry are basically a consequence of the timing of territory imprinting and the duration of the birds' stay in the natal place. Birds show fidelity for the site where territory imprinting occurred. If imprinting takes place prior to abandoning their native area, birds will show a high level of natal philopatry in subsequent years. If territory imprinting occurs after dispersal, philopatry will appear to be very low. Therefore natal dispersal distance in migratory species is mainly determined by postfledging dispersal distance in the postbreeding period. Philopatry is also affected by a number of other factors: hatching date, breeding success, constant habitat, age and experience, etc. The ratio of local birds and immigrants in populations depends mainly on the return-rate to the natal place. In more philopatric species the populations are maintained mainly by native birds. In such species, immigrants make up no more than 20% of the total number of individuals.
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