Population Dynamics and Partial Migration of the European Robin (Erithacus rubecula) in Different Habitats

Unbalanced reproductive success of the resident and migratory morphs and arguments for conditionality show that partial migration in the European robin is a conditional strategy in which the migrants are making the best of a bad job.

Abstract

SUMMARY (1) We studied differences in habitat distribution, local survival and mating success • between the two morphs (resident/migrant) of the partially migratory European robin near Antwerp (Belgium). (2) Mean local survival of resident males (50%) was higher than local survival of migrant males (17%). During cold winters survival of residents decreased with about 50%. (3) Mating success decreased with settling date from 74% for early settling residents, over 44% for migrants to 19% for late-settling birds of unknown status. (4) The probability of breeding is two to four times higher in residents than in migrants. (5) Resident and migratory robins were habitat separated both in the breeding season and in winter: 70% of breeding males were migratory in the woodland, but in the park and gardens most males were resident. Almost all females were migratory. (6) Unbalanced reproductive success of the resident and migratory morphs and arguments for conditionality show that partial migration in the European robin is a conditional strategy in which the migrants are making the best of a bad job. (7) We explain why our conclusions do not contradict experimental evidence for a strong genetic influence on migratory tendencies in the European robin.