Reproductive success decreases with colony size in the European bee-eater.

@enThe evolution of coloniality is usually explained by a benefit/cost ratio greater. than one. Alternatively, when costs exceed benefits,. a clumped. or restricted availability of limiting resources is used to-explain, coloniality. In this study we examine the relation between reproductive success and colony size in the European bee-eater (Merops apiaster). In our study population in Slovakia colony size varied from solitary breeding pairs up to 79 pairs per colony. We found no seasonal effects on reproductive success, however, there was a negative correlation between colon size and chick condition and survival. This relationship, although not significant, tended to be the same when examining only the earliest breeding pair of each colony site,. There was no relation. between reproductive parameters and, age of parents and no indication for age related settlement or any effect of the nest hole position within a colony. Limitation. of nesting sites and distribution of food are probably two important determinants. for colonial breeding in this species. Different aspects including the rare occurrence of helpers, Eire discussed as possible factors explaining the negative relationship between annual reproductive success and colony size.