European Bee-eater (Merops apiaster) Science Article 5
We studied breeding biology of the European Bee-eater (Merops apiaster) at a colony in southern France from 1983 to 1987. Approximately 50% of the breeding birds were juveniles (hatched the previous calendar year), and ca. 34% of the breeding birds in any year were known to return to the colony in a subsequent year. The proportion of birds banded as chicks and not recorded breeding until 2 years of age suggests that most females attempted to breed at 1 year of age, but that a larger proportion of juvenile males failed to attempt to breed. Pairs that survived tended to breed together in successive years, and the return to the colony in any year of one member of a breeding pair was not independent of the return of the other. Bee-eaters mated assortatively with respect to age. There was a nonsignificant tendency for breeding adults to be more likely than breeding juveniles to have helpers at the nest. At nests without helpers, adult females bred earlier and laid larger clutches than juveniles, brood size at fledging was unrelated to the age of either parent, recruitment rate of offspring of adults of both sexes was about twice that of offspring of juveniles, and provisioning rate was unrelated to parental age. Neither habitat saturation nor low breeding success of juveniles provide complete functional explanations of helping at the nest in Eu ropean Bee-eaters.
C. M. Lessells and J. R. Krebs, The Auk 106: 375-382. July 1989