Helpers-at-the-nest in European Bee-eaters (Merops apiaster): a Genetic Analysis

Summary

Helping-at-the-nest provides a classic example for the analysis of the costs and benefits of altruism in relation to kin selection. Most studies to date have relied on genealogical data obtained by ringing parents and offspring. However, growing evidence shows that both extra-pair copulations and intra-specific nest parasitism are sufficiently frequent in birds to produce patterns of relatedness that differ appreciably from those inferred from ringing studies. This could have major repercussions for calculations of the genetic costs and benefits of helping. We therefore used DNA fingerprinting, in conjunction with detailed field observations over eight years (1983–1990) to analyse the helping behaviour of European bee-eaters (Merops apiaster). Fingerprints of 11 unhelped (60 chicks) and 8 helped (40 chicks) families using 33.6, 33.15 and M13 probes showed that: (a) every chick from unhelped families could be correctly assigned to their putative parents; (b) helpers are invariably genetic relatives (r = 0.5) of one or both of the breeding pair they help; and (c) in a preliminary analysis of parentage in helped families, about 2% (1/40) chicks in helped nests are not sired by the putative father. The helper in this case did not appear to be the father, but the illegitimate offspring may have been sired by a close relative of the helper.