DO FEMALE BLACK-CAPPED CHICKADEES PREFER HIGH-RANKING MALES AS EXTRA-PAIR PARTNERS

Previous studies have shown that some female black-capped chickadees ( Poecile atricapillus) solicit copulations from males that rank higher in winter flocks than their social mates, and extra-pair paternity in nests occurs commonly enough to be considered a potential female matin g tactic. This study uses blood samples collected in 1992-1995 from 58 families of black-capped chickadees to test whether females with extr a-pair offspring have chosen extra-pair sires higher in social rank th an their mates. Paternity was assessed with multilocus DNA fingerprint ing in 1992-1994 nests and with microsatellite and single-locus minisa tellite DNA typing in 1995 nests. Seventeen of 58 nests (29.3%) contai ned young genetically mismatched with their social father. In 11 of 15 cases where the identity of the extra-pair male was known, the extra- pair male was dominant to the social father. Using data from 29 nests located in 1994 and 1995 for which we had the most data on relative ra nks of males, high-ranking males had reater realized reproductive succ ess than low-ranking males as a result of extra-pair fertilizations. T here was no significant difference between the number of nests contain ing extrapair young of females mated to low-ranked versus high-ranked males. Two nests in 1995 contained young either genetically mismatched with both social parents (intra-specific brood parasitism) or in one nest, genetically mismatched with the social mother but not the social father (quasi-parasitism). The implications of female strategies acqu iring genetic benefits through extra-pair copulations are discussed.