EXTRA-PAIR PATERNITY UNCOMMON IN THE COOPERATIVELY BREEDING BICOLOREDWREN

We investigated parentage using multilocus DNA fingerprinting for 222 juveniles produced during 99 group-years in the bicolored wren Campylo rhynchus griseus, a cooperatively breeding bird of the Venezuelan sava nna. Young adult bicolored wrens (auxiliaries) remain in their natal t erritories and substantially enhance the production of young there. We have previously used behavioral indicators of dominance by a single m ale/female pair (principals) to infer breeding status, resulting in th e commonly applied model of helping in which current fitness accrues t o auxiliaries only indirectly, in proportion to their relatedness to t he principals and the effect of their assistance on breeding success. Our parentage analysis has demonstrated that 8.6% of the juveniles fou nd on territories were not produced by the principal pair. Parentage o f 4.1% of the juveniles was completely outside the social group; these appear to result from early dispersal of juveniles rather than from b rood parasitism, most likely resulting from breakup of nearby groups. Principal females mated outside of their group (2.3%), or with an auxi liary male (2.3%), in the remaining cases of parentage outside the pri ncipal pair. No matings were detected between close relatives (e.g. mo ther-son); matings detected between the principal female and an auxili ary male followed a typical replacement of the principal female by an unrelated immigrant female. Our fingerprinting results indicate that: (1) current fitness benefits accruing to most auxiliaries do not excee d their likely reproductive success had they dispersed successfully to a breeding position; (2) nearly all wren mating is monogamous and (3) behavioral dominants (especially females) can monopolize breeding.