Extra-pair relations in zebra finches: differential male success results from female tactics

Abstract

Abstract. Extra-pair courtship and copulatory patterns were examined in a freely breeding laboratory population of wild-type, domesticated zebra finches, Taeniopygia guttata. Prior to release into the experimental aviary, each male received either two red bands (shown previously to be attractive in heterosexual tests) or two green bands (unattractive to females) as part of a unique combination of four leg bands; the remaining two bands were of neutral colours. Females received neutral combinations. Bill colour, which also affects heterosexual attractiveness, was also scored. Bill colour had only minor effects here, but band colour effects were substantial. Red-banded males participated in unforced extra-pair copulations more commonly than did green-banded males. Band colour did not influence male participation in forced extra-pair copulations. Mates of red-banded males (red-mated females) deterred extra-pair courtship more than green-mated females; green-mated females participated in extra-pair courtship and extra-pair copulation more frequently. Results indicate that females displayed active choice of extra-pair copulatory partners and employed conditional tactics for obtaining these partners. Males showed little differentiation in extra-pair tactics based on attractiveness or mating status. However, assuming that rates of extra-pair fertilization are proportional to rates of extra-pair copulation, red-banded males would appear to have both higher paternity confidence and greater success in obtaining extra-pair fertilizations.