Dunn Peter O, Cockburn Andrew
Evolutionary Ecology Group, Division of Botany and Zoology, Australian National University, Canberra, Australian Capital Territory, 0200, Australia.
Evolution. 1999 Jun;53(3):938-946. doi: 10.1111/j.1558-5646.1999.tb05387.x.
In many species of monogamous birds females copulate with males other than their social mates, resulting in extrapair fertilizations. Little is known about how females choose extrapair mates and whether the traits used to choose them are reliable indicators of male quality. Here we identify a novel male trait associated with extra-group mating success in the superb fairy-wren (Malurus cyaneus), a cooperatively breeding bird with one of the highest known frequencies of extra-group mating. Female fairy-wrens chose extra-group mates that molted earlier into breeding plumage. Males molted up to five months before the breeding season began, and only males that molted at least one month prior to its onset gained any extra-group fertilizations. This conclusion held after controlling statistically for the effect of age and social status on molt date. Once males acquired breeding plumage, they began courtship display to females on other territories. Thus, some males were displaying to females for several months before the breeding season began. This extraordinarily long period of advertisement by males may be facilitated by the long-term ownership of territories. We suggest that early acquisition of breeding plumage or the subsequent display behavior can be reliable cues for mate choice because they are costly to acquire or maintain.
在许多实行一夫一妻制的鸟类物种中，雌性会与社会配偶之外的雄性交配，从而导致异配受精。对于雌性如何选择异配配偶以及用于选择配偶的特征是否是雄性品质的可靠指标，我们知之甚少。在这里，我们识别出一种与华丽细尾鹩莺（Malurus cyaneus）异群交配成功相关的新的雄性特征，华丽细尾鹩莺是一种合作繁殖的鸟类，其异群交配频率是已知最高的之一。雌性细尾鹩莺会选择更早换上繁殖羽的异群配偶。雄性在繁殖季节开始前多达五个月就开始换羽，并且只有那些在繁殖季节开始前至少一个月就换羽的雄性才能获得任何异群受精机会。在对年龄和社会地位对换羽日期的影响进行统计控制后，这一结论依然成立。一旦雄性换上繁殖羽，它们就开始向其他领地的雌性进行求偶展示。因此，一些雄性在繁殖季节开始前几个月就向雌性展示自己。雄性这种格外长的展示期可能得益于领地的长期占有。我们认为，早早获得繁殖羽或随后的展示行为可能是配偶选择的可靠线索，因为获取或维持它们成本很高。
