Egg trading—the alternating exchange of egg parcels during mating by simultaneous hermaphrodites—is one of the best-documented examples of reciprocity between non-relatives. By offering eggs only to partners who reciprocate, traders increase their reproductive success in the male role, but...

Conspecific brood parasitism (CBP), where females lay eggs in nests of conspecifics, is taxonomically widespread. Following recent calls to consider CBP in a more integrative manner, we explore breeding strategies related to CBP by using a model of competing strategies that incorporates...

Males of many species defend resources to attract females. Surprisingly, defense of multiple female breeding sites (e.g., nests or burrows) appears to be rare, primarily reported in fish and birds. In fiddler crabs, burrows are a vital resource for reproduction and survival. Both sexes defend...

Female superb fairy-wrens Malurus cyaneus initiate extragroup fertilizations by forays to the territory of preferred males, just before sunrise, 2--4 days before egg laying. Over a prolonged breeding season, males advertise their availability to foraying females by singing during the dawn...

When dispersal options are limited and encounters with relatives are likely, individuals need to recognize and avoid mating with kin to avoid the fitness costs of close inbreeding. New Zealand robins and saddlebacks are genetically monogamous and possess life-history traits that predict they...

Divorce in socially monogamous species can result from different mechanisms, for example, chance events, active desertion of the partner, or the intrusion of a third individual ousting the partner. We compared the predictions associated with such mechanisms with data from common guillemots (Uria...