Date of this Version
Current Biology 20:21 (November 9, 2010), pp. R931–R933; DOI: 10.1016/j.cub.2010.09.056
High levels of conspecific brood parasitism are found in a communally breeding bird, with implications for the evolutionary links between brood parasitism and communal breeding. It also uncovers a novel egg recognition mechanism hosts use to foil brood parasites.
Avian breeding systems often reflect a mix of cooperation and conflict over allocation of the costs and benefits of parental care [1–4]. This interesting juxtaposition of cooperation and conflict is particularly evident in the communally breeding birds, where two or more females lay eggs in the same nest and typically cooperate to raise the offspring. Beneath the veneer of group cooperation often lurks severe competition among females within the breeding group to maximize their share of reproduction [5, 6]. The resolution to these conflicts results in communal breeding systems that range from nearly egalitarian—in terms of shared costs and benefits—to those that border on parasitism [5, 6]. Conflicts over the costs and benefits of parental care are taken to the extreme in another breeding system in which one female lays eggs in another female’s nest but fails to provide any subsequent parental investment—brood parasitism. Both of these strategies—communal breeding and brood parasitism—are widespread in birds, although usually they do not co-occur in the same species. Common threads between these two breeding systems include multiple females laying eggs in a single nest and the egg tossing behavior used to control whose eggs then remain in the nest [6, 7]. The difference has to do with who pays for the subsequent cost of parental investment: do all females share the cost, or do some cheat on investment? While theory suggests potential evolutionary links between brood parasitism and some forms of communal breeding [1, 8, 9], these ideas have been difficult to test empirically. A recent study in Current Biology by Christina Riehl  adds a new beam to the proposed bridge between parasitism and communal breeding. Riehl demonstrates for the first time high levels of conspecific brood parasitism in an obligate communal breeder and also reveals a novel mechanism that birds use to foil many instances of brood parasitism.