Females compensate for moult-associated male nest desertion in the Hooded Warbler

Uniparental offspring desertion occurs in a wide variety of avian taxa and usually reflects sexual conflict over parental care. In many species desertion yields immediate reproductive benefits for deserters if they can remate and breed again during the same nesting season; in such cases desertion may be selectively advantageous even if it significantly reduces fitness of the current brood. However, in many other species parents desert late-season offspring when opportunities to renest are absent. In these cases, any reproductive benefits of desertion are delayed, and desertion is unlikely to be advantageous unless the deserted parent can compensate for the loss of its partner and minimize costs to the current brood. We tested this parental compensation hypothesis in Hooded Warblers Setophaga citrina, a species in which males regularly desert late-season nestlings and fledglings during moult. Females from deserted nests effectively doubled their provisioning efforts, and nestlings from deserted nests received just as much food, gained mass at the same rate, and were no more likely to die from either complete nest predation or brood reduction as young from biparental nests. The female provisioning response, however, was significantly related to nestling age; females undercompensated for male desertion when the nestlings were young, but overcompensated as nestlings approached fledging age, probably because of time constraints that brooding imposed on females with young nestlings. Overall, our results indicate that female Hooded Warblers completely compensate for male moult-associated nest desertion, and that deserting males pay no reproductive cost for desertion, at least through the point of fledging. Along with other studies, our findings support the general conclusion that late-season offspring desertion is likely to evolve only when parental compensation by the deserted partner can minimize costs to the current brood.