Explore the vast range of titles available.

Brood parasitism can decrease the reproductive success of host species and contribute to population declines, especially in small populations with naturally low fecundity. The ability of host species to recognize foreign eggs varies, as do the behavioral responses of hosts to brood parasitism. We experimentally tested the ability of a putative host, the White-breasted Thrasher (Ramphocinclus brachyurus), to recognize and reject the eggs of a recently established generalist brood parasite. The White-breasted Thrasher is an endangered songbird restricted to 2 small Caribbean islands that are not known to ever have supported obligate brood parasites. We experimentally parasitized active nests within the stronghold of the species' distribution in Saint Lucia and found that White-breasted Thrashers rejected 83% of mimetic Shiny Cowbird (Molothrus bonariensis) eggs (i.e., wooden eggs painted to look like Shiny Cowbird eggs) within 5 d of being parasitized. Rejection of mimetic eggs was not associated with nest initiation date, distance to habitat edge or agricultural area, nest-attempt number, or presence of helpers or dependent young. We conclude that White-breasted Thrashers can detect foreign eggs and possess behavioral adaptations to counter brood parasitism, and propose that these anti-parasitism traits are likely retained from ancestors that evolved in the presence of brood parasites. Our results suggest that brood parasitism by Shiny Cowbirds is unlikely to become a major threat to the White-breasted Thrasher in Saint Lucia. However, ongoing anthropogenic land alteration is likely to increase contact between the 2 species, warranting continued monitoring of their nascent relationship.

The mass and body condition of pied flycatchers aged 13 days were analyzed in relation to nest quality of the natal nestbox and abundance of ectoparasitic mites to determine whether conditions experienced during growth have differential effects depending on sex. A higher fledgling mass was significantly related to a higher average mass at the adult stage in both sexes. Apparently, male and female fledglings did not differ in mean mass or condition but this was due to significant interactions between fledgling sex and environmental factors which affected the expression of both traits. Male fledglings were heavier and in better condition than females in nestboxes of low quality and also when the nest had a high abundance of mites. Sex-related effects of stressful environments on fledgling mass and condition were opposite to those previously reported for tarsus length in the same population. Differences in the susceptibility of traits to environmental stress are discussed. They might be due to differential growth allocation depending on sex, to selection pressures differing between the sexes, to compensatory gains in mass by males after tarsus growth has been almost completed, or because males have a greater competitive ability, especially under stressful conditions promoting sibling competition.