The frequency of conspecific brood parasitism and the pattern of laying determinancy in Yellow-headed Blackbirds

Article Abstract:

A field study was conducted to determine the incidence of conspecific brood parasitism (CBP) in the Yellow-headed Blackbird (Xanthocephalus xanthocephalus). Sixty-nine blackbird nests in British Columbia, Canada, were monitored for 522 days to calculate the frequency of CBP. The appearance of new eggs in nests both during and after the laying period of the host was documented and no cases of CBP were found. The study also showed that the bird was a determinate layer and an explanation for the absence of CBP was that parasitism would decrease the clutch size of the parasitic female.

Behavior, Birds, Bird breeding, Bird populations, British Columbia, Eggs, Parasitic birds, Eggs (Biology), Incubation, Fringillids, Fringillidae

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Unusual parasitism by the Bronzed Cowbird

Article Abstract:

Brood parasitism by the Bronzed Cowbird is studied. The rejector species like Couch's Kingbird can be parasitized and they can even suffer reduced reproductive success. They have developed anti-parasite strategies like egg discrimination and ejection due to strong selective pressure but the fact that Bronzed Cowbirds can develop in Couch's Kingbirds' nests suggest that they would have been used as a more common host in the past. The Bronzed Cowbird is a generalist brood parasite. Four unusual incidents of brood parasitism by the Bronzed Cowbird in south Texas are reported.

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Courtship displaying and intrasexual competition in the Bronzed Cowbird

Article Abstract:

Courtship behavior in Bronzed Cowbirds is analyzed applying behavioral observations. The sexual selection in Bronzed Cowbirds is regulated by potential reproductive rates (PRRs). The female reproductive rate is perhaps lower than that of males, though they have comparatively high PRRs because of their extraordinary fecundity. The females are thus choosy and they show little competition for access to males. Courtship behavior in Bronzed Cowbirds is analyzed applying behavioral observations.

Courtship of animals, Mating behavior

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