It’s Sunday, which means we get another batch of themed bird photos from John Avise. John’s narrative and IDs are indented, and you can click on the photos to enlarge them.
Brood Parasitism (also known as “egg dumping”)
This is a phenomenon in which a female lays one or more of her eggs in the nest of another bird, leaving the duties of incubation and hatchling rearing to the duped foster parents. Brood parasitism can be intraspecific (when the brood parasite and the host belong to the same species) or interspecific (when the brood parasite and the host belong to different species). Brood parasitism may also be facultative (when the brood parasite dumps her eggs only occasionally) or obligatory (when the brood parasite always employs this lifestyle). Here in Southern California we have two obligate interspecific brood parasites: the Pin-tailed Whydah (Vidua macroura) and the Brown-headed Cowbird (Molothrus ater), neither of which apparently ever rear their own young.
The Whydah is native to sub-Saharan Africa where it uses Estrildid finches as its parasitized hosts. In Southern California, the introduced Whydah uses another introduced species, the Scaly-breasted Munia (Lonchura punctulata) as its primary host. This Munia is an Estrildid finch that was introduced to California from its native home in Southeast Asia.
The Brown-headed Cowbird is native to North America where it parasitizes a wide range of native host species, sometimes so severely that it can seriously impair normal reproduction by its host. Indeed, brood parasitism by the cowbird can be so detrimental to the nesting success of other native species (including some endangered ones) that wildlife managers here in Orange County sometimes set out special traps to try to capture and eradicate the nest-parasitic cowbirds.
This week’s post shows these two obligate brood parasites and some of their commonly employed host species. All photos were taken in Southern California.
Pin-tailed Whydah adult male:
Pin-tailed Whydah female:
Pin-tailed Whydah juvenile:
Scaly-breasted Munia adult:
Another Scaly-breasted Munia:
Scaly-breasted Munia juvenile:
Brown-headed Cowbird male:
Brown-headed Cowbird female:
Brown-headed Cowbird juvenile:
Common Yellowthroat (Geothlypis trichas) male (this species is a commonly parasitized host for the Brown-headed Cowbird):
Common Yellowthroat female:
Bell’s Vireo (Vireo bellii) (this endangered species is another commonly parasitized host for the Brown-headed Cowbird):
Another Bell’s Vireo: