In 37 % of all nests of Pale-headed Brush-Finches the young, usually all of them, are infested with botfly larvae, sometimes heavily so. Infested young appear to grow and fledge normally, without noticeable delay.

Botfly parasitism has not stopped the Pale-headed Brush-Finch population from increasing markedly after cowbird control began.


Photo by Mery Juiña




Photo by Martin Schaefer