Observations on the range and nesting biology of the Mexican endemic rufous-capped brush-finch (Atlapetes Pileatus Pileatus)

The Rufous-capped Brush-finch (Atlapetes pileatus) is a species endemic to Mexico, whose breeding biology has received little attention. We studied two nests of the nominate subspecies from the mountains of southern Sonora. Nests were untidy, broad, open cups, placed in low, thick vegetation. Clutch size at one nest consisted of three immaculate white eggs. The second nest contained two Brush-finch nestlings and one cowbird (Molothrus sp.) nestling. Both parents brought food to the nestlings, but delivered significantly more food to the cowbird nestling. Most of our observations of nest architecture, egg coloration, and adult behaviors are consistent with previous descriptions for Rufous-capped Brush-finch and other members of the genus Atlapetes. This is the first report of cowbird brood-parasitism on the Rufous-capped Brush-finch, as well as the first confirmed record of breeding by this species in Sonora.