Interspecific parental care by a rufous⇂collared sparrow (zonotrichia capensis) at a nest of the pale⇂breasted thrush (turdus leuco-melas) parasitized by a cowbird (molothrus bonariensis)

Abstract

Interspecific parental care (IPC) in birds, when one individual helps to rear the offspring of another species, is rare outside the context of brood parasitism. Reports of IPC addressed to non‐brood‐parasitic bird species are mostly anecdotal, and in some cases have been explained as a non‐adaptive response to the begging calls of interspecific nestlings in the vicinity of the helper's own nest. Here, we report a case study of a Rufous‐collared Sparrow (Zonotrichia capensis) feeding three nestlings in a Pale‐breasted Thrush (Turdus leucomelas) nest, including one Shiny Cowbird (Molothrus bonariensis) nestling. The combined feeding rate of the nest owners was not significantly different from that of the helper, which fed all nestlings and removed their fecal sacs. To our knowledge, this is the first IPC case reported for South America, and we hypothesize that parasite begging sounds are one of the proximate causes of this behavior.