House Wren (Troglodytes aedon) provisions nestlings of Northern Cardinal (Cardinalis cardinalis)

Cases of interspecific parental care are rare and pose an evolutionary puzzle. We report a male House Wren (Troglodytes aedon) regularly provisioning Northern Cardinal (Cardinalis cardinalis) nestlings in a nest located near his own. The male wren continued to provision the cardinal nestlings after his own nestlings hatched, and provisioned the cardinal nestlings more than his own nestlings during the time that their nestling periods overlapped. The adult cardinals also provisioned their own nestlings. After the cardinal chicks fledged, the male wren provisioned only his own nestlings. This is most likely a case of nonadaptive misdirection of parental behavior on the part of the wren. That the wren provisioned both nests while both were in the nestling stage, but provisioned only the wren chicks as fledglings, may suggest that kin recognition in House Wrens is mutable rather than fixed. However, this behavior is also congruent with observations of polygynous male House Wrens transferring parental care from primary to secondary broods upon the fledging of the primary brood.