Double-scratching by Yellow-headed Blackbirds

Abstract

Some ground-foraging birds, including most New World sparrows in the tribe Emberizini, uncover food items in litter by double-scratching, a backward hop that displaces the litter posteriorly. I report double-scratching by Yellow-headed Blackbirds (Xanthocephalus xanthocephalus), a species not previously known to exhibit this behavior. Double-scratching by one individual that was observed in detail occurred with the bill pointed downward with its tip near or touching the ground, as in other icterines but unlike the behavior in Emberizini. This individual, between double-scratches, also used bill-sweeping to displace litter. Double-scratching has a similar form in at least three of the four icterine species reported to show the behavior, suggesting the trait is homologous among these species. However, phylogenetic relationships imply that double-scratching evolved convergently in these taxa.