Behavioral evidence for song learning in the suboscine bellbirds (Procnias spp., Cotingidae)
The Wilson Journal of Ornithology 125 (1):1–14.
Why vocal learning has evolved in songbirds, parrots, and hummingbirds but not in other avian groups remains an unanswered question. The difficulty in providing an answer stems not only from the challenge of reconstructing the conditions that favored vocal learning among ancestors of these groups but also from our incomplete knowledge of extant birds. Here we provide multiple lines of evidence for a previously undocumented, evolutionarily independent origin of vocal learning among the suboscine passerines. Working with bellbirds (Procnias spp.), we show that (1) a captive-reared Bare-throated Bellbird (P. nudicollis) deprived of conspecific song not only developed abnormal conspecific songs but also learned the calls of a Chopi Blackbird (Gnorimopsar chopi) near which it was housed; (2) songs of Three-wattled Bellbirds (P. tricarunculata) occur in three geographically distinct dialects (from north to south: Nicaragua, Monteverde, and Talamanca); (3) Three-wattled Bellbirds at Monteverde, Costa Rica, are often bilingual, having learned the complete song repertoire of both the Monteverde and Talamanca dialects; (4) immature bellbirds have an extended period of song development, lasting the 6 years in which they are in subadult plumage; and (5) adult male Three-wattled Bellbirds continually relearn their songs, visiting each others’ song perches and adjusting their songs to track population-wide changes. Perhaps female preferences and strong sexual selection have favored vocal learning among bellbirds, and additional surveys for vocal learning among other lekking cotingas and other suboscines may reveal patterns that help determine the conditions that promote the evolution of vocal learning.