Evidence of song learning among bellbirds is bolstered by data from a captive-reared Bare-throated Bellbird in Brazil.
By December 2000 through February 2002, when this bellbird was at least 6-8 years old, he no longer sang the blackbird whistles or prrrrs, only the Quoks of bellbirds.
The behavioral evidence for song learning among these suboscine bellbirds is extensive.
Second, many young Three-wattled Bellbirds, as well as a few adults, are completely bilingual, singing the entire set of both Monteverde and Talamanca songs.
A fourth line of evidence consistent with song learning is that young male bellbirds "babble," taking 6 years or more to perfect their songs, just as they take 6 years or more to acquire their adult plumage.
Our study extends the field observations of Barbara Snow (1970, 1973, 1977), who first suggested that suboscine bellbirds may learn their songs.
The most parsimonious conclusion is that vocal learning has arisen independently in bellbirds, rather than their having retained this trait from some shared, common ancestor among the song-learning oscines.
The origin of vocal learning in bellbirds is either the third or fourth well-documented, evolutionarily independent origin of vocal learning in birds.
We cannot be sure how vocal learning evolved among Procnias suboscine bellbirds in general, or why Three-wattled Bellbirds continually relearn their songs to track population changes, but we suspect that strong sexual selection has played a role, as suggested by Aoki (1989).
Habitat linkages and the conservation of tropical biodiversity as indicated by seasonal migrations of Three-wattled Bellbirds.
A possible fourth dialect of the Three-wattled Bellbird may occur on the Azuero Peninsula of Panama (Hamilton et al.