Open-ended song learning in a hummingbird

Vocal learning in birds is typically restricted to a sensitive period early in life, with the few exceptions to this rule reported in songbirds and parrots. Here we present evidence of open-ended vocal learning in a hummingbird, the third avian group with vocal learning. We studied vocalizations at four display leks of the long-billed hermit Phaethornis longirostris during a four-year period. Individuals produce a single song repertoire, although several song-types can coexist at a single lek. We found that nine of 49 birds recorded on multiple days (18%) changed their song-type between consecutive recordings. Three of these birds replaced song-types twice. Moreover, the earliest estimated age when song replacement occurred ranged from 186 to 547 days (mean= 307 days) and all nine birds who replaced song-types produced a crystallized song before replacement. The findings indicate that song-type replacement is distinct from an initial early learning sensitive period. As half of lekking m...