A tropical hummingbird sings a rapid, oscillating tune that resembles a cricket’s more than a bird’s — and is too high-pitched for other birds to hear.
The song of the black jacobin (Florisuga fusca), which lives in the Atlantic Forest of Brazil, can be heard by humans. But the song reaches a pitch higher than the known hearing range of any other species of bird, and it’s unclear whether black jacobins themselves can hear each other’s songs. Perhaps the birds have exceptional hearing, or maybe their vocalizations aren’t meant to be heard at all, say Claudio Mello of the Oregon Health and Science University in Portland and his colleagues, who recorded the birds’ song.
The black jacobin shares its forested habitat with up to 40 other hummingbird species and subspecies. The researchers speculate that the jacobins evolved high-frequency communication and hearing to identify each other amid the avian hubbub.