Black Jacobin hummingbirdFor decades, scientists have been intrigued by a black hummingbird that appears to be singing, its throat and jaw moving in all earnestness, but without making any obvious sound. Augusto Ruschi, a naturalist who catalogued dozens of hummingbirds in Brazil’s Atlantic Forest, first noticed it in 1959.

The bird, called a black Jacobin, appeared to have portions of its song that were ultrasonic, “inaudible to humans,” said Ruschi, “and while one would only perceive it with special equipment, one can notice the moment in which the bird emits it, as its guttural region makes characteristic movements, commonly observed when a bird sings.” » More …