For 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.”
Christine Portfors, a neurologist, tends a lair of 23 tropical moustache bats at WSU Vancouver in order to tease apart the question of how they distinguish between sounds-for example, between those they use for echolocation and those they use to communicate.
Bat communication sounds, like speech sounds, are very complex in terms of frequency and timing, says Portfors. Beyond that, “We don’t know anything about how the brain actually processes those types of sounds.”
Earlier work by Portfors revealed that bats have neurons that are very sensitive to the timing of the echolocation sound, between when they emit it and when the echo comes back. … » More …