Cave birds - Fascinating Oilbirds live in caves, forage at night, find food by smell, and navigate by sonar

摘要

Many large South American caves thatare eerily quiet by day grow increasinglynoisy at dusk, and then, as the skiesdarken, become quiet'again as residentnocturnal phantoms fly out. Not bats, these phantoms, but birds --thousands of crow-size Oilbirds venturing out for food. Their evening exodusesfrom the mouths of caves are some of theworld's greatest ornithological spectacles.