Since then, Indian white-backed vulture numbers have plummeted from 30 or 40 million birds to just thousands. This massive decline has left scientists scratching their heads about how many vultures are left in central and south Asia and other parts of the world. Because vultures move around a lot, it's been hard to keep track of individuals. There's never been an accurate total population count — anywhere. That's where Katzner and the National Aviary come in.
Source: tatoeba (12153228)