Perhaps the best known bird extinction is the passenger pigeon, a North American species. It may once have been the commonest bird that has ever lived on earth. There was a population of an estimated two billion birds in colonial days, when huge overflying flocks would darkened the sky. But even these phenomenal numbers could not guarantee the bird's existence. European colonists cut down the beech forests that provided food for the pigeons, and slaughtered the birds for food.
Birds living on small islands are highly vulnerable to extinction.
Many have become flightless in the absence of natural predators, and when man arrived, with rats, cats and other animals, the birds stand little chance. The wrybill has a unique curved beak The dodo is the tragic symbol of bird extermination. This large, flightless, turkey-sized pigeon lived on the tropical island of Mauritius. A fruit-eater, it had little reason to move fast or fly. It was easy prey for man the hunter.