It's as if humans had developed a hundred thousand different versions of the knife and fork. The Gouldian Finch High in the New Zealand Alps lives a bird that finds food with a unique beak. In shallow, gravelly streams the wrybill probes for larvae under heavy boulders it couldn't hope to shift. Today the main threat posed to birds comes from man, his destructive tendencies and his manipulation of the environment. The life of birds has changed enormously since man spread widely around the planet, and began to develop and despoil it.
Man is the primary force threatening the natural world.
Habitat destruction, hunting, introduction of alien species and pollution combine to threaten almost 1000 species of birds world-wide. 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.