Birdwatchers often travel great distances chasing a fleeting glimpse of a species teetering on the edge of existence. Some birds are found in remote mountain forests or on islands where they have become so scarce that they are like a natural lottery. These species have been driven into hiding by habitat loss, predators and decades of decline. This guide examines some of the rarest birds of various regions and why it is considered to have a stroke of luck when you see these rare birds.