Some birds live only in certain areas of the world, but the most successful birds are found almost everywhere.
Settlers introduced the starling and the sparrow into most countries. Like rats, these birds are so adaptable that they have increased in enormous numbers. The most common bird of all was the passenger pigeon, which lived in North America in such huge flocks that they darkened the skies for days during their migrations. These birds were hunted nearly to extinction during the 1800s, and the last one died in a zoo in 1914.
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