The ability of birds to fly and their warm-blooded metabolism has allowed them to colonize and take good advantage of a large variety of habitats. Only parts of the open ocean and the center of Antarctica are typically devoid of birds. There are about 10,000 species of birds in the world and different parts of the world have their own unique set of bird species; this unique assemblage is termed the avifauna of the areas.
The countries with the most diverse avifauna are Colombia with 1,821 bird species, Peru with 1,781, Brazil with 1,712, Indonesia with 1,604, and Ecuador with 1,515. You can get the full list here, but notice that rainforest countries have the greatest variety of bird species. Accordin gto some, though, the most popular countries for bird watching are the Galapagos, Costa Rica, Tanzania, and Botswana.
The IOC World Bird List lists the official English names for every bird in the world and is an extremely handy reference.
Indonesia / Malayasia
South America / Caribbean
Fatbirder – links to birders all over the world
International Ornithological Congress Bird Checklist
Sibley-Monroe Checklist of the Bird World
Web-Published Checklists of the Bird World
World Bird Database – Avibase