In judging the overall intelligence of animals, scientists may look at how successful they are at surviving and reproducing in many different environments. By this measure, birds trump nearly all vertebrates, including fish, amphibians, reptiles, and mammals. They are the one form of wildlife visible nearly everywhere. They live in every part of the globe, from the equator to the poles, from the lowest deserts to the highest peaks, in virtually every habitat, on land, sea, and in bodies of freshwater. In biological terms, they have a very big ecological niche.
