Birdwatching or birding means going outside to enjoy watching birds. It is a popular hobby. Someone who does this may be called a birdwatcher, but more often a twitcher or birder. They are usually amateurs. The scientific study of birds is called ornithology. People who study birds as a profession are called ornithologists.
Birdwatching is very popular in countries such as Britain and the United States. It can be especially rewarding in spring when a lot of birds are singing and building nests to raise their young. In spring and autumn many birds can be seen as they migrate. In winter some other kinds of birds may be visiting from colder areas such as the Arctic where there is no food in the winter.