Birdwatching or birding means going outside to enjoy watching birds. It is a popular hobby. Someone who does this is called a birdwatcher or birder. These two words mean the same thing, but people who spend a lot of their time watching birds, taking their hobby seriously, are more likely to call themselves “birders”, while “birdwatchers” may just be people who like watching birds when they happen to go for a walk. Both birdwatchers and birders are usually amateurs. The scientific study of birds is called ornithology. People who study birds as a profession are called ornithologists.