I don't think that bird is saying what you think he is!
I saw a play this weekend and one of the characters had a line saying something like, "Birds don't sing for practice; they sing because they are happy or sad." I wondered, "Really?"
According to Highlights magazine, bird sing to communicate different messages to each other. Usually the male is chirper, and he can sing to:
- claim property.
- attract a mate of the same kind.
- warn other birds to stay away from his family.
Birds only seem to sing to others of their own breed, because that is their only real competition. A sparrow, for example, won't try to steal the mate of a cardinal.
Sometimes birds can also use their singing to identify themselves:
Two scientists who studied white-throated sparrows found that these birds can even tell the difference between songs of individual birds of their own kind. White-throated sparrows have songs that seem to say “I’m your neighbor” or “I’m a stranger” or “I’m your neighbor to the west.” Other kinds of birds could tell neighbors from strangers by their songs, too.
So, there you go. They communicate a lot, but it doesn't seem like "happiness" or "sadness" is their motivation. But I guess the line in the play would have had a much different emotional impact if it read, "Birds don't sing for practice; they sing to claim territory or attract a mate!" :)