Birds sing for a variety of reasons, but the most common are:

• To attract mates. Birdsong is a way for males to show off their health, strength, and vitality to potential mates. The more complex and beautiful the song, the more likely it is to attract a mate.
• To defend territory. Birdsong can also be used to defend a territory from other birds. By singing, a bird is telling other birds that this is their territory and to stay away.
• To communicate with other birds. Birdsong can also be used to communicate with other birds, such as to warn them of danger or to let them know where food is located.
• To establish social bonds. Birdsong can also be used to establish social bonds between birds, such as between mates or between parents and their young.
• To relieve stress. Some scientists believe that birdsong can also be a way for birds to relieve stress. By singing, birds may be able to release pent-up energy and tension.

So, while birds may not sing because they are happy, they do sing for a variety of important reasons.

Here are some additional facts about bird song:

• Only about half of all bird species sing.
• The syrinx, a vocal organ located at the base of the trachea, is responsible for bird song.
• The complexity of bird song varies greatly from species to species. Some birds, such as the mockingbird, can mimic the songs of other birds.
• Bird song is often learned, and young birds learn the songs of their parents.