There's Elton John's Crocodile Rock, but that's about it. Not many fish songs, either. There are some songs about insects, but most of them are about trying to get the little bug to leave. My guess is that they are more noticeable than most other animals. Plus, there are more kinds of birds than nearly any other animal.
Birds fly, too.
That kind of goes without saying. You can see them flying in your yard, at your school, across the highway, in the mountains, at the beach, and so on. You are more likely to notice a bird than just about any other animal of similar size. Most similarly sized mammals usually are either hidden away in the grass or are nocturnal and asleep. They don't make themselves as known to us as birds do.