Mid-May is like rush hour in the bird world. Migrants have returned for the nesting season and the air is full of birdsong. As you might guess, birdsong is as varied as birds themselves. In fact, birdsong is defined generously to include any and all sounds they make with territorial or courtship intentions. Let's start with a traditional vocalization and then branch out.  

One of the most common and widespread backyard songsters is well named: The song sparrow. The male starts early and will sing all day especially if he hasn't been successful in attracting a mate. One male studied sang from dawn to dusk; fifteen hours! Two-thousand three-hundred and five songs performed in the day. Here's that song, recognized by a few repeated introductory notes followed by quite a mix.