
Why do birds make so many different sounds? A study gets at the underlying factors
Birds make sounds to communicate, whether to find a potential mate, ward off predators, or just sing for pleasure.
I agree. I also have that App. It’s terrific. In my backyard the App identified 33 species by either song or camera shot or both.My wife and I do quite a bit of birding though at the amateur level. A couple of years back we encountered an app called "Merlin" from Cornell University, https://merlin.allaboutbirds.org/. With the app you can record and id birds using their song, and you can visualize the song using the sonograms it generates. I believe a number of birds sing for the sheer pleasure of it, much like some birds like to play in the wind.