The cowbird is so named because it tends to live near herds at the edge of agricultural areas, but we had three shiny males in the back yard. The males go ahead to "case the joint" and females come along later to lay their eggs in other birds's nests! In this case, probably the cardinals' nest. I saw a brown female a day after the visit from the males...
The fate of these eggs varies. Some birds raise them, some recognize and toss them out, some build a new nest over the old. Yes, I've been working on a poem about this!
You can learn more about the cowbird and hear the song at the link above, and learn all about birds at All About Birds, the Cornell Lab of Ornithology. Another fun place to listen to bird calls is Birdjam, where you can even get an app for your phone. Great bird pix at both places.
her portfolio at Woman Made Gallery, or via the website and art studio she shares with her painter husband, Otter Creek Arts. You can see from the photos of their environment that they must hear plenty of birdsong all the time!