Back when I was a park ranger I learned about Brown-Headed Cowbirds and how they lay their eggs in the nests of other species of birds. These eggs hatch and then beat out the other chicks for food. There used to be cages in the park specifically made to catch the Cowbirds in order to keep them from lowering the population of other bird species. They're actually considered a parasite. I always thought it was sad to see these birds trapped in cages.
A few years later on the other side of the Country, there's a Brown-Headed Cowbird chick who is being raised by a little Chirping Sparrow right outside my apartment. It's the weirdest thing to watch because the Chirping Sparrow is half the size of the Cowbird but it rushes back and forth from the bird feeder the the chick in order to satisfy it's never ending appetite. The Chirping Sparrow can almost fit it's whole head inside the Cowbird's mouth. I've decided not to interfere more than I already have by providing the birdseed and just observe the live example of Darwinism.
