The Brown-headed Cowbird is the Northeastern United States version of bad parenting. All they do is eat and lay their eggs in the nests of other birds. They are very effective though. Usually, the other birds are smaller. When their babies hatch, they are raised by the unsuspecting little “foster parents“.
It would all be “Hunky Dorey” if not for one important fact. Cowbird eggs hatch sooner and the babies are bigger than the “host’s” bird babies. The Cowbird babies eat more of the available food and often just push their “foster brothers” out of the nest to their death.
Some small birds, like the Eastern Phoebes, are dwindling in numbers because of those lazy cowbirds!
One good thing is that the Phoebes have more than one nesting per season to make-up for the first disaster. I’ve yet to find cowbird eggs in a second nest. Doesn’t mean that Cowbirds won’t lay in the same nest again…I just haven’t witnessed it.