Brown-headed Cowbirds’ unconventional parenting tactics
How would you feel if you were forced to babysit someone else’s child forever? This is something that song birds from all over have to deal with. Cowbirds (referred to as brood parasites) routinely lay 30-80 eggs each season in other birds’ nests and expect those birds to raise that egg along with their own young.
This tactic allows cowbirds to solely focus on depositing eggs in other nests and to avoid the hassles that come with raising their own chicks.
For some reason, warblers are known to accept these foreign eggs into their nests without issue.
Why do warblers put up with this? It turns out there is something in it for them too. Studies were done by the National Academy of Sciences, that showed warblers couples who tolerated the extra egg would have four times as many successful chicks as those that didn’t. The reason for this is if the warbler destroys the invading egg, or tosses it out of the nest, the cowbirds will return raining terror by crushing warbler eggs, pushing them to the ground—basically destroying their nest. Accepting the extra egg and raising their chicks (plus one oddball) sounds like a great deal to the alternative.
These intimidation tactics of ‘take care of our eggs or we’ll take care of yours’ are a bit brutal, but, hey, it’s a wild, wild, bird world out there.