Cowbird Eggs

Tonya Smith put this picture in the new private Springfield Plateau photo album.  Even the untrained eye can recognize the egg of an intruder, the notorious cowbird.  It is hard to fight the temptation to remove it to "protect" the brood.  DON'T.

The first reason is usually pointing out that it is illegal under the Migratory Bird Act.  Cowbirds may be thugs but they are our native thugs.  You may say "nobody is looking" but it isn't necessarily true.  Mama cowbird will be watching and you don't want to make her mad.

Some reasons to keep hands off:

• Messing with the nest may lead to the natural parent abandoning the nest and starting over somewhere else.
• While the cowbird chick may out compete the others it may not be fatal.
• The cowbird mama frequently will come back to check and is likely to trash the nest and destroy the other eggs.

There is a very concise article from Audubon which will explain the research.

I have a confession.  I didn't learn to control my contempt for these hoodlums until later in life.  There are several reasons to appreciate the cowbird.  For one, they have a beautiful call, like a soprano gargling champagne.  Also, watching the interaction with the "adoptive parent" can be entertaining.  Linda Bower has this great Youtube video of a phoebe intent on raising the offspring even if it doesn't look quite like it should.

Finally, in this previous blog we counted the diverse insects that the phoebe fed the chick, an appreciation of the maternal instinct overcoming prejudice.

More on Cowbird habits at this Phys.org link.