Well, just like kids in school, sometimes the bold, obnoxious ones are the funniest. I watched a small flock of juvenile cowbirds at my deck fountain one day. They totally trashed it but they were so funny it was worth it. Also if you get a bunch calling in a tree, it sounds like a burbling brook.

CJ, Defender of Cowbirds

This time of year all the Cowbird babies are on their own. Taking down feeders wont help. They will be leaving soon and will be back next spring. The only way to keep them from taking over is to monitor your nests for their eggs and ...well not let them hatch in so may words. Its also ileagle but I didnt find any bird police at my door this year.

Thank you, you both were very helpful. I will try not to panic the next time I (think) I see a cowbird in my yard!

Cowbirds love millet. Try to not use any, or very little, in your feeders during the spring and summer. Winter, when they are gone, its fine to use millet for the juncos and tree sparrows. But come spring keep it out of your feeding selection.

Our poor little Song Sparrow valiantly fed one of those greedy monsters this summer. Now grown, it recently tried tried to raid my BOSS feeder, so I took the feeder down for a few days.

cowbirds are the only ones i know that lay their eggs in other birds nests. I get lots of red wing blackbirds here in spring thru summer. There are often juvenille cowbirds with the adult red wings. The cowbirds are bossy and pushy with other birds and take over the feeders. Lucky that the young are on their own soon after they can fly on their own and they leave out before the redwings. I put a couple of platform feeders out in a tree away from the other feeders and the blackbirds and cow birds and starlings seem to stay at the platform feeders mainly.

Maybe you should get one of those electric bird feeders like birdguy has.