Kaylee about to emulate a Wood Duckling :)

[Kaylee]

I actually like the cowbirds but I also liked the tiny bird that built the cute nest on the edge of my field... I had never seen that bird before so out went the cowbird eggs. I have plenty of cowbirds.

What did the "tiny bird" look like?
I'm not an expert, but have ID books and passion, so would be happy to try to help you (in particular!) ID 'em.

"MN C Van": I'm pretty sure it is legal to remove cowbird eggs. They're not endangered, or in any way threatened. There's considerable discussion among birders about how much damage they do to genuinely threatened species.
It could be a local law wherever you were.
I'm glad you're on the side of the victim species.