Bats v. Birds

Penny and I have had an interesting discussion the last few days. She didn't do it tonight, but the last three nights and yesterday morning almost as soon as she woke up she started up with, "Birds? Birds? Bats? Birds?" We were reading a sesame street counting book in which the nine page features the Count and nine bats and the facing page features Cookie Monster with ten cookies and ten pigeons on a park bench. She pointed to the pigeons and correctly identified them as birds. Then she pointed to the bats and also said, "birds." I said, "no baby, those are bats," and an epic discussion was born. She is totally confused. I have tried explaining it to her a hundred different ways, but really, "Bats are mammals, and birds are, well, birds" doesn't go over well. "Bats have live young and birds lay eggs?" "Bats have fur and birds have feathers?" Um, yeah. We've tried showing her pictures online, to no avail. Given that she just won't let it go, I dug into my keepsake box and pulled out the stuffed bat (it's a Ty beanie baby) that I used to hang from my rearview mirror in my goth-ironic days. I'm not sure if it settled the issue. I got her to call it a bat, but after I walked back into the kitchen I heard her softly call it a bird.