Well, you could always apply the filter theory to this. (And I actually think they do.)

Even weirder as Della canonicaly laid eggs rather than give birth.

You're right, I had completly forgotten that. Well, I believe the TV Tropes entry for the show explains. "It seems that in this setting "human" is just a synonym for Funny Animal."

Technically she’s talking about Gyro, who I believe is a chicken.

I know! That didn't make any FREAKING sense!