This was fun! The top two are similar to a Dark-eyed Junco. I am in Nebraska, US, middle of the country, and they spend winters here. They head back to Canada in the spring. The bottom two are just imagination, although the red one is similar to a male Cardinal which I've been drawing quite a few of lately. It was really fun seeing your reference picture for a Robin since our Robins look different. I'm including a photo of one that has been in my backyard even though I didn't draw him.