Thank you for the help! I just noticed that the easter egger pic had the tail feathers down. They're usually upright. Does that make any difference? Oh, I hope you both are right and is our neighbor's bird.
Unfortunately (because of our dang city ordinances), we heard crowing, but we're not sure which chick it was, or even (fingers crossed) if it was the neighbor next door's, who also has chicks. Since we're going out of town for the next couple weeks, we kind of need to rehome ASAP if one of these...