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Blue and black cockeral. See the hackles are pointy in the neck are?
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Chicks in brooders will flush out feather faster. The conditions are warmer. With mom, they run around more, burn more calories therefore are smaller early on. However, they learn how to be a chicken earlier and may be smarter and more alert as adults.
I don't think that yours is more developed. Only that yours has a more developed comb, lol. My stock comes from a breeder who focuses on SOP of the breed so in general I inherited chickens that will have smaller pea combs. Not everyone works on the comb size. For Ameraucana, the smaller the better - especially in males.