I'd look more at differences in feathering. From what I've seen females tend to feather a bit earlier than males, and when you've got mixed genders of the same breed the difference becomes pretty clear, at least with hatchery birds. Look for differences especially in the tail and back among birds of the same breed and age, kinda hard to see from the last pic you posted.
Comb development can vary a lot from breed standard with hatchery birds, where the focus is having birds that lay a lot and mature to point of lay as quickly as possible. Imho this makes feathering a more reliable indicator of gender differences at this age. That said, our Brahmas are about seven months old and pretty much mature. The pullets have very small combs, and the difference was recognizable early on.
Comb development can vary a lot from breed standard with hatchery birds, where the focus is having birds that lay a lot and mature to point of lay as quickly as possible. Imho this makes feathering a more reliable indicator of gender differences at this age. That said, our Brahmas are about seven months old and pretty much mature. The pullets have very small combs, and the difference was recognizable early on.
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