The extra wider white splashing on head and back of neck on Dom male chicks is a good indication it is a male but once in a great while a female has extra white splashing so also using the dark leg/toes method usually confirms female.
Although male and female chicks have dark spots on their top beak, a female's strip/tip will be clearer marked and not scattered. I always id'd my female chicks by all 3 features -- smaller tighter white head spot, darker beak strip, and the confirming feature was dark front legs/toe tops. This always worked for true Doms -- have no idea how this method would work on mixed Dom breeds. And as always a breeder will say there ARE exceptions to every accepted rule,
You probably had an easy job of id'ing Dom males as "lighter" because from above males' white splashing is so wide they just look lighter from the females cuz females have tighter much smaller white skull spot making them look darker than male chicks.
My female Dom chicks barely had a clear white spot but I also used the beaks and legs/toes to add to my final id. Just more white coloring is not enough to make positive id -- might be a good guess but not true confirmation and most breeders need to know up front how many males/females they have at hatch by using all 3 features. A lot of hatcheries just vent sex to be positive -- but not a method that can be used on delicate tiny bantam breeds.
BTW how did Doms work for you? Ours were about 5-1/2 lbs hens with small/med eggs and not every-day egg-laying. We didn't need lots of eggs for two of us, we don't use our birds for meat, plus we wanted friendly non-combative hens and Doms fit our need. Besides Blue Breda, Doms are people-friendly, love to chitter-chatter and talk back and forth with us, good flock temperament, have a lot of energy, and our remaining old Dom thinks she's a lap dog. Because she's older she's not in perfect coloration any more but we love her.
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