Identifying roosters at 2-4 weeks.

[Dogfish]

Can someone let me know what a foolprrof way is to ID roosters at the age of 2-4 weeks? I've got 13 chicks from my Austrolorp rooster covering a RIR, a BA, and a BR. I have already marked the ones with almost no tail feathers, someone said that was one sign. Any idea when they might start crowing?

Thanks in advance

 

[gritsar]

By the time some roosters start crowing, you'll already be getting fertile eggs from them. Some roos just don't feel the need to announce their presence, especially if there's a dominant rooster around.

Four to Six weeks is about the earliest you can tell with most breeds, by the secondary sex characteristics showing up:

According to UC Davis Veterinary Care Program.
2. Physical Characteristics (4-6 weeks of age)
a. Comb – The cockerels comb is medium size and pinkish, the pullets is small and yellowish.
b. Legs – The cockerel’s legs are sturdy and long, the pullets are finer and shorter.
c. Tail – The cockerel’s tail is stumpy and curved, the pullets is longer and straight.
d. Back – The cockerel has a thin line of stub feathers down the center of his back, the pullet has more advanced feathering along the center of her back.
e. Side of neck, flank and crop – The feathering in the cockerel in these areas is poorly advanced, the pullets feathering in these areas is well advanced.
f. Wing bows – In the cockerel the wing bows are bare, in pullets the wing bows are covered with small feathers.