The light brown ones are females & for the black ones, catch them, get someong to hold him so his belly is facing you & start moving feathers.. push with fingers on each size of the hole (sorry forget the proper term).. if a squiggly thing pops out (it reminded me of angel hair pasta), its a boy.. the longer the squiggly thing is, the older it is.. it shouldn't be longet then 1 cm as the adults I saw were a couple years old & they were 1 cm.

Yay, for Scouts & Ducks Unlimited