Sydney Acres
Songster
That is unusual. All my Sandhill Reds were very distinctive by the time they were 4 months old, and all but one were obvious by 2-3 months. There are several things you can look for apart from comb size and behavior.
Body mass -- the males will be "sturdier." Not only should they weigh more, but their legs will be thicker (legs like tree trunks is the quote I remember), their toes will be longer, they will have a larger spur bud, the legs will be further apart because the chest will be wider, the base of the comb will be wider as a foundation for the future huge structure that it will have to hold up, the skull will be wider, etc.
Males have different specialty feathers than females. Look closely at the saddle feathers and hackle feathers. The tips will be more rounded on the females and will "stay still" when running. The tips on the males will be more pointy and have a flowy/shimmery movement when the bird is running. Also, the tail feathers are quite different. The females have just plain tail feathers that they tend to hold in a point (instead of a fan or an arch). The males have the plain tail feathers, but tend to hold them more in an arch. Additionally, they have two sets of sickle feathers that arch over the shorter tail feathers. The first set, if it were to be stretched out straight, is only about 1 1/2 - 2 times the length of the tail itself, and is likely the only ones that 8 month olds would have. As they get older, the males develop a few relatively long sickles that are 3-4 times the length of the tail. The feathers around the head and face are different also. The tiny feathers right beside the comb on the male tend to stick straight up, whereas on the female these feathers lay flat, giving the head a smoother and more feminine appearance.
In the colored dorking, there should be an obvious color difference between the males and females. There are lots of specifics, but basically the female is mostly black/dark brown with beautiful straw shafting to many feathers, especially the hackles, whereas the male has straw colored hackles and parts of the wing and saddle feathers (and probably others -- I don't have colored dorkings so don't know all the specifics). But the colored dorkings are very hard (some say impossible) to breed the proper colors for both genders in the same breeding line, so your specific birds may not show the colors prescribed by the SOP. There are some wonderful pictures of colored dorkings in this thread, as well as the Dorking Breeder's Club web site.
The fact that no one is breeding and no one is crowing would make me suspect that you have all females, and three of them just don't want to lay this time of year. Even though dorkings are famous for being winter layers (my May 2012 pullets started in October/November 2012), laying this time of year is quite contrary to normal chicken physiology. They are regulated by photoperiod, which is the number of hours they are exposed to daylight. When the days start getting shorter (in August, right when yours were 6 months old and should be entering their point of lay), most chickens turn off their hormonal cascade that allows egg production. Then when the days start getting longer (late January/early February), they start up again. So it's not at all temperature dependant, it's light dependent. And for breeds that break the rules, like Dorkings, it's not consistant. My 2012 pullets that started laying in October 2012 layed all through the winter, then stopped in July/August 2013. They've not restarted, but based on the rooster's behavior I suspect they'll start again within another month (he stopped chasing the girls and became VERY sweet to me when they stopped laying-- this week he started the rooster dance again and is very suspicious of me whenever I'm holding one of his hens).
If any of your three undetermined chicks are males, their lack of breeding/crowing/(and I assume fighting) behavior is quite unusual. There's nothing like the sex drive and bravado of a teenage boy, regardless of the species!!
Please post pictures, ideally from multiple angles. An experienced breeder may be able to tell you which gender they are.
--April
