Q: How do you sex young birds? And, is there an instrument that can be puchased to do that with?
I assume the instrument you are speaking about is the one advertised in the magazines. I think we can easily save you $10.00. Get yourself 10 inches of fishline and attach a lead shot sinker to it. You now have the sexing instrument that is advertised for probably the price of a nickel. But I must warn you, this instrument is strictly reserved for the naive. It is also supposed to sex birds before they even hatch.
To actually sex youngsters, there is a procedure that is used in the chicken industry (before the chicks get feathers on them) where the curvature of the shape of the rectum is considered and also where the top overlaps the bottom. But this is not that easily learned and therefore not accurate unless you really do a lot of them.
Older youngsters are sexed by sight and of course their actions. There are people who also like to sex them by the length of their toes, but again, a little more "voodoo". The ultimate test for sexing them is when a hen lays an egg.