need to be able to pick a BR roo

[ol scratch]

So I got 4 BR chick's at Atwoods. Thought 1 was roo. Now I'm pretty sure that Jimmy is a she. So this Friday I'm going back to try to pick out a BR roo. What do I need to look for. These chick's will be 1 to 1.5 weeks old. Any and all advice will be greatly appreciated.