Hen's tails, in most breeds, stick up, like that one. Roo's tails droop, forming the sickle feathers. Also, you ca look at the neck, cape, and saddle feathers. Those are right where it sounds like they'd be. Roo feathers have pointy tips, the girls' feathers have rounded tips. Sometimes very young pullets feathers are hard to tell, they may appear a little pointy until they get about 3-4 months old. But they won't get droopy sickle shaped tail feathers.
Check out this website,
http://www.feathersite.com/Poultry/CGP/Sex-links/BRKSexLink.html they have great photos of a lot of breeds. They caption all photos, identifying the sex of the birds. That way you can study the wattles and feathers of both sexes at different ages, and become more familiar with what to look for.
BTW,
are those sex-links? If they are, the roos are a completely different color. That's why they do sex-link breeding, so you can color-sex the chicks right away. The page I linked is sex-links, there's a link to click, "The Making of Sex-Links", as well, on that page. At the bottom of the page you can click to go back to the poultry page. From there you can access dozens and dozens of breeds you can look at.
