I am not 100% certain I marked any pic then right, lol. But I used a twisty tie. All blue ABC's greens equal ones I think are males. I marked this one in question with a yellow twist tie to see what happens. Once they are around 2 weeks old I have the plastic ones that go on the legs to keep...
I am very new at sexing chicks at all, I have gone through my 17 chicks and marked the ones I'm guessing are cockerals. However, this 1 chick is having me still on the fence. I labeled it as a girl by wing, but I'm not very positive at all. Could be a week old today, sat or sun as my eggs...