I feel like I can vent sex chicks confidently. I had someone purchase straight-run grow-outs from me recently, 4-6 weeks old, and he vent sexed them to select pullets. Why have I never heard of people venting older birds? I just purchased 6 straight run lavender Ameraucanas- I swear 2 look like cockerels to me but I know better than to judge by appearance. I vented them and as far as I can tell they all look like ladies. How reliable is it on 1, 2, and 3 month old birds?