I don know how he does it, but my rooster seem to know when a hen is fertile, from pullets just days from point-of-lay to my seasoned layers. Since the entire fleet of layers have been molting, just one hen was still laying. She was the only one who got "attention" from my rooster Penrod. She quit laying a few weeks ago, and he has ignored her since. The last few days, Penrod has been honoring one hen with his favors, no one else. Behold! Today, she laid her first egg in three months! How does he do it? I'd sure love to know! I thought it might be the color of their combs, but his current "interest" has a pale pink comb same as before.