|Boo's lambs - Gobi and her brother|
We usually put the rams/bucks in with the flocks in October, so we have mostly March babies. If we are setting aside separate breeding or housing pens, we leave the boys in there and away from the main flock through January. But, our boys are protective of their girls and babies, so we put them back in the main flock in February. For 32 years, we've done it this way and never had baby born after the first of May.
Obviously, Mother Nature doesn't put much stock in the phrase "But we've always done it this way!"