That focusing on a bird's head is a great wing shooting asset, whether it is naturally acquired, or in some manner "learned". I have been conscious of it since my earliest boyhood shooting forays......The looking for the white cheeks on a Cock bird is just a refined extension of that task. I do concede, I find it much easier to do on bright sunlight days when I an not facing a glare or shadow. It is also something do a lot more when the pointing dog is a fully broke and trained veteran companion...... I freely admit to simply trying to get a bird or more down regardless of gender when shooting over a canine student in training
I have never put too much stock in the idea that the gunning of cocks only really has much impact on a populations in the grand scheme of things. More of a feel good thing to my way of thinking. But everyone to his own. I have noticed that the avian predators that I compete with for harvest rights on my property are not very selective in picking their prey.
Today looks promising for another outing with my girls....