Because there is no "animosity toward birds" to be corrected. He just likes to shoot shit, all the better if it's a living creature. Ever wonder who shoots road signs? This guy.
This is a human universal, not in all people, of course, but the urge to destroy for some sort of twisted pleasure is hardly limited to the domain of shooting in rural areas (and, heck, there's way too much unjustified shooting of people in urban areas), it just takes different forms elsewhere.
Ever see someone kill their own company, or division of it, just out of some similar sort of bloody mindedness and urge to destroy (even if they also have an urge to create)? Or regress to childhood, there are those who love to build sand castles, and those to love to destroy the sandcastles of others.