Yeah, I've done that for IV too.
Most of the pigeons can be exterminated from safe positions (like rooftops), using a sniper rifle or grenades.
There's a couple of tricky ones on Algonquin though.
To see what can be done, check out zmoonchild's topic: http://www.gtaforums.com/index.php?showtopic=389190
I think he also did a bunch of videos , search on youtube.