No crows at night
Crows are diurnal so there shouldn't be any flocks out on the roads at night. This would also help add some needed variety in gameplay between day/night missions making night missions faster and more aggressive (easily to stealth).
as much as I hate ducks and birds I think that element is important in the game. I like the idea of bats, and they could have different spawn locations compared to crows and ducks. Maybe more in the offroad sections/near trees or in houses?
I can see those pesky crows just fine. I'd be fine with removing them from bushes though. That is absurd.
I think getting rid of the crows from a night game would add a lot more immersion to the game but the crows should be replaced with something like owls. The owls don't have to fly away when startled but rather make a noticeable "who" noise every couple of seconds. Since seeing the crows fly away in the night sky is already hard enough, the owls would allow other players to still make a judgement on whether the area is clear or if you should be on high alert.
I think this question rises some good improvements ideas to make the game even more immersive. But somehow I think like Scott389 just removing the crows at night would just be impoverishing the game.
I give +1 to the idea of bats around some old buildings like crematorium or chapel and maybe the forest could also include nighthawks or some kind of owls to replace the crows and vary, with coherence, the stealth vs fauna challenge.
Maybe add bats inside old houses and other areas bats would be.