Hmm, I just looked into this and couldn't see any weird behavior. The damage calculation on the first shot is exactly the same as for all other shots. Maybe just bad luck?
If i should guess it seemed like he fired only 1 crow on the first shot. And then had to reload. But of i am ingame with some progress I'll try to reproduce. This may take a while though because I have barely time to play ATM.
I know what he's getting at. It does seem like rather than launch the whole batch on the first shot after not-firing (As in, it's sat and had no targets to fire at for at least the attack cooldown) it only shoots a single crow. Haven't experienced it myself for quite a while, but I do remember it being a weird thing.
You were right! I can confirm that the first shot of scarecrow ALWAYS shoots exactly one projectile. Thanks to your hints I was able to find and fix this bug. Cheers :-)