Why don’t birds collide when they are flying close together in tight flocks?

[h2ofwlr]

Answer: https://www.allaboutbirds.org/why-dont- ... ht-flocks/

[cstemig]

I don't agree with that, especially with a started flock just taking off the ground. Several years ago, we startled a resting flock of Snows/Blues on Sand Lake NWR and witnessed several birds falling down after the mass of them took off. Could be that they were already wounded, but I can't help but believing that there were some mid-air collisions with that chaos.