Two part answer:((USA)
1. Under Part 107 (USA) you must have remote ID, and register w/ FAAif you are flying commercially, regardless of drone weight.
2. Under Section 44809 (recreational flying), as long as the drone is under .55 lbs. (250...
None. I attribute that to a mixture of the bird's caution and my evasive tactics.
Clearly you could speculate that the birds were just trying to scare the drone away, and would not have actually hit it if I'd just ignored them. But that's not a...
I have definitely had birds attack my quadcopters dozens of times (over about 15 years of flying).
The easy ones are actively nesting birds, like swallow, kites, and some sea birds, but they give up easily when I fly away from their nests...