Found this bird ball under the wall of the building. The fight was over the ownership of a hole in the wall. I was holding the camera in one hand, and with the second I tried to disengage the fighting birds. Once one of swifts unhooked and flew away, the second switched to my hand and continued the fight with me. Yes, it hurts. Yes, that's my blood. Swifts have very strong though small legs, and very sharp claws. They fought so desperately that it seemed they might well kill each other. They didn't notice anything else around. I couldn't release the second swift with one hand, so I had to pause the camera and decouple it with the other hand. Then he flew away safely. Crazy, not cute harmless birds :)