I got swarmed by tiny black bugs a little while ago?

I was looking into a birdhouse in my yard to see if any were still in there. I pulled away and sat down and felt tickling on my hand. I look down to see about 100 little black bugs swarming on my hand. I smacked them all off then noticed i felt tickling on my thigh. I looked there and about 50 were crawling up my shorts. I jumped in the shower to exterminate the little bastards, im pretty sure a few of them bit me. What the hell were they?