Loud noises from roof at night?

I live on the top floor of a three-story building built in the 1970s. I have been hearing loud t noises on the roof on and off basically all summer long. They tend to come in twos and threes, a sort of "THUMP THUMP" or "THUMP THUMP THUMP" sound. I have at times thought it might be footsteps or someone jumping up and down on the roof, but I only ever hear three or so thumps before the noise stops, and never really anything before or after. (Once in a while, a sort of scraping sound follows the thumps.) I know it's not from trees, because they're all trimmed so that they don't hang over the roof. I do live in a woodsy sort of area in upstate NY, so it could be local wildlife, but I have no idea what. Can anyone explain to me what this is?