I've seen crows do that near a corner house with L-shaped roof. The wind was going from the backyard, hitting the sloped roof and blowing straight up in that co

I've seen crows do that near a corner house with L-shaped roof. The wind was going from the backyard, hitting the sloped roof and blowing straight up in that corner and a lot of crows were jumping from the roof, hovering on the wind for a few minutes and returning to the roof when they couldn't keep in the stream.