I passed quite close to a big hawk like bird at 2000' over the horshoe bend on the Severn last month. He was circling, presumably in a thermal, and wasn't at all concerned about me.
But I was once CHASED by a big black bird in monument valley. I could see him quite clearly out of the back windows of my 152 coming after me at 70kt as I flew level with his perch in one of the towers.
(OK, some wag already asked what he was squawking)