I don't know if it is an increase in numbers, thus competition for food, or just city hawks that are used to people, or what. After 8 years with only one hawk attack of no consequence, I can't leave them out for 5 minutes any more. I can't count the number of attacks in the last year, but I know of 6 hits, and 1 kill. And most all of it happening with me standing close by. I had a red-tailed that showed little fear of me, making passes at the hens with me running interference to the point it had to alter its course around me. It finally got run over in the road in front on our house. since then it has been Cooper's Hawks every time I let them run. I actually caught one immature male cooper's with my bare hands. It was under the butterfly bush where it had made the kill, looking for the corpse. I rushed the bush and got him entangled trying to escape. I didn't actually hurt the bird, but put the fear in him. Hard to believe that something that weighs less than a pound got take in a hen weighing 6 to 7 times that. He has not been back but now an adult female is chasing chickens right in front of me. She chased a hen around the table legs of the patio furniture with me insight last night. I guess I am just going to stop letting them out at all. Gone are the days of letting them run unwatched all day, that's for sure.