Are your birds being kept free range day-and-night, or confined to an enclosure or co-op at any part of the day or night? If you are using confinement for all or part of the day, is that where If your birds are being confined at any point, is that where and when the attacks are taking place where are the losses being taken place for the birds are in the open areas?
I've seen it from crows... they will try to pluck the feathers out of the hawk during flight to ground them. (they are opportunist though and have been known to steal chicks and eggs). Jays are in the same family as crows... so it isn't that surprising. Jays are also quite aggressive birds, even territorial IF I remember correctly. Aside from the feather plucking they do... when they sit around and squawk at the raptor, it blows the raptors cover who is an ambush predator... often causing them to move on as all the prey is aware of their presence.
They are confined to a coop at night. They are going missing early morning after being let out, in the evening. Dusk & Dawn. Recently we even caught someone driving up, shooting them, and stealing them. It's been a rough few months.
