Out of curiosity, are birdstrikes whilst maneuvering slowly or hovering in a helicopter common?
I can understand how a bird and a 150kt aircraft may meet before the bird has had time to get out of the way, but am guessing a goose or swan or for that matter a blue-tit will keep out of the way of a hovering helicopter? I suspect that in this mode of flight a drone is far likely to collide if they're anywhere near each other (i.e. filming or assisting at the same event).