What nickname is given to the adult male Northern Harrier due to its plumage?

Answer

Gray ghosts

Adult males are often called 'gray ghosts' because of their striking pale, silvery-gray plumage across most of the body, which contrasts with their dark wingtips.

What nickname is given to the adult male Northern Harrier due to its plumage?
birdraptorhawkFalconNorthern Harrier