This video from the USA says about itself:
28 October 2016
Northern Harrier in classic open marshland habitat near the St. Johns River in Florida. This unique hawk has an owl-like looking face. Also called a Marsh Hawk or Hen Hawk [Hen harrier] this is a first time species on film for me – this is a migratory hawk just arriving from the north. This is what extreme zoom lenses are for.
Circus cyaneus is a medium-sized bird of prey that is widely distributed across the Northern Hemisphere. There are two currently recognized forms, the Palearctic form C. c. cyaneus (Hen Harrier), and the Nearctic form C. c. hudsonius (Northern Harrier). The forms have recently been split by the British Ornithologists’ Union but the American Ornithologists’ Union and some other taxonomic committees have not yet made any change. Here we examine the phylogenetic relationship between the two forms using sequence data from multiple nuclear and mitochondrial genes and examine breeding biology, body size, morphology, dispersal and other behaviors.