This 2018 video from Belarus says about itself:
Montagu’s harrier. Birds in flight. Circus pygargus.
Female, male and juvenile bird.
From Good Animal News:
Birdwatcher makes first Ulster sighting of rare harrier over Larne coast
Published: April 11, 2007
And the birdwatcher who caught sight of the harrier believes climate change may have played a part in bringing it to more northerly climes.
It was initially thought that the bird was a female hen harrier, but, thanks to video footage taken by birding enthusiast Cameron Moore, the Northern Ireland Rarity Committee has just confirmed that it was a female Montagu’s harrier. …
Montagu’s harrier is known as Britain’s rarest breeding bird of prey, travelling north in summer to breed in southern and eastern England – the northern edge of its range, which stretches down through northern Africa.
“The Montagu’s is a little smaller than our common buzzard and has a wing span between 100cm and 120cm and is dark brown in colour,” Mr Moore said.
“The upper wing has a dark line along the secondaries, its tail is long and has a series of bands with a white rump. They eat small birds, rodents and rabbits.” …
The harrier is not the only rare bird Mr Moore has spotted.
In January this year he was walking with his grandson along the shore in Whitehead when he caught sight of a rare Bonaparte’s gull, a bird native to Canada.
Birds and climate change: here.
Hen harrier in Britain: here.