Circus cyaneus
Silhouette: Andy Wilson · PhyloPic
In 3 days ~20% in a week ~40%
The hen harrier (Circus cyaneus) is a bird of prey. It breeds in open areas such as marshes and grasslands in Eurasia and is migratory, moving further south outside of the breeding season. Birds in milder regions, such as France and Great Britain, may be resident year-round, but the higher altitudes are largely deserted in winter. The species is sexually dimorphic; males are smaller and mostly grey and white with black wingtips, whereas females average larger and are predominantly brown and have buff underparts with brown barring. Both sexes have a white rump patch, although it is more noticeable on females and juveniles.
The term "hen harrier" refers to its former habit of preying on free-ranging fowl. The northern harrier (Circus hudsonius) was formerly considered to be a subspecies of the hen harrier. In 1758 the English naturalist George Edwards included an illustration and a description of the hen harrier in the first volume of his Gleanings of Natural History. He used the English name "The blue hawk". Edwards based his hand-coloured etching on a bird that had been shot near London. When in 1766 the Swedish naturalist Carl Linnaeus updated his Systema Naturae for... Wikipedia →
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Novosibirsk | 🇷🇺 Russia | |
| 2 | León | 🇲🇽 México | |
| 3 | Daegu | 🇰🇷 South Korea | |
| 4 | San Francisco | 🇺🇸 United States | |
| 5 | San Diego | 🇺🇸 United States | |
| 6 | Beijing | 🇨🇳 China | |
| 7 | Vancouver | 🇨🇦 Canada | |
| 8 | Mesa | 🇺🇸 United States | |
| 9 | Los Angeles | 🇺🇸 United States | |
| 10 | Toluca | 🇲🇽 México |
| # | Zoo / Centre | Country | |
|---|---|---|---|
| 1 | Birds of prey | 🇨🇦 Canada | |
| 2 | Zoológico del Altiplano | 🇲🇽 Mexico | |
| 3 | California Raptor Center | 🇺🇸 United States | |
| 4 | Carolina Raptor Center | 🇺🇸 United States | |
| 5 | akwarium warszawskiego ZOO | 🇵🇱 Poland | |
| 6 | Chouette à voir! | 🇨🇦 Canada |
With luck
About 10% of wildlife watchers report a Hen Harrier sighting in Biebrza National Park on a given day, based on 111 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 135th most-seen of the 202 birds we can rate there. Over three days the chance rises to about 20%, and over a week to about 40%, if each day is a fresh chance.
October
In that month about 30% of wildlife watchers report a Hen Harrier in Biebrza National Park on a given day, against under 5% in May to July, the lowest months.
Between 10 am and 1 pm
Across all the parks we cover, that three-hour window holds the most Hen Harrier sightings with a recorded time, and nearly all of them come between 6 am and 6 pm: it is a daytime animal.
19th of 71
Of the 71 parks where we can rate Hen Harrier sightings, Biebrza National Park ranks 19th at about 10%. The best odds are in Padre Island National Seashore (United States, about 30%), Merritt Island National Wildlife Refuge (United States, about 20%) and Denali National Park (United States, about 20%).
Same genus: Circus
The closest relatives of the Hen Harrier that you can see in Biebrza National Park (genus Circus, Harriers) are Western Marsh-Harrier (about 50%) and Montagu's Harrier (about 20%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Hen Harrier is recorded against all the birds logged in Biebrza National Park (111 verified sightings from 2019 to 2026), calibrated against known sighting rates. Figures are rounded to the nearest 10% because citizen-science data supports honest approximations, not decimals, and months with records from fewer than five people show "—". How it works.
