Northern Harrier

Circus hudsonius

The northern harrier, also known as the marsh hawk or ring-tailed hawk, is a bird of prey. It breeds throughout the northern parts of the Northern Hemisphere in Canada and the northernmost United States. Source

Where it is now

In the last 8 weeks this bird was recorded 3,965 times across 54 areas (each area is a 5 degree square).

See the Northern Harrier on the live map

Movement and weather

Each season it is first heard regularly where daytime highs are around 21°C (typically 18 to 23°C, from 16 areas). That holds across 15° of latitude, which suggests its timing follows temperature more than the calendar.

Over the weeks it was present in the past year, its centre in North America ranged from 29°N in March to 50°N in June, about 2,300 km apart.

Arrival dates

The week it was first heard regularly in each region, after at least six weeks away. Dates differ from south to north, so a region has a range.

Download every area as CSV

Figures are effort corrected and come from automatic sound identification, which makes mistakes. How this is measured and how it compares with human observers.