Introduction

The Hen Harrier (Circus cyaneus) and the Northern Harrier (Circus hudsonicus) are two strikingly similar birds of prey that embody both beauty and conflict in the natural world. Once considered a single species, but since late 2016 they now represent two distinct lineages divided by the Atlantic Ocean. Each hunts low over open ground, moving with graceful, buoyant wingbeats, but their fates have diverged sharply.

Plumage and Identification

Hen Harrier (Circus cyaneus)

The male Hen Harrier is one of Britain’s most elegant raptors, pale grey above, white below, with black wing tips and a gleaming white rump. Females and juveniles are brown with a barred tail and heavily streaked underside. Their slender form and long wings make them unmistakable in open moorland.

Northern Harrier (Circus hudsonicus)

The Northern Harrier of North America shares the same structure but shows a few subtle differences. Males are slightly darker grey above and purer white below and have a dark trailing edge on the wings, females are larger and more robust. This species also exhibits a more clearly defined facial disc, an owl-like feature that improves hearing and helps pinpoint prey hidden in vegetation.

Quick comparison:

Feature Hen Harrier Northern Harrier

Adult male colour Pale grey, black wing tips Darker grey, whiter underside, dark wing tips

Female size Slightly smaller Bulkier

Facial disc Subtle More prominent

Range Europe and Asia North America

Rump patch Distinct white Distinct white

Legs Yellow beak/black tip Yellow beak/black tip

Beak Yellow legs & feet Yellow legs & feet

**Northern Harrier (f) (*Circus hudsonicus*) - Ontario, Canada.**

Hunting and Diet

Both species share the same hunting technique: they glide low over fields, moors, or marshes with wings held in a shallow “V” formation, scanning for movement below. Their diet includes small birds and mammals, especially voles, mice, and passerines.

Hen Harriers often hunt over heather moorland and rough pasture, taking prey such as meadow pipits and voles.
Northern Harriers prefer open prairies and wetlands, where they target rodents and small ground-nesting birds.

Their flight pattern is smooth, buoyant, and purposeful and is one of the most distinctive sights in open countryside.

Breeding and Life Cycle

Both harriers are ground-nesting species, a habit that makes them vulnerable to disturbance and predation.

The female builds the nest from heather, grass, or reeds.
She lays four to eight eggs, which hatch after around 30–35 days.
The male provides most of the food during incubation and early chick rearing.

Hen Harriers occasionally practise polygyny, with one male feeding several females at once. Courtship involves an aerial display known as the “sky dance”, where males perform acrobatic dives and twists to attract a mate, it’s certainly a sight to behold.

Range and Migration

Hen Harrier

The Hen Harrier breeds across northern Europe and Asia, nesting mainly on upland moorlands and bogs. In the UK, breeding strongholds include Scotland, Northern Ireland, Wales, and parts of northern England. In winter, many birds move south to lowland farmland and coastal wetlands.

Northern Harrier

The Northern Harrier breeds across much of Canada, Alaska, and the northern United States, wintering further south into Mexico and Central America. It is a highly migratory bird. Very rarely, individuals have been recorded in the UK and western Europe, carried across the Atlantic by strong westerly winds.

Conservation Status

Northern Harrier in North America

The Northern Harrier is currently classified as Least Concern by the IUCN, but populations have declined in parts of the United States. Habitat loss, wetland drainage, and pesticide use have contributed to regional declines, and in some states the bird is listed as a species of “Special Concern.”

Hen Harrier in the United Kingdom

In contrast, the Hen Harrier’s situation is far more serious. The species is Red Listed in the UK, meaning it faces the highest level of conservation concern. Although suitable habitat could support over 2,000 breeding pairs, only a fraction actually breed in England, sometimes fewer than 20 pairs in a given year.

The greatest threat remains illegal persecution associated with grouse moor management. Harriers are sometimes killed because they occasionally take young Red Grouse, a species reared for shooting. This persecution has severely limited the recovery of the species, despite full legal protection.

**Hen Harrier (m) (*Circus cyaneus*) - Cairngorms, Scotland**

Legal Protection and Licensing

The Hen Harrier is protected under the Wildlife and Countryside Act 1981 (Schedule 1), making it illegal to intentionally kill, injure, or disturb the birds or their nests. It is also listed on Annex I of the EU Birds Directive, requiring special conservation measures.

In Scotland, new wildlife management licensing laws have been introduced that allow authorities to suspend grouse-moor licences where raptor persecution occurs. Similar measures are being discussed in England.

Satellite Tagging and Monitoring

Satellite tagging has become a cornerstone of modern harrier research. Juvenile Hen Harriers are fitted with lightweight transmitters that send location data via satellite.

Many tagged birds travel widely across Britain and Ireland during their first year.
However, a significant number of tags stop transmitting unexpectedly, often over grouse moor estates.
Studies show a clear pattern: Hen Harriers are far more likely to “disappear” in such areas than elsewhere, strongly suggesting continued illegal killing.
Sadly, although the average lifespan of a Hen Harrier should be 7 years – and the oldest known was aged 15 years – many UK Hen Harriers live only a fraction of that time because of illegal persecution. A scientific study of 148 tracked UK Hen Harriers, published in the journal Biological Conservation in 2023, concluded that the typical lifespan was just 121 days, and that only 17% survived the first year, not even long enough to find a partner and breed. The risk of illegal killing increased significantly on or near grouse moor habitats. The data from these tags have transformed understanding of the species’ ecology and provided vital evidence for conservation enforcement.

More information can be found via this link from Hen Harrier Action

Current Recovery Efforts

Recent projects in the UK include:

Nest protection schemes run by conservation charities and volunteers.
A brood management trial, relocating chicks from conflict zones to safer release sites.
Habitat restoration and awareness campaigns to promote coexistence with upland landowners.

Although the number of breeding pairs has risen slightly in recent years, progress remains slow and fragile. Long-term recovery depends on enforcement of wildlife law and cultural change within upland management.

Interesting Facts

The term “ringtail” refers to brown female and juvenile harriers of both species.
Both species can detect prey by sound thanks to their facial disc, similar to owls.
The Hen Harrier sky dance is among the most spectacular courtship displays of any British bird of prey.
Males and females communicate through mid-air food passes, an impressive demonstration of precision flying.
Hen/Northern Harrier other names, Marsh Hawk, Blue Hawk, Frog Hawk and Grey Ghost.

Conclusion

The Hen Harrier and Northern Harrier illustrate two paths of the same evolutionary story, one stable and widespread, the other fragile and persecuted. The Northern Harrier continues to thrive across much of North America, while the Hen Harrier in Britain survives only through protection, perseverance, and public awareness.

Their future ultimately depends on human attitudes toward wildlife and land. If coexistence can be achieved on Britain’s moors, the Hen Harrier might once again become a common sight, a silver-grey bird drifting low over heather in the evening light, free from fear.

As a newly appointed Ambassador for Hen Harrier Action, my mission is to contribute to the protection of upland wildlife, with a particular focus on the hen harrier and other birds of prey. Through this appointment, I aim to raise public awareness of wildlife crime and the broader challenges posed by unsustainable land management practices in the UK uplands.

I hope you enjoyed reading this blog. If you have a moment, I’d greatly appreciate your thoughts or feedback in the comments below.

See you in next week’s post.

Rich :-)

References and Further Reading

The Hen Harrier and the Northern Harrier: Similar in Flight, Divided by Oceans