The hen harrier (Circus cyaneus) is a medium-sized bird of prey that belongs to the harrier family. It is found throughout Europe, Asia, and North America. Hen harriers are known for their spectacular aerial acrobatics during courtship displays. But just how big are these agile raptors? In this article, we’ll take a close look at the size of hen harriers from head to tail.
Wingspan
The wingspan refers to the distance between the tips of the wings when they are fully outstretched. This measurement gives a good indication of the overall size of a bird.
Adult male hen harriers have an average wingspan of 97-110 cm (38-43 inches). Females are noticeably larger with an average wingspan of 113-128 cm (44-50 inches). This makes the hen harrier a medium-sized raptor, smaller than eagles but larger than most hawks.
To put this in perspective, here is a comparison of the wingspans of some common raptors:
Bird of Prey | Average Wingspan |
---|---|
Golden Eagle | 180-220 cm |
Bald Eagle | 180-230 cm |
Red-tailed Hawk | 110-145 cm |
Hen Harrier | 97-128 cm |
Cooper’s Hawk | 80-100 cm |
Sharp-shinned Hawk | 55-70 cm |
As you can see, the hen harrier is dwarfed by massive eagles but is noticeably larger than agile accipiters like the Cooper’s hawk. The broad wings allow hen harriers to soar and glide effortlessly as they search for prey.
Body Length
Looking at the length of the body from head to tail also gives a good measure of a bird’s overall size.
Male hen harriers measure 36-41 cm (14-16 inches) in body length. As is typical among raptors, females are bigger with a body length of 41-48 cm (16-19 inches).
Here is a comparison of body lengths across some common raptor species:
Bird of Prey | Average Body Length |
---|---|
Golden Eagle | 65-95 cm |
Bald Eagle | 70-102 cm |
Red-tailed Hawk | 45-65 cm |
Hen Harrier | 36-48 cm |
Cooper’s Hawk | 30-41 cm |
Sharp-shinned Hawk | 23-35 cm |
The hen harrier is intermediate in length between the larger buteos like the red-tailed hawk and smaller accipiters. Their long tails and legs account for a significant portion of their body length.
Weight
The weight of a bird is also a key size metric. Male hen harriers weigh approximately 275-400 grams. Females are heavier at 450-700 grams.
For perspective, here are the average weights of some other common raptors:
Bird of Prey | Average Weight |
---|---|
Golden Eagle | 3-6 kg |
Bald Eagle | 3-6.3 kg |
Red-tailed Hawk | 690-1400 g |
Hen Harrier | 275-700 g |
Cooper’s Hawk | 220-480 g |
Sharp-shinned Hawk | 85-190 g |
The hen harrier is a lightweight raptor compared to massive eagles which can be over 10 times heavier. However, the hen harrier outweighs smaller accipiters like the sharp-shinned hawk. Their light weight allows them to hunt agile prey like voles and small birds.
Size Differences Between Sexes
There is considerable sexual dimorphism in hen harriers meaning that females are distinctly larger than males. This size difference is quite apparent across all key metrics:
Male | Female | |
---|---|---|
Wingspan | 97-110 cm | 113-128 cm |
Body Length | 36-41 cm | 41-48 cm |
Weight | 275-400 g | 450-700 g |
The larger size of females is common among raptors and birds of prey. This greater size allows female hen harriers to better incubate eggs and protect nestlings. Males meanwhile are more agile and athletic hunters due to their more compact size.
Changes in Size With Age
There are also noticeable differences in size between young and adult hen harriers:
- Hatchlings weigh approximately 35 grams and have a total body length around 10 cm
- Fledglings increase dramatically in size attaining a weight of 225-350 grams before leaving the nest
- Juvenile hen harriers resemble adults but have smoother, less distinct plumage and shorter tails
- By one year of age, hen harriers reach full adult dimensions
So there is rapid growth in the first few months until fledging. After leaving the nest, development slows but juveniles take another year to attain mature adult plumage and proportions.
How Their Size Helps Survival
The physical size and dimensions of hen harriers provides some key advantages that aid their survival:
- Their medium size allows them to hunt a wide range of prey including small birds, voles, other rodents, and some larger animals
- Their long wings and tail give them exceptional aerial maneuverability and lifting power for soaring
- Their lightweight build enables them to pursue and capture agile flying prey
- Their compact size relative to large eagles reduces energy requirements for flight and hunting
- Sexual dimorphism results in a division of roles between large females and more agile males
In essence, the hen harrier is a mid-sized specialist raptor excellently adapted for hunting in open habitats like grasslands, marshes, and moorlands. Their dimensions strike an optimal balance between power, speed, agility, and energy efficiency.
Comparison to Other Bird Groups
To further contextualize the size of hen harriers, it is useful to compare them to other groups of birds:
Vs. Other Raptors
Compared to most eagles, ospreys, buteos, and large owl species, the hen harrier is a small-medium sized raptor. However, they are larger than kestrels, kites, hobbies, and accipiters. Overall, hen harriers occupy a middling size class among raptorial birds.
Vs. Corvids
The hen harrier has a broader wingspan but shorter body length compared to most corvids such as crows, ravens, and magpies. In terms of weight, they are up to 5-10 times heavier than corvids of a similar length like the carrion crow.
Vs. Shorebirds
Shorebirds like plovers, sandpipers, and avocets have body lengths similar to a hen harrier. However, the harrier’s wingspan is 2-3 times as broad and they outweigh shorebirds by a factor of 5-10x. The large wings are key to the harrier’s flight capabilities.
Vs. Gamebirds
Some gamebirds like pheasants and grouse are potential prey for hen harriers. Most are around half the length and 5-10 times lighter in weight than a full grown hen harrier, making them vulnerable to predation. Only the largest gamebirds like capercaillie approach harrier size.
Vs. Songbirds
Any songbirds the harrier preys on like larks, pipits, finches, and buntings are dwarfed dramatically in size. A hen harrier is 5-20 times heavier than most songbirds with 3-5 times the wingspan, allowing them to easily prey on these species.
So compared to its common ecological associates, the hen harrier is a distinctly mid-sized bird of prey well equipped to hunt other birds, small mammals, and assorted wildlife. Their size stats them apart from smaller songbirds and larger eagles and buzzards they share habitats with.
Conclusion
In summary, hen harriers are a medium-sized raptor in terms of their key physical size metrics:
- Wingspan ranges from 97-128 cm
- Body length is 36-48 cm
- Weight ranges from 275-700 g
Females are noticeably larger than males across all size dimensions. Adults are also larger than juveniles, fledglings, and hatchlings.
The hen harrier’s medium size provides an optimal balance of speed, power, agility and energy efficiency. These attributes equip them perfectly for hunting in open habitats.
When compared to other raptors, shorebirds, corvids, gamebirds, and songbirds, the hen harrier occupies a middle size class – larger than most but smaller than eagles. Overall, their size allows them to exploit a range of prey while avoiding direct competition with other large predators.