The Northern Goshawk is a large and powerful bird of prey that is found across much of North America, Europe, and Asia. As raptors go, it is on the bigger side, though not as massive as eagles or vultures. The size of a Northern Goshawk can vary based on sex, age, and geographic location, but on average these birds measure between 50-66 cm (20-26 in) in length with a wingspan of 99-128 cm (39-50 in). Their weight ranges from around 850 grams to 2 kg (1.9-4.4 lbs).
Average Size by Geographic Location
There are several recognized subspecies of Northern Goshawk that occupy different regions. The largest subspecies on average tend to be found in the northernmost parts of the range, while the smallest are more southerly. Here are some average measurements of wingspan and weight for major Northern Goshawk subspecies:
| Subspecies | Region | Average Wingspan | Average Weight |
|---|---|---|---|
| A. g. atricapillus | Alaska, Canada, northern U.S. | 112 cm / 44 in | 1.4 kg / 3 lbs |
| A. g. apache | Southwestern U.S. | 99 cm / 39 in | 1 kg / 2.2 lbs |
| A. g. accipitrines | Northeastern Asia | 128 cm / 50 in | 2 kg / 4.4 lbs |
| A. g. palearcticum | Europe, western Asia | 115 cm / 45 in | 1.2 kg / 2.6 lbs |
As you can see, the largest subspecies on average is A. g. accipitrines of northeastern Asia, while the smallest is A. g. apache of the southwestern United States and Mexico.
Largest and Smallest Size Extremes
While the table above shows averages, there is some individual variation among goshawks. Extremely large males in the northern subspecies can reach weights approaching 2 kg (4.4 lbs) and wingspans of nearly 140 cm (55 in). Very small females, particularly of southern subspecies, may be as light as 700 grams (1.5 lbs) with wingspans under 90 cm (35 in). So while most goshawks measure within the typical ranges, exceptional individuals at both the high and low end can exist.
Size Differences Between Males and Females
There is a degree of sexual dimorphism when it comes to size in Northern Goshawks. As is the case with most raptors, females tend to be distinctly larger and heavier than males. Some key size differences include:
- Females are approximately 20-25% larger in overall body size
- Female goshawks are 10-20% heavier on average than males
- Wingspans of females may be 5-10% greater compared to males
- Females are noticeably bulkier and broader across the chest and wing area
These differences in size are an evolutionary adaptation where the larger female is better equipped to incubate eggs and protect the nest. The more agile and slender male is suited for faster flying and catching prey. So when evaluating goshawk size, sex must be taken into account along with geographic subspecies.
Example Size Comparison
To illustrate the size difference, a large adult male Northern Goshawk of the A. g. atricapillus subspecies may have the following dimensions:
- Length: 60 cm (24 in)
- Wingspan: 112 cm (44 in)
- Weight: 1.25 kg (2.75 lbs)
Whereas a large adult female of the same subspecies may be:
- Length: 66 cm (26 in)
- Wingspan: 128 cm (50 in)
- Weight: 1.8 kg (4 lbs)
So in the same population, the female may be nearly 10% longer, have a wingspan 14% greater, and weigh 44% more than the male. This shows the degree of sexual size dimorphism in the species.
Changes in Size with Age
Northern Goshawks, like most birds, grow continuously through their early years until reaching full adult size. Newly hatched chicks weigh only about 65 grams (2.3 oz) and are covered in white downy feathers. They grow rapidly, reaching fledging size of 500-900 grams in 4-6 weeks. However, they are still small and gangly, only about half of adult length with a narrow wingspan.
Fledglings will reach full adult dimensions by 2 years old, but their body may continue adding density and weight for another year or two after. The growth rate depends partly on food availability, with well-fed young often gaining full adult size by 18 months. Here is an approximate timeline of growth:
| Age | Size |
|---|---|
| Hatchling | 5-6 cm, 65 grams |
| 4-6 weeks | 25-30 cm, 500-900 grams |
| 3-4 months | 30-38 cm, 650-1200 grams |
| 6 months | 35-45 cm, 900-1500 grams |
| 1 year | 45-55 cm, 1-1.8 kg |
| 2 years | 50-66 cm, 1.2-2 kg |
So the first year represents the period of most rapid growth until they reach a similar weight and wingspan as adults. It takes a full two years for all body contours, plumage, and flight muscles to fully mature.
How Their Size Compares to Other Raptors
The Northern Goshawk is on the larger end of the scale when it comes to accipiters, a group of short-winged, long-tailed hawks adapted for maneuvering deftly through dense cover. Other accipiters include the Sharp-shinned Hawk, Cooper’s Hawk, and Eurasian Sparrowhawk. The goshawk dwarfs its smaller relatives like the Sharp-shinned.
Compared to longer-winged soaring hawks like Red-tailed Hawks and eagles, the Northern Goshawk has a stockier, more compact build with a proportionally much larger head and shorter wings designed for agile pursuit of prey. However, the goshawk is still larger than buteos like Red-tailed Hawks in overall body mass due to its dense muscles.
Only a few raptors notably surpass the Northern Goshawk in size. The largest North American hawks such as Ferruginous Hawks, Red-tailed Hawks, and Rough-legged Hawks may rival some goshawks. And large eagles like the Golden Eagle and Steller’s Sea Eagle are distinctly bigger in all dimensions. The following table compares the size of the Northern Goshawk with other major raptor groups:
| Raptor Group | Average Length | Average Wingspan | Average Weight |
|---|---|---|---|
| Northern Goshawk | 50-66 cm | 99-128 cm | 0.9-2 kg |
| Cooper’s Hawk | 35-46 cm | 65-78 cm | 0.3-0.6 kg |
| Red-tailed Hawk | 45-65 cm | 105-135 cm | 0.9-1.5 kg |
| Golden Eagle | 65-90 cm | 175-220 cm | 3-6 kg |
This gives a sense of how the Northern Goshawk fits on the spectrum of accipiter to buteo to eagle in terms of size and bulk. It overlaps with the largest buteos but is dwarfed by the large eagles at the top of the food chain.
Usefulness of Size to the Species
The Northern Goshawk’s medium-large size suits it well as an effective predator with minimal predators of its own. Important benefits of its size include:
- Ability to take large prey up to hares and grouse
- Strength to overpower prey quickly
- Bulk to fight off competing predators from kills
- Small enough for agile flight through dense forests
- Large enough to be less vulnerable to predators
Smaller accipiters are more maneuverable but limited in the prey they can capture. Large eagles can take bigger prey but lack the goshawk’s speed and precision in wooded terrain. The goshawk’s middle-ground size strikes an optimal balance of power, speed, and agility for its particular ecological niche.
Disadvantages of Large Size
There are also some drawbacks that come with the Northern Goshawk’s medium-large size:
- Higher energy requirements than smaller raptors
- Cannot take small, agile prey as well as smaller accipiters
- Maneuverability disadvantages in very dense cover
- Later maturation age than smaller raptor species
Their greater size means goshawks need more prey biomass overall to meet energy needs. And they reach breeding maturity at 2-3 years old compared to 1 year for smaller accipiters. But the advantages of great strength and speed with minimal vulnerability outweigh the costs of being a larger raptor for this species.
Conclusion
In summary, the Northern Goshawk is a sizable bird of prey, measuring 50-66 cm in length with a 99-128 cm wingspan and weight of 0.9 to 2 kg. Females are distinctly larger than males, and size increases along a geographic cline from south to north. The goshawk’s medium-large size gives it great hunting prowess, allowing it to take relatively large prey with its bursts of speed and power, while not hampering its ability to maneuver in dense forests. This optimizes its niche as a highly efficient forest-dwelling predator and accounts for why the Northern Goshawk has evolved to its present size.
