What is the biggest red-tailed hawk?

The red-tailed hawk is one of the most common and widespread hawks in North America. Known for its distinctive reddish-brown tail, this species exhibits considerable size variation across different regions. The largest red-tailed hawks are found in the western United States and Canada. In this article, we will explore what the biggest red-tailed hawks are, where they live, and how they compare in size to other red-tailed hawk subspecies.

What is the red-tailed hawk?

The red-tailed hawk (Buteo jamaicensis) is a medium to large-sized buteo hawk that is resident from southern Canada and Alaska to Panama. Adults have brownish upperparts and pale underparts with a streaked belly and a dark patagial mark on the leading edge of the wing. As their name suggests, their most distinctive field mark is a reddish-brown tail.

Red-tailed hawks occupy a wide range of habitats across North America including deciduous, coniferous, and mixed woodlands, agricultural areas, grasslands, deserts, suburbs, and cities. They are opportunistic generalist predators and feed mainly on small to medium-sized mammals such as rodents, rabbits, and squirrels. They also eat other small vertebrates like reptiles and amphibians, as well as insects.

Red-tailed hawks are monogamous and pairs will aggressively defend large nesting territories. They build large stick nests in trees, on cliffs, or on human-made structures. The female typically lays 1-3 eggs that are incubated for 28-35 days. Chicks fledge at about 6 weeks old but remain close to the nest and depend on the parents for several more weeks.

Size variation in red-tailed hawks

There is considerable variation in size among red-tailed hawk subspecies. In general, red-tailed hawks follow Bergmann’s rule – an ecogeographic principle that states that populations and species of larger size are found in colder environments, while species of smaller size are found in warmer regions.

The largest red-tailed hawks are found in Alaska, western Canada, and the northwestern United States. The subspecies B. j. calurus is the largest and heaviest subspecies, with females reaching lengths of up to 25 inches and weights of around 3 pounds. The smallest red-tailed hawks occur in Central America and the Caribbean islands. The tropical subspecies B. j. jamaicensis is the smallest, with some females being as small as 18 inches and weighing around 1.5 pounds.

This size variation is primarily attributed to differences in climate, habitat, abundance of prey, and Bergmann’s rule. The harsher climates and more extensive forests of higher latitudes select for larger hawks that can store more fat reserves to survive long cold winters with potentially erratic food supplies. Smaller tropical forest and urban red-tails experience more stable weather and food resources year-round.

The huge red-tailed hawks of western North America

Here we will take a closer look at the large red-tailed hawk subspecies of western and northern North America:

B. j. calurus

B. j. calurus, also known as the Northern or Northwest Coast Red-tailed Hawk, is the heaviest and largest subspecies. It ranges along the Pacific Coast from southeast Alaska to northern California. Males average 51-66 cm (20-26 in) long with a 127-142 cm (50-56 in) wingspan. Females are even larger, averaging 58-72 cm (23-28 in) long with a wingspan of 138-152 cm (54-60 in). Weights range from 1,050-2,100 g (2.3-4.6 lbs) for males and 1,500-3,000 g (3.3-6.6 lbs) for females, making them the heaviest red-tailed hawks.

These massive birds thrive in the extensive temperate rainforests of the Pacific Northwest. Their huge size provides an advantage for successfully hunting large prey like snowshoe hares, squirrels, grouse, and ptarmigans needed to sustain them through the long winters.

B. j. harlani

B. j. harlani, or the Harlan’s Hawk, inhabits the northern Great Plains and Rocky Mountains from Alberta to Texas. They are also very large, with males measuring 48-61 cm (19-24 in) long and have a wingspan of 115-127 cm (45-50 in). Females are even bigger at 56-65 cm (22-26 in) long with a wingspan of 130-140 cm (51-55 in). Weights range from 1,100-1,800 g (2.4-4.0 lbs).

The extensive grasslands and foothills of their range provide plentiful ground squirrels, prairie dogs, jackrabbits, and other prey to sustain their massive sizes even during harsh winters.

B. j. abieticola

The Northern California Red-tailed Hawk (B. j. abieticola) is also one of the largest subspecies. They range along the Pacific Coast and interior mountains from southwestern Oregon to central California. Males average 48-58 cm (19-23 in) long with wingspans of 115-135 cm (45-53 in). Females are much bulkier at 56-65 cm (22-26 in) long with wingspans of 130-145 cm (51-57 in). Weights are around 1,100-1,800 g (2.4-4.0 lbs).

These birds thrive in the extensive coniferous forests of the Pacific Northwest where they can find abundant prey like woodrats, squirrels, and grouse to sustain their large sizes. Their huge sizes likely provide an advantage for successfully hunting elusive forest prey.

How the largest red-tailed hawks compare in size

To summarize, the largest red-tailed hawks are:

Females

Males

The largest females and males come from the subspecies B. j. calurus of the Pacific Northwest, which can weigh up to 6.6 lbs and have wingspans over 5 feet across. The Harlan’s Hawk (B. j. harlani) and Northern California Red-tailed Hawk (B. j. abieticola) are nearly as large. In comparison, a “normal” female Red-tailed Hawk averages about 19-25 inches long with a wingspan of 48-57 inches and weighs 2-4 lbs.

Clearly, the red-tailed hawk subspecies of the northwest coast, Rocky Mountains, and California forests are in a heavyweight class of their own compared to red-tailed hawks across the rest of the country. Their massive size provides key advantages for survival in the expansive forests and montane habitats of western North America.

Why are some red-tailed hawks so big?

The huge sizes of red-tailed hawk subspecies like B. j. calurus and B. j. harlani are driven by a few key factors:

Climate

The colder climates of high latitudes and altitudes select for larger raptor sizes following Bergmann’s rule. Larger bodies can store more fat and energy reserves which provides an advantage in harsher climates.

Habitat

Western red-tailed hawks occupy more extensive open forests and montane habitats compared to eastern birds. Larger sizes likely help them successfully hunt elusive prey in this habitat.

Prey

Western hawks prey on larger mammals like hares, ground squirrels, and grouse compared to more mixed rodent prey in the east. Taking larger prey may select for their larger body sizes.

Migration

Western red-tailed hawks are more migratory. Larger bodies can store more energy reserves needed for long migrations.

Hybridization

Some western red-tailed hawk populations hybridize with smaller Ferruginous Hawks, possibly introducing genes for large sizes.

In essence, the combination of colder climates, extensive open habitats, large prey, and migratory habits have selectively favored the evolution of some of the largest and most formidable red-tailed hawks on the planet in western North America.

Conclusion

In conclusion, the largest red-tailed hawks are the northern subspecies B. j. calurus, B. j. harlani, and B. j. abieticola found in Alaska, western Canada, the northwest coast, the Rocky Mountains, and California. The heavyweights are B. j. calurus, which can weigh up to 4.6 lbs for males and 6.6 lbs for females with wingspans over 5 feet wide. These gargantuan birds are highly adapted to the cold climates, extensive forests, large prey, and migration patterns of western North America which have selectively favored their gigantic sizes over time. So if you are looking for monster red-tailed hawks, head to the northwest coast and mountain forests!