Species of the Month, September 2014: Broad-Winged Hawk

Species 09:14 Broad Winged Hawk-01-01.jpg

Note: This is the ninth post in our "Species of the Month" series, written by Park Ecologist Peter VanLinn. It's one of several 2014 initiatives meant to share knowledge we have about the Park with those who love it.

As the cooler temperatures continue to remind us that fall is just around the corner, be sure to take advantage of this transition while you are visiting Forest Park. This is a great time to see many of species of bird that use Forest Park and nearby areas during long migrations from Canada all the way down to northern South America.

One species that might be unfamiliar to many folks is the Broad-Winged Hawk. This species is one of the few hawks that actually migrates in flocks. These flocks (or "kettles," as they are referred to for hawks) can number into the thousands and make this otherwise solitary species a little more visible during this time of year. The short, stocky, size of this raptor species measures closer to a pigeon than most other raptors, making it less conspicuous during most of the rest of the time they spend in Missouri.  

Keep your eyes to the sky and you might just find a kettle of Broad-Winged Hawks on their 4,000-mile journey back to South America.

Broad-Winged Hawk (Buteo platypterus)

Photo courtesy of Brian K. Wheeler, via  Visual Resources for Ornithology

Photo courtesy of Brian K. Wheeler, via Visual Resources for Ornithology

Park Locations: Throughout woodland areas in the Park such as Kennedy Forest, Successional Forest and near the vista overlooking Round Lake.

Description: Broad-Winged Hawks are a more compact, stocky hawk with a large head. Adults are plain brown above and barred with rusty-brown and white below, with tightly banded black and white tail feathers. Immature individuals are similar looking but with sparsely spotted or blotched colors below and less distinct tail feather bands.

  • Height: 13-15 inches (33-38 cm)
  • Wing Span: 33 inches (84 cm)
  • Longevity: The average expected lifespan is 12 years
  • Call: A high-pitched “kee-eee” whistle is characteristic of this species

Distribution: Statewide throughout Missouri. Nationwide throughout eastern United States and into much of southern Canada. Winter range includes southern Florida, the Pacific slope of Southern Mexico, Central America and northern South America.

Status: A common (occurs regularly and in large numbers) transient migrant in spring and fall and an uncommon (occurs regularly but in small numbers) summer resident/breeder.

Habitat and Conservation: Broad-Winged Hawks prefer mature, dense, deciduous or mixed deciduous-coniferous forests for nesting. Nearby meadows, roadways and water bodies are required for hunting and foraging. They tend to avoid nesting near human dwellings.

Life Cycle: Broad-Winged Hawks form monogamous breeding pairs, meaning they will mate together for more than one breeding season. These breeding pairs are formed soon after arriving to breeding grounds in spring. Courtship behaviors include flight displays and possibly courtship feeding. Both males and females build the nest or utilize an existing next from another species. Breeding occurs between April and August, raising one brood per summer. Females will lay 1 to 4 eggs per breeding season. The female will incubate the eggs for about a month while the male collects and carries food to the female. Chicks will leave the nest after about 5 or 6 weeks and will begin catching prey on their own after 7 weeks. Most will not reach maturity for breeding until at least 2 years old.

Behavior: Broad-Winged Hawks are solitary, terrestrial birds except during migration. This is one of the few raptor species in North America that migrates in flocks ("kettles" for hawks). At the peak of migration these kettles can number in the thousands. Broad-Winged Hawk kettles rely on thermal air current to soar long distances without wasting energy flapping their wings during the long (up to 4,000 miles) migration. They can also be territorial during the breeding season and are active primarily during the day.

Food: Broad-Winged Hawks are carnivores that change diet seasonally, usually consisting of whatever insects, amphibians, reptiles, mammals and birds are available during the various seasons. Typically, these birds hunt from a perch and swoop down to the ground to capture prey.

Human Connection: This species feeds on insects and rodent species that might be considered pests to humans. This bird's solitary habits help it to avoid more direct contact with humans.

Ecosystem Connection: Broad-Winged Hawks affect the local populations of the animals they eat while also providing food to predators like raccoons and other climbing mammals or other predatory birds such as great horned owls. The best conservation practice for this species would inovle range-wide conservation of habitat throughout the speices migratory range.

Note: Information for this post was collected from the following locations: University of Michigan’s Museum of Zoology, Animal Diversity WebAudubon.org; and The Academy of Natural Science of Drexel University’s Visual Resources for Ornithology.