Rough-legged Hawk

On the wild side—January, 2014

by Tina Mitchell

Of all of the hawks in the Buteo genus, the Rough-legged Hawk is the only one so completely linked with cold climates.  In North America, Rough-legged Hawks breed primarily in the tundra of the Arctic and winter in open country of southern Canada and the northern United States.  You have to know that a bird loves cold if it happily chooses to winter in South Park.  Driving US 285 during the cold season, you will likely find them perched on power poles or fence posts surveying the snowy fields.  Ah, just like summer in the Arctic!  Their numbers in Colorado can vary quite widely from one winter to the next.  But in our almost 20 years of traversing South Park, I don’t think a winter has passed without our seeing at least a few.  On one memorable trip, we counted a whopping 18!

Rough-legged Hawks exhibit a lot of variability in their plumage.  Some birds are very dark (called “dark morphs”) while others are paler with a lot of mottling (called “light morphs”).  Most birds in North America are light morphs, so let’s focus on them.  A male Roughie has a whitish to light brown head, a dark eye-line and a light nape contrasting with a dark brown back dappled with white.  This mottled look contrasts quite clearly with our other common and similar-sized hawk of winter—the Red-tailed Hawk.  A Red-tail has a brown back marked with a V of white reaching from one shoulder, down the back, to the other shoulder (called the “scapular V”).  Since you often see just the back of a bird scanning the ground from a pole, this distinction is surprisingly easy to make.  The Roughie’s breast gleams white heavily marked with brown; his tail looks mostly white with a wide dark band toward the tip (easiest to see when the bird is flying).  The female resembles the male except that her back is more brown, with (usually) less mottling.  Both sexes have small beaks and small feet (small for a raptor, that is)—a good adaptation for life in year-round cold.  Also, when soaring, both sexes flash distinctive black patches contrasting with light underwing feathers about one third of the way in from the wingtips.  By most reports, Colorado hosts far more male Roughies than females, since females seem not to migrate as far south as the males do.

Roughies eat primarily rodents although they also take many birds.  In the winter, carrion can appear on the menu as well.  A bird of open treeless places, a Roughie hunts primarily on the wing, hovering over open habitat where it outcompetes more perch-dependent raptors such as Red-tailed and Ferruginous Hawks.  Although we typically spot them on sturdy power poles or fence posts, Roughies sometimes perch on surprisingly flimsy-looking treetops and shrubs or on less-than-steady power lines—all places other buteos rarely choose—because its smaller feet can grip slimmer perches.

The Rough-legged Hawk’s scientific name is Buteo lagopus.  “Buteo” arises from the Latin term for a species of hawk; the species name (“lagopus”) derives from Greek for “hare’s foot” (“lagos,” hare; “pous,” foot).  This name refers to the feathering that reaches all the way down the legs to the tops of the toes—another good adaptation for staying warm in constant cold.  The common name “rough-legged” describes this feathered feature as well, while “hawk” comes from the Anglo-Saxon word “hafoc”—their name for these types of bird.

The presence of Rough-legged Hawks in Colorado can be anticipated with surprising regularity—rarely before November or after early April. Their southern migration responds to lessening daylight rather than any particular weather events or frozen water:  Once the days get too short in the Arctic, daylight runs out before they can find sufficient food.  As the daylight period lengthens in early spring, they head back to the comforts of the Arctic.  (Comfort indeed lies in the eye of the beholder…)  We don’t see a lot of Roughies locally, but a few typically winter here.  In 11 years of the Salida Christmas Bird Count, we have found at least 1 Roughie every year—and at this year’s count on December 21, we counted 5!  Most often, we spot them around the agricultural fields along US 285 and CO 291 just a bit north of Salida.  So from November through early April, check out large birds on poles and wires.  Scapular V?  It’s a Red-tail.  A mottled-looking back?  It’s a Roughie.  It’s a great way to pass a long drive, but beware of this non-electronic form of distracted driving!

You can learn more about this winter hawk and see more photos here.