The other day as I was pumping gas and grumbling to myself about the cold, I happened to glance up while waiting at the pumps.

I stared and I tried to make sense of what I was seeing. I thought to myself that what I was seeing just couldn’t be.

Above me was a large bird of prey moving fast. I only got a good look for about 20 seconds and tried to look for obvious field marks. I knew what it wasn’t, and I couldn’t trust myself to be right. I hurried into work so I could check my field guides while this encounter was fresh in my mind’s eye.

Long ago, I was given incredibly good advice when it came to identifying wildlife: rule out the common species before trying to “ID” something as uncommon or rare. I kept doubting myself, but when I turned to the migration map, I knew that the large bird that soared past me was a rough-legged hawk.

Identifying these birds

Female rough-legged hawks have large dark belly patch, and light-colored tails with dark bands at the tips. Males have heavily streaked breasts, and the tails are banded.

Both have large wings that are longer and narrower than other hawks in buteo group.

The tails in males and females look longer than other hawks’ tails, too. The wings seem swept backward with a hint of an “M” shape to the silhouette. This is why I was confused because ospreys have that signature “M” shape as well, and I knew this wasn’t an osprey.

Rough-legged hawks live in the open country of the arctic, North America and Eurasia. Just like the name suggests, they have feathered legs all the way down to the toes.

These hawks, ferruginous hawks, and golden eagles are the only American raptors to have feathers all the way to the toes.

A distinctive characteristic

There are several theories as to why only these birds have these adaptations, and all of them sound reasonable.

One is that the feathers protect the skin in the harsh conditions where they live. I have compared this to people wearing snow pants for the very same reason.

Another theory is that the feathers offer protection from the teeth and claws of their prey, which makes sense because I wear heavy gloves to protect me from beaks and talons. Lastly, these feathers may offer protection from the stress put on the bare legs while migrating at high altitudes and speeds, but that doesn’t explain how other birds are able to ward off the cold, hunt and migrate when they are under the same stresses.

Nesting and mating

Nesting on cliffs, uplands and alpine regions, both inland and coastal, they hunt over open bogs and other clearings.

The males choose the nest site, and the pairs either reuse the same nest year after year or they build a new nest close to the old sites. Often gyrfalcons, peregrine falcons, and common ravens will share the same cliffs, although they will keep their nest sites at least ¼ mile from other nesting raptors.

Rough-legged hawks are monogamous for at least the duration of the breeding season, and pairs stay together on wintering grounds as well as their home range.

The nests are about 3 feet in diameter and about 2 feet deep, constructed with branches, sticks, arctic plants, and there have been nests found with caribou bones.

The lining includes grasses, sedges, small twigs, molted feathers and fur from prey. The females spend four weeks building the nest from materials collected by the males.

Like other birds of prey populations, the availability of prey determines breeding behaviors, and if the pairs have trouble finding food for themselves, they will not breed at all.

The females lay two to five white eggs covered with brown blotches.

After an incubation period of about a month, the downy chicks hatch and are completely helpless. They leave the nest around six weeks, and they will reach sexual maturity around 2 years of age.

Primary food sources

In the arctic, prey includes lemmings, shrews, ground squirrels, rabbits, gophers and birds such as ptarmigan. Hunting methods varying depending on the prey or habitats. They actively hunt down prey or hover into the wind and drop down on prey. They also hunt from elevated perches such as utility poles or trees.

When hunting is difficult, they have been known to steal from other birds such as ravens, crows and other birds of prey.

Partners in Flight estimates a global breeding population at about 500,000 individuals with a fairly even distribution half spending at least part of the year in Canada, and half wintering in the United States.

I am going to look to the skies more often for the next few days hoping to catch another glimpse of this uncommon raptor.

Be sure to let me know if you happen to see this winter visitor as well.

Jeannie Carl is a naturalist at the Carbon County Environmental Education Center in Summit Hill. The center rehabilitates injured animals and educates the public on a variety of wildlife found in the area. For information on the Carbon County Environmental Center, visit www.carboneec.org.