Montana's The Final Destination For Rough-Legged Hawks Flying South

Dec 4, 2016
Originally published on November 13, 2017 12:55 pm

As winter comes to the National Wildlife Refuges of the Mission Valley, we begin to see a whole different group of visitors. And I’m not just referring to the human kind. Strange as it may seem, the National Bison Range, Ninepipes National Wildlife Refuge and Pablo National Wildlife Refuge, along with other lands in the Mission Valley, are where a number of birds choose to spend their winter.

It turns out that this part of western Montana is their southern migration point. While many of the birds that spend the summer in the Arctic tundra fly over us on their way to Central and South America, a few intrepid types stop here. One such bird is the rough-legged hawk.

Named for their fully feathered legs, rough-legged hawks spend the summers nesting on the tundra in northern Canada and Alaska – and I don't mean on the tundra. In this treeless expanse, large birds have little choice but to nest on the ground. It may be the resemblance of the grasslands and marches of our area to the open tundra that attracts these birds to the Mission Valley. Or maybe the similarity of our fairly mild winters to the cool summer weather of the far north.

Whatever the reasons, large numbers of rough-legged hawks spend the winter here. The Mission Valley hosts one of the largest concentrations of wintering rough-legged hawks in the country. Researchers have documented communal winter roost sites along the base of the Mission Mountains, containing up to 200 birds.

During the winter season, rough-legs are the most common large hawk seen in the Mission Valley. Every once in a while I confuse one of theses birds for a bald eagle because they often have a very light creamy-colored head and a dark breast. But, since they are just the size of a re-tailed hawk, I soon realize my mistake. Like many types of hawks, rough-legs come in a variety of color phases, so some will have a light body and head, while others will be dark all over.

But one good clue to what you’re looking at is the white tail with dark terminal band, seen on all birds of all ages and color-phases. And on the lighter-colored birds, look for the characteristic black “wrist” seen on their underwing when they fly overhead.

These birds come to the Mission Valley looking for food to get them through the winter months so they can return to their northern nesting areas in the spring. Their main, and almost only, prey are mice and voles. Surprisingly, even though rough-legged hawks are the same size as red-tailed hawks, they are pretty much restricted to taking small prey because of the size of their feet.

Birds of prey catch their meals using strong, sharp talons on their feet. But rough-legs have very small feet for their size. So while a red-tailed hawk can easily take a rabbit or a grouse, our wintering hawks need to take small rodents. And the way they do it is unique for a bird that size.

Many large birds of prey soar on warm updrafts while looking for something to catch and eat. This is one reason most red-tailed hawks migrate out of western Montana in the winter – it is harder to soar when the weather gets cold. But rough-legged hawks over, facing into the wind and flapping their wings to hold their position over where they thought they saw a moving meal.

You may have seen American kestrels do this, a falcon about the size of a robin. But the only other large bird of prey able to hover is the osprey, which spends the summer hunting for fish in lakes and rivers. But osprey leave the Mission Valley as the rough-legs show up for the winter. Large birds seen hovering during this time of year will probably be our winter guest, the rough-legged hawk.

So, when the icy winds are howling, snow is drifting in the fields and Jack Frost begins nipping at your nose, remember this – the rough-legged hawk flew 2000 miles or more to spend the winter in this type of weather. Let them inspire you to brave the elements. Visit the National Wildlife Refuges of the Mission Valley and do some winter hawk watching. After all, the birds think this is a great place to spend the winter.

'Field Notes' is produced by the Montana Natural History Center

Broadcast: "Fieldnotes," 12/25/16. You can hear the program on the radio Sundays at 12:55 p.m., Tuesdays at 4:54 p.m., and Fridays at 4:54 p.m., or listen via podcast.

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