At 47° latitude and 3,000 ft elevation, winter has yet to turn the corner in Montana’s Mission Valley. While I’m envious of your reports of warming days and flowering fruit trees, I don’t mind slogging through another few weeks of cold, ice, and snow if it means enjoying the company of local wintering raptors.
Forgive me for prolonging your winter, but I didn’t think offering a photo diary of gorgeous raptors would be too tortuous for my Dawn Chorus comrades. This is my fifth winter in Mission Valley and I’ve gained a fair understanding of how raptors use this landscape. But each winter is different, and that insight is always getting upended. It’s humbling, but I’m here for it.
The focal area of this diary is Ninepipes National Wildlife Refuge, located in northwestern Montana on the Flathead Indian Reservation, with the spectacular, snow-capped Mission Mountains as backdrop. The refuge and surrounding state, tribal, and private lands make up an 18,000-acre sprawling complex of wetlands and grasslands managed as staging and breeding habitat for native birds, primarily waterfowl and waterbirds.
Ninepipes sits on a glacial terminal moraine left by receding glaciers some 11,000 years ago. Blocks of ice that were imbedded in outwash sediments slowly melted, leaving depressions that filled with water by precipitation and overland runoff. The resulting landscape is a prairie pockmarked with thousands of pothole wetlands and kettle ponds, connected by gently rolling grasslands.
Grassland cover types make up ~60% of the Ninepipes complex land base. A mix of grass species is maintained to seasonally benefit multiple wildlife species, with an emphasis on nesting waterfowl. In winter, however, the grasslands are the domain of raptors and thriving populations of rodents. Across my five years of observation, winter’s steadfast grassland raptors are Northern Harrier, Short-eared Owl, Rough-legged Hawk, and Prairie Falcon, with a few others making “guest” appearances.
Northern Harriers (NOHA) are probably the most common raptor of Ninepipes grasslands. These slender, agile Accipiters are often seen foraging on the wing, flying low over the ground, wings held slightly up in a “V” shape, often making cartwheel-like ambushes on their prey. NOHA’s disk-shaped face looks and functions much like an owl’s, with stiff “filo feathers” that funnel sound to their keen ears. The filo “disk” can be raised or lowered at will to home in on prey hiding in dense vegetation.
I’m unsure if the NOHAs I see in winter are resident or migrants. I know there is some emigration of adult male NOHAs in winter, as they are rarely seen. I would hazard to guess that 95% of the NOHAs I see in winter are adult females or juveniles. Where do all the males go in winter?
Ninepipes is meadow vole heaven (unless you’re on the receiving end of those talons!). Meadow voles likely make up the bulk of NOHAs’ diet, though in years when small flocks of Snow Buntings and Horned Larks wander through, these songbirds would certainly be targeted.
David Sibley describes NOHA as “generally solitary,” but I’m not sure that description fits in winter. At Ninepipes, I’ve observed a couple of early morning NOHA “fly-outs” from communal ground roosts (15 birds from one cattail patch). Communal roosting of NOHAs and Short-eared Owls is well documented across their winter ranges; I expect it also occurs in the Ninepipes grasslands. Occasionally, I’ll come across a group of 3 or 4 NOHAs engaged in impressive aerial scuffles. These usually involve a NOHA with a vole being harassed by others intending to pirate the prey item, a practice known as kleptoparasitism.
Short-eared Owls (SEOW) both winter and breed in the Ninepipes grasslands, and they are always a delight to see. Sibley calls them “essentially the nocturnal counterpart of the Northern Harrier.” My impression is that winter occurrence of SEOW changes each year, but I can only speculate as to why (snow depth? temperatures? prey abundance?). A cattail patch that held 20+ roosting SEOWs in December 2023 held zero owls a few weeks ago. In February 2021, I found a group of 30+ SEOWs group-hunting for voles during a winter storm (Dawn Chorus: A Winter Gathering of Owls). SEOW is known to be irruptive based on a 4-year cycle among tundra and grassland rodents. It’s possible this irruption dynamic occurs in Ninepipes, but a more basic explanation for annual population fluxes may be SEOW’s intrinsic sensitivity to local environmental conditions.
Rough-legged Hawks (RLHA) are strictly winter visitors to the Ninepipes grasslands. They arrive in early November and are probably departing to Arctic tundra breeding grounds as we speak. I am enthralled with this bird in its endless, absolutely gorgeous plumage patterns. I love their long-winged gracefulness, delicate beak and feet, and their shy wildness. It’s always a thrill to have one in my sights, and an even bigger thrill to have one in my camera viewfinder.
I usually see them perched on power poles, wheel lines, fence posts, or trees where they hunt by sight for voles and other rodents.
Of course, they’re also spotted soaring or hovering over grassland habitats. These in-flight observations are my favorites, as they reveal the unique and striking patterning of the undersides.
Montana ornithologists have documented RLHA communal winter roosts along the base of the Mission Mountains holding up to 200 birds. This past year, I noted a very loose communal roost of ~50 RLHA and Red-tailed Hawks in a Douglas-fir/cottonwood riparian forest bordering Ninepipes Refuge. This very well may be one of the earlier documented winter roosts, but it was still a thrill to see so many hawks bee-lining to this copse of forest at last light.
Prairie Falcons (PRFA) may be year-round residents of the Ninepipes complex or possibly short-distance migrants. In winter, they number few, but are consistently seen year to year. The PRFA’s entire mode of hunting is adapted to grasslands, and they use a variety of hunting techniques including the well-known “stoop” and mid-air blow; a fast, low-to-ground cruising tactic; and line-of-sight ambush from high perches. Their winter diet consists of small rodents and the occasional Horned Lark or Snow Bunting. I would wager they make a small dent in the local Red-winged Blackbird population as well.
Besides the four grassland specialists highlighted, the Ninepipes complex also hosts a few other raptors that are more “generalists” or make quick stopovers during migration.
Thanks for dropping by,
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