February 4, 2023
The prairie falcon perches on a power pole in the light rain drizzle, tearing apart a vole. Its talons glow faintly, a rich yellow against the gray sky. The electrical lines hiss faintly in the rain. Today I’m with avid birder and acclaimed children’s book author Sneed Collard (find out about his books at www.sneedbcollardiii.com). We’re driving slowly through western Montana’s Mission Valley, looking for birds in the snow-covered fields.
Nineteen thousand years ago, a glacier crept down from the north where Flathead Lake exists now, a slow but powerful conveyor belt of ice, reshaping the landscape. Where we are today, the glacier spilled into the watery vastness of Glacial Lake Missoula. As the ice transformed to frigid water, the glacier dropped its load of sediment into the lake.
These are the rocks, silts, and clays that make up the modern landscape around us. The gently undulating terrain is packed with pothole wetlands. After Glacial Lake Missoula emptied, permafrost heaved the ground. Chunks of ice mounded the earth with the power of their freezing. And when they melted, they left behind thousands of wetlands.
During the warm season, Sneed tells me, these wetlands can be full of cinnamon teals and other ducks. But today they’re all frozen and birdless. Instead, our attention is focused on the fence posts, power poles, and irrigation lines where the raptors are perching.
A valley of voles
This valley is excellent habitat for overwintering raptors. According to Beth Mendelsohn of the Owl Research Institute, there are lots of voles here this winter – an excellent food source for many of our raptors.
Even during today’s casual birding, we can see signs of this abundance of voles. It’s not just the prairie falcon. A few minutes before, we had watched a female northern harrier catching a vole in a hayfield.
The harrier’s success would prove short-lived, though. One of the many common ravens in the area saw her and flapped towards her, croaking. The harrier dropped her prey and then plunged to the snow, evidently trying to recover it. But apparently the vole had already managed to dive beneath the snowy blanket. The harrier took off with empty talons – and the harassing raven got nothing for its pestering, either.
Plants among the snow
The snow is soft on this relatively mild, drizzly winter day. To the east, the imposing Mission Mountains are shrouded in clouds, and a gray curtain of rain covers their flanks. We can see grasses poking up out of the snow in many areas.
From time to time we drive past extensive patches of teasel (Dipsacus fullonum). To me, the presence of this non-native plant in this valley is very noticeable. Around Helena, where the rain shadow of the Continental Divide makes the climate substantially drier, teasel is absent, except for a few minor patches along the edge of the Missouri River. Here, on the other hand, it’s extensive, covering entire fields. Evidently, it’s a plant that thrives with more moisture than the desert-like Helena area offers. We ask ourselves if any of the winter birds – American goldfinches or American tree sparrows, for example – might eat teasel seeds. But if they do, we haven’t yet seen any sign of it.
Winter raptors of the Mission Valley
The northern harrier and prairie falcon aren’t the only raptors searching for voles in the soft snow here. Frequently we spot red-tailed and rough-legged hawks on the power poles and irrigation lines. In fact, this valley is a well-known wintering locale for these raptors. According to Beth Mendelsohn, the Owl Research Institute (ORI) does monthly raptor surveys throughout the winter in this area, using multiple observers to conduct five 30-mile transects simultaneously in a single day. On some of these days, the ORI observers have counted an astounding 800+ raptors, largely red-tailed hawks and rough-legged hawks.
Extrapolating these results beyond the transects, ORI’s founder Denver Holt says that it’s reasonable to suppose that over 1000 raptors overwinter in this valley. Granted, it’s not a tiny valley, but nevertheless these numbers are phenomenal. Voles, grasslands, and extensive, large open spaces: in the Mission Valley, it’s a combination that supports a very impressive population of birds of prey.
The raptors are the most noteworthy birds we see today, but they aren’t entirely alone. Flocks of house sparrows chirp harshly from the shrubs near several of the farmhouses. Occasionally a small flock of American tree sparrows flies up from a field, and sometimes a house finch or American goldfinch flies over.
The birds of Post Creek
The water is open in Post Creek, a few miles south of Ninepipe National Wildlife Refuge. Long-lost fishing lures dangle from an alder over a deep, steely blue pool near the bridge. A few mallards and a hooded merganser flush from the water. A Townsend’s solitaire perches in the junipers nearby, guarding its supply of winter berries.
Farther downstream, we arrive at a cattail marsh along the creek. This spot, Sneed tells me, is where his son Braden saw his first-ever Wilson’s snipe. And today as well, it’s clear that the open water and the riparian habitat along it is supporting a diversity of birds.
We glimpse a pair of green-winged teals as they flush from the stream. They fly away and then glide rapidly back to the water, disappearing in seconds. A large flock of European starlings, around 300 of them, is very active in the cottonwoods downstream. They whistle and buzz cheerfully. Once in a while, I hear one of them doing an impressive imitation of a western meadowlark song. And the starlings aren’t alone. There’s an almost-constant chorus of red-winged blackbird song from the cottonwoods. The songs are frequent enough and interspersed with enough chak calls to assure us that we’re actually hearing red-winged blackbirds, not just the imitations of starlings.
Rumors of spring
Suddenly, something startles the flock and many of them take off in a cloud, hordes of starlings and a few red-winged blackbirds dancing across the sky. A few birds split off and fly past us, heading in the direction of another pothole wetland in the distance. As I raise my binoculars, I’m amazed to see that one of these blackbirds has an unmistakably yellow head. A yellow-headed blackbird in the waning days of winter – what’s it doing here? It’s a solid two months early for this species to show up – a definite surprise. But if we were to see a yellow-headed blackbird today, this certainly seems like a good place for it, with these marshes, cottonwoods, and the open water.
Spring isn’t here yet, but it’s inching closer. We can glimpse it in the heart-lifting song of the red-winged blackbirds, the gentle drizzle, and this unexpectedly early yellow-headed blackbird. And while winter lasts, these snow-covered fields and icy potholes are supporting hundreds of hawks and the occasional prairie falcon, gathering a bounty of voles.
Levish, D.R. (1997). Late Pleistocene sedimentation in Glacial Lake Missoula and revised glacial history of the Flathead Lobe of the Cordilleran Ice Sheet, Mission Valley, Montana. Ph.D. dissertation, University of Colorado. Retrieved from https://www.proquest.com/openview/106db1a37cacf0eb32bc90a0bbbc3639