31 January 2014

Friday Field Notes: Chinook Winds of Fortune

On my ride into the Montana Natural History Center this morning there was one thing that was impossible not to think about: WIND. Struggling against a current of wind on an icy bike path is no cakewalk. Missoula doesn't get this windy too often, but just a handful of miles across the Continental Divide onto Montana's high plains, it's another story.

Most of Montana is occupied by rolling grasslands, once dominated by bison, pronghorn, and prairie dogs. Beautiful shortgrass prairie stretched from the flanks of the Rockies and moated the island ranges of the central and eastern parts of the state. The rich soils that sustained the plentiful life were also ideally suited for growing crops like wheat and alfalfa and stock grazing. A short time after the advent of white settlers, much of the prairie had been checkered with farms and fences, altering the pristine landscape into an anthropomorphized version of its former self.

Looking out from Square Butte towards the Missouri River Breaks
Weather, however, remains indifferent to our terrestrial tillings, not appearing to care about our comfort or chapped faces.

Wind has played an important role in Montana's history, particularly on the eastern slope of the Rockies. From harnessing wind for energy production, to dispersal of seeds and pollen for various plants, wind, despite its indifference, is critical for life on the prairie.

Chinook winds have certainly made their mark on Montana history. A Chinook wind a is warm, dry air mass that rips down the east slope of high mountains and warms the plains it crosses. Chinooks form from  westerly humid cells of air from the Pacific that dump their moisture on the west sides of mountain ranges (the great and mighty Rockies in our case), then warm adiabatically on their way back down the eastern side. The Chinook winds reach temperatures up to 60 degrees F and tear across that landscape at speeds up to 100 mph, melting and sublimating snow in their wake.
These winds are most common and severe from Cutbank to Helena, Montana. The high, steep eastern slopes of Glacier and the Bob Marshall and Scapegoat Wildernesses warm more quickly. The greatest temperature change in a 24-hour period in the U.S. was due to a Chinook wind, and occurred in Loma, Montana. The temperature went from -54 to 49 F, a 103-degree change! It is plain to see that ranchers would have relied on these remarkable weather events to make it through the unforgiving winters that punctuate every year in central Montana.

Waiting for a Chinook by Charlie Russell
As I bike back home today against that not-so-warm wind coming out of the mouth of Hellgate Canyon, I'll be dreaming of warm, dry Chinooks on the prairie.

30 January 2014

Nature Notes: Tracking in the Seeley Lake Region

Oh, Animal Tracks
Left in the Snow
You provide a Story 
that I so long to know.

But with time and patience
I can follow each track
leading me to find you
at the back of the pack.

24 January 2014

Friday Field Notes: Icy Sentinels: Stalwart Herons in Winter

Riding my bike in the summer along the Clark Fork River sometimes feels like an exhibition of nature. Munching beavers, darting kingfishers, and watchful Osprey are rarely out of sight or unheard. Trout break the surface of the river and grebes and their allies dip to catch a morsel under the cool water. But, as the warm clear mornings start to turn into cold ones and ice forms along the river's bank, only the hardiest animals show themselves.

A watchful eye in winter will turn up some of these unyielding creatures. One not too hard to spot is the Great Blue Heron. I was amazed to see that these large graceful birds were waiting at the edge of the ice, staring motionless into the water, as if mesmerized by the chunks of ice floating by. My thoughts then turned to a poem by renowned poet Mary Oliver--Herons in Winter in the Frozen Marsh.


This poem captured much of the feeling I experience while watching these icy sentinels.

If you look carefully at some places on the river ice you can see their "pitchfork" footprints along the water's edge. You may be wondering how the herons can stand the cold with their long scaly legs in the frigid water or on the ice, and the answer is that they are equipped with a special routing of blood vessels in which the vessel carrying blood out to the leg lies directly against the vessel carrying blood back in. This is called "counter-current heat exchange," and is an adaptation used by many organisms across the globe. The blood going into the legs warms up the blood coming back into the body, keeping the heron's body temperature at a remarkable 103 to 106 degrees Fahrenheit (keep in mind that the average human body temperature is 98-99 degrees Fahrenheit). This allows them to stand at or in the water's edge and watch for fish and crustaceans for long periods of time.

As for me, I feel fortunate that I don't have to stand barefoot in the cold river to catch a bite to eat. I'm content just watching the pros at work.

So next time you find yourself along the river, make sure to scan for herons, motionless and cold, looking for lunch.