By Harvey Thommasen, with Photography by Mike Wigle

Even in the dead of winter an angler setting out to fish a coastal watershed in the Pacific Northwest may be lucky enough to have company in the form of birds.

Bird species that over winter in the Bella Coola Valley, where I like to fish, include the Brown Creeper, Varied Thrush, and grouse (Ruffled, Spruce, and Blue). The woodpeckers (Pileated, Hairy, and Downy) and the owls (Northern Pygmy, Saw-whet, Boreal, Great Horned, and Barred Great Gray Owl) also stay year round. The occasional Redwinged Blackbird, Song Sparrow, Robin, Rufous-sided Towhee, and Sharp-shinned Hawk will attempt to over-winter as well.

The other groups of birds you can see in the Bella Coola Valley during winter are the Redpoll, Bohemian Waxwing, and Northern Shrike that come to us from nesting grounds far to the north and also birds like the Evening Grosbeak, Purple Finch, Boreal Owl, cross-bills, Three-toed Woodpecker, Gray Jay, Pine Grosbeak, Rosy Finch, Boreal Chickadee and Mountain Chickadee that are driven down to the valley bottom from their high altitude homes because of weather or food shortages.

Those birds that choose to stay the winter must make use of a whole host of physical, physiological, and behavioral adaptations to help them survive winter in our coastal valleys. Birds, like mammals, are warm-blooded creatures. Their metabolism is geared for operating most efficiently at high body temperatures. Warmblooded animals have two basic strategies for surviving winter.

The first strategy for surviving winter is to become inactive and sleep the winter away. This deep, prolonged sleep is known as hibernation, and it is what bears, marmots, jumping mice, and bats do. Common to all hibernators is a depressing of the metabolic rate so as to try and stretch out the duration they can live off precious energy (fat) supplies.

Breathing and heartbeat slows down, and the need to burn calories goes way down as well. For example, when the Little Brown Bat goes into hibernation its heart rate drops from 100-120 beats/min. to only 5-10 beats/min., and its body temperature drops from 40C to 5C or so. The heart rate in a hibernating bear drops from 40 to 10 beats /min., and its body temperature drops from 37C to 32-35 C and oxygen consumption drops by over half.

While hibernating, animals live off the fat in their bodies. Not surprising is the fact that all of the hibernating animals are quite fat at the time they settle in for their deep wintertime sleep. The tiny Western Jumping Mouse is another hibernator. Like the bear and marmot, Western Jumping mice build up large quantities of fat over the summer and early autumn months, then fall into a death-like sleep to survive the winter. Its heart-beat drops from a normal rate of 500-600 beats/min. to 30 beats/min. or less. The body temperature falls to just four degrees above freezing. By doing this, the jumping mouse is able to decrease its oxygen consumption to a level that is only 5% of wheat it was when the mouse was active.

Scientists have recently discovered that some kinds of birds - the swifts and goatsuckers – hibernate in some North American sites for up to three months. But this appears to occur only in southern United States. Our coastal winters are far too cold and far too long for our local swifts. Animals that rely on speed and agility to escape predators do not undergo hibernation, because accumulating the necessary fat reserves would put them at too high a risk of being eaten. That is probably why deer, the snowshoe hare, the pike squirrels, and all of our local birds do not hibernate. In fact, the tiny local birds like the kinglets, nuthatches, and chickadees barely have enough fat to get them through the night.

The second strategy available to warm blooded animals is to keep active, cope with the cold days as best as one can, and feed the entire time. This is what our local birds do. One of the first things they do is replace their thinner summer coats with a thicker, bulkier feather jacket. By simply fluffing up the breast feathers, birds create an air layer between their skin and the oil-covered outer feather layer, which is closely overlapped. This air layer functions as a self-created additional insulation layer.

Huddling is another behavior which reduces heat loss, because the birds share their body heat and they decrease surface area exposed to the cold. On particularly cold nights, Red-breasted Nuthatches, Black-capped Chickadees, and Northern saw-whet owls are all known to huddle inside abandoned woodpecker cavities or in some kind of natural cavity. Apparently, someone once found 100 nuthatches together, stuffed together inside a tree.

The chickadees, nuthatches, and jays actually plan ahead and hide away food over the late summer and early fall months when there is more food than they need to satisfy their hunger. Seeds and nuts are among the most commonly stored foods - probably because they store so well. When winter comes and food is scarce, these birds go back to these food stores.

Few things are more delightful when walking along a river in winter, than the chirping of feeding birds in the bare branches around you. It’s a reminder that, despite the cold, life still flourishes - and that perhaps there is a trout waiting to stir in pursuit of your fly.

(End Note: Harvey Thommasen, one of the founding writers of A River Never Sleeps.com, is a medical doctor who currently lives in Prince George. He has a cabin on the Bella Coola River, where he can often be found fly fishing and bird watching. He is co-author of River of the Angry Moon, and is currently working on a book tentatively titled; Birds of a Salmon Stream.)