Friday, January 6, 2017

Snow Birds of the Sierra

A few days ago, I had the privilege of watching a beautiful winter storm descend on the hills of the Sierra, around 3,300 feet in elevation, between the towns of Murphys and Arnold.  Blowing snowflakes created a winter wonderland outside, while I watched from behind a window, snug and warm indoors.

The plant communities at this elevation are comprised of species typical of mid-mountain forests, found in the Sierra between 2,500 to 6,000 feet: Ponderosa Pine (Pinus ponderosa), Incense Cedar (Calocedrus decurrens) and Black Oak (Quercus kelloggii).  Gray Pine (Pinus sabiniana) and plants more typical of lower elevation foothill chaparral exist in this region on dry, warm south-facing slopes.  Manzanitas (Archtostaphylos spp.) and Ceanothus (Ceanothus spp.) make up most of the shrub component of the ecosystem.

Looking out on a snowy forest, one would assume all of its resident fauna are curled up in warm dens, old woodpecker holes, burrows and the like.  And plenty are, surviving out of the way of the icy wind, while others have long since migrated south or downslope to the snow-free Central Valley.  But if you watch long enough, you will see the hardy denizens of mid-mountain forests emerge.

This Steller's Jay fluffed up his feathers for warmth, and paid no mind to the blowing snow, though the wind tousled his jaunty crest.  Many birds endure cold temperatures by fluffing up their feathers, trapping warm air close to their bodies and increasing their feather's insulating properties.  Often, birds will then tuck their feet under their feathers, hunker down and ride out the storm.

Birds, like this Northern Flicker, also have waterproof feathers.  They are coated in waxy, water-resistant oil produced by preen glands at the base of the tail, which is distributed through their feathers as they preen.  Preening also serves to realign and interlock the tiny barbs along each feather, further sealing out moisture.  You've probably observed this characteristic of feathers.  Pick up a discarded, mussed feather and begin running your fingers along it, smoothing it out as you go.  The minute hooklets and barbules on each barb realign and connect, creating a smooth, tightly linked surface, which insulates and waterproofs the bird.  This is why carefully preened feathers are so critical to a bird's survival.

In the photo above, the Goldfinch on the left is fully fluffed, sitting on its feet to keep them warm; the bird in the middle is preening its feathers meticulously; and the bird on the right is posing for a photo!

This Dark-eyed Junco (Junco hyemalis) was taking refuge from the storm inside dense shrubs, periodically emerging to have a look around and forage on the ground for seeds and the like.  At this elevation during the winter months, you are also likely to see Ruby-crowned and Golden-crowned Kinglets, Mountain and Chestnut-sided Chickadees, Golden-crowned Sparrows, California Towhees and Spotted Towhees, California Quail, Ravens and California Scrub Jays, a variety of woodpeckers, and raptors, such as hawks and owls.  Down in a marshy area, I spotted a pair of Canada Geese.  And in a wooded, residential area, I found these tracks, made by...  Can you guess?

These large and rather dinosaur-like tracks were made by Wild Turkeys!  Wild Turkeys are large birds that primarily walk as a means of transportation, though they can fly well and, surprisingly, even swim!  These birds are always an impressive sight, strolling through the woodlands.  Though they are native to North America (specifically the eastern half of the continent) they were introduced to California as game birds. 

I will add a note that I have read Wild Turkeys, or at least an ancestral species of turkey, existed in California during the late Pleistocene (around 10,000 years ago), according to fossil records.  This would mean we can consider them to be reintroduced, rather than an introduced exotic species.  An interesting perspective, I think.  If you're really interested in the evolution of wild turkeys in California, check out this discussion, by Don Roberson, author of five books on California birds and creator of the natural history website Creagrus.

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