The physics of puffery

Scrub-jay, with peanut, of course.  Photo by May Woon.

Today was quiet along the hillside that was alive with birdlife yesterday.  The Waxwings seem to have gourmandized the place, taking every visible madrone berry.  Perhaps all the little white mistletoe fruits as well.  The Waxwing bathing pool is just as clear and inviting today,  Perhaps more so, because the sun is bright even though it lacks the ability to climb much above the Siskiyou ridges to the west.  It’s a clear, dry day.  Fine for a bath, if there were but bathers.

I was left with watching two Scrub-jays.  The pair sat with pale chests to the sun, maximizing the passive solar heat they could absorb.  And their feathers were fluffed up, maximizing the amount of air trapped between the fibers of their plumage.  Nature’s best insulation, still air.  I am sensitive to such things now because we are about to gut our fifty-year-old house with no wall insulation and rebuilt with the best of green design and engineering we can afford.  Solar water heating perhaps, but solar electricity out of the question because of the looming mountains that cut off our sun from the west much of the year.  A heat pump.  Radiant heating.  Deep overhangs to protect from the direct sun of high summer.  Interior materials without off-gassing, esp. formaldehyde.  Double-pane glass. 

The Jays meanwhile carry their fine insulation with them wherever they go.  Sleek and reflective of solar energy in summer, a fluffed-up absorbent belly toward the sun in winter.  Still air trapped between and amidst the feathers they so carefully maintain in all weather.  Air that does not quickly transmit the body heat to the cold outside air. Feathers, the world’s finest roofing/insulation/decoration/camouflage material.  The Jays’ many tiny air pockets preserve those precious calories they get from eating all the peanuts I provide and what little food they have to scrounge on their own.

Speaking of insulation, on the Dipper walk I learned the bouyant beauties have almost double the feather count of mere landbirds.  That’s how they survive winter streams that must be always less than 40-degrees even on a sunny day.  We should think of them as over-feathered, aquatic wrens.