Weathering the Storm

Sub-zero temperatures.  Winds gusting in excess of thirty miles per hour.  Drifting snow.  Near zero visibility.  Dangerous wind chills.  Not a pretty picture for most Iowans.  But those were the exact conditions that occurred when a good old-fashioned blizzard roared through Iowa last weekend.

Looking through the glass of my cozy dining room window, I wondered how anything could survive out there.  It’s the same thing I always wonder whenever whiteout conditions grip our local landscapes.  When the storm finally ends, I also never fail to marvel at how backyard birds suddenly reemerge to resume business as usual.  How do they manage to weather the storm? 

For Iowa birdlife, winter weather is no picnic; and survival tactics are nearly as varied and interesting as the species themselves.  Their first trick is simple.  In order to beat subzero cold, most birds consume all the food they can get their little beaks on.  There’s no calorie counting with this crowd.  Fat and carbs are a wintering bird’s best friends.  As long as chickadees, nuthatches, and cardinals can locate and combine high energy food sources with secure roosting cover, they can easily withstand the coldest temperatures.  Backyard feeders are never more beneficial to feathered visitors than when extreme weather puts daily survival on the line.

Birds further beat the cold by maintaining extreme, 105-degree or higher body temperatures.  For large birds such as wild turkeys or pheasants, maintaining those temperatures presents less of a challenge than it does for dinky, bundle of fluff birds weighing less than an ounce.  Most large birds gain an early advantage on future cold by slabbing on layers of fat during fall.  Many become downright obese by early December and, once the weather gets tough, can go for days without eating. 

But while the biggest birds can afford to dig in and wait for conditions to moderate, most little birds cannot.  At the approach of winter storm systems, they kick it into overdrive.  With comparatively lower fat reserves and extreme energy demands, species like chickadees, juncos and finches go on all out feeding rampage, swarming backyard feeders and voraciously consuming every bite they can get.

But there’s more to it than going to bed on a full stomach.  Secure winter habitat is a crucial component to winter survival.  At day’s end, birds head for the warmest cover they can find.  Ring-necked pheasants sail into cattail marshes, cardinals and juncos snuggle into spruce boughs, woodpeckers disappear into the dark recesses of excavated tree cavities.

But a bird’s daily struggle for survival doesn’t end at sunset.  As nighttime temperatures plummet even lower, many birds employ a final measure.  Some species go into a torpor; a state of deep, coma-like sleep where energy demands decline as metabolism and internal temperatures temporarily decline.  Other birds — like quail and gray [Hungarian] partridge — stay warm by sharing body heat with others.  As the sun sets, coveys form into a compact “tails in – heads out” circle.  This wagon wheel formation not only conserves communal heat, but provides added security as well, allowing birds to scan for predators from all directions.

There is no denying that winter is a rigorous and dangerous time of attrition for all wildlife.  During some years, mortality runs high.  But given adequate food and cover, enough birdlife will survive to replace winter loses during spring nesting.