Darkness and rainfall prevail during Pacific Northwestern winters and this year has been no exception. More than four inches of rain fell during a 48-hour period this week. Following this two-day deluge, the air smelled dank and musty like a giant worm bin. It’s hard for humans to endure this gloomy foul weather, let alone birds that have to survive outdoors — especially some that only weigh a few ounces.
Feathers are key. Their structure, design and maintenance enable birds to survive most stretches of cold and rainy weather. Bird feathers are water resistant; rain hits the surface of the bird and rolls away without being absorbed. Further, when rain is heavy, birds flatten their feathers to make them even more water-resistant.
Bird feathers have masterfully evolved to provide insulation. Barbs and barbules hook together to form tiny, loose tangles that trap air and heat while at the same time providing strength and suppleness. People who wear down “puffy” jackets appreciate this warmth. As Thor Hanson said in his masterpiece Feathers “With their intricate air-trapping microstructure, down feathers are the most naturally insulative material on earth, and birds have the ability to fluff them up manually, essentially adjusting their R-value at will.”
In heavy rain, notice how birds adopt a posture with their bodies upright and heads withdrawn with their beaks pointed toward the incoming weather. This allows them to conserve energy and reduces the penetration of the rain. You can also observe how often birds preen their feathers. They do so by reaching their bills into oil glands and applying that oil on to their feathers. The oil is the necessary ingredient that makes the feathers supple and water-resistant.
Some birds, like Anna’s Hummingbirds, chickadees and titmice are able to thermally-regulate to adapt to cold and wet periods. Anna’s Hummingbirds enter a state of torpor when outside temperatures drop. Other species like chickadees, kinglets and titmice do something similar called facultative hypothermia which also entails lowering their body temperatures temporarily to reduce heat loss and save energy.
Birding can be unproductive during rain storms because birds perch or hunker down instead of flying around. Since stormy weather generally occurs during barometric low-pressure periods, it is harder for birds to fly. Birds prefer dense air that provides an aerodynamic lift to fly. Falling rain and high humidity further reduce the density of the air making flight difficult. Birds can and will fly short distances in rain but their wings eventually become saturated with water making it harder to fly.
Despite all of these adaptations, birds still get hypothermia and can die during extreme cold and rainy periods. Having bird feeders helps them get through these stretches. The abundance of birds on our feeders in the winter is testimony to their need for food supplements to help them cope with cold and wet conditions.
Meanwhile here in Seattle, the rain has temporarily ceased. Birds are mobbing our feeders, flying around, calling and engaging in territorial scraps. Miraculously, most have survived another epic storm.
Sources:
The Cornell Lab of Ornithology Handbook of Bird Biology
Bird Note – National Public Radio program “Why Do Birds Avoid Flying in the Rain?” – July 10, 2017
Bird Spot.com – UK; “Where to Birds Go in the Rain?”
Feathers by Thor Hanson
Smithsonian Insider – “Keeping Warm in Winter is for the Birds” – January 30, 2015
