Laura Erickson's For the Birds

During a typical Minnesota winter, a bird’s most critical need is food, the fuel that keeps its metabolic furnace burning. If a bird has enough energy to shiver, it can easily maintain its body temperature at over a hundred degrees on the most frigid days.

Water is also important, but its value to wintering birds is exaggerated. Birds are vastly more efficient than mammals in conserving bodily fluids. They exhale virtually no water, making it almost impossible to detect steam as they breathe. They don’t sweat, and their urine is so concentrated that they lose very little water to excretion. During periods of extreme cold, birds will sometimes eat snow, but often just wait it out. Even on frigid January days, the sun heats up icicles enough to start them dripping. Chickadees and nuthatches cling to the slippery icicles and sip to slake their thirst, and they even take an occasional cold shower. Larger birds sit on the ground beneath, sipping and bathing in the icy puddle before the drips freeze. Sometimes the frenzy around a few dripping icicles looks like a winning World Series team’s shower room.

Our wintering birds are adapted to boom or bust water availability in winter, perfectly self­ sufficient as far as drinking water goes. But with the current interest in attracting birds to backyards, many people offer birds water year- round. On days when temperatures are in the 20s, I often set a plastic bowl filled with water on my platform feeder. My neighborhood birds have learned to recognize the bowl, and within minutes a variety of them zoom in for long drinks. But soon ice forms, and I close the bar for the rest of the day.

To solve this problem, some gardening and bird-feeding stores sell heated birdbaths that keep water thawed even when it’s below zero. But these are hazardous. If birds take even a momentary dip, water coating their outer feathers can freeze, making it impossible to fly.

Northland birds don’ t have an inborn instinct to avoid warm water when it’s cold, not because they’re stupid but because up here, liquid water isn’t naturally available during sub-zero weather except in lakes and streams with water too deep or fast-moving to bathe in. In the same way that hungry birds can be enticed to unnatural feeding stations, thirsty ones can be enticed to unnatural bird baths, and if they do what comes natural and take a quick dip in the invitingly warm water, it can lead to their death.

Val Cunningham, who serves as a volunteer at the University of Minnesota’s Wildlife Rehabilitation Center, had a personal encounter with an iced bird at her own heated bird bath. “Before I wised up and pulled the plug on our bird bath heater on extremely cold days, I once observed a European starling bathe, then fly away and manage to reach a distance of 50 feet from the bird bath before dropping like a stone. This bird I brought in to warm up and de-ice, and never again had the heater in the bird bath when the temperature dropped below zero.”

If you have a heated birdbath, the best solution is to do as Cunningham does and pull the plug on sub-zero days. If you can’t bear for your birds to go without water during a cold spell, at least fill the bottom of the birdbath with stones so the water is too shallow for a bath, or cover the entire bird bath with plastic-coated hardware cloth with a wide mesh, so birds can dip their beaks in to drink, but can’t get their feathers wet. Offering your backyard birds a thirst-quenching treat is a genuine kindness. Just take care that a heated birdbath doesn’t kill them with kindness.