I hardly dared to glance at the thermometer in my car as I headed to the North End Trailhead. The peak of afternoon temperatures had passed, and I knew it was only downhill from here. But the late-winter sun shone brightly, and the lure of the forest and ski trails pulled me along. Crossing a bridge across the Namekagon River, I took a moment to enjoy the rare beauty of flowing, swirling, glittering, liquid water.
The watery, wintery scene must have fired some memory synapses in my brain, because into my mind’s eye flashed the image of another river flowing through snow-covered banks in Yellowstone National Park. A coyote paused on the opposite bank, and an expansive valley stretched into the distance, illuminated by gaps in a snow squall. In the foreground, my memory followed the flight of a bird as it whirred upstream, just skimming the Lamar River’s quicksilver surface.
The small, dark gray darter with a wren’s jaunty tail landed on an ice-crusted rock just long enough for us to catch a glimpse. Then it dove under the current with a motion as fluid as the river itself. Seconds later it popped back up on the rock, with an insect larva in its beak. Gulp! The snack was followed by a series of high, clear, bubbling whistles and a few bobs—not just with its tail, but with its whole rear end. We were charmed.
John Muir fell in love with these little birds, too, during his many adventures in the Sierras. He wrote: “However dark and boisterous the weather, snowing, blowing, or cloudy, all the same he sings, and with never a note of sadness. No need of spring sunshine to thaw his song, for it never freezes…”
The American Dipper is North America's only truly aquatic songbird. It lives along clear streams and rivers out west, never venturing far from tumbling liquid. Even in winter, dippers continue to defend a feeding territory along the river.
The food dippers seek is the same stuff that bobbing Junior Naturalists catch every summer during our Museum programs on the Namekagon River: aquatic larvae of mosquitoes, dragonflies, caddisflies, mayflies; snails, worms, small fish, fish eggs; and a few flying insects, too.
Since aquatic invertebrates are found across the country, I’m not sure why dippers don’t live in the Midwest, too. Perhaps our rivers freeze over too frequently? Even out west, dippers may migrate a short distance to a river that stays open.
I love polar plunges as much as the next person, but I can’t imagine swimming for a living in the winter. According to one report, dippers even survive Arctic temperatures down to negative forty degrees Fahrenheit by swimming in spring-fed streams.
Of course, dippers have adaptations that help them achieve such feats, just like I have a bag full of cold-weather gear that will allow me to ski safely in sub-zero temps. Their feathers, like my wool sweater and windbreaker, are perhaps their most visible adaptations. Dippers have twice the number of contour feathers as a normal songbird. They also have thick down feathers interspersed between the rest, in places that would be bare skin on a different bird.
The density of their insulation is only part of the solution, though. The dipper’s preen gland that secretes water-proofing oil is ten times larger than the same gland on any other songbird. According to David Attenborough, dippers are so well-waterproofed and buoyant that they have trouble staying submerged!
Luckily, dippers’ short, powerful wings, and rudder-like tails give them the power to make short dives and overcome river currents that would knock a human down. Long legs and sharp claws allow them to wade for food as well. While most songbirds aren’t adapted to hold their breath, dippers use nasal flaps to plug their nose, and store extra oxygen in their blood.
I might put on goggles to protect my eyes from the cold, but dippers use clear eyelids called nictitating membranes. They have built-in contact lenses, too, in the form of muscles that change the shape of their lens to adjust between vision in air and water.
Air and frozen water were most of what I saw on my frigid ski, but I felt exhilaration from the sunshine and a crisp sort of cleanliness. I’m hardly ever sorry after an experience with nature’s extremes. Life on the edge keeps you sharp. Which, perhaps, is why the dipper so charmed us on that day in Yellowstone, with the snow squalls and coyotes, and furtive sunshine. Indeed, Muir has some excellent advice regarding the dipper: “Go see him and love him, and through him as though a window look into nature's warm heart."
|Dippers are the only
aquatic songbirds. With thick, oily feathers and lots of down, they can dive
into flowing rivers all winter long. |
Photo by Dave Menke, U.S. Fish and Wildlife Service.