Traffic is building on migratory highways
Inside the Outdoors: Our networks of waterways are guiding geese, swans, ducks, cranes, herons and other migrants—even songbirds—back to where they will compete for territories, build nests and rear their young.
Despite recent episodes of warm weather, open water is still in the distance for the still waters of lakes and larger wetlands. But the waters that are moved by slope and gravity—rivers and streams—are a different story, and their powers are already apparent. While many lakes still sleep under ice thick enough to support a truck or an SUV, moving waters have eroded and broken free of the covering that hid them during the deepest cold of winter.
It’s evident as you cross a river on a bridge span, or a creek small enough to be shunted under a road by a culvert. Near moving water is where we often see the vanguard of returning wildlife, those creatures that left us in October, November or December, bound for seasonal winter homes more suited to their survival.
Our networks of waterways are guiding geese, swans, ducks, cranes, herons and other migrants—even songbirds—back to where they will compete for territories, build nests and rear their young. Some will pass through on their way to nesting territories still farther north to complete the same mission.
I’ve been observing pairs of tundra swans on the broad Crow Wing River, Canada geese foraging on its banks for the green shoots of new grass, and goldeneye ducks—called “whistlers,” for the sound of their wings in flight—conspicuous with their high-contrast white and black plumage. I expect soon to see herons making their agonizingly slow stalks in the shallows, ready to spear an unsuspecting frog or small fish that didn’t sense danger nearby poised on those stilt-like heron legs.
Birds other than waterfowl may be less conspicuous, but are also influenced and guided by waterways in their returning migrations. The American woodcock, a gamebird not much larger than a robin—a member of the shorebird family that has evolved to live in wooded uplands—also routinely follows the well-defined pathways of rivers and streams in their north and south migrations. Though they feed on land—not on water, like waterfowl—it’s near stream banks and springs where their primary diet of earthworms will first be available. Some woodcock have already returned, though they will rarely be seen except at dawn or dusk in their spiraling courtship flights.
Waterways attract migrants for multiple reasons. One is navigation. They serve as visible and recognizable pathways past featureless fields, forests and urban landscapes that can barely be distinguished one from another. The instinct for creatures to migrate may be inborn, but there is credible evidence that for many species an important key in the mystery of migration is experience and learned behavior. What more reliable features to “map” a migratory brain than the visibility and constancy of rivers and streams?
This makes sense, even from a human’s perspective. Long before roads were built to accommodate horse-drawn wagons—and eventually self-propelled motor vehicles—waterways were efficient means to traverse great distances. Canoes, barges and steam-driven river boats hauled freight and passengers over river systems to cross-continent destinations. Voyageurs who plied the trade in beaver, mink and other furs in the far northern reaches of the U.S. and Canada did likewise, most conspicuously in canoes.
Flowing waters also feed the early migrants. Freed of their cap of ice, they provide metabolic fuel in the form of aquatic insects, snails, crustaceans, small fish and aquatic plants. This is vital not just for an individual migrant’s immediate survival, but as a source of energy for the exertions of courtship, reproduction and the raising of offspring that lies ahead.
Even roadway and drainage ditches—man-made streams, you could say—become attractive. They’re also part of the early thaw, being both shallow and conduits for moving water. Here, too, we’re likely to find waterfowl—pairs of early-arriving wood ducks, or mallards—or a stalking heron pursuing a meal.
It’s a stimulating and hopeful time of year. Spring has officially arrived, and the relief of warmer weather is upon us. Everywhere around us is mounting evidence that the forces of Nature are a comforting constant, no matter what uncertainties and challenges we might face.