Midnight in mid-channel, mid-coast in Maine and I am adrift between two tides. One carries my small boat away as I pull to shore against its tidal tug. The other also washes through the starry darkness but I cannot pull against it. And so, thus caught in the middle, with raised oars I drift…… listening. From above “Churrs,” “cheeps,” “tinks” and “seets” rain down upon me, the notes of dark birds slipping through the night. In my boat as the water gently holds me to the coast I am carried away to places I cannot row by this current unseen and unfelt. There is a river of wings heading south overhead. A river of heartbeats pumping strong all around. It is the flow of migration. It is the passage of place.
The Atlantic Coast ecoregion extends from the Gulf of St. Lawrence to the Gulf of Mexico, a distance of more than 6,000 miles. To the north the landscape is fresh and clean and still recovering from its addiction with glacial ice. Once buried under more than a mile of ice the maritime coast of Maine and Canada is literally rising from the sea as it rebounds from the weight of its recent icy burden. Now a topography of rocky headlands and granite ledges dressed in spruce caps and skirts of green seaweed, the northern Atlantic Coast quickly gives way to the spruce-fir and hardwood forests that press against it. Only the small beaches tucked along the rocky coast like forgotten hammocks slung between rock walls are reminders of the softer southern coast.
Cape Cod and the islands of Martha’s Vineyard, Nantucket and Long Island are depositional endpoints to the advance of the most recent glacial ice. Beyond these islands the coast turns south as soils thicken, headlands diminish and beaches, like long sandy ribbons, decorate the coast. From New Jersey south, barrier island beaches wrap the coast and cradle the breadth of the Gulf of Mexico and attract hordes of sand-crazed people. Yet despite the chaos of humanity and beyond the reach of dune-front bungalows these beaches, hunted by harriers and danced upon by sanderlings teasing the run of waves, are sandy slivers of wild land.
Also included within this ecoregion is the Piedmont of the Gulf and the Southern Atlantic states. This coastal upland includes all the area between the dunes and the edge of the southern Appalachians, a stout crescent of estuaries, meandering rivers and rolling hills that narrows once past the Chesapeake to a sinuous tail in New England. Once heavily forested, the Piedmont is now mostly a crazy quilt of agriculture held together by looping stitches of hardwood hedgerows and coarse patches of pine woodlots.
What ties together this most ecologically varied ecoregion is the pulse of migration that annually swings north and then south along the broad reach of the Atlantic. Caught between the mountains and the shore the ecoregion is a natural corridor to animals passing with the seasons. In fact, there is never a time when the passage of animal nations is stayed along this path. Somewhere, some kind of animal is on the move. And in someplaces, at certain times, some will be going north while others are going south.
A calendar of bird migration for the mid-Atlantic Coast is a chaotic amalgam of arrivals and departures. In January the earliest kestrels and red-tailed hawks arrive from the south, usually males first, to stake out breeding territories. Pintails, the first of the northbound waterfowl, arrive in late January followed by swans, loons and cormorants in early March. Bluebirds appear at this time as well, encouraging the reluctant spring north with their song.
Early spring is temperamental at best, deadly at worst. If winter is long many early migrants will perish, caught by late storms when their reserves are low. But if winter passes benignly to spring, the earliest migrants will get the best breeding territories and their families will prosper. Such is the push and pull of lives cast to the wind.
In April and May, the river of wings overflows and birds flood the coast. First to return are the blackbirds. Then sparrows, hawks, gulls, terns, herons, swallows, thrushes, warblers, seabirds and sandpipers drop out of the sky to rest and feed before again moving north. If over water a storm front collides with this passage of birds the fallout to first land is impressive. Enter a coastal Texas oak motte on a clearing April morning and songbirds, exhausted and hungry will adorn every branch. In two weeks they will be on home territory far to the north but now, for a little while, they will rest and feed among palms and live oak leaves.
Summer is the season of overlap, when opposite migratory currents collide and the eager and idle are often indistinguishable. In the third week of July adult red knots and sanderlings, having finished nesting on the Arctic tundra, are returning to coastal mudflats where semidedicated semipalmated sandpipers and tardy ruddy turnstones are still heading to the Arctic. Juvenile knots and semipalms, left on the tundra to forage on their own, find these mudflats in September when the adults are already on their wintering grounds.
By Fall, the migratory floodtide returns, now running even higher with the addition of birds born of the year. Fleeing cold weather and diminishing food supply there is a deliberateness to their southward push that is not present in the spring. It is a deliberateness to find high quality food and to store energy for the journey to come. Many birds make dangerous, long distance flights to get to their winter homes in South America. These are usually just the adults who are experienced migrants and in peak physical condition. Juveniles are inexperienced food collectors and are thus thinner than adults. More often than not they do not try to carry the treacherous water hazard but instead fly the longer, but safer land route.
Guided by the stars and the Earth’s magnetic field tiny birds will fly into the Fall far to the south before they rest. In order to fuel such flights, the metabolism of long distance migrants changes prior to migration allowing the birds to deposit layers of flight prolonging fat. A blackpoll warbler can fly 125 miles on one gram of fat, not so important if it is crossing a New England lake but imperative if, as a blackpoll does, it flies nonstop between Nova Scotia and the north shore of South America. Leaving on the winds of a passing high the blackpoll rides the winds of the front to the southeast. A course correction is made over Bermuda where the northeast tradewinds blow the tiny birds back to a safe landing in South America. With a tail wind this is a non-stop journey of at least 40 hours. Without a tail wind it is a fatal journey left unfinished.
For many people the flow of migration is realized when robins return to nest in backyard apple trees and swallows are seen shagging flies overhead. But the actual magnitude of migration is far greater. We notice powerlines packed with gathering swallows and marshes abustle with the stirrings of blackbirds but we have no idea how much of the river of migration these sights represent. Leave it to counters to add numbers to our wonder. For example, more than 21,000 hawks pushed past Cape May, New Jersey on one early October day and on another day in early November, 500,000 robins passed in just three hours! Offshore Cape May, beach bound watchers annually count more than 150,000 cormorants and 50,000 loons on the move. But even the counters were perplexed when night time apparitions appeared on Gulf Coast radar screens. These “angels” as they were called, turned out to be the echoes of a million birds, just one night of the seasonal passage of wings that flows along the Atlantic Coast.
Birds are not the only migrants that hug the sheltering lee of the coast. Humpback whales winter in the Caribbean Sea and migrate to the rich banks off Cape Cod to feed and sing wavesongs. Right whales winter along the Georgia bight and migrate to the Gulf of St. Lawrence to gulp schooling herring. More than a million shad and an increasing number of Atlantic salmon run the lower reaches of the Connecticut River every year. Sea turtles glide out of the Sargasso Sea to Carolina nesting beaches. Horseshoe crabs rise out of Delaware Bay to mate by the tens of thousands on narrow strips of sand. And even monarch and fritillary butterflies waft south in fluttering waves on blue Autumn days draping trees and weeds with papery wings.
For humans the pull of migration tolls to senses long diminished. Migrating birds have long been heralds of news both desired and desperate. Who has not been cheered by the wren’s first spring song or chilled by the winter’s hoot of an owl? Peter Mathiessan writes: “Both curlews and whimbrels were known as harbingers of death, and in the sense that they are birds of passage, that in the wild melodies of their calls, in the breath of vast distance and bare regions that attends them, we sense intimations of our own mortality, there is justice in the legend. Yet it is not the death sign that curlews bring, but only the memory of life, of a high beauty passing swiftly, as the curlew passes, leaving us in solitude on an empty beach, with summer gone, and a wind blowing.”
Who would not don wings, if wished, and follow the curlew’s cry? Who cannot watch a warbler cast to the sea and not wonder if winds will draw it to shore? And who cannot watch a whale in the waves and not wonder what worlds it travels below? Wonder is the beating heart of migration. They are reliable partners. Both take flights on wild air to settle on parts seldom visited. What directions would you ask of a phoebe fresh from the starry sky?