Lake Look - In Transit
Each February, the arrival of red-shouldered hawks signals the beginning of a procession of surprising regularity, the spring bird migrations. All up and down the Lake Champlain Basin, in woods, wetlands, and on the broad lake, the aerial parade of birds moving from warmer winter climes northward continues in fits and starts, ending with a few straggling ruddy turnstones in June. During the few months in between, and particularly during the peak times of late April and the first two-thirds of May, those who pay close attention to such things may note the travels of phoebes and bluebirds, snow geese and northern goshawks, upland sandpipers, chestnut-sided warblers and red-eyed vireos.
On a large scale, the Champlain Valley as a whole sees both more and more types of birds than the surrounding Green Mountains and Adirondacks. It is easy to understand the reason for this if one makes a March visit to the top of Coot Hill, near Port Henry, New York. From there you usually still see snow covering the High Peaks as well as Camels Hump and Mount Mansfield. In between is the relatively warm Champlain Valley, serving as a north-south corridor for migrants.
Unless one stumbles into one of the spots where the migrants congregate, however, it is possible to be aware of only a small fraction of the birds that pass through our area. The reason is that small-scale variations in topography and vegetation also concentrate birds into different areas. For instance, ends of north pointing peninsulas in Lake Champlain, such as Crown Point, New York, can become bottlenecks on the bird highway. Birds, like sailors and pilots, use the lakeshore as a navigational aid, following the shoreline north. When the shoreline doubles back to the south, the birds may pause, momentarily confused by conflicting messages that they receive from their instincts.
On the one hand, the birds' seasonal drive is to head north. But, when north is across the water, they hesitate despite their power of flight. For some birds such as hawks, there is a practical explanation behind this reluctance; hawks soar on warm rising air that is common where lake and land meet, or where mountains rise out of valleys. Out over the lake, where such contrasts in landform are absent, the updrafts are usually missing as well.
Thus at the end of Crown Point, Willsboro Point, and Shelburne Point, and anywhere else that northbound birds run out of land, an unusual variety of bird life can result. Other pockets develop when one species finds its ideal habitat. If one leaves the hustle and bustle of downtown Burlington, and wanders into the Intervale, a sprawling wetland north of the city, the sounds of traffic, horns, and buses gradually fade, to be drowned out by a new sound -- the raucous calls of thousands of red-winged blackbirds. Hanging on the sides of last season's faded cattails, each male blackbird puffs himself out, flaunts his red and yellow wing patches and screeches as loudly as possible. After a few good cries at one spot, a bird will fly to another cattail stalk, hanging on as it sways beneath his weight and displays his plumage once again. Each bird's pronouncements serve notice to his fellow thousands of his claim to the patch of marsh lying between his calling posts.
The male blackbirds arrive before the females to stake out their territories in prime locations -- namely mosquito-infested marshes with plenty of cattails and brush. These marshes provide the birds with food nesting sites safe from most predators. Time is of the essence for these birds, as there are typically fewer good territories than there are birds, and a male without a territory is a biological eunuch.
Thus, even as snow still falls and furnaces still crank out heat in Champlain Valley homes, the nearby wetlands resound with the throaty territorial cries of redwings. After weeks of calls, bluffs and chase flights the weaker males are forced out.
The timing of different bird migrations varies widely, but, as in the case of the redwings, it is usually dictated by the demands of providing food for nestlings. The early arrival of red-shouldered hawks ensures that their young hatch just as baby chipmunks emerge from their burrows, garter snakes begin to sun themselves and spring peepers emerge in the marshes, providing an abundant food source.
Phoebes, bluebirds, warblers and other birds that rely on insects for their food must wait until there are insects available. These birds can't eat seeds even if they wanted to due to the shape and size of their bills. While perfect for snatching insects out of the air or off of leaves are too thin for cracking seeds.
But insect populations vary with the vagaries of our spring weather, which is far beyond the predictive capabilities of a warbler that winters in Tennessee or Central America. Many of these birds begin their migrations based on the increasing day-lengths of spring, and occasionally a spate of bad weather in the Lake Champlain Basin will mean that they don't have food when they arrive. The result can be mass die-offs of an unlucky species, as happened to scarlet tanagers in the 1980s, when their May arrival corresponded with more than a week of cold rain. Such die-offs are one way that natural selection adjusts the biological clocks of different species. In this case birds whose genetic makeup told them to migrate a little later survived to breed and they consequently left more offspring than the early migrants. Over time, a series of such events and the warming climate can alter the migration time of an entire species.
In ways that no speaker or writer ever can, the migrants that pass through our area emphasize the importance of the lake to our area and the interconnections that tie Lake Champlain to distant and quite different landscapes. The yellow warbler that graces our wooded swamps must be able to find food in Central and South America for much of the year if it is to return. The tree swallow congregates in Florida's Everglades before moving north. The broad-winged hawk, recognizable by its bold white and black tail bands, spends the winter in Brazil.
Similarly, the Lake Champlain Basin provides a winter refuge for some far northern species, like the American tree sparrow and a stopover and resting point for certain other species, such as the snow goose.
Oblivious to changing politics and boundaries between towns, states, and nations, these birds send us a message each spring and fall. "We are all tied together," they say, "inescapably".
Looking for migrants:
To see migrating birds one needs only an alarm clock and a good pair of binoculars. A 5:00 AM start will help ensure that you are outside before other human activities disturb the birds and also corresponds to the greatest activity for many species. Crown Point State Historic Site in New York is an excellent location to see migrating songbirds, while in Vermont The Gut between North and South Hero islands is a good place to look for migrating waterfowl. However any patch of woodlands or edge of a field is likely to yield some avian rewards.