The other day I performed one of my favorite autumn rituals: watching migratory hawks above the Connecticut River. When viewed from the fire tower on Gile Mountain in Norwich, Vermont, one of a dozen or more excellent migratory access points along the length of the river, the hawks appear out of the northwest as they ride the air currents south, beyond the mountain. The 75-foot fire tower straddles a large outcrop of rock and rises well above the forest canopy.
I climb the tower and let myself in through the trap door. The sun is bright, the sky blue, and large cumulus clouds, pushed by a gentle breeze, move up from the southeast. Mount Moosilauke and Mount Ascutney are barely visible through the haze, but the immediate vicinity of Gile Mountain, including most of the Upper Valley, is clear. The first maples are beginning to redden; asters whiten open patches in the woodland. From the tower, I can see a bend in the Connecticut River glistening in the sun.
The effervescent calls of blue jays ring from the woods and rise up the mountain, louder and more distinct than any jays I’ve heard for months. Monarch butterflies, like animated leaves, float past my platform, en route to central Mexico.
Small groups of broad-winged hawks, separated by miles, materialize high above the corrugated landscape. These loose bands of hawks move toward a common point from distant perches in the sky, like tributaries of a river. Eventually, the hawks are overhead, circling, circling, drawn to a column of heated air, a thermal, which rises from the sun-warmed rocks below the tower. Sprawled on the current, the broad-wings rise to dizzying heights, wings and tails spread to the limit. Twenty-two hawks mill above me, circling in the vortex of the thermal, rising to the base of a cumulus cloud. Then, folding their wings back against their bodies, pinching in their tails, assuming the shape of a tear drop, they slide away, one behind the other, into the southern sky.
Broad-wings are perfectly shaped to hitch rides on the heat that springs up from rocks, roads, and any other heat-gathering feature in the landscape. Their large wings are wide, their tails short and fanned, which gives them a large surface-area-to-weight ratio, an advantage for ascending into the October sky. The fortunes of broad-wings are so tied to thermals because they are not strong fliers and cannot migrate great distances without them.
Broad-winged hawks leave Canada and New England a month before their food runs out to ensure that the presence of thermals will carry them south. Each flock spirals up a column of heated air, high, sometimes thousands of feet in the sky. At the summit of a thermal, they streamline their bodies and coast downward, often for miles, to the next rising column of air. Because thermals are not produced over large bodies of water, broad-wings do not migrate over the Gulf of Mexico, instead gathering in flocks, called kettles, which sometimes number in the hundreds of thousands as they travel down the length of Central America. By late October, the sun has sunk, thermals have weakened, and our portion of the sky is washed clean of broad-wings.
Most of October belongs to the migratory hawks with better flying ability: the red-tailed, the red-shouldered, the goshawk, and the diminutive, but spirited, sharp-shinned.
I turn around and watch the broad-wings as they glide toward another invisible column of warm air. Then they find another, and another, until they are finally out of binocular range. These same birds, no doubt, will be spotted from lookouts south along the Connecticut (Putney Mountain, perhaps), then along the mountain highlands of the Appalachians, angling southwest toward Texas. Eventually, they will reach the jungles of Brazil, all the while having hitched rides on thermals.
A flock of chimney swifts flies over the Gile Mountain tower, working much harder than the broad-wings. A raven rises in the east, and a red-tailed hawk hangs on a thermal above the northwest corner of the mountain, screaming for reasons known only to a fellow hawk. The raven and the red-tail are not migrating, not now, anyway; they play on the thermals, with the red-tail remaining in the sky long enough to watch the broad-wings fade in the distance. A pair of loons arrows past, in far more of a hurry than the hawks.