By BILL CHAISSON
Of a Feather
Last week I saw my first turkey vulture of 2019. It was soaring above Claremont, specifically over the park on the north side of the Sugar River downtown near the Santagate Bridge. Vultures look for rising thermals; perhaps the asphalt of North Street was re-radiating heat upward, or the rock outcrop at the turnoff onto Route 120. It doesn’t take much to keep a vulture aloft, and the one thing they don’t want to do is flap their wings. It is just too much work.
Turkey vultures are migratory and the bird I saw was essentially on time; I think of them as arriving in March. They are carrion feeders with relatively weak feet and beaks, so they would have a tough time finding food in the winter because carcasses tend to freeze solid. They therefore withdraw from the northern third of their range to latitudes that have enough above freezing days through the winter to keep their food supply edible.
I saw a lone bird, which is a little unusual; you usually see vultures in groups. Even if they appear to be alone, they are not. They have keen eyesight and keep an eye on each other as they soar over the land looking for a meal. You might be able to see more than one, but they can see each other. When one spots a carcass and begins to descend, the surrounding birds were converge and follow their peer to the ground.
They also roost in groups each night and the sight of a dozen or so of these large brown birds with their tiny, featherless red heads can make you feel like you woke up in the prehistoric past. They sit around through the early part of the morning, waiting for the sun to warm the ground enough to produce the updrafts that they need to spend the day in the air. As the sun hits the birds themselves, they might spread their wings and hold them out, which helps to get the moisture of the night out of their feathers.
Turkey vultures are larger than hawks and smaller than eagles. They have a 6-foot wingspan and stand about 2 feet tall. (Eagles have a wingspan of over 7 feet and large buteos a little over 4 feet.) In addition to their size and their small heads, they can be distinguished from eagles by their two-tone wings. When seen from below (which is the usual perspective), the primaries and secondaries have a silvery gray appearance, while the feathers of the wings themselves are darker. The whole bird appears black in poor light or from a distance, but they are actually a rich chocolate brown.
When you see them in flight, they hold their wings slightly above horizontal, which is called a dihedral position. Eagles and hawks hold their wings in a horizontal position and generally soar rather steadily, unless the weather is particularly rough. In contrast, turkey vultures teeter constantly even in apparently calm weather.
Your grandparents didn’t see any turkey vultures in New Hampshire. They have been expanding their range northward for about a century. They reached New Jersey and Pennsylvania by the 1930s and southern New York and southern New England by the 1940s and then stopped for a while.
David Kirk and Michael Mossman speculated in a 1998 monograph that pesticide use stalled the expansion. Many raptor populations declined in the post-war era when DDT was widely used. It thinned the shells of their eggs, which then broke when the birds tried to incubate them. After the banning of DDT in the 1960s the turkey vulture moved into northern New England and New York and is now found in southern Canada.
Many have asked why these birds are living further north. They are part of a group that includes cardinals, tufted titmice, red-bellied woodpeckers, Carolina wrens and blue-gray gnatcatchers, all southern species that expanded their ranges northward during the 20th century.
Many ornithologists did not think that warming climate had anything to do with it. In the late 20th century many ascribed the spread of turkey vultures to the growing deer populations, which were hit by cars more and more often as their numbers increased, supplying vultures with a ubiquitous meal. However, when researchers actually checked the contents of the pellets regurgitated by vultures, it turned out that deer were not a large part of their diet, even where deer were very abundant.
Members the Cayuga Bird Club in Ithaca, New York looked at records of first sightings in the spring, however, and found that in 1950s they were showing up in late April and that they now arrive in the Finger Lakes region in late March. This trend toward earlier spring arrivals over time has been observed in 49 out of 52 species for which there are good long-term records.
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