Tuesday, February 5, 2008

Balmy breeze brings Turkey Vulture return

Today, three Turkey Vultures joined neighborhood Black Vultures on this cell tower; the first TUVU's I've seen in Ross County, Ohio for nearly two months. Turkey Vultures are decidedly migratory, few linger. Black Vultures don't migrate, though they may wander widely*.

Black Vultures in spread-wing posture drip-dry after heavy morning rain. Turkey Vultures seen on lower deck.
(39.3454°N, 83.0209°W (NAD83/WGS84))

South winds brought more than rain to the Southeast U.S. during the previous 24 hours: Vultures are on the move. Watch for waterfowl to increase movements north as well. A line of low pressure systems connected by a trough is staged to bring heavy movements north tonight, February 5, and tomorrow.

The Real-Time Weather RUC (Rapid Update Cycle) forecast model predicts uniform south winds over large areas of the Southeast as far north as Ohio.

Birds are not the only wildlife influenced by warm February rain carried by moist Gulf air masses: Watch for migrating salamanders! Rainy roadways near vernal pools are salamander crossings.

Black Vultures, pictured above, are increasing annually in Ohio, and throughout the Southeast United States. Soon after the end of the Little Ice Age** in the later half of the 18th Century this southeastern species began its inexorable expansion northward. Initial population growth and range expansion may have been stalled by pollution, pesticides like DDT, and by human persecution during the early and mid-20th Century.

Bruce Peterjohn (The Birds of Ohio, 2001) summarizes Black Vulture abundance in Ohio beginning with John J. Audubon's early 18th Century note of summering Black Vultures at Cincinnati. They have been local and uncommon, though slowly expanding, in southern and southeastern counties along the Allegheny front through the 1980's. During the 1990's through the present they are expanding more rapidly northward as well as increasing their numbers in southern Ohio. A look at Christmas Bird Count data and Breeding Bird Survey data shows consistent increases as well.

Black Vultures are gregarious: They often gather in large local winter roosts. Roosting sites sometimes alternate between several favored locations like large dead snags, cell towers, barn or lodge roofs (Hocking Hills State Park Lodge is a sure-thing), and utility towers. During daytime they separate into small groups and survey many square miles of terrain using their exquisite vision to find carrion or vulnerable living prey. During warm seasons, Black Vultures, unable to forage by smell, will keep an eye on local Turkey Vultures because they can find carrion at great distances by following the smell. The Black Vultures follow the Turkey Vultures to their carrion prize, often ganging up on them and running the Turkey Vultures off!

*Black Vultures in the northern extremes of the U.S. breeding range wander widely and appear migratory. Hawk Migration Association of North American: "its wide ranging habits and the presence of wintering birds at the northern limits of its range confuses its migratory status."

**The Little Ice Age was a climatic minimum, especially in North America and Europe, lasting from about the late 12th or 13th Century through the middle or late 18th Century. North America was explored and pioneered during this period. Descriptions of cold weather in period literature are very interesting. Begin with the Flemish paintings of Brueghel the elder, and be sure to see Meriwether Lewis' descriptions for the winter of 1804 among the Mandan on the Missouri River in your favorite edition of The Journals of Lewis and Clark. I recommend the portable Dover Publishing edition; a three volume set edited by famed ornithologist, Elliott Coues.

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