As some local residents have noticed, Turkey Vultures have started to appear in the Tehachapi Mountains again lately as they make their return flight northward.
The big spectacle, of course, is in autumn, when Turkey Vultures (Cathartes aura) by the tens of thousands come through Tehachapi Pass as they migrate south. Many of these migrants spend a night roosting in local trees, and newcomers are often startled to see trees festooned in the late afternoon by dozens of vultures, scattered among the branches like giant dark Christmas ornaments.
The reason for these big birds' migration is simple: they are following the sun. As winter approaches, the sun makes an apparent move to the south. Days get shorter, especially in the north, so Turkey Vultures have a difficult time finding the warm air thermals that they use to gain elevation and stay aloft in search of carrion.
So they simply follow the sun, heading south to Mexico and possibly further where the days are still reliably warm. After the Winter Solstice on Dec. 21, the days begin to lengthen again. Vultures respond by starting to head back to the north again.
The first Turkey Vultures generally are spotted in the Tehachapi area as early as February, and throughout March and April more and more come through. Their northward migration is not as nearly as dramatic as their voyage to the south, however, and they seem to come back in a trickle rather than a flood.
Much of what we know about the annual Turkey Vulture migration through Tehachapi Pass comes from data gathered through the efforts of Clark and Jean Moore, a pair of Tehachapi birders who organized vulture counts here 20 years ago. Clark and Jean had participated in vulture counts in the Weldon area of Kern County, near Walker Pass, and biologists had urged them to start a count in the Tehachapi area, which they did.
The counts were conducted in September and October, from the top of Pauley Hill, owned by the Rombouts family, which is west of the Tehachapi Industrial Park and Home Depot. Vulture counters would stay on the hilltop in shifts all day long and count the big birds as they passed by.
The results surprised everyone. We knew many birds came through, but the totals were enormous: 20,042 in 1999; 38,743 in 2000; and 31,168 in 2001. Since we know that some birds were inevitably missed, it became clear that 30,000 to 40,000 Turkey Vultures migrate through Tehachapi Pass each fall, making our valley the scene of one of the largest Turkey Vulture migrations in the West. The hard work of the Moores and other Tehachapi Mountains Birding Club members made the collection of this data possible.
Ornithologists believe that the migrants include birds from British Columbia, Washington, Oregon and Northern California. These vultures funnel down the Great Central Valley (the combined Sacramento and San Joaquin Valleys) with the Sierra Nevada forming a barrier to the east.
When they reach the southern end of the Sierra, the birds cross over to the desert side of California, using Walker Pass and Tehachapi Pass as their main conduits.
And then, as early as February, the birds start heading back north in small groups, which is occurring now. These incredible flyers with their kite-like soaring abilities are part of the seasonal rhythm of life in the Tehachapi Mountains. . .
Have a good week.
Jon Hammond has written for Tehachapi News for more than 30 years. Send email to firstname.lastname@example.org.