Pen in Hand: A migration of feathered sailplanes
Pen in Hand: A migration of feathered sailplanes
By: Jon Hammond
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Posted by editor Mon Oct 16, 2006 14:41:51 PDT
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0 responses 0 comments It is officially autumn here when migrating flocks of turkey vultures sail through the Tehachapi Valley, sometimes forming cylindrical columns with hundreds of birds in a swirling, mesmerizing circle dance as they ascend a spiral staircase of rising warm air.
When the thermal reaches a higher altitude and cools off so that it no longer provides much lift, the kettle of circling turkey vultures unspools and each bird begins flying in a straight line as it reaches the top of the thermal. The birds generally fly directly towards the southeast in the direction of Oak Creek Pass.
This familiar sight has been repeated many times over the past two weeks as flocks of turkey vultures have made their way along the ancient flight routes that take them from the Central Valley and Sierra Nevada foothills over the mountains into the Mojave Desert and points south.
As years of vulture counts both in Kern Valley and the Tehachapi area have established, over 60,000 migrating turkey vultures annually use two main pathways to cross the mountains: Walker Pass and Tehachapi Pass.
These big birds don’t eat during their long migration, relying instead on stored body fat, so they must conserve energy as much as possible. To do this, they try to fly when conditions are more favorable and they utilize their supreme soaring ability, for turkey vultures are masters at unpowered flight — riding air currents instead of flapping their wings.
Turkey vultures are the sailplanes of the avian world, and while you can see winged Vs of geese as they migrate, their powerful wingbeats nearly synchronized as the flocks passes over the patchwork landscape beneath them, you can watch turkey vultures fly for hours without discerning a single beat of their large black wings.
They tip this way, then tip back, gliding and circling but not flapping their wings, exemplifying the term “economy of effort.”
Like sailplanes, however, they are more vulnerable to weather conditions and neither nightfall nor damp, cloudy skies provide much lift, so they land in trees late each afternoon or during rainy weather.
There are many places in Tehachapi that provide overnight lodging for turkey vultures each year. The Mourning Cloak Ranch, Phil Marx Central Park, and several other places along Old Town Road tend to receive yearly visits. Other places are just utilized on occasion as needed, and most of the large old trees in the Tehachapi area have provided a nighttime roost for migrating turkey vultures at least once in their lives.
The Nüwa (Kawaiisu) people of the Tehachapi area call turkey vultures wu-ku-ma-hazi and have observed their migrations for many centuries. The phrase “Pu-ken! Mutz oh-utt wu-ku-ma-hazi yoozidoom aga’a” means “Look! Very many turkey vultures are flying again.”
In addition to those hulking black visitors that have been appearing in the sky and in local trees in the past few weeks, the California quail have begun to form large coveys. These seasonal flocks appear in autumn and are comprised of pairs of adult birds and their grown offspring.
The coveys are always largest earlier in the season and then the numbers diminish through the winter as predators, weather and mishaps take their toll, especially on the young birds. The coveys are at full strength now, however.
Keep your eyes open, especially on bright sunny mornings, and you’ll probably still see migrating turkey vultures. The first day of sunshine after bad weather is an especially good time to look as rainy-weary vultures take to the skies to resume their southward trek.
Have a good week.
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