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April 16, 2007

Condors: Carrion Claws & Clutches

Sometimes mistaken for a distant airplane, the California Condor (Gymnogyps californianus) with an average wingspan of almost 3 meters, once ruled the skies along the Pacific coastline.

Natural declines in population, combined with slow maturity and complex breeding habits, made these large birds vulnerable when the huge rush of people arrived in the West in the 1800's. Ranchers assumed that if a condor was eating a dead cow, it must have killed it, and they were often shot on sight. Add to this that when a condor found a hunting carcass, it would also suffer from lead poisoning when it ingested the bullets. Soon the California Condor's numbers dwindled to 22, all of which lived in captivity.

Had the ranchers looked closer, they would have seen that the condor does not have sharp claws like a bird of prey and eats carrion almost exclusively. Instead, the condors have blunt, straight claws with an elongated middle toe meant for ripping through the tough hides of dead animals - something other birds of prey cannot do with much efficiency.

Weighing in at up to 30lbs, the condor prefers larger kills. They will travel long distances - in the hundreds of miles - in order to eat each day, homing in on a kill by watching where other birds have gathered for the feast instead of using scent. The California coastline, with its many seal and sea lion rookeries, provided a substantial food source for these birds.

In the past two decades, Condor breeding programs like the one at the San Diego Zoo have helped reestablish a wild population of California Condors. Today there are about 300 condors in the world, about a third living wild in California, the Grand Canyon, and Baja, Mexico.

While condor experts have managed to breed captive condors, breeding in the wild is a tougher problem. Condors mate for life, and though the pickings are slim, juvenile condors won't necessarily choose one another as mates.

Luckily, there has been quite a few positive signs recently that the wild condor programs are working. There's been some nesting activity in Big Sur since last year, as well as some evidence that the condors have been somewhat social, hanging out around a Gray Whale carcass. At least one chick has survived in Big Sur and is now at least 2 years old. Then this month, there was some great news from another condor hotspot - Baja.

This week biologists working with the California Condor Recovery Program discovered the first California condor egg laid in Baja California, Mexico since their reintroduction to the Sierra San Pedro de Martír National Park in 2002.

...

Condors #217, a 7-year-old female, and #261, a 6-year-old male, were introduced as juveniles and have only recently entered breeding age. “We had been suspicious of nesting activity over the past month and after repeated attempts we finally located the nest 800 feet (250 meters) off the canyon floor,” said Dr. Wallace. “It is situated in a deserted golden eagle nest. They made an excellent and spectacular choice.”

More At: CRES: Free-flying Condors in Mexico Reach Historic Milestone; Pair Lays Project's First Egg

This is not the first time that condors have had chicks in the wild, but it is the first documented case in the Baja condor range since almost a century ago.

Posted by sorsha at April 16, 2007 12:46 PM