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Ospreys make a comeback in Orange County

September 13, 2010 |  9:17 am

Osprey

Ospreys, birds of prey once threatened by hunters and the pesticide DDT,  have begun to spread their wings — and domain — in Orange County. A female osprey reared on a  platform in Upper Newport Bay recently hatched a chick at another specialized platform a few miles away in Irvine.

Experts say this is a positive sign for a species that for decades had no known nests in Southern California. The ospreys have been watched over locally by a group of dedicated conservationists who are just now understanding the species' breeding patterns. "Now we have an idea of how far they might go from their nest," said Scott Thomas, vice president of the Sea and Sage Audubon Society, an Orange County chapter of the National Audubon Society.

Thomas was one of the conservationists who temporarily removed the chick from its nest for a recent "banding" ceremony, in which a rubber band was attached to the bird's leg for tracking purposes. "They're really special birds," he said, "and at that age, they're pretty easy to handle."

Based on the chick's size, biologists believe it to be female — although they say it was too early to tell. Its mother was born in Newport and then nested with an unknown male in the San Joaquin Wildlife Sanctuary near UC Irvine.

Experts say it's typical for female ospreys to nest after three years, often in the same place or near where they were hatched. In this case, that was just five miles away — up an estuary and along a freshwater stream.

Last summer, wildlife experts at the Irvine Ranch Water District, which owns and manages the preserve, built a 40-foot-tall nesting platform. They added a few branches to get the parents started, Thomas said. The birds soon moved in.

Scientists were able to identify the female because she had a band around her leg from the Newport nest, which sits on Shellmaker Island. She was born there in 2008 on a platform built by Russ Kerr, a local naturalist, and representatives from the Department of Fish and Game.

It took more than a decade for them to entice ospreys to that platform. At first it was bare, and then they learned that the birds like to see a few branches. The first chicks were hatched on the platform in 2006.

Ospreys prey on fish in saltwater or freshwater. Some believe that the birds were competition for fishermen in the early 20th century and fell prey to hunters. Then, after World War II, many succumbed to DDT.

Thomas said the conservationists' next step may be to attach radio transmitters to the ospreys. That's expensive, but it will enable better tracking and monitoring of the birds.

--Mike Reicher

Photo: An osprey couple tend to their offspring. A chick recently hatched at a man-made platform in Irvine.  Credit: Karen Tapia-Andersen / Los Angeles Times

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