Escondido, California - Senior keeper Debbie Marlow carefully held a 2-week-old California condor egg up to a warm, bright light during a process known as candling this morning at the San Diego Zoo Safari Park. This egg, laid on Feb. 13, is one of two California condor eggs laid this year, marking the start of the breeding season for the highly endangered species.

After removing the egg from an incubator, staff carefully placed the egg on a scale to measure the weight. The egg weighed 249 grams this morning, and keepers were pleased to see a 14-percent weight loss for the egg from the previous weight check, which means the fluids inside the egg are decreasing and the chick is growing and developing at a healthy rate.

"All eggs lose weight as they develop," said Debbie Marlow, senior keeper at the San Diego Zoo Safari Park. "It seems counterintuitive because as the chick grows you would expect there to be a weight gain, but egg shells are porous and moisture is lost through the shell by evaporation during the incubation process."

Once weighed, staff will hold the egg up to the warm light to candle the egg and check the air cell, the position of the embryo, and monitor the growth and development of blood vessels.

This egg will remain in the incubator until the chick is ready to pip, or begin the hatching process. It is customary that condor eggs are removed from the nest and placed in the incubator so staff can monitor the development of the egg, and an artificial one is put in the nest in its place. Once the chick is ready to pip, which happens about 55 days after being laid, animal care staff will carefully remove the artificial egg and replace it with the fertile egg. By making this switch, it provides the parents with the opportunity to assist with the hatching of their chick and they can then attend to their chick.

In the 1980s, there were only 22 condors left in the world. The Safari Park has now hatched 185 chicks and released more than 80 birds into the wild. Currently, there are more than 400 condors, more than half of which are flying free in California, Arizona and Baja California, Mexico.

Bringing species back from the brink of extinction is the goal of San Diego Zoo Global. As a leader in conservation, the work of San Diego Zoo Global includes onsite wildlife conservation efforts (representing both plants and animals) at the San Diego Zoo, the San Diego Zoo Safari Park, and San Diego Zoo Institute for Conservation Research, as well as international field programs on six continents. The work of these entities is inspiring children through the San Diego Zoo Kids network, reaching out through the Internet and in children’s hospitals nationwide. The work of San Diego Zoo Global is made possible by the San Diego Zoo Global Wildlife Conservancy and is supported in part by the Foundation of San Diego Zoo Global.