Condors: Quest for the Egg

Posted at 10:00 am April 30, 2009 by James Sheppard

Female condor #284 enters her nest.

Female condor #284 enters her nest.

April has been a very busy and exciting month for the San Diego Zoo’s California condor project. Condor field managers and researchers have been using VHF and GPS telemetry to closely monitor the movement behaviors of the birds that have been reintroduced to Baja California, Mexico. Early spring is the condor breeding season, and we hope to observe breeding and nesting behaviors that will lead to successfully fledged chicks this year.

Condor Field Manager Juan Vargas rappels down the cliff face to a condor nest.

Program Field Manager Juan Vargas rappels down the cliff face to a condor nest.

Two pairs of condors are currently exhibiting breeding behaviors within the reintroduction site in Sierra de San Pedro Martir National Park in the northern Baja peninsula. The first condor pair, comprising birds #217 and #261, is nesting about 10 miles (16 kilometers) east of the reintroduction field station among the soaring, jagged peaks overlooking the desert toward the Gulf of California. The second pair, comprising birds #284 and #269, is guarding a nest site only a mile (1.6 kilometers) from the condor field station in the middle of a steep cliff face on the western, Pacific side of the Sierra ranges. These condors laid an egg in the same nest last year but, unfortunately, it was infertile. The field staff decided to conduct another inspection of this nest to determine whether the pair has laid a viable egg in the wild this year.

A condor egg in the nest.

A condor egg in the nest.

The nest site that condors #284 and #269 have chosen is isolated and well concealed from potential egg raiders such as bobcats and ravens. However, this meant that to access the nest we had to carry climbing equipment along the steep edge of a granite scree slope before program field manager Juan Vargas could make an extended 330-foot (100-meter) rappel in three stages from the top of the cliff down into the nest entrance. Juan found that these condors had indeed laid another egg within this nest. Using a powerful flashlight, Juan was able to candle the egg and determine that this time it was viable. During the candling process, the female condor #284 soared back and forth in front of the nest before landing on the ledge outside (see photo at top), entering and regurgitating her last meal all over Juan’s boots! This defensive, anti-predator behavior is actually an encouraging sign that the birds are determined to guard their nest and are therefore good breeders. Further nest entries will be conducted in the near future to determine the health of the condor chick once it hatches, inoculate it against avian viruses, and attach transmitters before it takes to the air for the first time.

After the western nest inspection, the field team traveled to the mountain ranges on the eastern side of the Sierras to search for the nest of condors #217 and #261. This trip took us across the parched lakebeds and deserts inland from the coastal tourist town of San Felipe toward the imposing mountains of Picacho del Diablo. At 10,000 feet (3,000 meters), these are the tallest peaks in Baja. Camped among the giant cardon cacti at the base of the mountains, the field team is now sweeping the area for the VHF signals broadcast by microtransmitters attached to the breeding pair. Once the location of the condor nest is confirmed, an expedition will be conducted to enter the site and inspect the (hopefully healthy) egg that lies within.

While based at the feet of the eastern ranges during the search for the second condor nest, we also installed the first of a series of meteorological stations on top of one of the nearby peaks. Hauling the station and the heavy equipment needed to install it up steep, spiny, cactus-covered slopes during 108 degree Fahrenheit (42 degrees Celsius) heat in the shade proved to be a challenging endeavor, and we greatly appreciate the assistance of the local Mexican neighborhood at Rancho Santa Clara. This meteorological station is currently transmitting data on wind speed and direction plus the temperature of the air at the eastern mountains for download via the Internet. These data on the climate conditions experienced by the condors in the region are providing valuable information on the environmental variables that determine the habitat preferences of the birds. Condors make extensive use of the strong winds and thermal updrafts that occur across the face of mountain ranges to make long-distance foraging flights without expending excessive energy. Enhanced understanding of how these winds shape condor movement behaviors will enable managers to better tailor the reintroduction program to the specific habitat requirements of the birds.

James Sheppard is a postdoctoral fellow for the San Diego Zoo’s Institute for Conservation Research.

Read more about his project

Read James’ previous post, Golden Eagle Helicopter Survey

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3 Responses to “Condors: Quest for the Egg”

  1. Marie says:

    Thank you James. I may never see these exceptional creatures but it is satisfying, in my heart, to know they are out there and doing what “mother nature” intended of them.

  2. nancy from michigan says:

    wow! what an ordeal that you and your crew undertake and go through to obtain all this important information! you have to be part desert rat to endure the heat,and part mountain-climber to get to the extreme location of their nests! you certainly get a good work-out in your job. how big is the crew that carries up all the equiptment? have you eve run into extreme weather conditions while cliff climbing? very interesting, and I must say dangerous work that you are envolved in. keep us posted okay?

  3. njr_sd says:

    Here’s hoping for a successful hatching for both pairs of condors!