Article

In the wild, a California condor can live 50 years.

Photograph by Stuart Thornton

Big Birds
An adult California condor can weigh around 10 kilograms (22 pounds) and have a wingspan of 3 meters (9.5 feet).

Ventana Wildlife Society
For students interested in wildlife biology and conservation, the Ventana Wildlife Society welcomes volunteers interested in preserving the habitat of the California condor.
For more information, contact the Ventana Wildlife Society.

By Stuart Thornton

Friday, January 21, 2011

On a steep mountainside feathered with blooming yucca plants, a team of wildlife biologists prepares to capture a flock of California condors.

The biologists, who work for the nonprofit Ventana Wildlife Society (VWS), are rounding up the condors to test their blood for the presence of lead, a metal whose toxicity has been the primary cause of death among the endangered species.

These birds, native to the Big Sur area in California, have already been lured into an aviary, and been given a calf carcass to feed on.

Still, the biologists have to net the condors and bring them into a small lab for the blood test. This is no small feat, considering that California condors are the largest North American land birds, with a wingspan that exceeds the height of a professional basketball player—3 meters (9.5 feet). 

Wearing gardening gloves to prevent injuries from a condor’s beak and holding an oversized net, VWS intern Ben Dudek walks through the door to the aviary. A condor in the pen flutters near the top of the enclosure like an oversized moth attracted to a giant light.

Meanwhile, VWS Senior Wildlife Biologist Joe Burnett explains his organization’s approach to the condor trap-ups, which occur twice a year. “The whole goal is not to injure the bird,” he says. “We catch them as softly as possible.”

A few minutes later, Dudek nets a condor and enlists VWS intern Johanna Dunlap and VWS wildlife biologist Mike Tyner to help carry the massive bird inside. Once in the room, the three sit down with the bird sprawled across their laps.

As the condor breathes heavily, the biologists spring into action.
With the bird restrained, Burnett takes out a syringe and draws a plastic tube’s worth of maroon blood from one of the condor’s hairless legs.

He then hands off the container to Terra Kelly and Daphne Carlson, from the University of California at Davis’ Wildlife Health Center. They’ve set up a portable lead check station in the corner of the room. The station consists of a collection of chemicals and testing equipment, as well as a machine called a tabletop lead analyzer. This machine can give a rough estimate of the lead in a condor’s bloodstream in just 180 seconds.

Ban on Lead Bullets

Kelly says that she is in the midst of a two- to three- year condor-monitoring project. “We’ll be taking blood from the birds to look at lead exposure,” she says. “We are really interested in seeing if the ban is working or not.”

The ban Kelly is referring to is a 2008 regulation prohibiting hunters from using lead bullets within the range of the California condor.  Condors are scavengers that feed on decaying animal carcasses. They can intake fragments from lead bullets when feeding on animals such as deer, coyotes, and wolves, that have been shot by hunters.

Burnett explains how lead wreaks havoc on a condor. “It just paralyzes their digestive tract so they can’t digest food,” he says. “They basically starve to death.”

Lead poisoning led to the bird being listed as endangered under the Federal Endangered Species Act in 1967. Twenty years later, in 1987, the last wild condor was taken into captivity, where it joined 26 other birds.

Since then, captive breeding efforts have increased the population of the California condors. Today, there are 52 condors flying above Central California.

Two condors have died from lead poisoning since the 2008 ban.
Routine Check-Up

During the three minutes the tabletop lead analyzer takes to study the condor’s blood, Burnett examines the restrained bird like a doctor giving a patient their annual check-up. As the condor’s eyes look away, he checks the bird’s feathers and feet.

Burnett also makes sure that the condor’s numbered tag and radio transmitter are properly attached. The tag allows the biologists to know which of the 52 local birds they are dealing with. The radio transmitter allows them to monitor the condor’s movements.

A beep from the tabletop lead analyzer means the verdict has come in. “10.3 [micrograms of lead per deciliter],” Kelly says.

“Good,” Burnett responds.

While anything greater than 10 micrograms per deciliter means the condors have been exposed to more than the naturally occurring levels of lead in the environment, the biologists only take in condors that have lead levels over 20 micrograms per deciliter.

If such high levels of lead are found in their bloodstream, the condors are taken to a clinic in nearby Monterey, California, where they begin a treatment of injections that help the bird to dispel the metal. In the worst cases, the condors are rushed to the Los Angeles Zoo and Botanical Gardens for more intense treatment and monitoring.

The process moves quickly as the biologists capture condor after condor and take blood samples while doing quick physical examinations. At one point, Burnett removes an old tracking device and attaches a new one on a condor’s wing.

On most days, the VWS biologists use radio transmitters to track the condors’ movements, feeding, and roosting. They also put out stillborn calf and deer carcasses for the birds.

“We supplement feed to provide a clean food source and to provide food for younger birds who have not learned to feed yet,” Burnett says.

As the afternoon heats up, a halo of flies appears around the biologists’ heads. They capture one last condor for testing. “It’s not over yet,” Burnett says. “It’s always the last bird [that is poisoned by lead] by Murphy’s Law.”

Just three minutes later, the tabletop lead analyzer beeps for the last time that day. “7.9 [micrograms per deciliter],” Kelly calls out.

The biologists seem to breathe a collective sigh of relief. “We thought for sure we’d find one with high levels of lead today,” Burnett says, “so this is a good day.”

Vocabulary

Term Part of Speech Definition Encyclopedic Entry

aviary

Noun

enclosed area where birds are kept.

biologist

Noun

scientist who studies living organisms.

California condor

Noun

largest land bird of North America, with a wingspan of 3 meters (9.5 feet).

captive breeding

Noun

reproduction of rare species controlled by humans in a closed environment, such as a zoo.

carcass

Noun

dead body.

decay

Verb

to rot or decompose.

deciliter

Noun

(dl) (6.1 cubic inches, or 3.4 U.S. fluid ounces) unit of volume equal to a tenth of a liter.

digestive tract

Noun

the stomach and the intestines, organs in the digestive system responsible for breaking down food into nutrients and waste products. Also called the gastrointestinal or GI tract.

dispel

Verb

to get rid of or cause to disappear.

enclosure

Noun

area surrounded by a wall, fence, or other physical boundary.

enlist

Verb

to use or employ someone for a specific purpose.

estimate

Verb

to guess based on knowledge of the situation or object.

flock

Verb

to gather.

havoc

Noun

violent destruction.

lead

Noun

chemical element with the symbol Pb.

lead poisoning

Noun

medical condition where excess amounts of lead accumulate in the body. Lead poisoning can be fatal to many animals, including humans.

maroon

Adjective

dark, brownish-red color.

microgram

Noun

unit of mass equal to one millionth of a gram.

midst

Noun

middle of an activity or program.

monitor

Verb

to observe and record behavior or data.

paralyze

Verb

to prevent movement.

primary

Adjective

first or most important.

prohibit

Verb

to disallow or prevent.

radio transmitter

Noun

device that sends out sound signals.

range

Noun

agricultural land where livestock graze.

regulation

Noun

rule or law.

restrain

Verb

to hold back or prevent movement.

scavenger

Noun

organism that eats dead or rotting biomass, such as animal flesh or plant material.

Encyclopedic Entry: scavenger

steep

Adjective

extreme incline or decline.

syringe

Noun

small device consisting of a hollow needle and tube, used for extracting or injecting fluid into the body.

tabletop lead analyzer

Noun

portable machine that quickly determines the amount of lead in an animal's bloodstream.

toxic

Adjective

poisonous.

wildlife

Noun

organisms living in a natural environment.

wingspan

Noun

the distance between the tips of a bird's wings when stretched out.

wreak

Verb

to inflict or bring about something painful.

yucca

Noun

shrub native to the Americas.

Credits

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Writer

Stuart Thornton

Editors

Jeannie Evers
Kara West

Producer

Caryl-Sue, National Geographic Society

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