California condor
16.09.2019 Animal tracking applications

Argos key tool for monitoring the reintroduction of California condors

Carrion birds in general, and especially the largest of them are often threatened species, even though they are providing huge ecological services. The California condors among them nearly disappeared. They are now recovering thanks to reintroduction efforts, but are still endangered, especially by lead poisoning. Pinnacles National Park and Ventana Wildlife Society staff are fitting some of those with Argos PTT to be able to track them and recover them if sick.

Photo: Adult condor (317) in flight, with an Argos PTT (Credit Ali Barratt).

Near-extinction

California condors are the largest land birds in North America, with impressive wingspans of 2.90 m. Condors are scavengers – they strictly eat carrion, and have been seen feeding on everything from ground squirrels to beached whales.

California condors (Gymnogyps californianus) once ranged from British Columbia, Canada down to Baja California, Mexico. By the end of the 19th century, naturalists were already making note of their declining numbers. In 1967, condors were listed as an endangered species. Despite this protection, their population continued to decrease and dropped to a low of 22 individuals in the 1980s. All wild condors were then trapped and placed in captive breeding programs in an effort to save the species from extinction.

Reintroduction

Since 1992, captive-bred condors have been released at five different sites in western North America, including Pinnacles National Park, which joined the recovery program in 2003. In 2016, the first condor chick since 1898 fledged from a nest within Pinnacles. Since their reintroduction, condor numbers in the wild have slowly increased thanks to wild nesting and the release of captive-bred condors.

Historic causes of their population decline include shooting and the collection of eggs and specimens. Most recently causes of mortality include consuming litter (microtrash), electrocution from power lines, and lead poisoning. One of the major concerns is mortality due to contaminated food, especially by lead. Lead is still the primary choice for ammunition, and upon impact, it shatters leaving fragments within the dead animal. Even small fragments can cause poisoning when consumed, and because condors are communal scavengers several birds at a time may become poisoned when feeding at just one carcass that was shot with lead. Fortunately, an increasing number of non-lead ammunition options are available for hunters use.

Satellite tracking of some of the birds

The Pinnacles staff tag every bird that they come in contact with using an identifier tag (plastic, numbered tags on the wings) and a VHF transmitter. Some birds also receive an Argos transmitter with a GPS receiver in order to get precise, fine scale movement data.

Biologists actively monitor the data coming from the Argos satellite tags to determine whether animals are on the move or if they are otherwise still. If a condor has not moved in 2-3 days (based on the transmitted GPS data) they will put together a team to go check on the bird. If the biologists determine it is injured or sick they may capture the bird for rehabilitation at a clinic. If a condor has lead poisoning, it can often be returned to the wild after one week to multiple months of treatment.

Argos tracks of two of the most well-traveled condors of the flock. 785 flew down to the southern California release site and then up into the Sierras south of Yosemite; while 564 flew north of San Jose, down into southern California, up the Sierras next to Mt. Whitney, and back to central CA within a month's time (Credit Pinnacles National Park)
Argos tracks of two of the most well-traveled condors of the flock. 785 flew down to the southern California release site and then up into the Sierras south of Yosemite; while 564 flew north of San Jose, down into southern California, up the Sierras next to Mt. Whitney, and back to central CA within a month’s time (Credit NPS)

Through tracking efforts, biologists are also able to recover deceased condors from the field and submit them for necropsy and analysis in an attempt to determine the cause of death. Gaining an understanding of threats to the species assists the recovery program in addressing these hazards. In 2012 researchers examined condor deaths in the wild from 1992-2009. A definitive cause of death was determined on 76 out of 100 condors recovered and the leading cause of death was lead poisoning, representing 30% of known condor mortalities. Efforts to reduce lead exposure in all wildlife have increased due to this understanding.

This video shows Condor 547 getting her first taste of freedom after a week of treatment. (Credit NPS/Rose Fielding)

Links:

Pinnacles National Park condors & update on them

For more information on lead poisoning and its effect on wildlife, please visit www.huntingwithnonlead.org

CLS America page on the condors’ fitting with tags, and retrieval using a goniometer