Natural history, conservation and management.
This beautiful photo is from Big Sur, an area of the California coastline where the Santa Lucía Mountains slope steeply into the Pacific Ocean. This mountain range is home to a flock of California condors and the setting of one of our educational fiction stories, Loliki the California Condor.
Photo credit: Ventana Wildlife Society
The California condor, also known by its scientific name Gymnogyps californianus, is the largest land bird in North America and it is endangered. The world population of this species reached an all-time low of 22 individuals in 1981, while currently there are 518 of them (VWS; including both captive and free-flying individuals). The California condor is a very large vulture with a wingspan of 9.5 feet or 3 meters (USFWS), measured from tip to tip, and it glides for long distances at speeds of up to 55 mph (CAFW). It feeds on carcasses of land mammals, such as deer, pigs, cattle, and smaller mammals, as well as marine mammals that wash up on the shore, such as California sea lions and whales. It nests in pairs in caves high on cliffs and in large cavities in the trunks of large coast redwood and giant sequoia trees. It lays one egg at a time, commonly every other year to care for its chick.
Photo credit: Ventana Wildlife Society
Time-lapse video of the birth and growth of California condor chick born in a cave nest:
Video credit: Ventana Wildlife Society
California condors belong to the family Cathartidae, a family of New World vultures and condors. Cathartidae originated independently from Old World vultures (which belong to the family Accipitridae along with eagles, hawks, kites, and harriers, among others), in other words, Cathartidae and some members of Accipitridae acquired their behavior of feeding on carrion and their “vulture-like” features convergently through independent evolutionary events. The species members of the family Cathartidae are scavengers and they evolved from a common ancestor with a unique suite of characteristics that distinguish them as a group. Cathartidae includes seven species: California condor, Andean condor, turkey vulture, yellow-headed vulture, black vulture, king vulture, and lesser yellow-headed vulture. Different analyses of the DNA sequences of birds yielded the phylogenetic tree depicted below. This tree shows how Cathartidae are related with their closest relatives among birds (Yuri et al., 2013; Jarvis et al., 2014; Mindell et al., 2018).
Conservation and Management of California Condors
Between 1987 and 1992, the only California condors alive were housed in zoos. They used to range in the wild from California to Florida and from western Canada to northern Mexico (USFWS). It is suspected that some of the causes of their decline are habitat loss, poaching, and lead poisoning. Condors get poisoned when they feed on carcasses that contain spent lead ammunition. Lead is a relatively soft metal and it disintegrates into many small pieces upon impact with the target animal. A team was formed to design a plan for the conservation of condors, the Condor Recovery Team, which generated the first recovery plan for an endangered species ever in 1975. It was focused on protecting condors in the wild but it did not ban hunting with lead ammunition. Despite its implementation, condors continued to decline. Years later, a new plan was developed, and this time it involved more of an interventionist strategy. It was implemented in 1980 by a newly formed Condor Recovery Team and it was a collaboration between U.S. Fish and Wildlife Service, the California Department of Fish and Game (which eventually became the California Department of Fish and Wildlife), National Audubon Society, U.S. Forest Service, Bureau of Land Management, Zoological Society of San Diego (now the San Diego Zoo Global), and Los Angeles Zoo (now Los Angeles Zoo and Botanical Gardens). The main goals were to determine what was holding back the growth of the California condor population and what were their main mortality causes, censusing, studying their reproductive biology, and establishing a captive population (reviewed by Finkelstein et al., 2020).
The last several condors that were living in the wild in 1987 were captured and taken to zoos to be included in the captive-breeding program (Snyder and Snyder, 2000). At the time there were 27 captive condors but the population of condors alive today descended from just 14 individuals (Ralls and Ballou, 2004). The captive-breeding program is still ongoing in the USA at the Los Angeles Zoo, San Diego Zoo Global, Oregon Zoo and the Idaho-based World Center for Birds of Prey of The Peregrine Fund, and in Mexico, at the Chapultepec Zoo in Mexico City. All these institutions form part of the The California Condor Recovery Program (Recovery Program), led by the U.S. Fish and Wildlife Service and in collaboration with the U.S. Forest Service, National Park Service, Bureau of Land Management, Arizona Game and Fish Department, California Department of Fish and Wildlife, Utah Department of Fish and Wildlife, the federal government of Mexico, Santa Barbara Zoo, Ventana Wildlife Society, the Yurok Tribe, and several other organizations.
In 1992 the Recovery Program started reintroducing condors in their natural habitats. The California condor is now living and reproducing in the wild in California, Arizona and Utah, in the USA, and in Baja California, Mexico (USFWS). Free-flying condors can be tracked because every condor is tagged with a radio transmitter and a number. They feed on carcasses that frequently contain spent lead bullets, so their mortality from lead-poisoning is still high (Meretsky et al., 2000, 2001; Sorenson and Burnett, 2007; Finkelstein et al., 2012). They are periodically recaptured to check their general health and the lead levels in their blood. If the levels are too high, they have to be taken to a zoo for chelation treatment, were the birds are given certain drugs that attach to lead in the blood and these get removed from the body in the urine. A law has been in full effect in California since July of 2019, by which it is forbidden to hunt with lead ammunition in that state. Lead ammunition can still be used to do target-shooting, however, so it is still available in stores. It is still unknown how effective the law is but it is an important initiative for the conservation of California condors and that of most scavenging raptors. The Ventana Wildlife Society, which manages California condor reintroduction in central California, provides free non-lead ammunition to hunters and rangers in the area it manages, in an effort to minimize condor poisoning (VWS no Pb).
Lead poisoning from feeding on carrion contaminated with lead ammunition is the foremost factor preventing condor recovery. It is not the only environmental factor, however. Depending on what geographical area they live in, some condors may feed on carcasses from marine mammals that wash up on beaches, besides feeding on land animals. The chances that a marine mammal carcass will contain lead in its tissues are lower. However coastal condors can contain 12 to 100 times higher plasma concentrations of mercury, chlorinated pesticides, polychlorinated biphenyls (PBCs), and polybrominated diphenyl ethers (PBDEs) than inland populations. These contaminants are associated with marine mammals. In addition, coastal condors and marine mammals have high levels of DDE, a metabolite of DDT, which persists even though DDT has been banned in the USA since 1972. Presence of DDE has been found to be associated with central California condor eggshell thinning, in other words, the eggshell is missing or has a reduced outer crystalline layer. A study found that their mean eggshell thickness was 34% lower than that of condors from interior southern California. There was also a 20 to 40% lower hatching success in central California (Burnett et al., 2013). Most California sea lions that visit the central California coast are seasonally exposed to DDT in the Southern California Bight, where they forage at least for several months during their breeding
season. The Southern California Bight is highly contaminated with PCBs and DDTs (mostly DDE) discharged by several companies. From late 1940s to early 1970s Montrose Chemical Corporation's manufacturing plant in Torrance, California, discharged over 2000 tons of DDTs into ocean waters (DofJ; MontSett; Phase2; Kurle et al., 2016). Because California sea lions (CASLs) are an important marine food source for condors and CASLs frequently contain high levels of DDE (Kurle et al., 2016; Randhawa et al., 2015), it has been inferred that CASLs are a major source of DDE to California condors in central California (Kurle et al., 2016). Biologists who manage condor reintroduction in central California are able to replace anomalous eggs laid in nests with normal eggs laid by condors in captivity or with dummy eggs until captive-laid eggs become available (VWS Marine; Burnett et al, 2013). This type of replacement is also done when an egg disappears from a nest. Here is a video from Sespe Condor Sanctuary, southern California, where an egg disappears presumably because of predation (see full story at AllAboutBirds):
Kofords Ridge video credit: Cornell Lab of Ornithology
Future reintroductions
There are plans to reintroduce California condors to other areas where they used to live in historical times, namely the Pacific Northwest, via a new release site in northern California (D’Elia et al., 2019). Several factors need to be taken into account to achieve a successful reintroduction or translocation, among which are protection of certain areas, making sure ecological resources will be sufficient for the reintroduced population, identifying and quantifying threats, and identifying any obstacles for movement and colonization. Selecting a release site involves analyzing the suitability of an area for the three different types of habitat condors use to live, specifically for nesting, roosting and feeding (D'Elia et al, 2015). Because the current California condor population was founded from only 14 individuals, there has been a considerable loss of genetic diversity: it has been estimated that 80% of unique haplotypes that were historically present in the California condor population, have been lost (D’Elia et al., 2016). It is therefore of upmost importance that any new reintroduction site be linked to other areas where condors live, in other words, that condors can move among the areas they occupy to maintain gene flow and connectivity. One of the conditions that condors rely on for flight as obligate soaring bids, is upward air movement for staying aloft (Pennycuick, 1968; Poessel et al., 2017). This can happen due to winds deflecting off mountains or due to thermal updrafts. Taking advantage of such air movement, condors can move long distances to find carrion and expend little energy in doing so. Therefore, California condors tend to appear mostly in areas of high topographic relief. Models have been developed to identify favorable new release sites that have high connectivity to other sites where condors already live (D'Elia et al., 2019).
Documentary
Check out this short film by Tim Huntington, "The California Condors of Big Sur," to learn more about their natural history and about recovery efforts by the Ventana Wildlife Society and the U. S. National Park Service in central California.
Acknowledgment
I am grateful to Kelly Sorenson for feedback that helped improve this post.
References
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