Justification of Red List Category
After the removal of all surviving birds into captivity in 1987, an intensive conservation programme involving reintroduction and release of captive-bred birds has led to a small but increasing population of this species in the wild. However, the population in the wild remains dependent on intensive conservation management efforts. The population currently numbers 93 mature individuals, with 62 mature individuals in the largest subpopulation and as a result, it currently meets the threshold for listing as Endangered. However, the population only increased sufficiently above the threshold for listing as Critically Endangered in 2019, hence the species continues to be listed as Critically Endangered under the five-year rule. Should such population increases continue, it will warrant downlisting in 2024.
There are currently 201 adults in the wild that are old enough to breed (age 5 and older), and 93 have produced viable offspring. Twenty-three wild birds turned five years old in 2019 and 17 more will turn five years old in 2020. A total of 141 wild birds are 8 years old or older, the observed average age of productivity (i.e. producing young when greater than or equal to eight years of age). Since mature individuals (as defined by IUCN) only includes individuals in the wild that are currently capable of reproduction, and re-introduced individuals must have produced viable offspring before they are counted as mature individuals, the current global population sensu IUCN is 93 mature individuals as of March 2020 (USFWS California Condor Recovery Program, unpublished data).
Wilbur (1978) states that the vulture population during the period 1920-1950 numbered more than 70 birds. Today, owing to an intensive captive-breeding and reintroduction programme, the world population comprises 518 individuals and is continuing to increase (USFWS 2019, S. Kirklank in litt. 2020). However, population growth in all three sub-populations (Arizona/Utah, California and Mexico) is currently occurring as a result of the continued release of captive bred birds as mortality currently exceeds natural recruitment into the population from wild fledged birds (USFWS 2019).
This species declined rapidly throughout its historic range from British Columbia to Baja California during the 19th century and reportedly disappeared from outside California, U.S.A., in 1937 (Wilbur and Kiff 1980, L. Kiff in litt. 2009). The population had dropped to an all-time low of just 22 birds by 1981, and in 1983 eggs were first taken from wild nests for captive-rearing; in 1987 the species became extinct in the wild when the last of the six wild individuals was captured to join a captive-breeding recovery programme involving 27 birds (Wilbur and Kiff 1980, Toops 2009). Due to intensive captive breeding and reintroduction efforts the population increased to 223 birds by August 2003, comprising 138 in captivity, and 85 reintroduced in California and northern Arizona (L. Kiff in litt. 2003). Breeding in the wild resumed in 2002 and now occurs in all wild subpopulations (California, Arizona/Utah and Baja, Mexico).
The sub-population in California comprises 200 wild individuals in two distinct but loosely intermixing flocks. The Southern Californian flock is managed by the USFWS Hopper Mountain National Wildlife Refuge Condor Recovery staff and the Central California flock is managed collectively by the Ventana Wildlife Society and Pinnacles National Park. Each of the California flocks includes approximately 100 free flying individuals as of December 31st 2019 (S. Kirkland in litt. 2020). The Arizona sub-population includes 98 free-flying individuals and there are an additional 39 free-flying individuals in the Baja, Mexico subpopulation. The combined total wild population as of December 2019 stands at 337 with an additional 181 captive individuals, for a total world population of 518. The regular movements of the Arizona birds are mostly confined to Coconnino County (Arizona) and Kane County (Utah), although several individuals have been documented wandering in Wyoming, southwestern Colorado and New Mexico before returning to the Vermilion Cliffs release area (C. N. Parish in litt. 2020). The California birds occur regularly in Ventura, Kern, Santa Barbara, San Luis Obispo, Monterrey, San Benito, Tulare and Fresno Counties. Currently, range expansion has been documented as far north as Alameda County in the west and Madera County in the east along the foothills of the Central Sierra Nevada Mountains. The species's geographic range continues to expand as the population grows in size (Bakker et al. 2017).
The reintroduction programme continues and has expanded its geographic coverage, with six birds released into the Sierra de San Pedro Martir in Baja California, Mexico in 2002 (USFWS 2002). A release site in Baja was established in October 2003. The first chick hatched in Mexico for over 75 years hatched in April 2007. The Baja California birds are largely confined to the Sierra de San Pedro Martir (L. Kiff in litt. 2006), where release efforts are ongoing to augment the wild population; these birds have continued to expand their range and have reached both the Pacific and Gulf of California coasts (S. Kirkland in litt. 2020). It is hoped these birds will range widely enough to be effectively connected with birds in the southern U.S.A., and a bird from the Baja population was seen in San Diego County in April 2007. Second generation birds have matured to breeding age and wild fledged pairs have now fledged their own chicks into the wild however, no population can be deemed sustainable, and without substantial reductions in the use of lead-based ammunition within the condor's range, none are likely to become so (Finkelstein et al. 2012). The recovery programme for the species continues to address threats to the wild population, but lead contamination remains the greatest of these threats (Finkelstein et al. 2012, Bakker et al. 2017); lead poisoning represents approximately 50 percent of all known causes of death in the total population (S. Kirkland in litt. 2020).
Its range includes rocky, open-country scrubland, coniferous forest and oak savanna. Cavities in ledges on cliffs, rocky outcrops or in large trees are used as nest sites (USFWS 1996). It scavenges on the carcasses of large mammals and also feeds on the carcasses of small mammals. California ground squirrels are a documented small mammal food source in California and a source of lead poisoning as they are routinely shot as nuisance animals on private ranges. Investigations into the amount of small mammal use as a food source in the Arizona/Utah population is ongoing (S. Kirkland in litt. 2020). Relative to foraging, released birds reach independence soon after release, and may range more than 400 km from release sites (Anon. 1998), though the distance an individual ranges can vary depending on season and individuals released at different sites have shown significantly different home range sizes (Rivers et al. 2014), suggesting local ecological factors may play a role.
The drastic population decline during the 20th century is principally attributed to persecution and accidental ingestion of fragments and residues from lead bullets and lead shot from carcasses (C. N. Parish in litt. 2012), resulting in lead poisoning. Lead poisoning remains a key threat and the leading cause of death for released birds (Rideout et al. 2012, Kelly et al. 2014) and has caused many fatalities and resulted in the treatment of many more birds (Anon. 2001, Parish et al. 2007, Walters et al. 2010). As a result of their life history strategy, characterised by high adult survival, long life expectancy, and low reproductive rates, condor populations are particularly sensitive to lead poisoning, which severely impacts adult survival; lead can build up initially in the blood, but then in the bone and tissues to dangerous levels over longer periods having been ingested over a broad area (Hunt et al. 2007, S. Kirkland in litt. 2020). Lead poisoning therefore continues to be the principal threat to condors and at current levels threaten the long-term sustainability of reintroduced populations (Cade 2007, Finkelstein et al. 2012, Rideout et al. 2012). It was reported in 2009 that over 90% of condors released in Arizona still test positive for lead (Toops 2009) whilst Rideout et al. (2012) determined that lead toxicosis was the leading, identifiable cause of death in juvenile (26% of deaths where the cause could be determined) and adult (67%) free-ranging California Condors since the inception of the reintroduction program in 1992. A study conducted in California, using samples collected in 2004-2009, suggests that around one third of condors have blood lead values associated with toxicological effects based on inhibition of the heme biosyntheticenzyme δ-aminolevulinic acid dehydratase (Finkelstein et al. 2012). Sequential feather samples have been used to reconstruct a condor’s lead exposure history over the 3-4-month time frame of feather growth and this data demonstrates that condors are exposed to lead more frequently, and at higher levels than indicated by blood monitoring data (Finkelstein et al. 2010, 2012). A study using samples collected between 1997 and 2011 showed that blood lead concentrations increased as birds became less reliant on provisioned food, as they became older and as their home range size increased (Kelly et al. 2014) and Bakker et al. (2017) found that condor survivorship was negatively related to time spent feeding on provisioned food. In 2017, 69 of the 78 birds in the Arizona/Utah population showed high levels of lead exposure; despite a treatment, two individuals died from severe lead-poisoning (Vulture Specialist Group 2017).
The population along the Central Pacific Californian coast also suffers from reduced eggshell thickness, consistent with the effects of DDE exposure, a breakdown compound of the pesticide DDT, compromising reproduction in the wild (Burnett et al. 2013). Apparently restricted to condors feeding on the coast, DDE exposure has been linked to feeding on the carcasses of California Sea Lions that had been exposed to the pesticide during their lifetimes (Kurle et al. 2016). The lack of additional DDT inputs suggests that these effects will decrease over time, though at present this is an impediment to sustainable wild reproduction in the coastal population. Ingested anthropogenic material has been responsible for the deaths of nestlings and strongly implicated in a number of other nestling deaths. The dead condors were found to have swallowed significant quantities of micro-trash (e.g. glass fragments, wire, plastic cartridge cases, etc.) and Rideout et al. (2012) observed this to be the leading cause of death in nestlings (76% of identifiable causes); micro-trash has however, recently been observed not to be significant source of lead poisoning and that the vast majority of lead micro-trash items were related to lead-ammunition (Finkelstein et al. 2015). Shooting still occurs and is often identified in live birds that have been radiographed during lead testing or in relation to other injuries. Eleven birds have been killed as a result of being shot since 1998 (USFWS 2019, unpublished data).
Puppet-reared birds were initially thought to exhibit greater problematic human-oriented behaviour, such as tameness and vandalising property, than parent-reared birds (Meretsky et al. 2000). However, there is no apparent difference in mortality between released birds that were puppet-reared and those which were parent-reared (Woods et al. 2007). Clark et al. (2007) modified puppet rearing practices to try and address concerns with initial captive reared birds. Wallace et al. (2007) compared the post-release results of birds reared with modified puppet rearing techniques in an isolated population in Baja, Mexico, with those released in the United States and evidenced that changes in socialisation techniques of young captive reared birds largely alleviated early problems with captive reared birds. At present, condors in the current wild subpopulations are not entirely immune to some interactions with human structures (i.e. perching on communication towers, mountain homes, South rim of the Grand Canyon) and behavioural modifications including attempts to haze them when possible are still employed. Cade et al. (2004) identified three types of interactions with humans and human structures where Type 1 and 2 were acceptable, while Type 3 was considered unacceptable and associated with birds showing no fear of humans, approaching them with no escape route. These categories remain the general benchmarks for the Recovery Program in determining whether or not a condor is exhibiting problematic behaviour and few condors are now removed from the wild due to behavioural problems. In the early 1990s a number of captive-reared birds were lost owing to collisions with power-lines and a conditioning programme with mock power poles was initiated to address it (L. Kiff in litt. 2005). This practice has since been adopted in the field to help avoid power pole electrocutions in wild-fledged condors. However, collisions and subsequent electrocution following mid-span collisions continue to periodically occur. Seventeen total cases of electrocution have been documented since 1993, including several in 2015, 2016 and 2019, with lead poisoning being identified as a cofactor in at least one of these deaths (USFWS 2019, unpublished data).
The spread of west Nile virus has not been a significant problem for the species as most birds are still vaccinated (L. Kiff in litt. 2005) however, as the wild population continues to grow, it is anticipated that it will not remain feasible to vaccinate all wild nestlings. Therefore, efforts to understand the potential significance of west Nile virus on the recovery of the species are under way. Lead poisoning however, continues to represent the most significant known cause of mortality in the wild; approximately 50% of all deaths with a determined cause are lead poisoning (USFWS 2019, unpublished data). The effect of treating individual birds for lead poisoning is currently being studied to assess whether it has any effect on survivorship in the wild California population (S. Kirkland in litt. 2020). Currently, the population would not continue to grow without the continued release of captive-bred birds.
Conservation Actions Underway
CITES Appendix I and II. A large-scale, integrated captive-breeding programme, managed by the Peregrine Fund (at the World Center for Birds of Prey), Los Angeles Zoo, Oregon Zoo, San Diego Wild Animal Park and Chapultepec Zoo, Mexico City, and reintroduction program, managed by the U.S. Fish and Wildlife Service, Ventana Wildlife Society, Peregrine Fund, Pinnacles National Park and Government of Mexico, is maintaining and growing the population in the wild (USFWS 2019). The success of the captive breeding program has seen an increase from one chick hatched in 1988 to approximately 30 birds produced for release to the wild annually. The genetic diversity of the population is maintained through careful distribution and representation of founder genotypes at each captive-breeding facility and reintroduction site. Consequently the current population retains 99.5% of the likely heterozygosity of a wild panmictic population (Ralls and Ballou 2004). 'Aversion training' to avoid power poles appears successful in preventing electrocution from perching on power poles and is ongoing (S. Kirkland in litt. 2020). Condors still periodically collide with powerlines during flight hence California power companies have buried and replaced some above ground power lines with insulated lines in areas with high levels of condor activity; insulated lines protect condors from electrocution following mid-span collision and anecdotally may be more visible to the birds since they are darker and slightly thicker (S. Kirkland in litt. 2020).
A total of 287 condors were released into the wild between 1992 and 2019 (USFWS 2019, unpublished data). Clean carcasses are provided for reintroduced birds to supplement the food they would otherwise receive from their parents in the wild, and to assist in trapping to replace transmitters, test for lead, and assess general health. Education programs aim to minimise persecution and educate the public about the conservation benefits of using non-lead ammunition for hunting and land management (Hunting with non-lead 2020, North American Non-lead Partnership 2020). However, as the recovery of the species has continued, individuals are now ranging further than when the population was younger and smaller, and are less likely to take the food provided for them after age two (Bakker et al. 2017). A huge step has been taken towards trying to eliminate the threat of lead-poisoning with the signing in 2007 of the Ridley-Tree Condor Preservation Act, and Assembly Bill 711 which requires the use of non-lead ammunition for the taking of all wildlife species throughout the state of California; lead-based ammunition can however, still be used for the putting down of livestock, impacting condors that frequent livestock ranch lands for foraging (A. Brickey in litt. 2020). The effectiveness of these regulatory bans on the survivorship and recovery of the species remains to be seen. Meanwhile, there is a growing program to promote the use of non-lead ammunition in hunting and wildlife management. The Ventana Wildlife Society, Arizona Game and Fish Department and Utah Division of Wildlife Resources are distributing non-lead bullets free of charge to hunters within the foraging range of the condors. In 2008 an agreement was struck between the Tejon Ranch and five conservation organisations in California to preserve 240,000 acres of the 270,000 acre property as an open space in return for not opposing the development of the remaining land, providing a vast amount of foraging habitat for the condor (L. Kiff in litt. 2009). This conservation program has certainly reduced the amount of lead available to condors, as larger and larger percentage of the Southern California flock continue to forage there, however this area only represents approximately 2.5 % of the 9,600,000 acre geographic range this flock occupies. The North American Non-lead Partnership is engaging State Wildlife Management Agencies, to promote the voluntary use of non-lead ammunition as a traditional wildlife management practice that benefits non-target trust wildlife resources by eliminating secondary poisoning from the ingestion of spent lead ammunition. A willing partnership between hunting and endangered species conservation that facilitates a cultural shift away from hunting with traditional lead ammunition, may be the most practical way a significant reduction in the use of lead ammunition is likely to occur.
Conservation Actions Proposed
Continue to monitor population trends. Revise the recovery plan using updated population modeling (Bakker et al. 2017) and management information, to determine survivorship and demographic parameters for a self sustaining population of condors. Resume release programme in Mexico and establish new release sites in northern California. Maintain and increase the productivity of the captive population. Continue releases of captive-bred birds. Maintain suitable habitat (USFWS 1996, Anon. 1998). Continue supplemental feeding as a food source for newly reintroduced birds and to maintain suitable flock behaviors and facilities for population management and maintenance. Continue and expand information and education programmes (USFWS 1996, Anon. 1998, Walters et al. 2010). Continue supplying alternative lead-free ammunition to hunters and ranchers.
117-134 cm. Huge and unmistakable. Black with white wing-linings and silvery panel on upper secondaries. Head naked and orange/red. Immatures with black head and underwing mottled dark. Soars on horizontal wings with primaries curled up. Hints Only likely to be seen near reintroduction sites, but expanding in range, occasionally 70-100 miles from release sites as observed in northern Arizona and southern Utah.
Text account compilers
Hermes, C., Martin, R., Everest, J.
Ashpole, J, Battistone, C., Benstead, P., Bird, J., Brickey, A., Calvert, R., Cooper, D., Finkelstein, M., Grantham, J., Harding, M., Isherwood, I., Khwaja, N., Kiff, L., Kirkland, S., Palmer, B., Parish, C., Sharpe, C.J., Symes, A., Taylor, J., Temple, H., Toone, W.D., Wege, D. & Westrip, J.R.S.
BirdLife International (2023) Species factsheet: Gymnogyps californianus. Downloaded from http://www.birdlife.org on 02/02/2023. Recommended citation for factsheets for more than one species: BirdLife International (2023) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 02/02/2023.