California Condor Research Articles

Eggshell Thinning and Depressed Hatching Success of California Condors Reintroduced to Central California

From 1997 through 2010, in collaboration with the National Park Service, we released 84 captivereared California Condors (Gymnogyps californianus) to the wild in central California; from 2006 through 2010 we recorded 16 nestings by nine pairs and recovered eggs or eggshell fragments from 12 nests. Mean thickness of shell fragments, without membrane, was 0.46 mm, 34% lower than the average thickness of 0.70 mm of fragments recovered from nine successful nests in interior southern California, 2007–2009. Hatching success in central California was 20–40%, significantly lower than the 70–80% recorded in southern California. The outer crystalline layer was absent or greatly reduced, as in thin-shelled condor eggs laid in southern California in the 1960s. Shell thickness was not related to egg size. Weight/water loss during incubation in the wild averaged three times greater than the normal rate associated with successful hatching; the rate of loss increased significantly with decreasing shell thickness. At least four failures, three from death of the embryo, we attribute to excessive weight/water loss; two other eggs losing substantial weight hatched successfully after artificial incubation at elevated humidities. DDT/DDE from wastes of a DDT factory discharged into the Southern California Bight had previously caused extensive eggshell thinning and reproductive failures of fish-eating and raptorial birds. Feeding on carcasses of California sea lions (Zalophus californianus), reintroduced condors now occupy a higher level of the food web. Like that of other species previously affected, the thickness of condor eggshells should recover as DDE contamination continues to decline.

Discrimination Factors for Stable Isotopes of Carbon and Nitrogen in Blood and Feathers from Chicks and Juveniles of the California Condor

Stable-isotope ratios of carbon (13C/12C; δ13C) and nitrogen (15N/14N; δ15N) in animal tissues are analyzed to estimate animal foraging ecology because these ratios reflect those of an animal's diet. This reflection is generally indirect, as stable-isotope ratios change with trophic level. These differences, called discrimination factors (reported as Δ), vary considerably by species and tissue. Variations in discrimination factors used in stableisotope mixing models can lead to inaccurate estimates of diets. Therefore, determining accurate discrimination factors specific to species and tissue is important. We established the Δ13C and Δ15N values between diet and blood and feathers from chicks and juveniles of the California Condor (Gymnogyps californianus). Hatchlings were fed rats for 76–119 days, whereas juveniles were fed dairy calves for 64 days. The mean Δ13C and Δ15N values (± SD) between chick feathers and rat muscle were 0.4 ± 0.4‰ and 3.1 ± 0.2‰, respectively; those between chicks' whole blood and rat muscle were -0.7 ± 0.1‰ and 1.7 ± 0.1‰, respectively. The mean Δ13C and Δ15N values between juvenile condors' plasma and calf muscle were 0.9 ± 0.2‰ and 3.3 ± 0.7‰, respectively; those between juveniles' red blood cells and calf muscle were 0.3 ± 0.3‰ and 1.8 ± 0.1‰, respectively; and those between juveniles' whole blood and calf muscle were 0.3 ± 0.3‰ and 1.9 ± 0.2‰, respectively. We report the first discrimination factors for the Cathartidae (New World vultures), and our findings will have important applications in studies of the critically endangered California Condor's foraging ecology.

Health Risks from Lead-Based Ammunition in the Environment

Lead is one of the most studied toxicants, and overwhelming scientific evidence demonstrates that lead is toxic to several physiological systems in vertebrates, including the nervous, renal, cardiovascular, reproductive, immune, and hematologic systems (Health Risks from Lead-Based Ammunition in the Environment—A Consensus Statement of Scientists 2013). Furthermore, there is no level of lead exposure in children known to be without adverse effects [Centers for Disease Control and Prevention (CDC) 2012a, 2012b]. In light of this evidence, there is an urgent need to end a major source of lead for animals and humans: spent lead bullets and shotgun pellets. Notably, production of lead-based ammunition in the United States accounted for > 69,000 metric tons consumed in 2012; this is second only to the amount of lead used to manufacture storage batteries (U.S. Geological Survey 2013). However, there are few regulations regarding the release of lead into the environment through discharge of lead-based ammunition. For other major categories of lead consumption, such as lead batteries and sheet lead/lead pipes, environmental discharge and disposal are regulated. Therefore, lead-based ammunition is likely the greatest largely unregulated source of lead that is knowingly discharged into the environment in the United States. In contrast, the release or distribution of other major sources of environmental lead contamination (e.g., leaded gasoline, lead-based paint, lead solder) have been substantially regulated and reduced since the mid-1970s (Health Risks from Lead-Based Ammunition in the Environment—A Consensus Statement of Scientists 2013). There is a national discussion—polarized at times—of the health risks posed to humans and wildlife from the discharge of lead-based ammunition. To inform this discussion, a group of 30 nationally and internationally recognized scientists with expertise regarding lead and environmental health recently collaborated to create an evidence-based consensus statement (Health Risks from Lead-Based Ammunition in the Environment—A Consensus Statement of Scientists 2013) supporting the reduction and eventual elimination of lead released to the environment through the discharge of lead-based ammunition. The discharge of lead bullets and shotgun pellets into the environment poses significant health risks to humans and wildlife. The best available scientific evidence demonstrates that the discharge of lead-based ammunition substantially increases environmental lead levels, especially in areas with higher shooting activity (U.S. Environmetal Protection Agency 2012) and that the discharge of lead-based ammunition poses risks of elevated lead exposure to gun users (National Research Council 2012). When lead-containing bullets are used to shoot wildlife, they can fragment into hundreds of small pieces, many of which are small enough to be easily ingested by scavenging animals or to be retained in meat prepared for human consumption (Hunt et al. 2009; Knott et al. 2010; Pauli and Burkirk 2007). Consequently, lead-based ammunition may be a significant source of lead exposure in humans that regularly ingest wild game (Hanning et al. 2003; Johansen et al. 2006; Levesque et al. 2003; Tsuji et al. 2008). In addition, lead pellets and fragments have been reported in gastrointestinal tracts of hunters who consume meat from animals shot with lead-based ammunition (Carey 1977; Reddy 1985). The use of lead pellets in shotgun shells for hunting waterfowl posed a serious threat to wetland birds, and secondarily to bald eagles, in the United States, leading to the U.S. Fish and Wildlife Service’s 1991 nationwide regulations requiring use of nontoxic shotgun pellets for hunting waterfowl (Anderson 1992). However, lead poisoning from ingestion of spent lead-based ammunition fragments continues to pose a particularly serious health threat for scavenging species. These lead-containing fragments remain the principal source of lead exposure to endangered California condors and continue to prevent the successful recovery of these birds in the wild (Church et al. 2006; Finkelstein et al. 2012; Green et al. 2008; Parish et al. 2009; Rideout et al. 2012; Woods et al. 2007). Other wildlife species, such as golden eagles, bald eagles, ravens, turkey vultures, and pumas, are also exposed to the fragments of spent lead ammunition (Burco et al. 2012; Clark and Scheuhammer 2003; Craighead and Bedrosian 2008; Cruz-Martinez et al. 2012; Fisher et al. 2006; Kelly and Johnson 2011; Stauber et al. 2010; Wayland and Bollinger 1999). No rational deliberation about the use of lead-based ammunition can ignore the overwhelming evidence for the toxic effects of lead, or that the discharge of lead bullets and shot into the environment poses significant risks of lead exposure to humans and wildlife. Given the availability of non-lead ammunition for shooting and hunting (Thomas 2013), the use of lead-based ammunition that introduces lead into the environment can be reduced and eventually eliminated. This seems to be a reasonable and equitable action to protect the health of humans and wildlife.

Hierarchical dominance structure in reintroduced California condors: correlates, consequences, and dynamics

Populations of reintroduced California condors (Gymnogyps californianus) develop complex social struc- tures and dynamics to maintain stable group cohesion, and birds that do not successfully integrate into group hierar- chies have highly impaired survivability. Consequently, im- proved understanding of condor socioecology is needed to inform conservation management strategies. We report on the dominance structure of free-ranging condors and identi- fy the causes and consequences of rank in condor populations by matching social status with the behavioral and physical correlates of individual birds. We characterized the hierarchical social structure of wild condor populations as mildly linear, despotic, and dynamic. Condor social groups were not egalitarian and dominance hierarchies reg- ulated competitive access to food resources. Absence of kin- based social groups also indicated that condor social structure is individualistic. Agonistic interactions among condors were strongly unidirectional, but the overall linearity and steepness of their hierarchies was low. Although one aggressive male maintained the highest dominance rank across the 3-year observation period, there was considerable fluidity in social status among condors within middle and lower rank orders. Older condors were more dominant than younger birds and younger males supplanted older females over time to achieve higher status. Dominance rank did not predict the amount of time that a bird spent feeding at a carcass or the frequency that a bird was interrupted while feeding. Thus, younger, less dominant birds are able to obtain sufficient nutrition in wild social populations.

California Condors in the Pacific Northwest by Jesse D'Elia and Susan M. Haig Noel Snyder

 Reviews simple is a critique one could just as easily make of Pauling.Carson noted that Pauling was hurt in 1962 when her husband alone won the Nobel Peace Prize, apparently concurring with many others who thought the award should have gone to both Paulings. It seems that despite her criticism of Friedan, she too recognized the benefit of public acknowledgement of one’s “occupation” and felt stung when such appreciation was not forthcoming. Pauling’s feminist awakening was a feminist pacifist awakening, which also soured her on Friedan’s thinking, since Friedan endorsed U.S. involvement in the Korean War. Pauling is best known for her activism on behalf of many U.S. and international women’s peace organizations.Her undaunted support of those organizations explains her many admirers and the heartfelt praise she won for a most worthy occupation. Ava Helen Pauling: Partner, Activist ,Visionary will be a welcome addition to any library and will inspire many readers to learn more about this important American figure. Erika Kuhlman Idaho State University California Condors in the Pacific Northwest by Jesse D’Elia and Susan M. Haig foreword by Noel Snyder Oregon State University Press, Corvalllis, 2013. Illustrations , maps, tables, bibliography, index. 184 pages. $19.95 paper. The largest land bird of North America, the California Condor (Gymnogyps californianus), went extinct in the wild in 1987 and existed only in captivity at that time. Beginning in 1991, due to the Herculean efforts of zoos and conservationists, condors have been returned to the wild in California and a few places in the southwest.At present,formidable obstacles still threaten viability of the wild condor populations, and without extensive and costly human involvement, it is unlikely they could survive.(The current major threat to wild condors is feeding on the remains of game that has been shot with ammunition containing lead.) The California Condor’s geographic range spread widely across North America during the late Pleistocene Epoch. By the end of that  OHQ vol. 114, no. 4 period, however, their range contracted drastically , and the birds inhabited only the far western part of the continent. Although the last condors lived in southern California, their range had extended further as late as the first decades of the nineteenth century. At present, there is interest in attempting to reintroduce the birds to the Pacific Northwest,and the Oregon Zoo has been actively involved in raising and breeding condors. Jesse D’Elia and Susan Haig argue in their short but valuable book that evaluating the chances of contemporary reintroduction efforts in the Northwest necessitates understanding historical distribution of condors and the causes of their demise.California Condors in the Pacific Northwest concisely summarizes what is known about the distribution of the California Condor in the region, the likely causes of their extinction there, and how current conditions have changed or not changed. For those interested in the prospect of reintroducing condors to the Northwest,the book is a valuable aid and resource. The book begins with some background information on the life history of condors and an account of the condor recovery program. It then moves to the prehistoric distribution of condors that has emerged from a number of sources. Because some scientists have doubted thevalidityof claimsthatcondorswere resident in the Pacific Northwest, D’Elia and Haig have included a chapter on the migratory habits of vultures in general, including what is known about the historical movement patterns of the California Condor. A long chapter examines in detail the timing of the condor’s range collapse and explores the various hypotheses that have been advanced to explain that collapse. The primary causes appear to be secondary poisoning (much of it the use of strychnine intended to kill wolves) that is exacerbated by humans directly killing condors. The volume concludes with a discussion of overcoming problems associated with any attempt to reintroduce condors to the Northwest and reminds readers of the likely cost. D’Elia and Haig have demonstrated,however,that available evidence supports the claim that the California Condor did indeed reside in the Northwest, and although numerous obstacles still exist, most of the original causes of their collapse have been mitigated. Paul Farber Corvallis, Oregon...

Organochlorine Contaminants in Blubber from Stranded Marine Mammals Collected from the Northern Oregon and Southern Washington Coasts: Implications for Re-introducing California Condors, Gymnogyps californianus, in Oregon

Re-introduction of California Condors into Oregon is currently being considered, but there are concerns about the safety of potential food sources of this species. Condors are opportunistic feeders and a largely available food source for this species will be stranded marine mammal carcasses. We analyzed 37 blubber samples from 7 different marine mammal species collected from the Oregon and Southern Washington coasts for 18 organochlorine (OC) pesticides and 16 polychlorinated biphenyls (PCBs). Dichlorodiphenyldichloroethylene (DDE) was the most prevalent OC contaminant, making up more than 58 % of the total OC concentration measured. There were no significant differences in OC content between species or sexes.

Analysis of California Condor (Gymnogyps californianus) Activity Using Satellite Telemetry Data

We describe new methods for quantifying specific in-situ activities of wildlife, in this case the endangered Cali- fornia condor (Gymnogyps californianus). These methods extract information from hundreds of thousands of temporally continuous and spatially explicit satellite telemetry reports. Visual observations and ground-based telemetry can provide behavioral data, although the information is often spatially and temporally limited and sample sizes can be small for wide- ranging species. Automated satellite telemetry offers continuous position reporting and unbiased spatial coverage, but to date has lacked thematic content such as the time, place, and duration of particular activities. Procedures developed for this study use a combination of models and geographic information systems (GIS) to identify condor transit flight, perch- ing, roosting, and nesting activity based only on hourly telemetry position reports. This approach combines the temporal and spatial advantages of automated telemetry with increased thematic quality from activity models. The analytical meth- ods were applied to 340,694 satellite-based position records from 51 California condors which were collected from June 2005 to April 2012. We identified 31,268 extended perch locations and an additional 15,483 overnight roost locations by translating basic location, speed, and time data into characterizations of bird activities. This approach correctly identified nine of the ten known nest sites occupied by condors outfitted with telemetry transmitters based only on the telemetry da- ta. The spatial locations of these activities were mapped using GIS. This represents a significant advantage over simple location and movement data normally associated with wildlife telemetry, and is applicable to a wide range of species.

Ingluviotomy Tube Placement for Lead-induced Crop Stasis in the California Condor (Gymnogyps californianus)

Six free-flying California condors (Gymnogyps californianus) were diagnosed with acute lead toxicosis that caused crop distension and stasis. Between January 2006 and January 2007, the birds were referred to the Phoenix Zoo in Arizona for emergency treatment. In 5 birds, an ingluviotomy was performed to place a feeding tube from the crop to the proventriculus, which allowed a temporary bypass of the dysfunctional esophagus until normal function and motility were regained. A crop-support pressure bandage was placed in 4 birds to improve crop emptying into the proventriculus and to prevent crop distension. Although chelation therapy is the gold standard treatment for lead toxicosis, severe cases of lead-induced crop stasis are not acutely reversible with pharmaceuticals. In these condors, placement of a feeding tube was deemed prudent to ensure a viable enteric route of nutritional support during the standard treatment and recovery period in acute lead toxicosis with crop stasis.

Traditional Ecological Knowledge and Endangered Species Recovery: Is Ethnobiology for the Birds?

Perhaps the most often-cited quote in biological conservation circles is this ominous warning from E. O. Wilson (1990:182): ‘‘The one process now going on that will take millions of years to correct is the loss of genetic and species diversity by the destruction of natural habitats. This is the folly our descendants are least likely to forgive us.’’ If there is a cultural corollary to Wilson’s principle, it is that the loss of and disregard for traditional ecological knowledge may regrettably keep us from maintaining or recovering the species now at risk due to habitat destruction, fragmentation or mismanagement. Nonetheless, there remains sufficient indigenous knowledge about endangered species, their life histories and habitats, to give us hope that it can guide both species recovery and habitat restoration in order to prevent the further loss of biodiversity. This hope is grounded in our discussions with tribal elders and indigenous resource managers who retain detailed oral histories of the behavior and habitats of critically endangered species such as the ‘‘California’’ condor (Gymnogyps californianus), a species that was never geopolitically restricted to California alone. This North American condor is one of 1253 species of birds considered to be threatened with extinction by the International Union for Conservation of Nature (IUCN); another 853 avian species are considered ‘‘near threatened’’ as well. Together, the birds in these two categories amount to roughly twenty percent of all avian species already described by Western science. But something remarkable has happened to condors in North America over the last quarter century, something which flies in the face of the global trends regarding other endangered birds. While the conservation status of nearly all of the IUCN Red Listed birds at risk has deteriorated since 1988 (Butchart et al. 2004), condor numbers have increased from the 22 individuals captured in 1987, to over 386 individuals today. At least 213 condors now live and thrive in the wilds of Arizona, Baja California, California, and Utah. Notably, both ethnobiologists and keepers of traditional knowledge have played roles in the recovery of condors in North America, and we believe will continue to do so. It was the Society for Ethnobiology’s first elected president, Amadeo Rea, who first discovered that lead poisoning might be playing a disproportionately large role in condor deaths. He is also recognized as the first scientist who ‘‘recommended the Grand Canyon region as the best place to

Lead poisoning and the deceptive recovery of the critically endangered California condor

Endangered species recovery programs seek to restore populations to self-sustaining levels. Nonetheless, many recovering species require continuing management to compensate for persistent threats in their environment. Judging true recovery in the face of this management is often difficult, impeding thorough analysis of the success of conservation programs. We illustrate these challenges with a multidisciplinary study of one of the world's rarest birds-the California condor (Gymnogyps californianus). California condors were brought to the brink of extinction, in part, because of lead poisoning, and lead poisoning remains a significant threat today. We evaluated individual lead-related health effects, the efficacy of current efforts to prevent lead-caused deaths, and the consequences of any reduction in currently intensive management actions. Our results show that condors in California remain chronically exposed to harmful levels of lead; 30% of the annual blood samples collected from condors indicate lead exposure (blood lead ≥ 200 ng/mL) that causes significant subclinical health effects, measured as >60% inhibition of the heme biosynthetic enzyme δ-aminolevulinic acid dehydratase. Furthermore, each year, ∼20% of free-flying birds have blood lead levels (≥450 ng/mL) that indicate the need for clinical intervention to avert morbidity and mortality. Lead isotopic analysis shows that lead-based ammunition is the principle source of lead poisoning in condors. Finally, population models based on condor demographic data show that the condor's apparent recovery is solely because of intensive ongoing management, with the only hope of achieving true recovery dependent on the elimination or substantial reduction of lead poisoning rates.

California condors face lead menace

California condors face lead menace

Random Sample

The Innovative Medicines Initiative has launched a new €220 million collaboration of companies and public partners to combat antimicrobial resistance. Some organisms from sea-floor vent systems may survive long enough on deep-sea submersibles to travel to another undersea spot. The speedy digging strategy of a humble clam may help underwater robots stay parked over the sea floor. And this week's numbers quantify California condors required for delisting under the U.S. Endangered Species Act, the percentage of the U.S. Southern High Plains that won't sustain irrigation within 30 years, and metric tons of carbon dioxide emitted globally in 2011.

PATTERNS OF MORTALITY IN FREE-RANGING CALIFORNIA CONDORS (GYMNOGYPS CALIFORNIANUS)

We document causes of death in free-ranging California Condors (Gymnogyps californianus) from the inception of the reintroduction program in 1992 through December 2009 to identify current and historic mortality factors that might interfere with establishment of self-sustaining populations in the wild. A total of 135 deaths occurred from October 1992 (the first post-release death) through December 2009, from a maximum population-at-risk of 352 birds, for a cumulative crude mortality rate of 38%. A definitive cause of death was determined for 76 of the 98 submitted cases, 70% (53/76) of which were attributed to anthropogenic causes. Trash ingestion was the most important mortality factor in nestlings (proportional mortality rate [PMR] 73%; 8/11), while lead toxicosis was the most important factor in juveniles (PMR 26%; 13/50) and adults (PMR 67%; 10/15). These results demonstrate that the leading causes of death at all California Condor release sites are anthropogenic. The mortality factors thought to be important in the decline of the historic California Condor population, particularly lead poisoning, remain the most important documented mortality factors today. Without effective mitigation, these factors can be expected to have the same effects on the sustainability of the wild populations as they have in the past.

Plight of the condors.

The article discusses the efforts of biologists to ensure the survival of the California condor. The condor recovery program run by the U.S. Fish and Wildlife service uses telemetry data to track the birds, find breeding caves, and remove any obstacles in their flight paths. By linking flight information to weather records scientists can learn how the condors travel across the landscape.

Impact of the California Lead Ammunition Ban on Reducing Lead Exposure in Golden Eagles and Turkey Vultures

Predatory and scavenging birds may be exposed to high levels of lead when they ingest shot or bullet fragments embedded in the tissues of animals injured or killed with lead ammunition. Lead poisoning was a contributing factor in the decline of the endangered California condor population in the 1980s, and remains one of the primary factors threatening species recovery. In response to this threat, a ban on the use of lead ammunition for most hunting activities in the range of the condor in California was implemented in 2008. Monitoring of lead exposure in predatory and scavenging birds is essential for assessing the effectiveness of the lead ammunition ban in reducing lead exposure in these species. In this study, we assessed the effectiveness of the regulation in decreasing blood lead concentration in two avian sentinels, golden eagles and turkey vultures, within the condor range in California. We compared blood lead concentration in golden eagles and turkey vultures prior to the lead ammunition ban and one year following implementation of the ban. Lead exposure in both golden eagles and turkey vultures declined significantly post-ban. Our findings provide evidence that hunter compliance with lead ammunition regulations was sufficient to reduce lead exposure in predatory and scavenging birds at our study sites.

Red List reveals conservation pay-offs

Summary Efforts to protect species are paying off amid otherwise widespread declines. Nigel Williams reports

Replication of a 1970s Study on Domestic Sheep Losses to Predators on Utah's Summer Rangelands

Lamb losses to predation have historically ranged from 4% to 8% in the western United States but most data are over 30 yr old. We repeated a sheep depredation study conducted from 1972 through 1975 on Cedar Mountain, Utah, to determine how predation rates have changed in the last three decades. Pastures and herd sizes were similar (1 730 lambs) between our study (2006 and 2007) and the prior one. Additionally, 40% of the ranchers in our study also participated in the prior study. During 2006 and 2007, 5.8% of all lambs on Cedar Mountain were lost to all causes compared to 9.5% during the 1970s. Predators were responsible for 87% of all verified lamb losses during our study versus 83% during the 1970s. We estimated that 4.9% of all lambs on Cedar Mountain were killed by predators during our study compared to 7.9% during the 1970s. During our study, coyotes (Canis latrans Say) were responsible for 67% of the depredated lambs, cougars (Felis concolor Linnaeus) for 31%, and black bears (Ursus americanus Pallas) for 2%. During the 1970s, coyotes killed 98% of all depredated lambs, cougars killed 2%, and bears killed 0%. In addition to the increase in cougar kills, the other change on Cedar Mountain since the 1970s is that California condors (Gymnogyps californianus Shaw) have begun scavenging lamb carcasses. Our results indicate that increasing populations of cougars, black bears, and condors have complicated the task of protecting lambs from predators.

Status of the California Condor (Gymnogyps californianus) and Efforts to Achieve Its Recovery

The Auk, Vol. , Number , pages  . ISSN -, electronic ISSN -.  by The American Ornithologists’ Union. All rights reserved. Please direct all requests for permission to photocopy or reproduce article content through the University of California Press’s Rights and Permissions website, http://www.ucpressjournals. com/reprintInfo.asp. DOI: ./auk.... JEFFREY R. WALTERS,1,7 SCOTT R. DERRICKSON,2 D. MICHAEL FRY,3 SUSAN M. HAIG,4 JOHN M. MARZLUFF,5 AND JOSEPH M. WUNDERLE, JR.6

An optimal and near-optimal strategy to selecting individuals for transfer in captive breeding programs

As species extinction rates continue to rise, zoos have adopted a more active role in the conservation of endangered species. A central concern is to preserve genetic diversity of zoological populations. Accordingly, when selecting individuals to transfer to new or existing populations, zoo managers must consider the genetic effects on all populations involved. We propose a quadratic integer programming (IP) model to identify a group of individuals to transfer that maximizes genetic diversity within two subpopulations. We then reduce this model to a linear IP formulation and apply it to the California condor ( Gymnogyps californianus) studbook. After simplifying the linear IP model, optimality is achieved within a reasonable time limit when a limited number of individuals are relocated. We also develop a local improvement algorithm (LIA) to efficiently provide near-optimal solutions when we increase the number of transferred individuals. The LIA quickly obtains optimal solutions when few individuals are transferred and in most cases, the LIA outperforms MetaMK, an existing program used to select animals for transfer.

Feather Lead Concentrations and 207Pb/206Pb Ratios Reveal Lead Exposure History of California Condors (Gymnogyps californianus)

Lead poisoning is a primary factor impeding the survival and recovery of the critically endangered California Condor (Gymnogyps californianus). However, the frequency and magnitude of lead exposure in condors is not well-known in part because most blood lead monitoring occurs biannually, and biannual blood samples capture only approximately 10% of a bird's annual exposure history. We investigated the use of growing feathers from free-flying condors in California to establish a bird's lead exposure history. We show that lead concentration and stable lead isotopic composition analyses of sequential feather sections and concurrently collected blood samples provided a comprehensive history of lead exposure over the 2-4 month period of feather growth. Feather analyses identified exposure events not evident from blood monitoring efforts, and by fitting an empirically derived timeline to actively growing feathers, we were able to estimate the time frame for specific lead exposure events. Our results demonstrate the utility of using sequentially sampled feathers to reconstruct lead exposure history. Since exposure risk in individuals is one determinant of population health, our findings should increase the understanding of population-level effects from lead poisoning in condors; this information may also be helpful for other avian species potentially impacted by lead poisoning.