Chronic lead exposure is epidemic in obligate scavenger populations in eastern North America

Lead poisoning of raptors: state of the science and cross-discipline mitigation options for a global problem

Lead poisoning is an important global conservation problem for many species of wildlife, especially raptors. Despite the increasing number of individual studies and regional reviews of lead poisoning of raptors, it has been over a decade since this information has been compiled into a comprehensive global review. Here, we summarize the state of knowledge of lead poisoning of raptors, we review developments in manufacturing of non-lead ammunition, the use of which can reduce the most pervasive source of lead these birds encounter, and we compile data on voluntary and regulatory mitigation options and their associated sociological context. We support our literature review with case studies of mitigation actions, largely provided by the conservation practitioners who study or manage these efforts. Our review illustrates the growing awareness and understanding of lead exposure of raptors, and it shows that the science underpinning this understanding has expanded considerably in recent years. We also show that the political and social appetite for managing lead ammunition appears to vary substantially across administrative regions, countries, and continents. Improved understanding of the drivers of this variation could support more effective mitigation of lead exposure of wildlife. This review also shows that mitigation strategies are likely to be most effective when they are outcome driven, consider behavioural theory, local cultures, and environmental conditions, effectively monitor participation, compliance, and levels of raptor exposure, and support both environmental and human health.

Trace elements and heavy metals in black vultures (Coragyps atratus) and turkey vultures (Cathartes aura) in the southeastern United States

Many vulture species worldwide are declining at alarming rates due to a variety of anthropogenic causes, including exposure to pollutants and pharmaceuticals through consumption of contaminated carrion. However, little is known about the extent to which vultures are exposed to various contaminants as well as toxicity thresholds for trace elements and heavy metals. Our objective was to quantify levels of trace elements and heavy metals within black vulture (Coragyps atratus) and turkey vulture (Cathartes aura) tissues to determine the extent to which populations in the Southeastern United States are exposed to carrion that contains high levels of contaminants. We collected 34 black vulture liver samples and examined differences in trace element and heavy metal concentrations between sexes and age classes (adult and juvenile). Further, we collected 81 blood and 42 feather samples from additional black and turkey vultures and compared differences between species and age classes. We found similar element concentrations between juvenile and adult black vultures with the exception of Cu, where levels were higher in juveniles compared to adults. However, we did observe substantial differences in element concentrations between species for both blood and feather samples, with black vultures generally having higher concentrations of most elements. Our data revealed higher element levels in both species compared to toxicity thresholds found in other bird of prey species, such as blood and liver toxicity threshold suggestions for Pb poisoning in Falconiformes. Further, while average contaminant levels were generally low, extreme outliers were observed for some elements, including Pb, suggesting some individuals were exposed to high levels of potentially toxic elements. More research is needed to better understand contaminant exposure in black and turkey vultures across a broader geographic region, as well as elucidate toxicity thresholds and non-lethal impacts of contaminant exposure in these species.

Bridging Evolutionary History and Conservation of New World Vultures

The New World Vultures (Cathartidae) include seven species of obligate scavengers that, despite their ecological relevance, present critical information gaps around their evolutionary history and conservation. Insights into their phylogenetic relationships in recent years has enabled the addressing of such information gaps through approaches based on phylogeny. We reconstructed the ancestral area in America of the current species using two regionalization schemes and methods: Biogeography with Bayesian Evolutionary Analysis (BioGeoBears) and Bayesian Binary Model-Monte Carlo Markov Chains (BBM-MCMC). Then, we identified the priority species and areas for conservation by means of the Evolutionary Distinctiveness index (ED), as a proxy of the uniqueness of species according to phylogeny, and the Global Endangerment index (GE), mapping phylogenetic diversity. We found that the ancestral area of New World Vultures in America corresponds to South America, with dispersal processes that led to a recolonization of North America by Coragyps atratus, Gymnogyps californianus and Cathartes aura. We identified the Black Vulture, G. californianus and Vultur gryphus as priority species based on ED and "Evolutionary Distinct Globally Endangered" (EDGE) indexes, and the lowlands of Amazon River basin and the Orinoco basin and some tributaries areas of the Guiana Shield were identified as the priority areas when mapping the phylogenetic diversity. This study highlights the importance of filling knowledge gaps of species of conservation concern through the integration of evolutionary and ecological information and tools and, thus, developing adequate strategies to enhance the preservation of these species in the face of the current loss of biodiversity.

Sentinel animals for monitoring the environmental lead exposure: combination of traditional review and visualization analysis

In nature, certain animals share a common living environment with humans, thus these animals have become biomonitors of health effects related to various environmental exposures. As one of the most toxic environmental chemicals, lead (Pb) can cause detriment health effects to animals, plants, and even humans through different exposure pathways such as atmosphere, soil, food, water, and dust, etc. Sentinel animals played an "indicative" role in the researches of environmental pollution monitoring and human health. In order to comprehend the usage of sentinel animals in the indication of environmental Pb pollution and human Pb exposure completely, a combination of traditional review and visualization analysis based on CiteSpace literature was used to review earlier researches in this study. In the first instance, present researches on exposure sources and exposure pathways of Pb were summarized briefly, and then the studies using sentinel animals to monitor environmental heavy metal pollution and human health were combed. Finally, visualization software CiteSpace 5.8.R3 was used to explore and analyze the hotspots and frontiers of lead exposure and sentinel animals researches at home and abroad. The results showed that certain mammals were good indicators for human lead exposure. Sentinel animals had been widely used to monitor the ecological environment and human lead exposure. Among them, the blood lead levels of small mammals, particularly for domestic dogs and cats, had a significant correlation with the blood lead levels of human living in the same environment. It indicated that certain biological indicators in animals can be used as surrogates to monitor human body exposure to heavy metals. This study also explored the challenges and perspectives that may be faced in sentinel animal research, in order to provide a certain theoretical basis and train of thought guidance for future research.

Blood lead concentration in an urban parrot: Nestling Kaka (Nestor meridionalis) demonstrate evidence of exposure to lead via eggs and parental feeding

Lead is a persistent, highly toxic heavy metal known to affect physiological function and survival in birds. Nestlings are particularly at risk as exposure during critical stages of development can result in life-long deficits. Urban environments are increasingly associated with high levels of contamination and lead exposure at the urban-wildlife interface can have significant population health effects on wildlife. Wellington has an established population of Kaka (Nestor meridionalis) and provides the ideal opportunity to study the risks of lead exposure in an urban context. We sampled 139 nestlings over two breeding seasons (2015/16 and 2016/17) and examined concentrations of lead in blood samples. Nestlings were subjected to a clinical and neurological examination. Lead concentrations of egg shells were measured to evaluate maternal transfer of lead to nestlings. Overall, 36.7 % of nestlings showed evidence of lead exposure based on blood lead concentrations, ranging from <3.3μg/dL to 42.9μg/dL, with no detectable clinical signs of toxicity. The pattern of exposure in the majority of nestlings is indicative of exposure from hatch via eggshells and also direct parental feeding of lead following hatch. Lead concentrations in this cohort of Kaka have the potential to contribute to morbidity and mortality in this species. The lack of measurable neurological or physiological deficits associated with lead exposure is suggestive of an innate tolerance to these concentrations of lead in this population. However, the well-described subclinical and persistent effects of lead suggests a need for continued monitoring of this toxicant and its effects on Kaka behaviour and neurodevelopment.

Blood Lead Concentrations of Free-ranging North Florida Raptors: 2008-17

Whole blood samples for lead analysis were collected from 441 raptors admitted to the Zoological Medicine Service at the University of Florida between 1 January 2008 and 31 December 2017. The species included Bald Eagles (Haliaeetus leucocephalus), Ospreys (Pandio haliaetus), Black (Coragyps atratus) and Turkey (Cathartes aura) Vultures, Barred (Strix varia) and Great Horned (Bubo virginianus) Owls, and Red-tailed (Buteo jamaicensis) and Red-shouldered (Buteo lineatus) Hawks. Our hypothesis was that geography, seasonality, and hunting strategies of these species would all affect the blood lead concentrations. Blood lead concentrations were found to vary significantly between species, with known scavengers having higher values. Additionally, seasonal differences were seen between winter and summer, but the county in which these individuals were found did not alter the blood lead concentrations. We found lead contamination to be a common and considerable problem in Bald Eagles and vultures but not as evident in nocturnal and other diurnal raptors in North Florida. Furthermore, concentrations were highest during winter in this temperate location, suggesting a possible relationship with hunting seasons despite a lack of big game.

Major lead exposure from hunting ammunition in eagles from Sweden

Exposure to lead (Pb) from ammunition in scavenging and raptorial birds has achieved worldwide recognition based on incidences of lethal poisoning, but exposure implies also sublethal levels with potential harmful effects. Background and elevated Pb levels in liver from 116 golden eagles (GE, Aquila chrysaetos) and 200 white-tailed sea eagles (WTSE, Haliaeetus albicilla) from Sweden 2003-2011 are here examined, with supporting data from a previous WTSE report and eagle owl (EO, Bubu bubo) report. GE and WTSE display seasonal patterns, with no Pb level exceeding a generally accepted threshold for subclinical effects during summer but strongly elevated levels from October. Fledged juveniles show significantly lower levels than all other age classes, but reach levels found in older birds in autumn after the start of hunting seasons. Pb levels in EO (non-scavenger) show no seasonal changes and indicate no influence from ammunition, and are close to levels observed in juvenile eagles before October. In all, 15% WTSE and 7% GE were lethally poisoned. In areas with high-exposure to hunting ammunition, 24% of WTSE showed lethal Pb levels, compared to 7% in both eagle species from low-exposure areas. Lethal poisoning of WTSE remained as frequent after (15%) as before (13%) a partial ban on use of Pb-based shotgun ammunition over shallow waters (2002). Pb levels increased significantly in WTSE 1981-2011, in contrast to other biota from the same period. A significant decrease of Pb in WTSE liver occurred below a threshold at 0.25 μg/g (dry weight), exceeded by 81% of the birds. Trend patterns in Pb isotope ratios lend further support to this estimated cut-off level for environmental background concentrations. Pb from spent ammunition affects a range of scavenging and predatory species. A shift to Pb-free ammunition to save wildlife from unnecessary harm is an important environmental and ethical issue.

Framing of visual content shown on popular social media may affect viewers' attitudes to threatened species

Content published on social media may affect user's attitudes toward wildlife species. We evaluated viewers' responses to videos published on a popular social medium, focusing particularly on how the content was framed (i.e., the way an issue is conveyed to transmit a certain meaning). We analyzed videos posted on YouTube that showed vultures interacting with livestock. The videos were negatively or positively framed, and we evaluated viewers' opinions of these birds through the comments posted. We also analyzed negatively framed videos of mammalian predators interacting with livestock, to evaluate whether comments on this content were similar to those on vultures. We found that the framing of the information influenced the tone of the comments. Videos showing farmers talking about their livestock losses were more likely to provoke negative comments than videos not including farmer testimonies. The probability of negative comments being posted on videos about vultures was higher than for mammalian predators. Finally, negatively framed videos on vultures had more views over time than positive ones. Our results call for caution in the presentation of wildlife species online, and highlight the need for regulations to prevent the spread of misinformed videos that could magnify existing human-wildlife conflicts.

The urban lead (Pb) burden in humans, animals and the natural environment

Centuries of human activities, particularly housing and transportation practices from the late 19th century through the 1980's, dispersed hundreds of millions of tons of lead into our urban areas. The urban lead burden is evident among humans, wild and domesticated animals, and plants. Animal lead exposures closely mirror and often exceed the lead exposure patterns of their human partners. Some examples: Pigeons in New York City neighborhoods mimicked the lead exposures of neighborhood children, with more contaminated areas associated with higher exposures in both species. Also, immediately following the lead in drinking water crisis in Flint MI in 2015, blood lead levels in pet dogs in Flint were 4 times higher than in surrounding towns. And combining lead's neurotoxicity with urban stress results in well-characterized aggressive behaviors across multiple species. Lead pollution is not distributed evenly across urban areas. Although average US pediatric lead exposures have declined by 90% since the 1970s, there remain well defined neighborhoods where children continue to have toxic lead exposures; animals are poisoned there, too. Those neighborhoods tend to have disproportionate commercial and industrial lead activity; a history of dense traffic; older and deteriorating housing; past and operating landfills, dumps and hazardous waste sites; and often lead contaminated drinking water. The population there tends to be low income and minority. Urban wild and domesticated animals bear that same lead burden. Soil, buildings, dust and even trees constitute huge lead repositories throughout urban areas. Until and unless we begin to address the lead repositories in our cities, the urban lead burden will continue to impose enormous costs distributed disproportionately across the domains of the natural environment. Evidence-based research has shown the efficacy and cost-effectiveness of some US public policies to prevent or reduce these exposures. We end with a series of recommendations to manage lead-safe urban environments.

High Frequency of Lead Exposure in the Population of an Endangered Australian Top Predator, the Tasmanian Wedge-Tailed Eagle (Aquila audax fleayi)

Lead poisoning, mainly through incidental ingestion of lead ammunition in carcasses, is a threat to scavenging and predatory bird species worldwide. In Australia, shooting for animal control is widespread, and a range of native scavenging species are susceptible to lead exposure. However, the prevalence of lead exposure in Australia's scavenging and predatory birds is largely unknown. We evaluated the degree to which the Tasmanian wedge-tailed eagle (Aquila audax fleayi), an endangered Australian raptor and facultative scavenger, showed evidence of lead exposure. We detected lead in 100% of femur and liver tissues of 109 eagle carcasses opportunistically collected throughout Tasmania between 1996 and 2018. Concentrations were elevated in 10% of 106 liver (>6 mg/kg dry wt) and 4% of 108 femur (>10 mg/kg dry wt) samples. We also detected lead in 96% of blood samples taken from 24 live nestlings, with 8% at elevated concentrations (>10 μg/dL). Of the liver samples with elevated lead, 73% had lead^207/206 isotope ratios within the published range of lead-based bullets available in Tasmania. These first comprehensive data on lead exposure of an Australian raptor are comparable to those for raptor studies elsewhere that identify lead-based ammunition exposure as a conservation threat. Our findings highlight the importance of further research and efforts to address lead contamination throughout the Tasmanian ecosystem and in other Australian regions. Environ Toxicol Chem 2021;40:219-230. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

Foraging behavior, contaminant exposure risk, and the stress response in wild California condors (Gymnogyps californianus)

Wild California condors (Gymnogyps californianus) are frequently exposed to lead via lead-based ammunition ingestion, and recent studies indicate significant exposure to organochlorines (e.g. dichlorodiphenyldichloroethylene (DDE) and polychlorinated biphenyls (PCBs)) for condors feeding on beach-cast marine mammals. We investigated the influence of contaminant exposure on condor glucocorticoid response through comparisons between wild and captive populations and identification of modifiers of glucocorticoid release in wild condors. We assessed the glucocorticoid response to routine trapping and handling events through measurement of plasma corticosterone and urate glucocorticoid metabolites (GCM). Comparison of peak urate GCM levels showed wild condors exhibited higher responses to handling-associated stressors (2300 ± 1400 ng/g dry wt, average ± SD, n = 27) than captive condors (910 ± 490 ng/g dry wt., n = 6, U = 28, p = 0.003). Multiple linear regression models and an information theoretic approach (AIC_c) identified several extrinsic variables (e.g., time captive in flight pen before sample collection) that were negatively associated with plasma corticosterone and urate GCM levels in wild condors, which explained ~25% of glucocorticoid variation. When accounting for these extrinsic variables we found that behavioral variables associated with increased lead and organochlorine exposure risk were positively associated with GCM levels, explaining an additional 15% of glucocorticoid variation among wild condors. Days absent from management area, a variable associated with reduced survival attributed to increased lead exposure risk, had a positive influence on plasma corticosterone levels (β = 53 ± 20 SE) and peak urate GCM levels (β = 1090 ± 586 SE). Years observed feeding on marine mammals, a variable positively associated with DDE and PCB exposure, positively influenced peak urate GCM (β = 1100 ± 520 SE) and the magnitude of GCM response (peak GCM - 1st urate GCM) (β = 1050 ± 500 SE). Our findings suggest that individual propensities for contaminant-associated foraging behaviors predict higher stress-induced glucocorticoid levels in wild condors, and that accounting for variables associated with trapping and handling is essential for assessing the impact of environmental stressors such as contaminants on the condor stress response. As an abnormal glucocorticoid response to stress is associated with reduced reproduction and survival in vertebrates, this work indicates the need for further investigations into the physiological impacts of sub-lethal contaminant exposures in scavenging species worldwide.

Feeding Ecology Drives Lead Exposure of Facultative and Obligate Avian Scavengers in the Eastern United States

Lead poisoning of scavenging birds is a global issue. However, the drivers of lead exposure of avian scavengers have been understood from the perspective of individual species, not cross-taxa assemblages. We analyzed blood (n = 285) and liver (n = 226) lead concentrations of 5 facultative (American crows [Corvus brachyrhynchos], bald eagles [Haliaeetus leucocephalus], golden eagles [Aquila chrysaetos], red-shouldered hawks [Buteo lineatus], and red-tailed hawks [Buteo jamaicensis]) and 2 obligate (black vultures [Coragyps atratus] and turkey vultures [Cathartes aura] avian scavenger species to identify lead exposure patterns. Species and age were significant (α < 0.05) predictors of blood lead exposure of facultative scavengers; species, but not age, was a significant predictor of their liver lead exposure. We detected temporal variations in lead concentrations of facultative scavengers (blood: median = 4.41 µg/dL in spring and summer vs 13.08 µg/dL in autumn and winter; p = <0.001; liver: 0.32 ppm in spring and summer vs median = 4.25 ppm in autumn and winter; p = <0.001). At the species level, we detected between-period differences in blood lead concentrations of bald eagles (p = 0.01) and red-shouldered hawks during the winter (p = 0.001). During summer, obligate scavengers had higher liver lead concentrations than did facultative scavengers (median = 1.76 ppm vs 0.22 ppm; p = <0.001). These data suggest that the feeding ecology of avian scavengers is a determinant of the degree to which they are lead exposed, and they highlight the importance of dietary and behavioral variation in determining lead exposure. Environ Toxicol Chem 2020;39:882-892. © 2020 SETAC.

Effects of lead from ammunition on birds and other wildlife: A review and update

Poisoning of wild birds following ingestion of lead from ammunition has long been recognised and considerable recent research has focused on terrestrial birds, including raptors and scavengers. This paper builds upon previous reviews and finds that both the number of taxa affected and geographical spread of cases has increased. Some lead may also be absorbed from embedded ammunition fragments in injured birds which risk sub-lethal and welfare effects. Some papers suggest inter-specific differences in sensitivity to lead, although it is difficult to disentangle these from other factors that influence effect severity. Sub-lethal effects have been found at lower blood lead concentrations than previously reported, suggesting that previous effect-level 'thresholds' should be abandoned or revised. Lead poisoning is estimated to kill a million wildfowl a year in Europe and cause sub-lethal poisoning in another ≥ 3 million. Modelling and correlative studies have supported the potential for population-level effects of lead poisoning in wildfowl, terrestrial birds, raptors and scavengers.

Lead in piscivorous raptors during breeding season in the Chesapeake Bay region of Maryland and Virginia, USA

Sources of lead exposure of many bird species are poorly understood. We analyzed blood lead concentrations from osprey (n = 244; Pandion haliaetus) and bald eagles (n = 68; Haliaeetus leucocephalus) and documented potential sources of lead they may encounter. Adult bald eagles had higher blood lead concentrations than did adult osprey. However, blood lead concentrations of nestlings were similar for both species. Although 62% of osprey had detectable lead concentrations ( x¯  = 1.99 ± 4.02 μg/dL, mean ± standard deviation [SD]), there was no difference in the detection frequency or lead concentrations between osprey adults and nestlings. Likewise, we found no differences in the detection frequency or lead concentrations in osprey adults and nestlings from high- and low-salinity areas. Of the bald eagle samples tested, 55% had detectable lead levels ( x¯  = 6.23 ± 10.74 μg/dL). Adult bald eagles had more detectable and higher lead concentrations than did nestlings or pre-adults. Among environmental samples, paint had the highest lead concentrations, followed by sediment, blue catfish (Ictalurus furcatus), and gizzard shad (Dorosoma cepedianum). There was no correlation between blood lead concentrations of osprey adults and their offspring. Our results indicate that, in the Chesapeake Bay region of Maryland and Virginia (USA), there are multiple sources by which piscivorous raptors may be exposed to lead. Environ Toxicol Chem 2019;38:862-871. © Published 2019 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

What do we know about lead contamination in wild vultures and condors? A review of decades of research

Vultures and condors (hereafter vultures) make up one the most threatened avian guilds in the world due to a variety of human-mediated impacts and disturbances. In fact, 70% of vulture species are currently suffering impacted by significant conservation threats, with lead contamination being particularly important. Unfortunately, lead contamination in vulture species remains poorly studied in many regions of the world. We reviewed the existing scientific knowledge about this threat to vultures. We found 62 scientific articles studying lead contamination in vultures. Seventy-two percent of these articles were from North America and Europe, with the rest corresponding to Asia (13%), South America (8%), and Africa (7%). Most (92%) were published recently (2001-2018). Published articles included information on 13 vulture species out of a total of 23 from both the Old (9) and New World (4). Eighty-eight percent of the articles showed individuals with lead concentrations above threshold levels in some tissues sampled, with New World (Cathartidae) vultures more affected than Old World vultures (Accipitridae). The most suspected but rarely probed source of lead was lead ammunition, but other sources such as pollution or industry were also reported. It is concerning that lead contamination is considered a major threat for just 8% (2/23) of the vulture species categorized by the IUCN Red list. Our review shows that lead contamination is an important threat for several vulture species worldwide, but remains undiagnosed and not well-recognized in some species and geographical areas. The effect of this contaminant on vulture demography is not well known but merits particular attention since it may be leading to population declines in several species.

Habitat use strategy influences the tissue signature of trace elements including rare earth elements in an urban-adapted omnivorous bird

Concentrations of trace elements vary naturally between geological environments and as a result of emissions from anthropogenic activities. Habitat use strategy is an important determinant of trace element concentrations in tissues and eggs of wild birds. However, a scarcity of studies have documented the relationships between individual bird movements related to foraging activities and exposure to contaminants including trace elements. The objective of the present study was to investigate the influence of habitat use strategy, determined using GPS-based telemetry, on the liver concentrations of selected trace elements including rare earth elements (REEs) as well as lead (Pb) isotope ratios in an urban-adapted omnivorous bird, the ring-billed gull (Larus delawarensis). Male (n = 20) and female (n = 18) ring-billed gulls breeding near Montreal (QC, Canada) in one of the largest colony in North America were tracked using miniature GPS devices to characterize their movements over a 10-days period. The time spent foraging by both male and female gulls in landfills and wastewater basins positively correlated with liver Pb concentrations. A positive correlation was also found between the time spent foraging in agricultural fields and liver concentrations of yttrium (Y) in male and female ring-billed gulls. Heavy REE concentrations were significantly greater in female gull liver relative to those of males, although this was not associated with the time spent in any foraging habitats. Pb isotope ratios (²⁰⁸Pb/²⁰⁶Pb and ²⁰⁶Pb/²⁰⁷Pb) in the liver of male ring-billed gulls tended to be lower in individuals that foraged in landfills, thus indicating that they may have been exposed to different Pb sources relative to birds that visited other sites. This study provided valuable information on the potential sources of trace elements at the landscape level in free-ranging birds spanning urbanized environments.

Acute and Chronic Lead Exposure in Four Avian Scavenger Species in Switzerland

Despite irrefutable evidence of its negative impact on animal behaviour and physiology, lethal and sublethal lead poisoning of wildlife is still persistent and widespread. For scavenging birds, ingestion of ammunition, or fragments thereof, is the major exposure route. In this study, we examined the occurrence of lead in four avian scavengers of Switzerland and how it differs between species, regions, and age of the bird. We measured lead concentration in liver and bone of the two main alpine avian scavengers (golden eagle Aquila chrysaetos and bearded vulture Gypaetus barbatus) over the entire area of the Swiss Alps and two of the main avian scavengers occurring in the lowlands of Switzerland (red kite Milvus milvus and common raven Corvus corax). Of those four species, only the bearded vulture is an obligate scavenger. We found that lead burdens in the two alpine avian scavengers were higher than those found for the same species elsewhere in Europe or North America and reached levels compatible with acute poisoning, whereas lead burdens of the two lowland avian scavengers seemed to be lower. Several golden eagles, but only one red kite with abnormally high bone lead concentrations were found. In all four species, a substantial proportion of birds had elevated levels which presumably represent recent (liver lead levels) or past (bone lead levels) uptake of sublethal doses of lead.

Association between hunting and elevated blood lead levels in the critically endangered African white-backed vulture Gyps africanus

Lead (Pb) toxicity caused by the ingestion of Pb ammunition fragments in carcasses and offal is a threat to scavenging birds across the globe. African vultures are in critical decline, but research on whether Pb exposure is contributing to declines is lacking. In Africa, recreational hunting represents an important economic activity; however, Pb in leftover hunted carcasses and gut piles represents a dangerous food source for vultures. It is therefore important to establish whether recreational hunting is associated with Pb exposure in African vultures. We explored this issue for the critically endangered white-backed vulture (Gyps africanus) in Botswana by examining their blood Pb levels inside and outside of the hunting season, and inside and outside of private hunting areas. From 566 birds captured and tested, 30.2% birds showed elevated Pb levels (10 to <45 μg/dl) and 2.3% showed subclinical exposure (≥45 μg/dl). Higher blood Pb levels were associated with samples taken inside of the hunting season and from within hunting areas. Additionally, there was a significant interaction between hunting season and areas, with Pb levels declining more steeply between hunting and non-hunting seasons within hunting areas than outside them. Thus, all our results were consistent with the suggestion that elevated Pb levels in this critically endangered African vulture are associated with recreational hunting. Pb is known to be highly toxic to scavenging birds and we recommend that Pb ammunition in Botswana is phased out as soon as possible to help protect this rapidly declining group of birds.

Levels of blood lead in Griffon vultures from a Wildlife Rehabilitation Center in Spain

Lead is considered a highly toxic contaminant with important impacts to bird wildlife. Griffon vultures (Gyps fulvus) are a sensitive indicator of the level of environmental contamination due to their position at the top of the food chain and their dependence on human activities. The aim of this study was to assess susceptibility to lead intoxication in Griffon vultures admitted to Wildlife Rehabilitation Centers (WRC), measuring blood lead levels and determining if blood lead concentrations are related to clinical signs, hematological, biochemical or radiographic findings. Also, the influence of age, gender, body condition, season and primary cause of admission were evaluated. This study was realized in all Griffon vultures admitted during a period of one year in the Rehabilitation Center GREFA. Blood lead levels are measured by using anodic stripping voltammetry. In Griffon vultures, we observed that 26% of the analyzed birds presented lead levels above 20µg/dL with 74% below 20µg/dL ([Pb]_<20 =9.34±5.60µg/dL). In our study, statistically significant differences were found for lead according to sex, season of admission to the center and body condition. A negative correlation was found between levels of metal and hematocrit. No association was found between clinical signs and blood lead levels in Griffon vultures, except for digestive signs as stasis and weight loss. On numerous occasions, the intoxication in this specie is related to ingestion of lead ammunition; however, we have not detected radiographic lead in our vultures. Compared with other studies, we generally found low levels of lead in blood of Griffon vultures but the blood of all birds admitted to WRC presented detectable lead concentrations. This species apparently presents a higher sensibility to the toxic effects of this metal than that described by other authors. It have been observed that there is some evidence that suggests that subclinical levels of lead could be related with a predisposition to injury or diseases, even though these birds might be admitted for other causes. The detection of levels of blood lead in animals that are admitted to a recovery center will give valuable information which could be used to monitor spatial and temporal variations and provide a clearer picture of temporal levels of this contaminant in this emblematic avian specie.

Assessing multi-tissue lead burdens in free-flying obligate scavengers in eastern North America

Avian scavengers are regularly exposed to anthropogenic lead. Although many studies evaluate lead concentrations of either blood or tissues of lead-poisoned birds, there is comparatively less research on lead burdens of free-flying, apparently healthy individuals and populations. Here, we address this lack of information by assessing lead levels of multiple tissues (femur, liver, kidney, breast muscle, thigh muscle) in free-flying black vultures (n = 98) and turkey vultures (n = 10) collected outside the hunting season. We found only one individual had a soft tissue lead concentration indicative of acute exposure (6.17 mg/kg wet weight in the liver), while the other 107 vultures showed consistent low-level lead exposure throughout the soft tissues. All vultures, however, had femur lead concentrations indicative of chronic lead exposure (black vultures [Formula: see text]31.80 ± 20.42 mg/kg (±SD); turkey vultures 23.21 ± 18.77 mg/kg). Lead levels were similar in all tissues in both vulture species (in each case, p > 0.05) and were generally highest in the femur, intermediate in the kidney and liver, and lowest in the breast and thigh muscle. Despite the consistency of these patterns, there were few strong correlations between lead levels in different tissues within each species, and those correlations that did exist were not consistent between species. Because these vultures were free flying and apparently healthy, the organism-wide lead distributions and between-species trends we report here provide important insight into the sublethal lead burdens that black vultures and turkey vultures commonly carry. Furthermore, these data offer a framework to better interpret and contextualize lead exposure data collected from these and other species.

Repeated conservation threats across the Americas: High levels of blood and bone lead in the Andean Condor widen the problem to a continental scale

Wildlife lead exposure is an increasing conservation threat that is being widely investigated. However, for some areas of the world (e.g., South America) and certain species, research on this subject is still scarce or only local information is available. We analyzed the extent and intensity of lead exposure for a widely distributed threatened species, the Andean Condor (Vultur gryphus). We conducted the study at two different scales: 1) sampling of birds received for rehabilitation or necropsy in Argentina, and 2) bibliographic review and extensive survey considering exposure event for the species' distribution in South America. Wild condors from Argentina (n = 76) presented high lead levels consistent with both recent and previous exposure (up to 104 μg/dL blood level, mean 15.47 ± 21.21 μg/dL and up to 148.20 ppm bone level, mean 23.08 ± 31.39 ppm). In contrast, captive bred individuals -not exposed to lead contamination- had much lower lead levels (mean blood level 5.63 ± 3.08 μg/dL, and mean bone level 2.76 ± 3.06 ppm). Condors were exposed to lead throughout their entire range in continental Argentina, which represents almost sixty percent (>4000 km) of their geographical distribution. We also present evidence of lead exposure events in Chile, Ecuador, and Peru. Lead poisoning is a widespread major conservation threat for the Andean Condor, and probably other sympatric carnivores from South America. The high number and wide range of Andean Condors with lead values complement the results for the California Condor and other scavengers in North America suggesting lead poisoning is a continental threat. Urgent actions are needed to reduce this poison in the wild.

Ground Squirrel Shooting and Potential Lead Exposure in Breeding Avian Scavengers

Recreational ground squirrel shooting is a popular activity throughout the western United States and serves as a tool for managing ground squirrel populations in agricultural regions. Belding's ground squirrels (Spermophilus beldingi) are routinely shot in California, Nevada, and Oregon across habitats that overlap with breeding avian scavengers. Ground squirrels shot with lead (Pb)-based bullets may pose a risk to avian scavengers if they consume carcasses containing Pb fragments. To assess the potential risk to breeding avian scavengers we developed a model to estimate the number, mass, and distribution of Pb fragments in shot ground squirrels using radiographic images. Eighty percent of shot carcasses contained detectible Pb fragments with an average of 38.6 mg of Pb fragments. Seven percent of all carcasses contained Pb fragment masses exceeding a lethal dose for a model raptor nestling (e.g. American kestrel Falco sparverius). Bullet type did not influence the number of fragments in shot ground squirrels, but did influence the mass of fragments retained. Belding's ground squirrels shot with .17 Super Mag and unknown ammunition types contained over 28 and 17 times more mass of Pb fragments than those shot with .22 solid and .22 hollow point bullets, respectively. Ground squirrel body mass was positively correlated with both the number and mass of Pb fragments in carcasses, increasing on average by 76% and 56% respectively across the range of carcass masses. Although the mass of Pb retained in ground squirrel carcasses was small relative to the original bullet mass, avian scavenger nestlings that frequently consume shot ground squirrels may be at risk for Pb-induced effects (e.g., physiology, growth, or survival). Using modeling efforts we found that if nestling golden eagles (Aquila chrysaetos), red-tailed hawks (Buteo jamaicensis), and Swainson's hawks (B. swainsoni) consumed shot ground squirrels proportionately to the nestling's mass, energy needs, and diet, 100% of the nestling period would exceed a 50% reduction in delta-aminolevulinic acid dehydratase production threshold, the last 13-27% of the nestling stage would exceed a reduced growth rate threshold, but no nestlings would be expected to exceed a level of Pb ingestion that would be lethal.

Multi-locus phylogenetic inference among New World Vultures (Aves: Cathartidae)

New World Vultures are large-bodied carrion feeding birds in the family Cathartidae, currently consisting of seven species from five genera with geographic distributions in North and South America. No study to date has included all cathartid species in a single phylogenetic analysis. In this study, we investigated the phylogenetic relationships among all cathartid species using five nuclear (nuc; 4060bp) and two mitochondrial (mt; 2165bp) DNA loci with fossil calibrated gene tree (27 outgroup taxa) and coalescent-based species tree (2 outgroup taxa) analyses. We also included an additional four nuclear loci (2578bp) for the species tree analysis to explore changes in nodal support values. Although the stem lineage is inferred to have originated ∼69 million years ago (Ma; 74.5-64.9 credible interval), a more recent basal split within Cathartidae was recovered at ∼14Ma (17.1-11.1 credible interval). Two primary clades were identified: (1) Black Vulture (Coragyps atratus) together with the three Cathartes species (Lesser C. burrovianus and Greater C. melambrotus Yellow-headed Vultures, and Turkey Vulture C. aura), and (2) King Vulture (Sarcoramphus papa), California (Gymnogyps californianus) and Andean (Vultur gryphus) Condors. Support for taxon relationships within the two basal clades were inconsistent between analyses with the exception of Black Vulture sister to a monophyletic Cathartes clade. Increased support for a yellow-headed vulture clade was recovered in the species tree analysis using the four additional nuclear loci. Overall, these results are in agreement with cathartid life history (e.g. olfaction ability and behavior) and contrasting habitat affinities among sister taxa with overlapping geographic distributions. More research is needed using additional molecular loci to further resolve the phylogenetic relationships within the two basal cathartid clades, as speciation appeared to have occurred in a relatively short period of time.