Experimental lead poisoning in turkey vultures (Cathartes aura)

Blood lead levels in an endangered vulture decline following changes in hunting activity

Lead ammunition stands out as one of the most pervasive pollutants affecting wildlife. Its impact on bird populations have spurred efforts for the phase-out of leaded gunshot in several countries, although with varying scopes and applications. Ongoing and future policy changes require data to assess the effectiveness of adopted measures, particularly in the current context of biodiversity loss. Here, we assessed the long-term changes in blood lead (Pb) levels of Egyptian vultures from the Canary Islands, Spain, which have been severely affected by Pb poisoning over the past two decades. During this period, the reduction in hunting pressure and changes in legislation regarding firearms usage for small game hunting likely contributed to a decrease in environmental Pb availability. As anticipated, our results show a reduction in Pb levels, especially after the ban on wild rabbit hunting with shotgun since 2010. This effect was stronger in the preadult fraction of the vulture population. However, we still observed elevated blood Pb levels above the background and clinical thresholds in 5.6% and 1.5% of individuals, respectively. Our results highlight the positive impact of reducing the availability of Pb from ammunition sources on individual health. Nonetheless, the continued use of Pb gunshot remains an important source of poisoning, even lethal, mainly affecting adult individuals. This poses a particular concern for long-lived birds, compounding by potential chronic effects associated with Pb bioaccumulation. Our findings align with recent studies indicating insufficient reductions in Pb levels among European birds of prey, attributed to limited policy changes and their uneven implementation. We anticipated further reductions in Pb levels among Egyptian vultures with expanded restrictions on hunting practices, including a blanket ban on Pb shot usage across all small game species.

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.

Toxicity and bioremediation of the lead: a critical review

Lead is a naturally occurring, bluish-gray metal that is found in small quantities in the earth's crust. The existing literature demonstrates that non-biodegradable character and continuous use results in accumulation of lead concentration in the environment and causes various ill effects such as neurotoxicity, change in psychological and behavioral development of different organisms. Nowadays the most effective technique in the revival of the environment is bioremediation and it is environmentally friendly and cost-effective. Bacterial strains such as Oceanobacillus profundus and Lactobacillus acidophilus ATCC4356 have the ability to reduce lead 97% and 73.9%, respectively. Similarly some species of algae and fungal strains also showed lead removal efficiency as 74% (spirulina), 97.1% (Chlorella kessleri), 95.5% (Penicillium janthinillum) and 86% (Aspergillus flavus). Biodegradation of lead by various microbes would be the most efficient and sustainable approach. This review focuses on toxicity, fate of lead in the environment and its microbial degradation.

Sub-lethal impacts of lead poisoning on blood biochemistry, immune function and delta-aminolevulinic acid dehydratase (δ-ALAD) activity in Cape (Gyps coprotheres) and white-backed (G. africanus) Vulture chicks

Although the prevalence of lead poisoning in southern Africa's Gyps vultures is now well-established, its finer physiological effects on these endangered species remain poorly characterised. We evaluated the sub-lethal impact of acute lead exposure on Cape and White-backed Vulture chicks from two breeding colonies in South Africa, by analysing its possible effects on key blood biochemistry parameters, immune function, packed cell volume and δ-aminolevulinic acid dehydratase (δ-ALAD) activity. All 37 White-backed Vulture nestlings sampled displayed elevated lead levels (>10 μg/dL), and seven had blood [Pb] >100 μg/dL. Eight of 28 Cape Vulture nestlings sampled had blood [Pb] exceeding background exposure, with one showing blood [Pb] >100 μg/dL. Delta-aminolevulinic acid dehydratase (δ-ALAD) activity was significantly and negatively related to blood [Pb] in nestlings from both species, with 50% inhibition of the enzyme predicted to occur at blood [Pb] = 52.8 μg/dL (White-backed Vulture) and 18.8 μg/dL (Cape Vulture). Although no significant relationship was found between % packed cell volume (PCV) and blood [Pb], the relatively lower mean PCV of 32.9% in White-backed Vulture chicks, combined with normal serum protein values, is likely indicative of depression or haemolytic anaemia. The leukogram was consistent in both species, although the presence of immature heterophils suggested an inflammatory response in White-backed Vulture chicks with blood [Pb] >100 μg/dL. Values for cholesterol, triglycerides, total serum protein, albumin, globulin, albumin/globulin ratio, alanine aminotransferase (ALT) and gamma-glutamyl transferase (GGT) were consistent with values previously reported. Calcium and phosphorus concentrations suggested no adverse effects on bone metabolism. A significant decrease in urea: uric acid (U:UA) ratio at blood [Pb] >100 μg/dL in White-backed Vulture chicks, brought about by a decrease in urea production, raises the possibility of hepatic abnormality. These results suggest that δ-ALAD activity may serve as a sensitive biomarker of lead toxicity in both species, while highlighting the need to better understand the significant variability in sensitivity that is observed, even between closely related members of the same genus.

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.

Heavy metal exposure and behavioral assessment of vultures in a captive environment

Heavy metals are a heterogeneous group of metals that can cause detrimental biological disruptions in vultures. Heavy metals play a threatening role and affect vulture populations around the globe. However, various conservation organizations are working for the captive breeding of these endangered animals so that they can reintroduce these captive-bred animals back to their natural environment. This research study was conducted at Changa Manga Vulture Conservatory, Punjab, with the help of Punjab Wildlife Department. A non-invasive technique was used to collect vulture feathers and fecal samples to study the exposure of heavy metals. The behavior of vultures in captivity was also recorded. Samples were chemically digested in aqua regia and analyzed for the detection of five heavy metal concentrations such as chromium (Cr), cadmium (Cd), lead (Pb), zinc (Zn), and magnesium (Mg) using flame atomic absorption spectroscopy (FAAS). Among the selected heavy metals, non-essential metals such as Pb, Cr, and Cd were recorded in the least concentration, whereas essential metals Zn and Mg were recorded in the highest concentration. Behavioral studies showed that vultures in captivity become excessively hostile and afraid of any human interaction; they flew to the top of the trees if they felt any danger. It was concluded in the study that the higher levels of both essential and non-essential metals recorded in feathers and fecal samples might be due to the type of feed, even though a controlled food is provided to vultures in captivity. However, regular monitoring of the environment can bring improvements to the health of vultures in captivity and help to find accurate sources of contamination.

Diagnosis and Treatment of Heavy Metal Toxicosis in Six Waldrapp Ibis (Geronticus eremita)

Six adult Waldrapp ibis (Geronticus eremita) were presented with heavy metal toxicosis secondary to paint chip ingestion after being placed in an indoor confinement enclosure because of a regional highly pathogenic avian influenza epornitic and government restrictions. Four of the ibis developed clinical disease signs between 45 and 64 days of confinement, including weakness, lethargy, inability to fly, low body condition, and bilateral wing droop while 2 birds appeared to remain normal during that period. Common clinicopathological findings included elevated plasma aspartate aminotransferase, creatine kinase, glutamate dehydrogenase, and bile acids values. Erythrocyte morphological changes included prominent hypochromasia, decreased size of polychromatophils with occasional cytoplasmic stippling, abnormal shapes, and D cells. Whole-body radiographic imaging revealed particulate radio-opaque material in the ventriculus of all affected birds. One bird died before chelation therapy could be instituted and heavy metal testing of the liver revealed increased concentrations of lead and zinc. Lead toxicosis was diagnosed in the 5 remaining birds by plasma lead analysis. These 5 birds were hospitalized for an average of 40 days and treated with sodium calcium edetate and fluid therapy, which resulted in resolution of the toxicosis. Plasma biochemistry, complete blood counts, and blood lead values were performed repeatedly on all 5 birds and were used to guide therapy and monitor treatment response. This case series emphasizes the importance of early contingency planning and reviews the treatment of lead toxicosis in birds with a focus on long-term clinical monitoring and hematology.

High Levels of Heavy Metals detected in Feathers of an Avian Scavenger Warn of a High Pollution Risk in the Atacama Desert (Chile)

The Atacama Desert represents the highest levels of mining exploitation in Chile, which inexorably results in high levels of pollution. Raptors, and particularly scavengers, have shown their usefulness to evaluate exposure to environmental contaminants in polluted scenarios. In this study, we used primary feathers from a local avian scavenger, turkey vulture Cathartes aura, to evaluate the exposure to cadmium (Cd), lead (Pb), copper (Cu) and zinc (Zn) in two locations from the southern Atacama Desert (coastal and inland) and a third location from the bordering semiarid region, in northern Chile. All metals were detected in all analyzed samples (n = 54). Mean concentrations in Coastal Atacama were 0.68 ± 0.84 ppm for Cd; 1.97 ± 2.01 ppm for Pb; 59.11 ± 80.69 ppm for Cu; and 107.96 ± 51.00 ppm for Zn, while mean concentrations in Inland Atacama were 0.55 ± 0.42 ppm for Cd; 3.37 ± 2.61 ppm for Pb; 91.66 ± 77.74 ppm for Cu; and 214.03 ± 99.08 ppm for Zn. Mean concentrations in Coastal Coquimbo were 0.63 ± 0.69 ppm for Cd; 1.57 ± 0.92 ppm for Pb; 18.09 ± 6.12 ppm for Cu; and 149.37 ± 105.56 ppm for Zn. These differences could be explained by differences on abundance of mining settlements among areas. According to the literature, these values are very high for all metals, exceeding in some cases those values referred as responsible of health disorders in birds. We strongly recommend further research looking at potential adverse effects caused by heavy metal pollution on the health of human and wildlife populations in the southern Atacama Desert.

Lead in terrestrial game birds from Spain

We analysed exposure to Pb and its relationship with lead-based ammunition in seven species of terrestrial game birds-common woodpigeon (Columba palumbus), rock dove (Columba livia), stock dove (Columba oenas), European turtle-dove (Streptopelia turtur), red-legged partridge (Alectoris rufa), Barbary partridge (Alectoris barbara) and common quail (Coturnix coturnix)-from rural and urban areas in different parts of Spain (Valencia, Castilla-La Mancha, Castilla y León, Madrid, Islas Canarias and Navarra). A total of 530 liver samples were analysed, and the presence of Pb pellets was studied in the crop, gizzard and intestine; the state and appearance of these organs were also analysed. The number of specimens suspected to have ingested Pb shot was 28 (5.6%), and the geometric mean concentration of hepatic Pb was 0.054 μg g^-1 (wet weight, ww). A low percentage of samples (4.8%) were above the abnormal exposure threshold (0.65 μg g^-1 ww), and, in these specimens, renal Pb concentrations were determined. Common woodpigeons and rock doves from Madrid were found to have high concentrations of Pb in their livers, and, so, both species can be considered to be good bioindicators of Pb contamination in rural (common woodpigeons) and urban (rock doves) environments. Partridges bred for hunting may be more prone to ingesting pellets from the environment, a fact that should be taken into account in management decisions.

Alleviating effects of silicate, selenium, and microorganism fertilization on lead toxicity in ginger (Zingiber officinale Roscoe)

The aim of this work was exploring the effects of silicon, selenium, and a microorganism fertilizer on alleviating the effects of lead (Pb) toxicity in ginger. Ginger plants were grown in soil containing 500 mg/kg Pb(NO3)2 without (CK) or with Si, Se, or microorganism fertilizer (T1, T2, T3) as soil conditioners. Morphology indexes, Pb accumulation and distribution rates, and antioxidant enzyme activities were investigated. The Pb transfer and Pb absorption coefficients were calculated, and Pb accumulation in plant organs at various developmental stages were determined. All three soil conditioners alleviated Pb stress in ginger plants. The rhizome fresh weight in T1, T2, and T3 was increased by 96.06, 85.81, and 41.58%, respectively, compared with CK. The accumulation of Pb in organs was lower in all treatments than in CK. The chlorophyll and carotenoid contents in leaves, and root activity, root length, and the tolerance index, were higher in the treatments than in CK. The reactive oxygen species content in ginger leaves and roots was significantly lower in all treatments than in CK. Soil conditioners alleviated the negative effects of Pb stress on ginger plants: Si was the most effective, followed by Se, and then the microorganism fertilizer.

Effects of experimental lead exposure on physiological indices of nestling great tits Parus major: haematocrit and heterophile-to-lymphocyte ratio

Lead (Pb) is recognized as one of the most toxic trace elements that can induce a wide range of negative health effects in wildlife. Because the investigation of basic environment-sensitive physiological indicators is easy to perform in wild birds, they have been considered as valuable bioindicators of lead contamination. The harmfulness of lead poisoning can depend on the type of exposure, and in most studies of birds, an effect of chronic lead exposition has been considered. In this study, we investigated whether a single exposure to specific doses of lead affected such physiological indices as haematocrit and the heterophil-to-lymphocyte ratio (H/L ratio). For this purpose, we conducted an experiment based on intentional lead supplementation, with the use of two different doses, applied to randomly chosen great tit (Parus major) nestlings from randomly selected broods. A few days after the exposure (when the nestlings were 15 days old), we determined haematocrit and the H/L ratio as potentially sensitive physiological indicators of lead intoxication. We found that the treatment with lead resulted in a significant decline in haematocrit level. In addition, we found that the age when lead exposure occurred can be considered as an important factor influencing haematocrit variation. A decrease in haematocrit was observed on consecutive days of nestling life. In contrast, the H/L ratio did not show any significant response to lead exposure. These results clearly show that the assessment of haematocrit level for nestling great tits can provide a simple and rapid method of indirect evaluation of physiological effects of lead intoxication caused by a single exposure.

Blood and bone lead levels in South Africa's Gyps vultures: Risk to nest-bound chicks and comparison with other avian taxa

Poisoning, including secondary lead poisoning, is cited as the single most important cause of vulture mortalities in Africa. To evaluate the prevalence of lead poisoning among South Africa's Gyps vultures compared to other, non-scavenging birds, we obtained blood and bone samples from Cape (Gyps coprotheres) and White-backed (G. africanus) vultures. We found that 66% of White-backed Vultures (n = 110, including 85 nest-bound chicks sampled at Dronfield Nature Reserve) and 80% of Cape Vultures (n = 15) had blood [Pb] in excess of 10 μg/dL, the upper limit of background exposure. Average blood [Pb] were 15.4 μg/dL and 29.7 μg/dL for White-backed and Cape vultures, respectively. Bone samples revealed that 12% of White-backed Vultures (n = 18) and 9% of Cape Vultures (n = 75) suffered from subclinical to severe clinical lead poisoning upon their deaths. By contrast, none of the 40 blood, bone or liver samples obtained from non-scavenging bird species were found to exceed background exposure levels. Our results suggest that, unlike non-scavenging birds, the scavenging lifestyle of Gyps vultures subjects them to lead poisoning on a regular basis. Had environmental sources of lead (e.g., dust) been the source of the lead poisoning at the White-backed Vulture breeding colony at Dronfield, all the chicks would have displayed similar blood lead concentrations. Instead the values ranged from barely detectable to very high, leading us to conclude that metallic lead fragments regurgitated by parents during feeding are responsible for the elevated lead levels in some of the chicks at this site. We conclude the likely source of these particles to be fragments of lead ammunition embedded in the carcasses of hunted animals. These results add to a growing body of evidence underscoring the threat posed by the use of lead ammunition and its potential role in the declines of vultures and other scavenging taxa.

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.

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.

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.

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.

VIGILANCE POISON: Illegal poisoning and lead intoxication are the main factors affecting avian scavenger survival in the Pyrenees (France)

A specific surveillance program has been set up to monitor avian scavenger populations in the French Pyrenean Mountains, hosting a high proportion of the French populations. The two main purposes of the study were to identify all causes of death and to investigate poisoning cases. All 170 birds found dead during the 7-year program were submitted to full necropsy, X-Ray, parasitological investigations and consistent analytical toxicology screenings (Cholinesterase inhibitors, anticoagulant rodenticides, organochlorine insecticides, Pb, Cd). Over the study period, 8 Bearded Vultures, 120 Griffon Vultures, 8 Egyptian Vultures and 34 Red kites were eventually collected. Mortality events were often multifactorial, but poisoning was by far the most common cause of death (24.1%), followed by trauma/fall (12%), bacterial diseases and starvation (8%) and electrocution (6%). Illicit use of banned pesticides was identified as a common cause of poisoning (53% of all poisoning cases) and lead poisoning was also identified as a significant toxicant issue (17% of all poisoning cases). Lead isotopic signature could be associated primarily with ammunition. Last, a positive association between trauma and lead contamination was detected, indicating that lead could be a significant contributor to different causes of death. These results urge for severe restrictions on the use of lead ammunition to prevent scavengers from detrimental exposure.

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

Lead is a prominent and highly toxic contaminant with important impacts to wildlife. To understand the degree to which wildlife populations are chronically exposed, we quantified lead levels within American black vultures (Coragyps atratus; BLVU) and turkey vultures (Cathartes aura; TUVU), two species that are useful as environmental sentinels in eastern North America. Every individual sampled (n=108) had bone lead levels indicative of chronic exposure to anthropogenic lead (BLVU: x¯=36.99 ± 55.21 mg Pb/kg tissue (±SD); TUVU: x¯=23.02 ± 18.77 mg/kg). Only a few showed evidence of recent lead exposure (BLVU liver: x¯=0.78 ± 0.93 mg/kg; TUVU liver: x¯=0.55 ± 0.34 mg/kg). Isotopic ratios suggested multiple potential sources of lead including ammunition, gasoline, coal-fired power plants, and zinc smelting. Black and turkey vultures range across eastern North America, from Quebec to Florida and individuals may traverse thousands of kilometers annually. The extent to which vultures are exposed suggests that anthropogenic lead permeates eastern North American ecosystems to a previously unrecognized degree. Discovery of an epidemic of chronic lead exposure in such widespread and common species and the failure of soft-tissue sampling to diagnose this pattern has dramatic implications for understanding modern wildlife and human health concerns.

Assessment of the exposure to heavy metals in Griffon vultures (Gyps fulvus) from the Iberian Peninsula

Griffon vultures (Gyps fulvus), by virtue of their position at the top of the food chain and as obligate scavengers, are at risk of accumulating and concentrating heavy metals in their tissues and may be more predisposed to their toxic effects. The aim of this study is to investigate heavy metal concentrations in Griffon vultures in Portugal and Catalonia, Spain and to determine if heavy metal concentrations in the blood of weak and/or injured Griffon vultures admitted to wildlife rehabilitation centres (WRC) reflect contamination profiles in the local, free-living and outwardly healthy population. Whole-blood samples taken from 121 Griffon vultures caught in the wild or admitted to WRC in Portugal and Catalonia, Spain were examined for cadmium (Cd), mercury (Hg) and lead (Pb) by inductively coupled plasma mass spectrometry (ICP-MS). Cd and Hg were not detected in most samples (98.3% and 95%, respectively), while Pb was detected in all birds in concentrations ranging between 4.97 and 300.23 µg/dl. Birds admitted to WRC had significantly lower Pb concentrations (24.15 ± 15.07 and 25.98 ± 18.04 µg/dl in Portugal and Catalonia, Spain, respectively) than animals caught in the wild (29.67 ± 13.19 and 42.22 ± 50.08 µg/dl in Portugal and Catalonia, Spain, respectively) (p<0.05). This may be explained by the fact that malnutrition was the main cause of admission of Griffon vultures to WRC, as ingestion has been described as the most significant pathway for Pb exposure in raptors. Therefore Griffon vultures admitted to WRC do not seem to be representative of the local, free-flying populations, so it remains necessary to continue catching when one intends to monitor Pb exposure in this species. The population of vultures captured in Catalonia, Spain showed the highest mean blood Pb concentration, perhaps due to the municipal rubbish dump located near the feeding station, with rubbish providing a significant fraction of their trophic needs. The ingestion of game meat with bullet fragments in carcasses or with Pb shots embedded in their flesh could also be the cause of the high blood Pb concentrations found in some vultures. The potential risk of Pb exposure in Griffon vulture populations must be given consideration, since most individuals evaluated had Pb concentrations between 20 and 100µg/dl, which is considered to be subclinical exposure to Pb, and which is above the threshold level at which Pb can affect antioxidant system in this species (15 µg/dl).

Delta-aminolevulinic acid dehydratase (δALAD) activity in four free-living bird species exposed to different levels of lead under natural conditions

The purposes of this study were: (1) to determine the δALAD activity and δALAD ratio in blood of four free-living bird species (Griffon vulture, Eagle owl, Slender-billed gull and Audouin's gull); (2) and to investigate the correlations between δALAD activity/ratio and Pb concentrations in blood samples. A decrease was observed in δALAD activity in Griffon vultures and Eagle owls exposed to Pb. In addition, negative relationships were found between δALAD ratio or δALAD activity and Log blood Pb levels in Griffon vultures and Eagle owls, and these relationships were stronger in areas with the highest Pb exposure. We provide equations that may be helpful to estimate δALAD activity and δALAD ratio using blood Pb concentrations. Regarding gull species, δALAD activity found in the present study may be considered the normal activity in Slender-billed gull and Audouin's gull species, since very low blood Pb concentrations and no correlations were found in these species. Although both δALAD activity and δALAD ratio are sensitive biomarkers of Pb exposure and effect in birds, the use of δALAD ratio may improve the results. Besides, this study provides blood threshold concentrations at which Pb bears effects on δALAD enzyme (5µg/dl in Eagle owl; 8µg/dl in Griffon vulture; and probably >2µg/dl in Slender-billed gull and Audouin's gull). Our findings show that Eagle owl seems to be more sensitive to δALAD enzymatic inhibition by Pb than Griffon vultures. Eagle owls and Griffon vultures exhibited up to 79% and 94% decrease in δALAD activity when blood Pb concentrations exceeded 19 and 30µg/dl, respectively. Regarding the effects related with δALAD inhibition, significant negative correlations were found between δALAD activity and hematocrit in Eagle owls and Griffon vultures, which may be related to compensatory response associated with a decrease in δALAD activity. In addition, an effect on creatine kinase activity and total proteins in plasma was found in Griffon vultures. The significant negative correlations found between δALAD activity and tGSH in Griffon vulture, and between δALAD activity and Log CAT activity in Eagle owls, may be related to a protective response of antioxidant system against reactive oxygen species (ROS). The negative relationship found between δALAD activity and TBARS levels in Griffon vulture is probably related to an induction of lipid peroxidation by ROS that may be generated by δALA accumulation when δALAD activity is depressed. δALAD activity and δALAD ratio in blood are suggested as important nondestructive biomarkers for Pb exposure and effect for future biomonitoring studies in Griffon vulture and Eagle owl. Further studies are recommended to provide new data on Pb concentrations at which δALAD activity is affected in different wild bird species and to elucidate why different species tolerate Pb in different ways.

Lead and eagles: demographic and pathological characteristics of poisoning, and exposure levels associated with other causes of mortality

We conducted a retrospective analysis to evaluate demographic and pathologic characteristics in 484 bald eagles (Haliaeetus leucocephalus) and 68 golden eagles (Aquila chrysaetos) diagnosed with lead poisoning at the U.S. Geological Survey National Wildlife Health Center. As part of our analysis, we compared characteristics of lead poisoned eagles with those that died of other causes. Odds of lead poisoning were greater for bald eagles versus golden eagles, females versus males, adults versus juveniles, and eagles from the Mississippi and Central flyways versus the Atlantic and Pacific flyways. In addition to spatial, species, and demographic associations, we detected a distinct temporal trend in the collection date of lead poisoned bald eagle carcasses. These carcasses were found at greater frequency in late autumn and winter than spring and summer. Lesions in lead poisoned birds included emaciation, evidence of bile stasis, myocardial degeneration and necrosis, and renal tubular nephrosis and necrosis. Ingested lead ammunition or fragments were found in 14.2% of bald eagles and 11.8% of golden eagles. The overall mean liver lead concentration (wet weight basis) for eagles diagnosed with lead poisoning was 28.9 ± 0.69 SE mg/kg in bald eagles and 19.4 ± 1.84 SE mg/kg in golden eagles. In eagles diagnosed with collision trauma, electrocution, poisoning (other than lead), emaciation, infectious disease, trapping death, other, and undetermined causes, average liver lead concentrations were low (<1 mg/kg) and did not differ among causes of mortality. Thus, based on our data, we found no evidence that lead exposure of eagles predisposed them to other causes of mortality.

Lead exposure from backyard chicken eggs: a public health risk?

Although the USA has made significant strides in reducing lead exposure, new and emerging sources are raising cause for public concern. Recent reports of finding lead in eggs from chickens raised in urban gardens has highlighted the need to consider the potential health risks of consuming eggs from backyard chickens. Following the detection of 0.33 μg/g lead in the edible portion of eggs submitted for lead analysis from a backyard chicken owner, further investigation was conducted to determine the source and extent of lead exposure in the flock. Several birds, almost two dozen eggs, and environmental samples were submitted to the California Animal Health and Food Safety Laboratory for further testing. Lead was detected in the blood, liver, kidney, and bone at varying concentrations in all birds but was not detected in the muscle tissue. All egg shells contained detectable amounts of lead, while only a little over half of the edible portion of the eggs contained lead. The detected concentrations in the edible portion approached or exceeded the recommended threshold of lead consumption per day that should not be exceeded by young children if a child consumed one average-sized egg. Peeling paint from a wooded structure adjacent to the flock's coop was the likely lead source containing 3,700 μg/g lead. Thus, removal of the chickens from the source and periodic testing of eggs for lead were recommended. This case illustrates the need for consumers and health care workers to be aware of potential sources for lead exposure such as backyard chickens.

Raptor gastroenterology

Free-living raptors are frequently presented to wildlife rehabilitation centers. Conditions affecting the gastrointestinal tract can be the primary reason for presentation. The gastrointestinal tract can also be affected secondary to debilitation from other injuries or from the stress of the rehabilitation process. A thorough understanding of the anatomy, physiology, and natural history of these species is crucial to successful treatment and rehabilitation. This article addresses raptor gastroenterology with an emphasis on conditions affecting free-living birds.

Lead in ammunition: a persistent threat to health and conservation

Many scavenging bird populations have experienced abrupt declines across the globe, and intensive recovery activities have been necessary to sustain several species, including the critically endangered California condor (Gymnogyps californianus). Exposure to lead from lead-based ammunition is widespread in condors and lead toxicosis presents an immediate threat to condor recovery, accounting for the highest proportion of adult mortality. Lead contamination of carcasses across the landscape remains a serious threat to the health and sustainability of scavenging birds, and here we summarize recent evidence for exposure to lead-based ammunition and health implications across many species. California condors and other scavenging species are sensitive indicators of the occurrence of lead contaminated carcasses in the environment. Transdisciplinary science-based approaches have been critical to managing lead exposure in California condors and paving the way for use of non-lead ammunition in California. Similar transdisciplinary approaches are now needed to translate the science informing on this issue and establish education and outreach efforts that focus on concerns brought forth by key stakeholders.

In vitro evaluation of cell death induced by cadmium, lead and their binary mixtures on erythrocytes of Common buzzard (Buteo buteo)

Cadmium and lead are persistent and ubiquitous metals that can cause several deleterious effects in living beings. Apoptosis and necrosis are two types of cell death that can be found after in vivo and in vitro exposure to these metals. In this study, isolated red blood cells from living captive Common buzzard (Buteo buteo) were exposed in vitro to different concentrations of lead, cadmium, and the mixture lead-cadmium in a proportion of 1:10 (similar to that found in previous field studies). Data obtained from dose-response curves were used to evaluate the interactive effects of metal mixtures on cell viability. In general, except for the exposure to NOEC, additivity was the most frequently observed response. As described in human, after in vitro exposure, lead was highly accumulated in buzzard erythrocytes, while cadmium accumulation was scarce. Finally, the type of cell death (apoptosis or necrosis) induced by the exposure to different concentrations of these heavy metals and their mixtures was evaluated in the red blood cells. Apoptosis was found to be the main type of cell death observed after cadmium and/or lead exposure. However, this exposure caused an increase in lysis or necrosis, especially if red blood cells were exposed to high doses.

Lead exposure in free-flying turkey vultures is associated with big game hunting in California

Predatory and scavenging birds are at risk of lead exposure when they feed on animals injured or killed by lead ammunition. While lead ammunition has been banned from waterfowl hunting in North America for almost two decades, lead ammunition is still widely used for hunting big game and small game animals. In this study, we evaluated the association between big game hunting and blood lead concentration in an avian scavenger species that feeds regularly on large mammals in California. We compared blood lead concentration in turkey vultures within and outside of the deer hunting season, and in areas with varying wild pig hunting intensity. Lead exposure in turkey vultures was significantly higher during the deer hunting season compared to the off-season, and blood lead concentration was positively correlated with increasing wild pig hunting intensity. Our results link lead exposure in turkey vultures to deer and wild pig hunting activity at these study sites, and we provide evidence that spent lead ammunition in carrion poses a significant risk of lead exposure to scavengers.

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.

Ingestion of lead from ammunition and lead concentrations in white-tailed sea eagles (Haliaeetus albicilla) in Sweden

In this study we show for the first time that lead poisoning from ammunition is a significant mortality factor for white-tailed sea eagle (WSE) (Haliaeetus albicilla) in Sweden. We analyzed 118 WSEs collected between 1981 and 2004 from which both liver and kidney samples could be taken. A total of 22% of all eagles examined had elevated (>6 microg/gd.w.) lead concentrations, indicating exposure to leaded ammunition, and 14% of the individuals had either liver or kidney lead concentrations diagnostic of lethal lead poisoning (>20 microg/gd.w.). Lead concentrations in liver and kidney were significantly correlated. In individuals with lead levels <6 microg/g, concentrations were significantly higher in kidney than in liver; in individuals with lead levels >20 microg/g, concentrations were significantly higher in liver. The lead isotope ratios indicate that the source of lead in individuals with lethal concentrations is different from that of individuals exhibiting background concentrations of lead (<6 microg/gd.w.) There were no significant sex or age differences in lead concentrations. A study from the Baltic reported in principle no biomagnification of lead, but background lead concentrations in WSE liver in this study were still four to >10 times higher than concentrations reported for Baltic fish from the same time period. In contrast to other biota there was no decrease in lead concentrations in WSE over the study period. The proportion of lead poisoned WSE remained unchanged over the study period, including two years after a partial ban of lead shot was enforced in 2002 for shallow wetlands. The use of lead in ammunition poses a threat to all raptors potentially feeding on shot game or offal. The removal of offal from shot game and alternatives to leaded ammunition needs to be implemented in order to prevent mortality from lead in raptors and scavengers.

Lead toxicity to wildlife: derivation of a critical blood concentration for wildlife monitoring based on literature data

Generic risk assessments of lead (Pb) toxicity to wildlife puts soil Pb limits below the natural background. The Tissue Residue Approach (TRA) is an alternative method by which the current risk of Pb to wildlife can be assessed and avoids uncertainties about Pb exposure routes or bioavailability of environmental Pb. About 80 toxicity studies were reviewed of which 19 experimental and 6 field studies with mammals and birds were selected. Blood lead concentration (Pb-B, microg Pb/dL) was used as the index of exposure. The highest No Observed Effect Concentrations (NOECs) varied about 1600-fold among species and tests when expressed as external doses (mg Pb/kg body weight/day) whereas this range reduced to 50-fold when expressed as Pb-B. This illustrates that variation in Pb absorption from diet largely contributes to the variation in critical doses. A critical Pb-B concentration protecting mammals and birds from Pb toxicity was calculated with the HC(5) approach, i.e. the 5th percentile of species NOEC values with data of 15 different species and using growth, reproduction or hematology as endpoints. The HC(5) was significantly lower for mammals than that for birds (p<0.05), suggesting that the association between blood lead concentration and systemic toxicity was different between the two groups. The HC(5) was 18 microg/dL for mammals and was 71 microg/dL for birds. The dose-response relationship between hematological effects (hemoglobin concentration, hematocrit) and Pb-B was aggregated for different species. These relationships were highly significant and significantly different between mammals and birds. The relationships predict that the % inhibitions of hematological endpoints at the calculated HC(5) values are only 1.5% in mammals and 2% in birds, clearly within the natural variation.

Raptor toxicology

Birds of prey have demonstrated the negative impact that toxic agents can cause on animal populations and ecosystem dynamics. Lead, cholinesterase inhibitors (eg, organophosphates, carbamates), and anticoagulant rodenticides (eg, brodifacoum) are the most common toxic agents that currently affect the health of wild birds of prey in the United States. For raptors held in captivity, the list of toxic agents expands and includes toxic inhalants such as carbon monoxide and polytetrafluoroethylene. This article provides diagnostic and treatment guidelines for the toxic agents discussed.

High levels of blood lead in griffon vultures (Gyps fulvus) from Cazorla Natural Park (southern Spain)

The blood lead of 23 griffon vultures (Gyps fulvus) trapped in 2003 was analyzed in order to evaluate exposure to lead in the vulture population of Cazorla Natural Park (in southern Spain). In 2001 the use of leaded gasoline in vehicles was banned in the European Union; however, lead ammunition is still used in Spain in big-game hunting for red deer, fallow deer, mouflon, and wild boar, which are ingested by vultures from September to March. The mean concentration of lead in blood was 43.07 +/- 31.96 microg/dL with a range of 17.39-144.80 microg/dL. Only two vultures had lead levels below 20 microg/dL, and two others had blood lead concentrations close to 150 microg/dL. In view of the results, we think the population of vultures from Cazorla Natural Park is suffering subclinical exposure to lead, with some individuals exposed to high toxicity risk. We concluded that ingestion of lead in the metallic form alone is sufficient to produce these blood lead concentrations, and we recommend the prohibition of lead ammunition for big-game hunting in order to preserve the vulture population.