A Global Update on Lead Poisoning in Terrestrial Birds
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A GLOBAL UPDATE OF LEAD POISONING IN TERRESTRIAL BIRDS FROM AMMUNITION SOURCES 1 2 3 DEBORAH J. PAIN , IAN J. FISHER , AND VERNON G. THOMAS 1Wildfowl and Wetlands Trust, Slimbridge, Gloucestershire, GL2 7BT, UK E-mail: [email protected] 2Royal Society for the Protection of Birds, The Lodge, Sandy, Bedfordshire SG19 2DL, UK 3Department of Integrative Biology, College of Biological Science, University of Guelph, Guelph, ON N1G 2W1, Canada. ABSTRACT.—Lead poisoning mortality, through the ingestion of spent shot, is long established in water- fowl, and more recently in raptors and other avian taxa. Raptors (vultures, hawks, falcons, eagles and owls) are exposed to lead from spent ammunition (shot, bullets, or fragments from either) while feeding on game species, and other avian taxa are exposed when feeding in shot-over areas, including shooting ranges. Here we review the published literature on ingestion of and poisoning by lead from ammunition in terrestrial birds. We briefly discuss methods of evaluating exposure to and poisoning from ammunition sources of lead, and the use of lead isotopes for confirming the source of lead. Documented cases include 33 raptor species and 30 species from Gruiformes, Galliformes and various other avian taxa, including ten Globally Threatened or Near Threatened species. Lead poisoning is of particular conservation concern in long-lived slow breeding species, especially those with initially small populations such as the five Globally Threat- ened and one Near Threatened raptor species reported as poisoned by lead ammunition in the wild. Lead poisoning in raptors and other terrestrial species will not be eliminated until all lead gunshot and rifle bul- lets are replaced by non-toxic alternatives. Received 29 May 2008, accepted 24 July 2008. PAIN, D. J., I. J. FISHER, AND V. G. THOMAS. 2009. A global update of lead poisoning in terrestrial birds from ammunition sources. In R. T. Watson, M. Fuller, M. Pokras, and W. G. Hunt (Eds.). Ingestion of Lead from Spent Ammunition: Implications for Wildlife and Humans. The Peregrine Fund, Boise, Idaho, USA. DOI 10.4080/ilsa.2009.0108 Key words: Ammunition, global, lead, poisoning, terrestrial birds. TERRESTRIAL BIRDS AT RISK Norris 1995, Beck and Granval 1997). Poisoning LEAD POISONING IN WILDFOWL AND WADERS from from the ingestion of lead from both gunshot and the ingestion of spent lead gunshot has been exten- bullets by terrestrial birds initially received less at- sively studied, documented and reviewed over the tention, but today a considerable and increasing lit- last half century (Bellrose 1959, Kaiser and Fry erature exists. While ingestion of discharged lead 1980, Hall and Fisher 1985, Veiga 1985, Pain from firearms has been recorded in a diverse range 1990a, 1990b, 1991a, 1992, 1996, Locke and of terrestrial birds, two groups of birds are particu- Friend 1992, Sharley et al. 1992, Scheuhammer and larly susceptible. 1 ‐ PAIN ET AL. ‐ One group includes birds that are exposed in a simi- flesh. In some cases exposure rates can be high, lar way to wildfowl and waders, while feeding in e.g., 25% and 36% of first year and adult live- any shot over areas where spent lead is deposited. trapped Pink-footed Geese (Anser brachyrhynchus) Such areas include upland and lowland game shoot- carried shot (Noer and Madsen 1996). However, ing areas, shooting ranges including clay-pigeon species that scavenge, or both hunt and scavenge, shoots, and areas where species such as squirrels are likely to be at particular risk from lead ingestion and other rodents are shot as pests. Exposure is through feeding on injured or hunter-killed but un- likely to be higher in species that, like wildfowl, retrieved prey. Season and local hunting intensity deliberately ingest grit to help break down food play an important part in determining the level of and/or ingest food items similar in appearance to dietary lead exposure (Pain et al. 1993, Mateo lead shot (such as seeds) and may therefore mistak- 1998a). For example, of Bald Eagles (Haliaeetus enly ingest lead. Many species fall into this cate- leucocephalus) found sick, injured or dead with gory, but species are predominantly Gruiformes and significantly elevated lead exposure in British Co- Galliformes (Table 1). The second group at risk lumbia, the greatest number were found between comprise species that ingest lead from bullets or January and March when they were feeding heavily shot while preying upon or scavenging game or on wintering waterfowl (Elliott et al. 1992). The other species of mammals or birds (such as ‘pest’ prevalence of Bald Eagles with elevated lead expo- species, e.g., Knopper et al. 2006) that have been sure was found to be higher in areas of high water- shot but survived, or killed but unretrieved. Species fowl hunting intensity than areas with low hunting at risk are predominantly raptors, herein defined as intensity (Wayland and Bollinger 1999). Similarly, vultures (New and Old World), hawks, falcons, ea- Pain et al. (1997) found a significantly higher gles and owls (Table 1). Here, risk of exposure is prevalence of elevated blood lead concentrations in likely to be particularly high in species that feed Marsh Harriers (Circus aeruginosus) in France dur- more frequently on hunter-shot quarry and have a ing than outside the hunting season. propensity to scavenge. Species are also more likely to be exposed if there is intensive hunting Raptors are at risk both from prey killed with shot- within their foraging range (e.g. Mateo et al. 1998a, guns, such as wildfowl, rabbits and rodents, and Wayland and Bollinger 1999) and during the hunt- with rifles, such as deer and other large game. The ing season (Elliott et al. 1992, Pain et al. 1997). prevalence of exposure to lead from bullets is likely to be higher in larger raptors, and poisoning from One of the earliest reports of lead poisoning from bullet fragments has been reported in wild Bald Ea- lead shot ingestion in a non-wildfowl species in- gles, Golden Eagles (Aquila chrysaetos), Steller’s volved a Ring-necked Pheasant (Phasianus col- Sea Eagles (Haliaeetus pelagicus), White-tailed chicus) in the UK (Calvert 1876), and a recent Eagles (H. albicilla), and California Condors study from British shooting estates found an overall (Gymnogyps californianus) (Table 1). shot ingestion rate of 3%, with correspondingly elevated bone lead levels (Butler et al. 2005). Evi- Both captive and supplementary-fed wild birds may dence for lead poisoning in this species therefore also be at risk if food includes animals that have spans 125 years. Species of Galliformes and Grui- been killed with lead ammunition, even when shot formes have been reported to have ingested shot and bullets have been removed (e.g., Pain et al. and/or suffered lead poisoning through exposure to 2007). Until recently, the extent to which lead shot lead shot in a wide range of countries across and bullets fragment while passing through the tis- Europe, and North America (Table 1). sues of prey was not realised. However, radio- graphs have shown that both shot and bullets un- In areas where lead ammunition is used, all raptors dergo considerable fragmentation and fragments that feed on game or other hunted species are po- may be both distant from the wound canal, and too tentially at risk from lead poisoning. Species that small to be visually detected (e.g., Pain et al. 2007). take live prey, such as the Goshawk (Accipiter gen- Many authors have now shown that feeding on spe- tilis), are exposed through ingesting animals that cies killed by lead gunshot or bullets can present a have been shot but survived carrying shot in their significant risk to scavengers, whether or not they 2 ‐ LEAD POISONING IN TERRESTRIAL BIRDS ‐ are exposed to whole shot or bullets (Scheuhammer or fragments found and the degree of abrasion or et al. 1998, Sergeyev and Shulyatieva 2005, Hunt et dissolution may provide supplementary evidence to al. 2006, Knopper et al. 2006, Pain et al. 2007). For help in the diagnosis of lead poisoning. Occasion- example, Scheuhammer et al. (1998) found that ally, large numbers of shot are ingested, and in 11% (92 of 827) of pectoral muscle pools from Spain, where Golden Eagles have been found with hunter-killed game (predominantly waterfowl) had lead toxicosis from shot ingestion, one bird had 40 elevated lead concentrations, in excess of 0.5 µg g-1 pellets in its proventriculus (Cerradelo et al. 1992). ww (mean of 12± 38 µg g-1ww). While no lead could be detected visibly in the samples, radiogra- It is possible that birds that have not ingested lead phy showed tiny embedded metal fragments. from ammunition but carry shot-in lead in their tis- sues may also have elevated blood lead concentra- EXPOSURE TO LEAD GUNSHOT AND BULLETS tions, as has been found in humans that have been shot with lead bullets (McQuirter et al. 2004), al- Lead exposure is usually measured through the though these are likely to be far lower than in birds presence of lead shot or lead fragments in pellets that have ingested lead fragments. regurgitated by raptors (e.g., Platt 1976, Pain et al. 1997, 2007), or the presence of shot, bullets or EVALUATING LEAD POISONING fragments in the alimentary tracts of birds post- mortem (e.g. Church et al. 2006 and numerous Lead is not an essential element, and is a non- authors in Table 1). specific poison affecting all body systems. Lead poisoned birds often exhibit a distended proven- The regurgitation of ingested shot in pellets illus- triculus, green watery faeces, weight loss, anaemia trates that not all exposure to lead need be fatal, and and drooping posture, among other signs (Redig et regurgitation will undoubtedly reduce the amount al.