Lead Shot Ingestion Research Articles

Lead poisoning and other causes of mortality in trumpeter (Cygnus buccinator) and tundra (C. columbianus) swans in western Washington.

Lead poisoning and other causes of mortality of 115 trumpeter (Cygnus buccinator) and 21 tundra (C. columbianus) swans from northwestern Washington (USA) from 1986 to 1992 are reported. Necropsies were performed on all 136 swans, liver lead analysis conducted on 110, and differentiation between lead and steel shot pellets recovered from gizzards in 97 swans. Shot pellets were detected in 44 (32%) of 136 gizzards. Lead shot was recovered from 32 (33%) of 97 gizzards and steel shot from 16 (16%). Mean intensity of lead shot in gizzards was nearly five times greater than steel shot. Thirty-nine (35%) of 110 livers had lead concentrations diagnostic of lead poisoning (> 6 ppm, wet weight). Mean (+/- SE) weight for 61 non-lead poisoned trumpeter swans was 9.8 (+/- 0.30) kg, significantly heavier (P < 0.05) than 30 lead poisoned trumpeters (mean = 6.8 +/- 0.23 kg). There was no significant difference (P > 0.05) in weights between lead poisoned (n = 9) and non-lead poisoned (n = 12) tundra swans. Lead poisoning was the primary cause of death, accounting for 29% of the mortalities. Other causes of mortality identified were aspergillosis (17%), illegally shot (11%), and other traumatic factors (12%). The cause of death for 43 swans was not determined. Lead poisoning from the ingestion of lead shot continues to be a principal cause of mortality in swans overwintering in northwestern Washington.

Prevalence of ingested lead shot in American Black Duck, Anas rubrips, and Ring-necked Duck, Aytha collaris, gizzards from Nova Scotia and Prince Edward Island

Prevalence of ingested lead shot in American Black Duck, Anas rubrips, and Ring-necked Duck, Aytha collaris, gizzards from Nova Scotia and Prince Edward Island

Further Evidence of Biases Associated with Hunter-Killed Mallards

Assessment of waterfowl management strategies depends upon data that evaluate hypotheses that mallards (Anas platyrhynchos) killed by hunters are similar to those in the general population. Moreover, data are needed to provide further insight into mallard molt progression, the apparent influence of body mass on survival, and direct and indirect mortality caused by lead shot ingestion. Thus, we compared body mass, percentage completion of the prealternate molt, and presence of lead shot in gizzards between mallards killed by hunters (hunter-killed) and those concurrently collected by researchers (researcher-collected) from the free-living population in the Mingo Basin of southeastern Missouri. Researcher-collected mallards were heavier (P < 0.05) than hunter-killed mallards of the same age and sex

Tissue lead concentrations and shot ingestion in nine species of waterbirds from the camargue (France)

This study investigates the relationship among lead exposure (shot ingestion), current lead impregnation (liver lead values), current and previous lead impregnation (bone lead values), and lead excretion (feather lead) in nine species of waterbird from the Camargue (Rhone river delta), France. Results indicate that for individuals there is no readily predictable relationship between ingested shot and liver or bone lead concentrations. However, at the “population” level, and interspecifically, significant positive relationships exist between the susceptibility to shot ingestion and the degree of lead impregnation. Shoveler ( Anas clypeata) proved to be an exception, with a high level of shot ingestion and no elevated tissue lead values. This is probably related to dietary factors. Species with a high degree of current lead contamination tended to be those that had also previously absorbed elevated levels of lead. Feather lead concentrations were not clearly related to the vulnerability of a species to shot ingestion or lead poisoning. There was no significant absorption of arsenic and antimony from gunshot associated with lead absorption.

Availability and Ingestion of Lead Shot by Mourning Doves (Zenaida macroura) in Southeastern New Mexico

Availability and Ingestion of Lead Shot by Mourning Doves (Zenaida macroura) in Southeastern New Mexico

Treatment of lead poisoning in wild geese

Summary Twenty-seven wild geese (Anser albifrons) suffering from lead poisoning caused by ingestion of lead shot were treated with disodium calcium ethylenediaminetetraacetate. The concentration of lead in blood ranged from 0.4 to 23.0 μg/ml, with a mean concentration of 5.6 μg/ml. In 22 of the birds, 1 to 48 lead pellets (mean, 10.5 pellets/bird) were seen on radiographs of their gizzards. Eleven of 27 birds recovered 3 to 8 weeks after the initiation of treatment. In the birds that recovered, the lead pellets were rapidly eroded as the birds recovered their appetites in response to treatment, and disappeared radiographically between treatment days 17 and 52. The birds that did not survive died within 4 weeks, despite decreased concentrations of lead in blood. Of these 16 birds, 15 had radiographic evidence of impaction of the proventriculus at the first examination and no evidence of resolution of the impaction at the time of death. In contrast, only 2 of the 11 geese that recovered had impaction of the proventriculus at the time of admission. Thus, the condition of the proventriculus seems to be the first consideration to evaluate in the prognosis of lead poisoning in geese.

EFFECTS OF LEAD SHOT INGESTION ON SELECTED CELLS OF THE MALLARD IMMUNE SYSTEM

The immunologic effects of lead were measured in game-farm mallards (Anas platyrhynchos) that ingested lead shot while foraging naturally, mallards intubated with lead shot, and unexposed controls. Circulating white blood cells (WBC) declined significantly in male mallards exposed to lead by either natural ingestion or intubation, but not females. Spleen plaque-forming cell (SPFC) counts were significantly lower in mallards intubated with lead pellets compared to controls. Declines in WBC and SPFC means with increasing tissue lead concentrations provide further evidence that lead exposure reduced immunologic cell numbers. Hormonal activity and diet may have influenced the immunologic effects of lead exposure in this study.

Lead shot ingestion and lead poisoning of magpie geese anseranas semipalmata foraging in a Northern Australian hunting reserve

Sediments at Howards Springs Hunting Reserve in tropical Northern Territory have accumulated high densities of lead shot (330 000 shot ha −1), most of which is at depths (<20 cm) accessible to foraging magpie geese Anseranas semipalmata. Mean shot density is approximately 9% of density of sedge Eleocharis dulcis tubers, a favoured dry-season food which overlaps with shot in size. Large quantities of grit are available on the fringes of the swamp, but densities of the larger, shot-sized items (> 2 mm) that appear to be preferentially ingested or retained in gizzards are sometimes absent in areas where magpie geese forage. Lead shot are frequently ingested. Over two years 21·4% of a sample of mobile birds ( n = 103 ) had ingested shot in their gizzards. In 1989, 45·2% (n = 65) showed lead concentrations in their livers, indicating lead exposure. However, few birds had accumulated high concentrations of lead in wingbones, suggesting that repeated sublethal exposures are uncommon. We suggest that the combination of high shot ingestion rates and limited recurrence of exposure implies high mortalities from lead toxicosis. This conclusion is supported by the presence of substantial numbers of incapacitated lead-poisoned birds at Howard Springs and other wetlands in the Darwin region. If criteria developed in the USA were applied, these observations would justify immediate prohibition of the use of lead shot at Howard Springs. We discuss steps to inhibit exposure of waterbirds to existing lead shot deposits following a conversion to steel shot.

Lead shot densities and settlement rates in Camargue marshes, France

Recent research has shown levels of lead shot ingestion by waterfowl in the Camargue (Rhone delta) to be higher than in most other places worldwide. The primary factors influencing shot ingestion are shot density and depth distribution in feeding marshes. Shot densities were investigated in 14 Camargue marshes and depth distributions in five of these. Depth distributions varied with marsh type (temporary or permanent) and maximum shot densities approached two million/ha, higher thatn have previously been recorded at similar sites worldwide. Shot settlement rates were investigated experimentally over a two-year period in Camargue marshes with different physical characteristics. Settlement rates varied according to plant density and sediment composition, but >97% of shot remained in the first 6 cm of sediment (thus available to feeding waterfowl) two years after seeding. Management practices (local and global) to reduce lead shot availability to waterfowl are discussed.

Influence of Ingested Lead on Body Mass of Wintering Canvasbacks

The authors determined the prevalence of lead shotgun pellets in gizzards of canvasbacks (Aythya valisineria) collected at Catahoula Lake and the Mississippi River Delta, Louisiana, during winter 1987-88 to assess the influence of ingested lead shot on canvasback body mass. The prevalence of ingested lead shot was significantly higher at Catahoula Lake (27%) than at the Mississippi River Delta (4%). Canvasbacks collected at Catahoula Lake showed significant differences in prevalence of ingested lead shot by age and month. The authors attributed age-related and seasonal variations to differences in foraging effort and exposure time. Body mass of canvasbacks at Catahoula Lake, after accounting for age, monthly variation, and body size, was significantly reduced (120 g or 10%) in birds that had lead shot in their gizzards.

Lead shot ingestion by waterbirds in the Camargue, France: An investigation of levels and interspecific differences

Between January 1988 and February 1989, gizzards were collected from 1155 birds from the groups; Anatidae, Charadriidae, Scolopacidae and Rallidae, shot in the Camargue, and examined for the presence of ingested lead shot. Shot was found in nine out of ten Anatidae species, three of 15 Scolopacidae species and all of three Rallidae species. Twenty-seven per cent of Anatidae sampled had ingested shot, 13·8% had one shot present and 6·3% had more than five. Shot ingestion levels ranged from 3–60% of birds examined according to species. The incidence of shot ingestion did not appear to vary seasonally. In Anatidae, a strong interspecific relationship was found between the grit size ingested and susceptibility to ingest shot ( r = 0·94). In Scolopacidae, shot ingestion may have been related to grit size ingested, feeding method and bill length. The levels of shot ingestion presented are for most species higher than have been reported elsewhere in the world. This may result from the absence of grit and presence of high shot densities in Camargue marshes.

Effects of lead shot ingestion on free-ranging mourning doves.

Mourning doves (Zenaida macroura) may develop Pb toxicosis from ingesting spent Pb shot from hunted fields in which they feed. One to 6.5 percent of the dove population may ingest Pb shot based on analysis of gizzard contents. No Pb shot toxicity studies have been conducted on free-ranging mourning doves. Mortality data for Pb-dosed, free-ranging doves would help determine the actual effects of Pb shot ingestion on the mourning dove population. Causes of death of Pb-treated doves also could help to estimate exposure of predators and scavengers to secondary Pb toxicosis. The objectives of this study were to compare mortality and causes of death of free-ranging Pb-treated and untreated mourning doves.

Lead-Shot Ingestion by Bald Eagles in Western Arkansas

A study was conducted on Holla Bend National Wildlife Refuge, in western Arkansas, to determine the extent to which bald eagles (Haliaeetus leucocephalus) wintering on the area were exposed to lead shot. Waterfowl comprised a significant portion of the diet; 61% of egested bald eagle castings contained waterfowl remains. Lead shot was found in 9 of 31 waterfowl carcasses that provide much of the winter food supply of bald eagles on the refuge. Lead shot was found in 7% of 82 egested castings, indicating that eagles do ingest lead shot in the process of feeding. In recent years, a great deal of interest has been directed toward lead-poisoning as a mortality factor among bald eagles (Haliaeetus leucocephalus; Pattee and Hennes, 1983; Feierabend and Myers, 1984). It has long been recognized that large numbers of waterfowl succumb annually to lead (Bellrose, 1975). How- ever, only recently has there been an attempt to compile and analyze information on the extent to which lead may affect bald eagles feeding on dead or crippled waterfowl. Feierabend and Myers (1984) reported that: 1) a growing body of evidence suggests that significant numbers of bald eagles die annually from lead- poisoning; 2) a minimum of 77 bald eagles died of lead-poisoning between 1966 and 1984; and 3) these data probably under-estimated the actual extent of the problem as most eagle carcasses are never recovered. Bald eagles are particularly vulnerable because population levels are low and because they readily feed on dead or crippled prey, particularly waterfowl (Pattee and Hennes, 1983). Arkansas is one of 27 states with documented cases of bald eagle mortality due to lead poisoning (Feierabend and Myers, 1984). Holla Bend National Wildlife Refuge, Pope Co., Arkansas, is a major wintering area for bald eagles and waterfowl and has had documented cases of lead poisoning in waterfowl. Therefore, the report by Feierabend and Myers (1984) listed Pope Co. as one of 89 counties nationwide where there is a high risk of bald eagles being poisoned by lead after ingesting lead pellets present in dead or crippled waterfowl. While there was a clear potential for poisoning of eagles wintering on Holla Bend, no quantitative data were available for assessing the extent to which eagles were actually exposed to lead shot. This report summarizes the results of a study conducted on Holla Bend during the winter of 1985-1986 to evaluate the extent to which wintering bald eagles were exposed to lead shot. The objectives of the study were to: 1) determine the frequency of occurrence of waterfowl in the diet of wintering bald eagles using the area; 2) evaluate the extent of lead shot in waterfowl carcasses on the area; and 3) determine the frequency of occurrence of lead shot in egested castings produced by bald eagles using Holla Bend.

Lead poisoning of northern pintail ducks feeding in a tidal meadow contaminated with shot from a trap and skeet range.

Lead poisoning of waterfowl from the ingestion of lead shot is well documented and widespread throughout the United States. Research and remedial regulations have focused on waterfowl hunting as the major source of this lead shot. Mortalities of cattle from ingestion of silage contaminated with lead shot from trap shooting have been documented in the United States, the United Kingdom and Ireland. Although ingestion of lead shot by cattle grazing on silage from a trap range was documented in Denmark, no mortalities were reported. This paper describes lead poisoning of northern pintail ducks (Anas acuta) from ingestion of lead shot deposited on a tidal meadow as the result of trap and skeet shooting. This is the first published report linking trap and skeet shooting with lead poisoning of waterfowl. It also describes and evaluates the management procedures taken to prevent the poisonings.

The prevalence of lead shot ingestion in wild mallards (Anas platyrhynchos) in the Netherlands.

During the hunting season 1986-1987, 2859 gizzards from mallards shot in the Netherlands were collected. Gizzards were selected radiographically and examined visually for ingested lead shot. The 95% confidence interval of the prevalence of lead shot ingestion was calculated to be 1.7 to 2.9%. In some gizzards a large number of lead shot (12-16) were seen. This is an indication for locally heavily contaminated areas. Especially places where mallards are attracted for hunting purposes, by daily feeding of corn, predispose these birds to lead poisoning. A ban with regard to these hunting practices will probably drastically reduce the prevalence of lead shot ingestion. A change from lead shot to steel shot will solve the problem completely.

The nature of cumulative impacts on biotic diversity of wetland vertebrates

There is no longer any doubt that cumulative impacts have important effects on wetland vertebrates. Interactions of species diversity and community structure produce a complex pattern in which environmental impacts can play a highly significant role. Various examples show how wetlands maintain the biotic diversity within and among vertebrate populations, and some of the ways that environmental perturbations can interact to reduce this diversity. The trophic and habitat pyramids are useful organizing concepts. Habitat fragmentation can have severe effects at all levels, reducing the usable range of the larger habitat generalists while threatening the genetic integrity of small, isolated populations. The complexity of trophic interactions, and the propensity, or necessity, of vertebrates to switch from one food source to another—something we know little about—makes using food chain support as a variable for predicting environmental impacts very questionable. Historical instances illustrate the effects of the accumulation of impacts on vertebrates. At present it is nearly impossible to predict the result of three or more different kinds of perturbations, although long-range effects can be observed. One case in point is waterfowl; while their ingestion of lead shot, harvesting by hunters during migration, and loss of habitat have caused waterfowl populations to decline, the proportional responsibility of these factors has not been determined. Further examples show multiplicative effects of similar actions, effects with long time lags, diffuse processes in the landscape that may have concentrated effects on a component subsystem, and a variety of other interactions of increasing complexity. Not only is more information needed at all levels; impacts must be assessed on a landscape or regional scale to produce informed management decisions. I conclude that a system of replicate wetland reserves that are allowed to interact naturally with the surrounding landscape will be more effective in preserving biotic diversity than isolated sanctuaries.

Heat exposure and the toxicity of one number four lead shot in mallards, Anas platyrhynchos.

Lead poisoning from ingested shot is a major cause of mortality in waterfowl throughout the world. In North America, most waterfowl that die from lead poisoning succumb following the hunting season. Cold and harsh winter weather is generally thought to exacerbate lead toxicity in birds. Although largely undocumented, there is considerable opportunity for birds to ingest lead shot in the summer during periods of extreme heat. Substantial lead exposure in over 50% of the American black ducks (Anas rubripes) captured in late summer has been observed in areas of the Chesapeake Bay. Moreover, investigations with rodents, rabbits, and man have demonstrated that the toxicity of lead is increased by high environmental temperature, possibly caused by elevated metabolic rate, dehydration, and impaired lead excretion. A recent study in which black ducks were dosed with a single number 4 lead shot suggested that toxicity may be enhanced during periods of extreme hot weather. To further investigate this finding, the authors examined lead toxicity in mallards maintained at thermoneutral temperature (21/sup 0/C) and at an elevated temperature (35/sup 0/C) approaching the upper critical limit.

Ingested lead shot in northern red-billed whistling ducks (Dendrocygna autumnalis) and northern pintails (Anas acuta) in Sinaloa, Mexico.

Ingested lead shot in northern red-billed whistling ducks (Dendrocygna autumnalis) and northern pintails (Anas acuta) in Sinaloa, Mexico.

Effects of Lead Shot Ingestion on Captive Mourning Dove Survivability and Reproduction

Effects of Lead Shot Ingestion on Captive Mourning Dove Survivability and Reproduction

Lead Shot Poisons Bald Eagles

This article describes the controversy between the US Fish and Wildlife Service, the National Wildlife Federation and the increased mortality of bald eagles. The eagles are being poisoned by preying on waterfowl which have ingested lead shot or have been wounded by shot and not recovered. The controversy has resulted in the establishment of new criteria for so-called non-toxic shot waterfowl hunting.