LEAD EXPOSURE IN WISCONSIN

SEAN M. STROM, JULIE A. LANGENBERG, NANCY K. BUSINGA, AND JASMINE K. BATTEN

Wisconsin Department of Natural Resources, Bureau of Wildlife Management, 101 S. Webster St., P.O. Box 7921, Madison, WI 53707, USA. E-mail: [email protected]

ABSTRACT.—The Wildlife Health Program of the Wisconsin Department of Natural Resources has moni- tored lead (Pb) exposure in numerous avian species including Bald Eagles (Haliaeetus leucocephalus), Trumpeter Swans ( buccinator), Common Loons (Gavia immer), and American Woodcock (Scolo- pax minor). A comprehensive review of health data indicated approximately 25% of Trumpeter Swan fatalities were attributed to lead toxicity. Similarly, approximately 15% of live-sampled Trumpeter Swans had blood lead levels above background concentrations (20 µg/dL). A similar review of necropsy data for Bald Eagles revealed approximately 15% of all deaths in Wisconsin were at- tributed to lead toxicity. A noticeable increase in the percent of fatalities attributed to lead toxicity began in October and peaked in December. This pattern overlapped with the seasons in Wisconsin suggest- ing lead ammunition could be a major source of lead exposure in eagles. A surveillance program examining lead toxicity as a factor in mortality of Common Loons was initiated in 2006. To date, approximately 30% of the dead loons submitted for necropsy were found to be lead poisoned. Lead fishing gear was recovered from the GI tracts of loons in all cases where lead toxicity was a major contributor to the cause of death. A comprehensive study investigating lead levels in woodcock from Wisconsin was completed in 2002. The results of the study indicated American Woodcock were exposed to lead on their breeding grounds in Wis- consin, resulting in high accumulations of lead in bone tissue. Bone lead concentrations considered to be toxic in waterfowl were observed in all age classes of woodcock. Stable isotope analysis was conducted on a subset of bone samples from young-of-year birds in order to identify the source of the lead. The results were inconclusive but did not rule out anthropogenic sources, and although the pathway of lead exposure was not identified, the data suggest a local and dietary source. It is clear that numerous species of Wiscon- sin wildlife are being exposed to potentially harmful levels of lead, and lead poisoning remains a significant mortality factor for many of these species. The prevalence of lead poisoning cases in Wisconsin is unlikely to decrease until the amount of lead discharged into the Wisconsin environment is reduced. Received 9 July 2008, accepted 3 September 2008.

STROM, S. M., J. A. LANGENBERG, N. K. BUSINGA, AND J. K. BATTEN. 2009. Lead exposure in Wisconsin birds. In R. T. Watson, M. Fuller, M. Pokras, and W. G. Hunt (Eds.). Ingestion of Lead from Spent Ammu- nition: Implications for Wildlife and Humans. The Peregrine Fund, Boise, Idaho, USA. DOI 10.4080/ilsa.2009.0205

Key words: American Woodcock, Bald Eagle, Common Loon, lead, Trumpeter Swan, Wisconsin.

THE DELETERIOUS IMPACTS on waterbirds of ingest- numerous waterfowl species (Bellrose 1959, Sand- ing spent lead (Pb) shot have been recognized for erson and Bellrose 1986) and as a result, non-toxic over 100 years (Grinnell 1894). Ingestion of spent shot has been required to hunt waterfowl in the shot has been implicated in substantial die-offs of United States since 1991 (Anderson 1992). Even

1 ‐ STROM ET AL. ‐ though the federal ban on lead shot for has been in effect for nearly 20 years, lead poisoning continues to be a significant mortality factor for several species of birds in Wisconsin. Lead is still regularly deposited in the environment as a result of lead shot used for upland game hunt- ing, lead in rifle bullets, and lead fishing weights.

Lead is one of the most toxic metals known, with adverse impacts ranging from slight alterations of biochemical and physiological systems to serious damage in organs leading to death of the individual. Lead modifies the function and structure of the kid- ney, bone, the central nervous system, and the he- matopoietic system and also has adverse biochemi- cal, histopathological, fetotoxic, teratogenic and reproductive effects (Eisler 1988). Mortality asso- ciated with exposure of birds to lead has been shown to result from direct consumption of spent lead shot, consumption of lead shot or bullet frag- ments embedded in food items, and from the inges- Figure 1: American Woodcock collection sites tion of lead fishing weights (Franson 1996). 1999–2001.

In Wisconsin, lead exposure has been monitored in euthanized via cervical dislocation for tissue analy- numerous avian species including Bald Eagles sis. (Haliaeetus leucocephalus), Trumpeter Swans (Cygnus buccinator), Common Loons (Gavia im- For sample collection, the humerus and radius/ulna mer), and American Woodcock (Scolopax minor). were excised and excess tissue and cartilage re- In this paper, we report on lead as a mortality factor moved. This process was followed for all wood- for Bald Eagles, Trumpeter Swans, and Common cock collected, regardless of age or year collected. Loons. In addition, we report on concentrations of The GI tracts of all woodcock were radiographed lead in bone of American Woodcock of different and the radiographs were evaluated for any objects ages. of comparable radiodensity with metal. The GI tracts were also dissected and visually inspected for METHODS lead pellets or metallic particles. The sex of the was confirmed at the time of dissection. All American Woodcock.—Detailed methods of wood- lead analyses were conducted at the Wisconsin cock sample collection and analysis can be found in Veterinary Diagnostic Laboratory, Madison, Wis- Strom et al. (2005). Briefly, woodcock were har- consin. vested between 1999 and 2001 at selected locations in Wisconsin using steel shot (Figure 1). Birds were Bone samples were forced-air dried overnight at collected a minimum of two weeks prior to the 100ºC to remove water, finely crushed in a mortar, regular hunting season (late September through and extracted with diethyl ether to remove fat prior early November) to increase the probability that to weighing for lead analysis. All tissue samples only locally exposed birds (young of year) would (bone, liver and blood) were digested in Teflon mi- be collected. Woodcock age and sex were deter- crowave vessels, under pressure with nitric acid in a mined via characteristics as described by microwave. After the samples cooled to room tem- Sepik (1994). Pointing dogs were used to assist in perature, the contents were transferred to a volu- finding woodcock nests and broods. When a brood metric flask and brought to volume with purified was found, one chick was randomly selected and water. Samples were analyzed on a Perkin-Elmer

2 ‐ LEAD EXPOSURE IN WISCONSIN BIRDS ‐

Table 1: Bone lead concentrations (µg/g dry weight) in Wisconsin American Woodcock.

Collection Site n Mean Median SD Range Navarino Chick 7 30.1 27.9A 22.5 9.6 – 72.0 Young of Year (YOY) 12 18.4A 11.25 18.0 <3.0–48.0 Adult 14 22.0A 15.9 12.8 8.1–48.0 Mead Chick 3 76.0 87.0B 24.4 48.0–93.0 YOY 13 39.2A 29.1 50.0 4.5–198.0 Adult 10 63.8B 33.3 56.0 18.9–171.0 Peshtigo YOY 6 67.5A 40.5 80.7 6.9–222.0 Adult 9 25.7AB 18.0 23.7 5.1–81.0 Pembine YOY 6 18.45A 19.7 11.3 <3.0–33.0 Adult 11 18.4A 15.6 12.0 5.1–45.0 Danbury YOY 5 12.5A 5.7 14.8 4.8–39.0 Adult 5 32.6AB 22.8 22.2 8.7–63.0 Douglas YOY 4 10.5A 7.4 8.9 3.9–23.4 Adult 3 6.4AB 6.6 0.62 5.7–6.9

For each age class, means or medians sharing the same letter are not significantly different.

Table 2: Mortality factors of Trumpeter Swans, Bald Eagles and Common Loons submitted to the Wisconsin Department of Natural Resources for necropsy.

Diagnosis (%) Lead Species N Poisoning Trauma Undetermined Gunshot Electrocution Drowning Other Trumpeter 143 25 25 19 12 10 1 7 Swan

Bald Eagle 583 16 48 16 0 12 0 9

Common Loon 26 29 31 4 7 0 4 25

5100ZL graphite furnace atomic absorption spec- lead analysis as described above. For Trumpeter trometer. A tissue and/or blood control sample was Swans, data accumulated between the years 1991– tested with each analytical run to ensure accuracy. 2007 were reviewed and causes of mortality were summarized. A similar review was performed for Trumpeter Swan, Bald Eagle and Common Loon.— Bald Eagle data collected between the years 2000– Trumpeter Swans, Bald eagles, and Common 2007. A program investigating causes of Common Loons were submitted to the Wisconsin Department Loon mortality was initiated in 2006. of Natural Resource’s Wildlife Health Program for necropsy, as part of statewide mortality monitoring Data Analysis.—For statistical analyses, samples programs for these species. At the time of necropsy, with metal concentrations below the detection limit all carcasses were evaluated for metal foreign bod- were assigned a value equal to one-half the detec- ies using radiography. If radio-dense objects were tion limit. All statistical analyses were carried out observed, attempts were made to recover the object using Excel and SYSTAT software packages. Non- from the carcass. Liver samples were collected parametric methods (Kruskal-Wallis tests) were from all individuals and submitted for laboratory utilized to determine differences between tissue

3 ‐ STROM ET AL. ‐

lead concentrations from woodcock collected at various sites across the state. The level of statistical significance was set at α = 0.05.

RESULTS

American Woodcock.—The mean bone lead con- centrations from chicks, young-of-year, and adult woodcock collected at various sites throughout Wisconsin are listed in Table 1. No significant dif- ferences were observed between bone lead concen- trations in young-of-year woodcock from any of the areas sampled (p = 0.174). However, a significant difference was observed with the adult data (p = 0.006), with bone lead concentrations of Figure 2: Blood lead concentrations (µg/dL) of Navarino adults being significantly different than Trumpeter Swans from Wisconsin (n = 1172 indi- those of Mead adults. Furthermore, bone lead con- viduals). ND = below the limit of detection (detection centrations of Pembine adults were significantly limit range 2.0–5.0 µg/dL). different than those of Mead adults. The concentra- tion of lead in the wing bones from Mead chicks was significantly different than those from Navarino (p = 0.03). Radiography of the GI tracts of the woodcock did not reveal any lead pellets or metallic particles. Furthermore, no lead pellets or metallic objects were observed during the visual inspection of the GI tracts.

Trumpeter Swans.—Between 1991 and 2007, 143 swan fatalities were investigated. Approximately 25% of the fatalities were attributed to lead toxicity. The diagnosis of lead toxicity as a cause of mortal- ity was often based only on tissue lead concentra- tions, as clinical history and histologic assessment Figure 3: Percent of Bald Eagle fatalities attributed of tissues were not available. Collisions with power to lead toxicity according to month. lines as well as shootings also appear to be signifi- cant mortality factors.

During this same period, 1,172 blood samples were collected from swans and analyzed for lead (Fig- ure 2). Lead was detected in 38% of the blood sam- ples, with a geometric mean of 16 µg/dL. Ap- proximately 15% of all sampled swans had blood lead concentrations above 20µg/dL. The over- whelming majority (80%) of the blood samples were collected from juvenile swans. Therefore, due to the age bias in sampling, age-specific differences in lead accumulation could not be not examined.

Bald Eagles.—Between 2000 and 2007, nearly 600 Bald Eagles were submitted to Wildlife Health for

4 ‐ LEAD EXPOSURE IN WISCONSIN BIRDS ‐ necropsy. Lead toxicity was diagnosed as the cause peter Swans from the tri-state area of Idaho, Mon- of death for 16% of the eagles during this period. A tana, and Wyoming (Blus et al. 1989), but much unique temporal pattern in eagle mortality was ob- lower than that observed in Trumpeter and Tundra served, with a dramatic increase in the percent of Swans (81%) in Washington State (Degernes et al. fatalities attributed to lead toxicity beginning in Oc- 2006). tober, peaking in December, and then decreasing through the winter months (Figure 3). This pattern The geometric mean of blood lead levels observed overlaps with the hunting seasons in Wisconsin in Trumpeter Swans from Wisconsin (16 µg/dL) which suggests lead ammunition could be a major was greater than the geometric mean reported in source of lead exposure in eagles. blood from Trumpeter Swans in the western U.S. (Blus et al. 1989). A blood lead concentration be- Common Loons.—Between 2006 and 2008, 26 low 20 µg/dL has been suggested as a background Common Loons were submitted for necropsy. Ap- level in waterfowl (Pain 1996, Beyer et al. 2000). proximately 30% of the dead loons submitted for Considering over 60% of the blood samples ana- necropsy were judged to have died from lead poi- lyzed in the present study were below the detection soning. Remnants of lead fishing tackle were re- limit (detection limit range 2.0–5.0 µg/dL) it is covered from the GI tracts of loons in all cases plausible the true background blood lead concentra- where lead toxicity was a major contributor to the tion for apparently healthy Trumpeter Swans is be- cause of death. low the 20 µg/dL threshold.

DISCUSSION The occurrence of lead poisoning in Bald Eagles from Wisconsin (15%) is higher than that reported Our data indicate lead exposure is a significant in other studies where prevalence ranged from 0% health problem for several species in Wiscon- to 5% (Coon et al. 1970, Deem 2003, Harris and sin, accounting for 15–30% of fatalities in Trum- Sleeman 2007, Morishita et al. 1998, Wendell et al. peter Swans, Bald Eagles, and Common Loons. For 2002). However, our findings are consistent with our study, liver lead levels of >6.0 µg/g (wet those of Elliot et al. (1992) who observed that 14% weight) were considered indicative of lead toxicosis of Bald Eagles found dead in British Columbia, and bone lead levels >20 µg/g dry weight were Canada, between 1988 and 1991 died as a result of considered significantly elevated (Franson 1996, lead poisoning and Wayland et al. (2003) who ob- Pain 1996). Blood lead levels >20 µg/dL were con- served 14% of 546 Bald Eagle deaths in western sidered above background (Pain 1996). Canada were attributable to lead toxicosis.

Scheuhammer et al. (1999) documented a high in- The proportion of lead poisoning among loon fatali- cidence of elevated lead levels (>20 µg/g dry ties in Wisconsin is comparable to that observed in weight) in wing bones from adult (52%) and Canada (26%–30%) (Daoust et al. 1998, Scheu- young-of-year woodcock (29%) from eastern Can- hammer and Norris 1996) but lower than that of ada. Strom et al. (2005) found elevated lead levels breeding loons in the New England states (44%– in wing bones of woodcock from Wisconsin in 43% 52%) (Pokras and Chafel 1992, Sidor et al. 2003). of young-of-year woodcock and 64% of woodcock The contrast of our results to the New England chicks sampled. studies may be due to the much smaller sample size in the present study (n = 26), and may also reflect Although the prevalence of lead exposure in water- differences in regional landscape, human popula- fowl has declined following implementation of tion, or land and wetland usage (Sidor et al. 2003). non-toxic shot for waterfowl hunting (Samuel and It nevertheless appears that lead exposure is a major Bowers 2000), exposure to lead continues to be a mortality factor for loons in Wisconsin. significant factor in Trumpeter Swan mortality. The incidence of lead related mortality in Trumpeter The percentages of lead poisoning cases in Wiscon- Swans in Wisconsin (26%) is slightly higher than sin birds from this study are likely underestimated the 20% lead-related mortality observed in Trum- because, in many cases where cause of death was

5 ‐ STROM ET AL. ‐ undetermined, liver lead analysis was not per- with the hunting seasons in Wisconsin, suggesting formed. Moreover, human-related mortality agents lead ammunition is likely the primary source of ex- tend to occur in areas frequented by humans, posure in Bald Eagles. In addition to lead shot, lead whereas lead-poisoned fatalities are more randomly bullet fragments may be a significant source of lead distributed and thus less likely to be discovered. exposure in eagles. This pattern of increased lead exposure during hunting seasons has also been ob- Sources of Lead.—Scheuhammer et al. (2003) served in Golden Eagles (Aquila chrysaetos) found no evidence of lead shot ingestion in wood- (Bloom et al. 1989), California Condors (Gym- cock from Canada with elevated bone-lead concen- nogyps californianus) (Cade 2007, Hall et al. 2007, trations. Likewise, we did not detect any ingested Hunt et al. 2007, Sorenson and Burnett 2007), and lead shot in any of the woodcock radiographed for Common Ravens (Corvus corax) (Craighead and the present study. However, ingestion of lead shot Bedrosian 2008). Hunt et al. (2006) observed that has been observed in other species related to wood- as lead bullets pass through deer, the bullets often cock, such as godwits, dowitchers, and snipe (Hall fragment, leaving numerous lead fragments which and Fisher 1985, Pain 1990). Scheuhammer et al. are distributed throughout the carcass or the gut pile (2003) suggest that because woodcock do not have left on the landscape after the animal is field a large muscular gizzard, it is possible that lead pel- dressed. It is likely eagles feed on either unretrieved lets ingested by woodcock are quickly voided, and or scavenge the gut piles, thus exposing thus not observed in studies of woodcock gizzard themselves to harmful levels of lead. and stomach contents. Conclusions.—Multiple species of Wisconsin wild- Stable lead isotope analysis on a small number of life are being exposed to potentially harmful levels bone samples from Wisconsin young-of-year of lead, and lead poisoning remains a significant woodcock produced inconclusive results. The ob- mortality factor for some of these species. The as- served lead isotope ratios in Wisconsin woodcock sociation of lead-related mortality in Bald Eagles overlapped with ratios of both lead shotgun pellets with the major hunting seasons in Wisconsin im- and lead, i.e. soil-associated lead plies that exposure to spent lead ammunition should (Strom et al. unpub. data). Similarly, Scheuhammer be considered as a potentially significant mortality et al. (2003) observed lead isotope ratios in wing factor in species which feed upon hunter-killed bones of woodcock that were consistent with, animals. It is unlikely the prevalence of lead poi- though not proof of, lead shot ingestion because the soning cases will decrease until the amount of lead range of ratios for wing bones overlapped with ra- discharged into the Wisconsin environment is re- tios of lead shot pellets. In any case, ingestion of duced. lead shot used for upland game bird hunting cannot be ruled out as a primary source of high bone-lead LITERATURE CITED accumulation in woodcock from Wisconsin. ANDERSON, W. L. 1992. Legislation and lawsuits in The feeding habits of Trumpeter Swans and Bald the United States and their effects on non-toxic Eagles may predispose these species to lead expo- shot regulations. Pages 56-60 in D. J. Pain sure. Trumpeter Swans typically forage by digging (Ed.). Lead Poisoning in Waterfowl. Proceed- up large amounts of sediments in lakes and streams ings of an IWRB Workshop, Brussels, Belgium, (Banko 1960). Ingestion of these large volumes of 13–15 June 1991. International Waterfowl and sediments increases the likelihood of birds ingest- Wetlands Research Bureau Special Publication ing lead shot or sinkers (Blus et al. 1989). Of the 16, Slimbridge, UK. lead poisoning cases observed in Trumpeter Swans BANKO, W. E. 1960. The Trumpeter Swan. North in this study, 39% had lead artifacts in their ven- American Fauna No. 63, US Fish and Wildlife triculus at the time of necropsy. Service, Washington, DC, USA. BELLROSE, F. C. 1959. Lead poisoning as a mortal- The increased prevalence of lead poisoning cases in ity factor in waterfowl populations. Illinois Bald Eagles during October to January overlaps Natural History Survey Bulletin 27:235-288.

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