Lead Toxicosis in Michigan Loons from Ingestion of Lead Sinkers and Jigs:
A Real Problem
by Gerald D. Purdy, M.D.
Since the publication of the Michigan Loon Recovery Plan in 1989, it appears that the Common Loon has, at best, merely held its own.
Common Loon Periodic surveys have previously been conducted in Michigan, in 1991 and 1996. The most recent survey was in 2000. The 1996 survey, conducted by Schuett and Robinson, estimated that breeding pairs increased from 368 to 416. Chicks per brood, however, decreased from 1.09 chicks to 0.78 in the same time period. Only the northern Lower Peninsula and the southern Lower Peninsula met the goals of the recovery plan. More recently, Schuett reports that the Michigan breeding loon population is decreasing. The 2000 Common Loon survey by Bowerman et al estimated a lower bound of 987 and an upper bound of 1403 adult loons. Breeding pairs were not estimated. The methodology in the 2000 survey was different from previous estimates, and will have to be corroborated by time and subsequent surveys.
The Michigan Loonwatch database records 183 chicks fledged from 199 nests of 279 pairs for the year 2000, as compared to a 1991 production of 175 chicks from 211 nests of 324 pairs. While this database cannot by its nature be totally comprehensive, it does suggest a worrisome trend.
The relatively stable production of loon chicks may be at least in part through the efforts of the Michigan Loon Preservation Association/Michigan LoonWatch in the protection of nesting loons, and through implementation of the Michigan Loon Recovery Plan. Though it is encouraging that success remains relatively stable, the fact that the number of nesting pairs may have fallen may be an indication that Michigan is about to experience a dramatic fall in loon numbers as these long lived adults reach the end of their 20-30 year life span. With the known high mortality of chicks, and the long delayed breeding of this species, it appears that all available means need to be employed to ensure the loons’ continued survival in Michigan. Clearly, continuing Common Loon Surveys will be critical to our knowledge of how our loons are doing.
Among the known causes of loon mortality are trauma, drowning in commercial fishing nets, aspergillosis and botulism, mercury and lead poisoning, and others.
The recently completed commercial fishing treaty may help to reduce the numbers of loons lost to drowning. The MLPA believes that all efforts should be made to ensure that the large mesh trap nets already demonstrated to decrease loon mortality be placed into service. We are working with the DNR Fisheries division and the Native American Tribal fisheries to educate the fisherman about the altered nets, through an educational brochure. We are committed to diminishing the "by-catch" numbers as quickly as possible.
It appears that periodic die-offs of loons due to botulism will continue, but this is poorly understood and it may be impossible to intervene without a better understanding of the pathogenesis of this phenomenon.
The Michigan Loon Preservation Association, with funding provided by the Michigan Natural Heritage Nongame Wildlife Fund, and with the cooperation of the Michigan Lake and Stream Association, is now distributing a brochure entitled "Michigan’s Loons and Responsible Watercraft Use". This educational effort should help watercraft users understand the needs of the Common Loon, and help the loon co-exist with its human neighbors. It is hoped that a reduction in trauma from watercraft collisions will be one benefit of this effort.
Mercury has been demonstrated to have profound health implications on the health of humans and other life. The Michigan Mercury Pollution Prevention Task Force has published specific recommendations to reduce these risks. While an increasing body of literature continues to document the threats mercury poses to loons, and without minimizing the level of concern for wildlife, aggressive pursuit of remediation with the intent to protect humans will undoubtedly also be beneficial in protection of the loon and other wildlife. Mercury remains one of our most critical concerns, but will not be discussed here in any more detail. The interested reader is referred to the numerous citations available at the Biodiversity Research Institute website.
Environmental Lead has been long known to represent a health risk to humans, and this knowledge has lead to a ban on lead based paint as well as its use as a fuel additive and household plumbing pipes. Significant efforts have been made towards education of the public and health professionals about the hazards of lead. Many people are aware of this risk.
There is significantly less public awareness however, of the hazards that lead represents to waterfowl. In spite of this, scientists have known of these risks for some time.
Birds commonly eat small pebbles to grind food for digestion. Small lead sinkers and jigs may be mistaken for these pebbles, or lures with fish and lead attached may be consumed by the bird directly.
A bird that eats lead will become ill and die. Ingested lead enters the gizzard, where a combination of stomach acids and abrasion breaks down the metal. It then is absorbed into the bloodstream.
A bird with lead poisoning will exhibit physical and behavioral changes including loss of balance, gasping, tremors, and an impaired ability to fly. The weakened bird is more vulnerable to predators, or it may have trouble feeding, mating, nesting, and caring for its young. It becomes emaciated and often dies within two or three weeks after eating the lead. Just one lead sinker or jig can poison a water bird.
An extensive literature documents the risks of lead toxicosis in water birds that ingest lead. Direct ingestion, rather than other environmental sources, is clearly the path of lead poisoning in birds.
Lead, once dispersed into lakes, may persist for up to 300 years, though degradation can be more rapid depending on soil conditions and other factors. At least 27 different species are known to be affected by lead poisoning, including numerous duck species, the Trumpeter, Tundra and Mute swans, Bald eagles, Sandhill cranes, and the Common Loon. A systematic New England study has found that in some areas, over 50% of loon mortality is due to lead poisoning from lead sinker and jig ingestion; it is by far the most frequent cause of loon deaths in New Hampshire. Up to 17% of Minnesota loon deaths are the result of lead poisoning. Likewise, the Canadian Wildlife service has demonstrated significant mortality in the Common Loon from ingestion of lead sinkers and jigs.
Because of this, the United States Department of the Interior has proposed to establish "Lead Free Fishing Areas" on specific units of the National Wildlife Refuge System. Included in this proposal, which will take effect 2001-2002, is the Seney National Wildlife Refuge in Upper Michigan.
The United States banned the use of lead shot for hunting migratory waterfowl in 1991. Great Britain has banned the use of lead sinkers after a voluntary effort there did not produce results. (The Canadian Wildlife Service and the US EPA have previously suggested that voluntary efforts are not likely to result in a significant impact on lead exposure in these water birds.) Subsequently, the Mute Swan reversed its decline there. New Zealand has recognized the problem. The Loon Preservation Committee of New Hampshire recently successfully proposed legislation that banned lead from use for fishing sinkers and jigs. Canada has banned the use of lead sinkers in national parks and wildlife preserves, and is considering a total national ban, (to include lead shot, which is still allowed for the hunting of migratory waterfowl in Canada). Maine has enacted a partial ban and New York is the latest to pass legislation banning the sale of lead tackle. (Details not known currently) Similar legislative efforts have been or are planned in some other states. In Minnesota; intense education efforts are underway. Legislation to ban lead was introduced there in January of 2003.
All of these attempts to eliminate or reduce the risks of lead toxicosis have been because of the consistent and incontrovertible evidence of some 13 scientific studies that document the direct link between the ingestion of lead sinkers or jigs and subsequent lead poisoning in Common Loons.
In spite of the serious nature of these problems, our concerns are not new. Indeed, in 1992 the Michigan Loon Preservation Association joined with the Environmental Defense Fund, the Trumpeter Swan Society, the Federation of Fly Fishers and the North American Loon Fund in urging the state of Michigan to take action to limit the use of or ban the use of lead fishing sinkers, or at the very least to require labeling of the sinkers to include language explaining lead’s dangers.
Of note, that letter, dated October 27, 1992 cites Rose Lake Wildlife Research Center data from 1988 to 1992 documenting 40 % of post mortem examinations of loons to find the cause of death to be lead poisoning. This is consistent with studies published elsewhere, notably the data from Pokras et al.
Alternatives to lead sinkers and jigs are available, but not commonly stocked in sporting goods stores. A recent check at a large chain sporting goods store found none in stock! The US EPA has estimated that replacement of lead would result in an additional cost of $10 or less per angler per year, a trivial cost in comparison to that spent overall. Lead sinker exchanges have been implemented in other states with some success.
Loon Mortality in Michigan, 1987-2001
Courtesy of Tom Cooley, Michigan DNR Wildlife Biologist
|Year||Lead Poisoning||Drowning||Trauma||Others||Total Examined||Others Key|
|1988||4||5||1||1N, 1S||12||H-Hatching Defect|
|1990||6||0||2||1A, 5N||14||N-No Diagnosis|
|1992||3||1||5**||2A, 1S, 1V, 2N||15||V-Visceral Gout|
|* 1 with fish hooks||** 2 with fish hooks||*** 3 with fish hooks|
Sources of Lead
|Piece of Lead||5|
Bell, D.V., Odin, N., and Torres, E. 1985. Accumulation of angling litter at game and coarse fisheries in South Wales, UK. Biological Conservation 34:369-379.
Bowerman, W; Zimmerman, G; Majkrzak, K and Otis, D.: Final Report-2000 Michigan Common Loon Survey. A report to Natural Heritage Program Nongame Wildlife Fund, Michigan Department of Natural Resources. Feb, 2001.
Birkhead, M. 1982. Causes of mortality in the mute swan on the River Thames. Journal of the Zoological Society of London 198:15-25.
Blus, L.J. 1994. A review of lead poisoning in swans. Comparative Biochemistry and Physiology 108C: 259-267.
Borkowski, R. 1997. Lead poisoning and intestinal perforation in a snapping turtle due to fishing gear ingestion. Journal of Zoo and Wildlife Medicine 28:109-113.
Canadian Wildlife Service
Occasional Paper Number 88 : A review of the environmental impacts of lead shotshell ammunition and lead fishing weights in Canada.
Ensor, K.L.; Helwig, D.D.; Wemmer, L.C. 1992. Mercury and lead in Minnesota Common Loons (Gavia Immer) Water Quality Division, Minnesota Pollution Control Agency, St. Paul, MN 32pp.
Evers, D.C, Reaman, P.S., Kaplan, J.D., and Paruk, J. D. 1996. North American Loon Biomonitoring Program: 1995 Field Season Final Report, 1989-1995 Comprehensive Report.
Franson, J.C. and Cliplef, D.J. 1992. Causes of mortality in common loons, p. 2-12 in Morse, L, Stockwell, S., and Pokras, M. (Eds.). Proceedings of the 1992 Conference on the Loon and its Ecosystem: Status, Management, and Environmental Concerns, August 22-24, 1992, College of the Atlantic, Bar Harbor, Maine. Published by U.S. Fish and Wildlife Service, Concord, NH.
Franson JC: Interpretation of tissue lead residues in birds other than waterfowl. In Beyer WN,
Heinz GH, Redmon-Norwood AW (eds): Environmental Contaminants in Wildlife: Interpreting Tissue Concentrations. Boca Raton, Lewis Publishers, 1996, pp 265-279.
Kramer, J.L. and P.T. Redig. 1997. Sixteen years of lead poisoning in eagles, 1980-95: an epizootiological view. Journal of Raptor Research 31:327-332.
Locke, L.N., Kerr, S.M., and Zoromski, D. 1982. Lead poisoning in common loons. Avian Diseases 26:392-396.
Michigan Loon Recovery Plan, 1989
Michigan Loon Preservation Association-Michigan LoonWatch Statistics:WWW.MichiganLoons.org/statistics.htm
Miller, Harry. MLPA President, In letter to Roland Harmes, MDNR, October 27, 1992.
O’Halloran, J., Myers, A.A., and Duggan, P.F. 1988. Lead poisoning in swans and sources of contamination in Ireland. Journal of the Zoological Society of London 216:211-223.
Perry, C. 1994. Lead Sinker Ingestion in Avian Species. Division of Environmental Contaminants Information Bulletin 94-09-01. U.S. Fish Wildlife Service.
Pokras, M.A. and Chafel, R. 1992. Lead toxicosis from ingested fishing sinkers in adult common loons in New England. Journal of Zoo and Wildlife Medicine 23:92-97.
Scheuhammer A.M. and Norris, S.L. 1996. The ecotoxicolgy of lead shot and lead fishing weights. Ecotoxicology 5:279-295.
Schuett, P. and Robinson, W. Status Report on Upper Great Lakes: Michigan Report, in McIntyre, J. W. and D. C. Evers (eds.) 2000 Loons: Old History and New Findings, Proceedings of a Symposium from the 197 meeting, American Ornithologists’ Union. North American Loon Fund, Holderness, N.H.
Sears, J. 1988. Regional and Seasonal variations in lead poisoning in the mute swan in relation to the distribution of lead and lead weights, in the Thames area, England. Biological Conservation 46:115-134.
Tufts University School of Veterinary Medicine. 1992. The Status of lead poisoning in Common Loons (Gavia Immer) in the Northeast United States as associated with the ingestion of lead fishing sinkers. U.S. Fish and Wildlife Service Report RY92-NEFO-2-EC.
U.S. Environmental Protection Agency. 1994. Lead fishing sinkers: response to citizens’ petition and proposed ban. Federal Register 59:11122-11143.
Washington, Thomas, Executive Director, MUCC. In Response to US EPA Proposal to ban lead sinkers in selected National Wildlife Refuges, May 16, 1994
Minnesota Pollution Control Agency - Probably the best and most up to date site. The Minnesota State Government takes this issue very seriously.
Contacts for Lead-Free Tackle Manufacturers
1027 18th St., Myrtle Point, OR 97458. Contact: Oren Reed, (541)572-2109 Sinkers made from steel and cotton.
P.O. Box 187, Alda NB 68810. Contact: Doug Crumrine, (308)382-7436 Variety of steel sinkers, steel jig systems.
1576 Howard Ave., Windsor, Ontario, Canada, N8X3T5 (519)256-8076 Complete line of bismuth jigs and spinnerbaits, tin split shot.
P.O. Box 176, Wyncot, PA 19095. Contact: Grahame Maisey, (215)886-1804 Variety of tin sinkers.
P.O. Box 801Natick, MA 01760
P.O. Box 50, Logansport, ID 46947 (219)722-4455 Variety of tin sinkers.
10174-89 Street, Edmonton , Alberta , Canada Contact: Gary Love (780)424-2876. Full line of bismuth products, including jigs and spinner baits
P.O. Box 798, Camdenton, MO 65020 Contact: Randy Dickerson, (573)346-4305 Variety of bismuth jigs.
7737 W. Mossy Cup St., Boise, ID (800)580-3811 Putty weights (tungsten)
Peterborough, Ontario, Canada (705)743-3849. Tin sinkers and bismuth jigs.
P.O. Box 297, Hood River, OR 97031 (800)535-1711 Rubber sinkers ( "Bouncing Betty")
251 Lisa Lane, Pasco, WA 99301 Contact: Brian Marquez, (509)545-5095 Organic weights, currently developing jig products.
Box 1599 C-148, Medicine Hat, AB., Canada. T1A 7Y5
510 Sabil Dr., Fruita, CO 81521 Contact: Cameron Garcia, (970)858-4019 Ceramic weights from recycled alumina, currently developing jig products
1610 Whitaker Ave., White Bear Lake, MN 55110 Contact: Geoff Ratte, (504)838-9440. Tin split shot egg sinkers and worm weights of plastic composite/steel resin