Loon Health and Mortality
Loon carrying chicks on its back. © Photo by Daniel Poleschook, Jr. and Virginia R. Gumm, used with permission.
The Common Loon is often seen as a symbol of northern wilderness and the beauty and serenity of northern lakes. They winter on estuaries or along the ocean, but move into lakes during the spring to breed very soon after ice-out. They make their nests along the shores of the lakes so that they can easily move in to the water if they are threatened by predators. While they are excellent divers and can fly at speeds up to 75 miles per hour, loons cannot walk, and move on land with difficulty by pushing their bodies forward. They usually lay two eggs a year. Although loon chicks can swim very soon after hatching, they still need help and support from their parents. A memorable sight is that of an adult loon swimming along a lakeshore carrying a chick or two on its back. Adults care for the young for the first few weeks of life, but by fall migration time, the immature loons can care for themselves and are prepared to make the journey to the sea.
To learn more about loon biology, go to these sites:
What Do We Like About Loons?
Loons are beautiful and distinctive birds with a call that can sound like a haunting wail. Their striking looks during the breeding season - a slick black head, a necklace of white stripes and ruby red eyes - and their threatened status in the Northeast make them popular as models for magazines and brochures of very different groups and organizations. Their fascinating image is often use to adorn catalogues for outdoor sporting equipment as well as for environmental conservation.
Because of their captivating beauty and unforgettable call, loons are popular symbols of
natural wilderness. Loons are often emblazoned on coffee mugs, key chains and other tourist souvenirs. They attract public attention and interest because of their unique contribution to the experience of living and vacationing in the northeast. The Royal Canadian Mint has even issued a commemorative Common Loon coin. How
ever the likeness of the loon is portrayed, its appeal is almost certain.
Visit this site to hear loon calls, www.adkscience.org
Why are Loons Dying?
Over 1500 dead and dying loons have been examined by veterinarians at the Wildlife Clinic at Cummings School of Veterinary Medicine at Tufts University in North Grafton, Massachusetts. The birds were classified into four categories, chicks, immature loons, wintering adults and breeding adults. The charts below show the various causes of death for each of the four categories.
A large number of deaths are categorized as "unknown" because many of the bodies are found in such bad condition that the cause of death can not be determined with any certainty.
Common Loon, in non-breeding plumage, trying to free itself from fishing line with attached lead sinker. Sinker is on its breast, indicated by arrow.
© Photo by Latafat Correa, used with permission.
Is Lead Really a Problem for Loons?
Almost half (44%) of the dead and dying breeding loons submitted to the Wildlife Clinic at Cummings School of Veterinary Medicine at Tufts University in North Grafton, Massachusetts suffered from lead poisoning. Virtually all of this is from eating lead fishing gear. Loons can come in contact with lead in several ways. Loons pick up small stones and grit from the bottom of lakes to help them digest their food. Lead sinkers can be about the same size as these stones and so the loons may pick them up as well. In addition, loons eat
fish that have ingested lead or even ingest fishing line with lead in it and still attached to a hook and live bait fish.
Most lead objects eaten by loons are:
- Less than one ounce
- Less than an inch long
- Less than a half inch wide
For more information on lead poisoning and loons, check out these web sites:
Left: Radiograph of a loon showing lead sinker in gizzard. Right: Enlargement showing lead sinker along with stones (paler objects) in loon's gizzard.
How do you know itís lead and not something else?
Lead is a toxic metal that can have a negative affect on many body systems including an animalís nervous system and reproductive system. In people, we have known of the dangers of lead for many years and as a result have seen limits imposed on leaded gasoline, lead in paint and lead in other commonly used consumer products.
A loon suffering from lead poisoning will appear disoriented, and unable to dive or catch fish. It will have a slower reaction time than normal. Often, it can no longer digest itís food and will have trouble breathing. Poisoned birds frequently beach themselves. When researchers examined the dead loons, they found levels of lead in blood and body tissues high enough to cause poisoning. Radiographic findings often show the lead inside the digestive system of the dead bird. Of the birds examined at Tufts, every loon that had eaten a piece of lead gear had toxic levels of lead in its body, but the loons without the fishing gear did not.
To learn more about lead, go to these sites:
What type of fishing gear is really killing loons?
Because of where loons breed and because of their eating habits, they most often ingest 1/4 - 1 ounce lead weights. The gear can be split shot, worm weights, sinkers, jigs, bass rigs and lead containing lines. Below is a chart detailing the types of gear recovered from the loons examined at Tufts.
What can we do to protect loons?
- Use lead-free fishing tackle
- Dispose of monofilament line properly
- Keep shorelines clean
- Watch for and stay away from loons on your lake
Adult Common Loon that has swallowed a fish with broken line and tackle. Fishing tackle indicated by arrow. © Photo by Daniel Poleschook, Jr. and Virginia R. Gumm, used with permission.
To read more about lead toxicity and loons
Publications on Loons and Lead
- Pokras, M., M. Kneeland, A. Ludi, et al. 2009. Lead Objects Ingested by Common Loons in New England. Northeastern Naturalist 16(2): 177-182.
- Abstracts of eleven papers presented at the "Lead Sinker Symposium" held during the 32nd Aquatic Toxicity Workshop (October 2-5, 2005) in Waterloo, Ontario.
- Evers, D. C. 2004 Status assessment and conservation plan for the Common Loon (Gavia immer) in North America. U.S. Fish and Wildlife Service, Hadley, MA.
- Wilson, H., J. Oyen, and L. Sileo. 2004. Lead Shot Poisoning of A Pacific Loon in Alaska. Journal of Wildlife Diseases 40(3): p. 600-602.
- Sidor, I.F., et al. 2003. Mortality of Common Loons in New England 1987 to 2000. Journal of Wildlife Diseases 39(2): p. 306-315.
- Scheuhammer, A.M., et al. 2003. Lead fishing sinkers and jigs in Canada: Review of their use patterns and toxic impacts on wildlife, in Canadian Wildlife Service Occasional Papers, C.W.S.o.E. Canada, Editor. Canadian Wildlife Service: Ottawa, Ontario. p. 3-45.
- Franson, J.C., et al. 2001. Size Characteristics of Stones ingested by Common Loons. The Condor 103(1): p. 189-191.
- Stone, W.B. and J. Okoniewski. 2001. Necropsy findings and environmental contaminants in common loons from New York. Journal of Wildlife Diseases 37(1): p. 178-184.
- Stone, WB; Okoniewski, JC. 2001. Necropsy findings and environmental contaminants in common loons from New York Journal of Wildlife Diseases Vol. 37(1):178-184.
- Twiss, M.P. and V.G. Thomas. 1998. Preventing fishing sinker induced lead poisoning of common loon through Canadian policy and regulative reform. Journal of Environmental Management. 53(1): p. 49-59.
- Daoust, P., et al. 1998. Interactive mortality factors in common loons from Maritime Canada. Journal of Wildlife Diseases, 34(3): p. 524-531.
- Augspurger, T., et al. 1998. An epizootic of common loons in coastal waters of North Carolina: Concentration of elemental contaminants and results of necropsies. Environmental Toxicology and Chemistry 17(2): p. 205-209.
- Scheuhammer, A. M. and S. L. Norris 1996. The ecotoxicology of lead shot and lead fishing weights. Ecotoxicology 5:279-295.
- Scheuhammer, A.M. and S. Norris. 1995. A review of the environmental impacts of lead shotshell ammunition and lead fishing weights in Canada, in Occasional Papers, C.W.S.o.E. Canada, Editor. Canadian Wildlife Service: Ottawa, Ontario. p. 1-54.
- Pokras, MA, and RM Chafel. 1992. Lead toxicosis from ingested fishing sinkers in adult common loons (Gavia immer) in New England. Journal of Zoo and Wildlife Medicine 23: 92-97.
- Pokras, M., C. Press, and S. Rohrbach. 1992. The Mortality of Loons. Massachusetts Wildlife 62(4): p. 18-25.
News on Lead and Loons