Loon Health and Mortality

  • About loons
  • What do we like about loons?
  • Why are loons dying?
  • Is lead really a problem for loons?
  • How do you know it’s lead and not something else?
  • What type of fishing gear is really killing loons?
  • What can we do to protect loons?
  • Publications on Loons and Lead
  • News on Lead and Loons
  • Images of Loons and Lead Poisoning
  • Loon Links

About loons

The Common Loon (Gavia immer) 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 very soon after ice-out in the spring, move onto lakes to breed. They nest along the shores of the lakes so that they can easily move into the water to feed, preen or 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 roughly the first ten weeks of life, but by fall migration, 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 sounds 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 equipment as well as for environmental conservation.

Because of their captivating beauty and unforgettable calls, 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 (the one dollar “loony”). However 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 2500 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 age categories, chicks, immature loons, wintering adults and breeding adults. The charts below show the various causes of death for each of the four categories.

causes of mortality in adult loon

 

loon chick mortality

 

immature loon mortality

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 cannot be determined with any certainty.

loon swimming
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?

Of the dead and dying adult loons from New England’s freshwater lakes submitted to the Wildlife Clinic almost half (44%) 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 might 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 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:

radiograph of loonradiograph of loon

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 it’s lead and not something else?

Lead is a toxic metal that can have a negative affect on many body systems including an animal’s 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 its 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 (xray) 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.

chart of gear

What can we do to protect loons?

  • Use lead-free fishing tackle
  • Dispose of monofilament line properly, using biodegradable line
  • 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.
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

News on Lead and Loons