Common Loon

A Common Loon swimming close up.
Adult Common Loon in summer breeding plumage.

NPS/ Paul Brown

Come spring, the iconic, eerie call of the loon echoes across open waters and reminds all that they have returned from their wintering on the Atlantic Ocean. The Common Loon (Gavia immer) is a waterfowl that can be found across the northwoods; however, Isle Royale is one of the few places they breed on all Great Lakes’ shorelines.
Adult Common Loon in summer breeding plumage.
A Common Loon swimming close up.


Common Loon Characteristics

  • Loons have distinctive black and white checked plumage. The plumage pattern helps it camouflage with the surface of a sparkling lake.

  • Red eyes, that allow improved underwater vision while fishing.

  • Loons are larger than ducks, but smaller than a goose.

  • The a length of a loon is 30 inches long.

  • Loons weigh an average of 8-12 pounds.

  • Loons have solid bones which allows them to dive to depths up to 100+ feet while fishing.

  • Loons have a wingspan of up to 60 inches.
  • Their body is built for swimming, diving, and catching fish.
  • Loons do not have hollow bones.
  • Loons can dive up to 100+ feet while fishing.
A loon swims with a chick on it's back.
An adult loon swims with it's chick on it's back.


Loon Breeding and Young

  • Pairs are likely monogamous and tend to occupy the same territory each year, sometimes reusing the same nest.
  • Nests are built of dead grasses and dead vegetation on shorelines of protected, weedy areas of calmer water bodies to raise their chicks.
  • Females lay an average of 2 olive-brown or greenish lightly spotted eggs and incubate them for about 1 month.
  • Chicks hatch during the month of July and remain close to the parents for the first 2-3 months of their lives and will catch a ride on a parent’s back.
  • Due to their awkward walking on land, loon nests are usually constructed within 3 feet of the shoreline to allow for quick escape from predators. Being closer to the water edge, however, leaves the nest and eggs at risk of being damaged by waves, boat wakes, and changes in water levels.


Isle Royale's loon population is unique in North America by having breeding territories on Great Lake shorelines, while also having pairs nest on interior lakes. The Isle Royale Common Loon survey has been ongoing for 35 years to observe the park’s loon population and breeding success within both habitats. In 2019, surveyors identified a minimum of 126 breeding territories containing 201 adults and 50 young in total. This represented a slightly lower number of adults than the long-term average of 220 individuals, while 50 chicks was among the highest counts recorded.


Where Can You View Loons?

Loons can be seen throughout Isle Royale, floating on any body of water that is deep enough to hunt for fish. In later summer, loons can be found in quiet, protected bays with young chicks.

Things to do to help loons:

  • Slow your boat down when coming ashore to minimize wave action effect on loon nests.

  • Scan the shoreline to make sure your boat will not be parked on a loon nest.

  • If you notice an active nest near a campsite or day-use are, report this information to park staff and stay distant from nest site.

  • When fishing, use lead-free tackle, as ingestion can cause birds to become very ill.

Last updated: March 22, 2022

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