Colonial Nesting Birds

Two American white pelicans swimming on a lake.
American white pelicans—and other colonial nesting birds—nest primarily in the southeast arm of Yellowstone Lake.

NPS/Diane Renkin


Colonial nesting birds nest primarily on the Molly Islands in the southeast arm of Yellowstone Lake. These two small islands are cumulatively just 0.7–1.2 acres in size, depending on lake water levels, yet hundreds of birds have nested there in a single year. The birds have been surveyed for more than 30 years, with some data going back to 1890 when nesting American white pelicans (Pelecanus erythrorhynchos) and California gulls (Larus californicus) were first noted in this area. Currently, pelicans, California gulls, and double- crested cormorants (Phalacrocorax auritus) nest with varying rates of success. Very wet and cold late spring weather and the declining cutthroat trout population could be factors. In 2015, 291 pelican chicks, and 9 cormorant chicks fledged. No California gull chicks were observed.



Birds nesting on the Molly Islands are subject to extreme environmental conditions ranging from flooding, frosts that can occur at any time of year, and high winds. As a result, birds nesting there experience large year-to-year fluctuations in the number of nests initiated and fledglings produced. Populations of American white pelicans, California gulls, and double-crested cormorants have declined over the last 20 years. Caspian terns (Hydroprogne caspia) have not nested on the islands since 2005. The reason(s) for the declines is unknown, but is likely related to cutthroat trout population diminishing in Yellowstone Lake.

Caspian terns are suspected of nesting on the Molly Islands as early as 1917, although information on breeding status was not collected until 1933. Double-crested cormorant nests were confirmed by 1928. Prior to the late 1970s, the Molly Islands were surveyed only intermittently, but have been surveyed annually since that time.

American white pelicans spend the summer mainly on Yellowstone Lake and the Yellowstone River. These large white birds are often mistaken for trumpeter swans until their huge yellow beak and throat pouch are seen. Their black wing tips also distinguish them from swans, which have pure white wings.

Bald eagle standing over a fish that it's eating.

Bald Eagle

Bald eagles can be seen along Yellowstone's many rivers and lakes.

An osprey comes in for a landing on a nest, where its mate tends the nest.


Osprey summer in Yellowstone, fishing and raising young.

A peregrine falcon perched on a branch.

Peregrine Falcon

Peregrine falcons are some of the fastest birds.

A loon swimming on a lake.

Common Loon

Loons in Yellowstone are some of the southern most breeding populations.

A pair of swans swimming on a lake.

Trumpeter Swan

Trumpeter swans are the largest wild waterfowl in North America.

A white-breasted bird with gray and black wings and black beak on a mound of snow

Songbirds and Woodpeckers

Passerine and near passerine species comprise the majority of bird species in Yellowstone.

A small, gray bird perched on a rock along a stream holding an insect in its beak.

American Dipper

Also known as the water ouzel, these birds dive into water for aquatic insects.

Profile of a raven's head and chest


Ravens are smart birds, able to put together cause and effect.

A sandhill crane walking through a marshy landscape.

Sandhill Crane

Sandhill cranes nest in Yellowstone during the summer.

A yellow-breasted bird with black markings calls out as it stands on a stick


About 150 species build their nests and fledge their young in Yellowstone.

An eared grebe near Mammoth Hot Springs

Sound Library

Immerse yourself in the aural splendor of Yellowstone.



Annual Bird Program Reports. National Park Service, Yellowstone National Park.

Evans, R.M., and F.L. Knopf. American white pelican. The Birds of North America Online.

Last updated: July 17, 2018

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Yellowstone National Park, WY 82190-0168



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