Ancient Murrelet Life History

Habitat

Ancient Murrelets breed in colonies along the shorelines of North Pacific islands, usually within 1,000 feet of the shoreline. They use rocky crevices or build earthen burrows for nesting. They use both grassy sites and forested areas with Sitka spruce, western hemlock, or western red-cedar. Up to 10,000 birds may occupy a colony, but most colonies are smaller. Soon after chicks hatch, they go to sea with parents, sometimes foraging close to shore (especially in Alaska’s Aleutian Islands) but often farther from shore. Some birds remain near breeding areas year-round, while others move southward in autumn, to winter well offshore along the continental shelf edge. Key to this species’ marine habitats are upwellings and other currents that concentrate food and bring it to the surface. Back to top

Food

Ancient Murrelets eat mostly small fish and zooplankton. They catch their food by swimming underwater, typically diving straight downward until they reach the depth of their prey. When foraging in a flock, they sometimes dive nearly simultaneously. Black-legged Kittiwakes and other gulls sometimes gather above groups of Ancient Murrelets, perhaps attracted to fish murrelets drive toward the surface (or to steal fish from them). Prey includes shiner perch, capelin, walleye pollock, rainbow smelt, Pacific herring, Pacific saury, Pacific sandlance, rockfish (genus Sebastes) and sculpins (genus Triglops). They also eat large quantities of shrimplike krill (euphausiids).

Nesting

Nest Placement

Ancient Murrelets construct earthen burrows for nesting but also use existing cavities under logs or tree roots, crevices in rocky areas, or gaps between grass tussocks. They readily use wooden nest boxes and sometimes even nest in walls or huts.

Nest Description

Burrow entrances are 3–5.5 inches in diameter, and burrows may be 6 feet long but are usually shorter, averaging about 40 inches long. At the end of the burrow, a small nest is made of grass, twigs, and leaves.

Nesting Facts

Behavior

Ancient Murrelets often return to the breeding grounds already paired. Each night they begin to arrive at their underground nest sites about 90 minutes after sunset and depart an hour before first light, making them hard to study. Males call near the nest site, a rhythmic, repeated chip…chirrup, often from the burrow entrance, or sometimes from prominent rocks or trees. Males occasionally chase or battle other males near their small nest territory of just a few feet. Males that claim adjacent territories take turns calling to emphasize their claims. Unmated males spend much time above ground (often calling or singing), but mated males usually enter the nest burrow soon after returning from sea. Both male and female excavate or renovate their burrow from the previous season. On dark, moonless nights after adults have laid eggs, younger, pre-breeding birds (mostly 2-year-olds) fly around and attend the colony, probably familiarizing themselves with the territories and the landscape in the season before they first breed. Sometimes, at the end of the breeding season, they begin excavating burrows to use the following year.

This species is socially monogamous. While gathered in offshore flocks, waiting for darkness so they can return safely to the nest site, Ancient Murrelets may perform comical displays, raising their wispy white crown feathers and calling, sometimes springing into the air a foot or so above the water, then crashing back down, one wing extended, into the sea. Once the young have hatched, the adults call to them to join them at sea, where they tend and feed them through fledging.

Conservation

Partners in Flight estimates a global breeding population of 1 million, and rates the species a 13 out of 20 on the Continental Concern Score, indicating a species of relatively low concern. Like other seabirds, Ancient Murrelets are threatened by chemical pollution in the food chain and by oil spills, which can cause direct mortality and lower breeding success. Introduced foxes, rats, and raccoons have severely reduced numbers in Ancient Murrelet colonies. Removal of these predators has allowed rapid recovery in some cases. However, raccoons have been able to repeatedly recolonize some islands, and this remains the most pressing conservation issue for Ancient Murrelets in British Columbia.

Credits

Gaston, A. J. and A. Shoji (2020). Ancient Murrelet (Synthliboramphus antiquus), version 1.0. In Birds of the World (A. F. Poole, editor). Cornell Lab of Ornithology, Ithaca, NY, USA.

Lutmerding, J. A. and A. S. Love. (2020). Longevity records of North American birds. Version 2020. Patuxent Wildlife Research Center, Bird Banding Laboratory 2020.

Partners in Flight. (2020). Avian Conservation Assessment Database, version 2020.

Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, NY, USA.

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