Marbled Murrelet Life History

Habitat

Habitat Oceans

The Marbled Murrelet’s breeding habitat requirements have been the subject of intense study since the first nests were discovered in the 1970s. This species nests in moist coastal coniferous forests, usually within a few miles of the ocean and especially in old-growth forests, where large trees with broad, mossy limbs provide ideal natural nest platforms. Epiphytic moss is important for Marbled Murrelets’ nesting; these plants only grow in moist forests, usually where winter rains are plentiful and fog is common. Key tree species for nesting are Douglas-fir, Alaska yellow cedar, western redcedar, western hemlock, mountain hemlock, Sitka spruce, and coast redwood. Ideal nesting habitat has a partly open canopy, which probably facilitates access to the nest. Most nest near sea level, but the species may nest up to about 4,000 feet elevation, especially where continuous forested habitat is present from the coast into the interior. In Alaska, this species also nests on the ground near the coast, usually on rocky talus slopes, cliffs, or in lightly vegetated areas with alder or dwarf spruce trees.

Less is known about the species’ habitat requirements at sea, both during the breeding season and outside of it. Marbled Murrelets often feed near shorelines, especially where tides or river currents concentrate prey. However, they also forage far as far as 180 miles offshore at times, at least in the Gulf of Alaska.

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Food

Food Fish

Marbled Murrelets eat mostly small fish and zooplankton, which they capture underwater with the bill, usually not far from land. They dive quickly, opening the wings to “fly” underwater, steering with both wings and feet in rapid pursuit of prey. Dives generally last less than a minute, and are fairly shallow. Marbled Murrelets may forage alone, in pairs, or in flocks, but in the northern part of their range they also join mixed-species seabird flocks. Multiple studies suggest that they forage cooperatively, herding small fish together as a team to make capturing them more efficient. Their prey may be concentrated by tides, upwellings, rip currents, river outflow, or other features of the marine environment, and large numbers of murrelets may gather at any time of year where food is plentiful. Adults eat smaller prey but feed their young larger (up to 4.3-inch-long) fish, which they capture mostly at dusk and dawn. Prey species Pacific sandlance, northern anchovy, Pacific herring, Pacific sardine, Pacific sandfish, capelin, seaperch, surf smelt, walleye pollock, California needlefish, candlefish, sockeye salmon, Kokanee salmon, rockfish, codfish, scorpionfish, and prickleback. In addition to fish, they eat small shrimp such as northern prawn and squid such as opalescent inshore squid. In the northern part of the range, they often feed heavily, especially in spring, on zooplankton—tiny shrimplike crustaceans called euphausiids, mysids, and amphipods. During summer in the Pacific Northwest, they also forage in freshwater lakes, where they take juvenile and larval fish.

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Nesting

Nest Placement

Nest Tree

Marbled Murrelets make tree nests on large, moss- and lichen-covered branches high (usually over 40 feet) above the ground in mature and old-growth coniferous forest, normally in the largest tree in the area. Less commonly, they make ground nests in a depression in a rocky talus slope, boulder field, or similar area, sometimes on moss, matted vegetation, or beneath taller vegetation such as alders.

Nest Description

No actual nest is built. The female lays one egg directly onto a mossy branch or on the ground, in a depressed site where the egg is unlikely to roll away, sometimes in a disused bird or squirrel nest or platform of dead vegetation. Nests average about 4.2 inches along the length of the branch and 3.7 inches wide, with the interior about 1.5 inches deep.

Nesting Facts
Egg Description:

Pale olive green to greenish yellow, spotted with black, brown, or purple.

Condition at Hatching:

Covered in down, can walk, but stays in nest.

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Behavior

Behavior Surface Dive

The Marbled Murrelet’s nesting habits remained a mystery until the late 20th century. The first nests in North America were found in the 1970s, with the surprising discovery that these murrelets nest high in old-growth trees of the Pacific Coast. In late winter and early spring, Marbled Murrelets court at sea, and that courtship continues into summer. Displaying birds (likely males) raise the wings above the back in a V-shape while swimming, giving an odd-sounding, whiny call. The partner then comes to swim side by side, and both extend the necks, then point the bills skyward, giving soft calls. They swim and call in unison, then dive and surface simultaneously, repeating their sky-pointing display. Pairs often chase each other in flight during the breeding season, even diving into the sea while still flying—and continuing the pursuit underwater. Courtship behavior may continue year-round, and scientists suspect that monogamous pair bonds are maintained through the nonbreeding season.

In the southern part of the range, pairs appear to nest solitarily, but farther north, pairs may nest fairly close together. Most nests have been found in large trees in old-growth forest, a few in rocky slopes. Very few humans have observed Marbled Murrelets at the nest, but the birds have been seen making close chases through the forest, calling, diving steeply, and making loud wing noises. It is unclear whether these are territorial flights or social displays, since up to 12 birds may be involved. Marbled Murrelets also court at sea in groups at this time. Like many seabirds, they gather at dawn and dusk on the ocean nearest the nest site. They visit the nest under cover of low light or darkness, to reduce the chances of encountering a predator. Both parents feed the young chick. After it fledges, the young bird flies to the ocean by itself, where it eventually joins others of its species. At the end of the breeding season, large flocks may gather in the northern part of the range, up to about 5,000 birds, and in areas of greatest abundance they remain social through much of the nonbreeding season. Pairs appear to forage together, staying in contact with calls. Records from interior lakes and forests in late winter could be of birds displaced from the ocean by storms or possibly birds that are prospecting for nest sites.

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Conservation

Conservation Declining

Marbled Murrelet populations are in decline, particularly in Washington, Oregon, and California. Partners in Flight estimates a global breeding population of 260,000, ranks the species a 15 out of 20 on the Continental Concern Score, and includes it on the Yellow Watch List for species in decline. The California, Oregon, and Washington populations are listed as Threatened under the federal Endangered Species Act by the U.S. Fish and Wildlife Service. Logging and development of forested nesting habitat have been extensive, and large portions of this species’ nesting grounds have been cut already. Logging poses a significant threat to the species’ survival, both because of the birds’ reliance on old-growth trees and because forests become fragmented, exposing the birds to greater risk of predation. Because they forage near shore, many Marbled Murrelets have died as a result of oil spills and other marine contamination. Spills may also harm the murrelets’ prey species. Commercial fishing using gillnets can result in thousands of murrelets and other seabirds becoming entangled and drowning.

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Credits

Kushlan, J. A., M. J. Steinkamp, K. C. Parsons, J. Capp, M. A. Cruz, M. Coulter, I. Davidson, L. Dickson, N. Edelson, R. Elliott, R. M. Erwin, S. Hatch, S. Kress, R. Milko, S. Miller, K. Mills, R. Paul, R. Phillips, J. E. Saliva, W. Sydeman, J. Trapp, J. Wheeler and K. Wohl (2002). Waterbird conservation for the Americas: The North American waterbird conservation plan, version 1. Washington, DC, USA.

Lutmerding, J. A. and A. S. Love. Longevity records of North American birds. Version 2015.2. Patuxent Wildlife Research Center, Bird Banding Laboratory 2015.

Nelson, S. Kim. (1997). Marbled Murrelet (Brachyramphus marmoratus), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Partners in Flight (2017). Avian Conservation Assessment Database. 2017.

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

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