The Marbled Murrelet
is a small seabird
Seabirds are birds that have adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same environmental problems and feeding niches have resulted in similar adaptations...
from the North Pacific. It is a member of the auk
An auk is a bird of the family Alcidae in the order Charadriiformes. Auks are superficially similar to penguins due to their black-and-white colours, their upright posture and some of their habits...
family. It nests in old-growth forest
A forest, also referred to as a wood or the woods, is an area with a high density of trees. As with cities, depending where you are in the world, what is considered a forest may vary significantly in size and have various classification according to how and what of the forest is composed...
s or on the ground at higher latitudes where trees cannot grow. Its habit of nesting in trees was suspected but not documented until a tree-climber found a chick in 1974 making it one of the last North American bird species to have its nest described. The Marbled Murrelet has experienced declines in their numbers since humans began logging their nest trees beginning in the latter half of the 19th century. The decline of the Marbled Murrelet and its association with old-growth forests have made it a flagship species in the forest preservation movement.
The Marbled Murrelet is a small (25 cm), chunky auk with a slender black bill. It has pointed wings and plumage
Plumage refers both to the layer of feathers that cover a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage vary between species and subspecies and can also vary between different age classes, sexes, and season. Within species there can also be a...
that varies by season. The non-breeding plumage is typically white underneath with a black crown, nape, wings and back. The bird closely resembles its closest relative, the Long-billed Murrelet. In fact, these species were considered conspecific up until 1998. They are virtually identical. In breeding plumage, both have a brown mottled body and face. The Long-billed has a pale white throat, lacking in the Marbled. In winter plumage, the Marbled Murrelet has a white neck collar, absent in Long-billed. The Marbled Murrelet is shorter billed and slightly smaller than the Long-billed Murrelet.
Behavior and breeding
The Marbled Murrelet feeds at sea both in pelagic offshore areas (often associating with upwelling
Upwelling is an oceanographic phenomenon that involves wind-driven motion of dense, cooler, and usually nutrient-rich water towards the ocean surface, replacing the warmer, usually nutrient-depleted surface water. The increased availability in upwelling regions results in high levels of primary...
s) and inshore in protected bays. It feeds principally on sandeels, also taking herring
Herring is an oily fish of the genus Clupea, found in the shallow, temperate waters of the North Pacific and the North Atlantic oceans, including the Baltic Sea. Three species of Clupea are recognized. The main taxa, the Atlantic herring and the Pacific herring may each be divided into subspecies...
The capelin or caplin, Mallotus villosus, is a small forage fish of the smelt family found in the Atlantic and Arctic oceans. In summer, it grazes on dense swarms of plankton at the edge of the ice shelf. Larger capelin also eat a great deal of krill and other crustaceans...
and shiner perch
The shiner perch Cymatogaster aggregata is a common surfperch found in estuaries, lagoons, and coastal streams along the Pacific coast from Alaska to Baja California...
. The bird has not been known to wander from the Pacific coast of North America, all inland and eastern Brachyramphus
records being of the closely related Long-billed Murrelet
The Long-billed Murrelet is a small seabird from the North Pacific. It is an unusual member of the auk family, often nesting far inland in old growth forests...
The nesting behaviour of the Marbled Murrelet is unusual, since unlike most alcids it does not nest in colonies on cliffs or in burrows, but on branches of old-growth and mature conifers such as Western Hemlock
Tsuga heterophylla. the Western Hemlock, is a species of hemlock native to the west coast of North America, with its northwestern limit on the Kenai Peninsula, Alaska, and its southeastern limit in northern Sonoma County, California.-Habitat:...
, Sitka Spruce
Picea sitchensis, the Sitka Spruce, is a large coniferous evergreen tree growing to 50–70 m tall, exceptionally to 95 m tall, and with a trunk diameter of up to 5 m, exceptionally to 6–7 m diameter...
, Douglas Fir and Coastal Redwood, as far as 80 km inland. It lays one egg
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
on a platform of lichen
Lichens are composite organisms consisting of a symbiotic organism composed of a fungus with a photosynthetic partner , usually either a green alga or cyanobacterium...
Mosses are small, soft plants that are typically 1–10 cm tall, though some species are much larger. They commonly grow close together in clumps or mats in damp or shady locations. They do not have flowers or seeds, and their simple leaves cover the thin wiry stems...
on these branches (less often on the ground). In northern populations, murrelets nest on the ground among rocks, as do other related murrelet species. The egg is incubated for a month, then fed for around 40 days until the chick is able to fledge
Fledge is the stage in a young bird's life when the feathers and wing muscles are sufficiently developed for flight. It also describes the act of a chick's parents raising it to a fully grown state...
. The chick then leaves the nest and flies unaccompanied to the sea. Breeding success is low and chick mortality high.
Marbled murrelets occur in summer from Alaska's Kenai Peninsula, Barren islands, and Aleutian islands south along the coast of North America to Point Sal, Santa Barbara County, in south-central California. Marbled murrelets winter mostly within the same general area, except that they tend to vacate the most northern sections of their range and have been recorded as far south as Imperial Beach of San Diego County, California.
In northern regions where coniferous forests nest sites are unavailable, marbled murrelets occupy alpine or tundra near the ocean. In Washington and Oregon, marbled murrelets commonly nest in Douglas-fir (Pseudotsuga menziesii
) dominated stands. They also select stands dominated by mountain hemlock (Tsuga mertensiana
), western redcedar (Thuja plicata
), and Sitka spruce (Picea sitchensis
) for nesting. In California, nests are most often located in redwood (Sequoia sempervirens
) dominated stands with scattered Sitka spruce, western hemlock (Tsuga heterophylla
) and Douglas-fir. Marbled murrelets also occur in stands dominated by Port-Orford-cedar (Chamaecyparis lawsoniana
Major life events
Marbled murrelets do not breed until they are at least 2 years old. Marbled murrelets nest from mid-April to late September. Peak activity occurs from mid-June to late July in California, and the second week of July to mid-August in Oregon. Marbled murrelet are semicolonial in nesting habits. Two nests found in Washington were located only 150 feet (46 m) apart. Not all mature adults nest every year. Marbled murrelets lay only one egg. The egg is incubated by both parents for about 30 days. Adults fly from ocean feeding areas to inland nest sites, mostly at dusk and dawn. They feed nestlings at least once and sometimes twice per day or night. Usually only one fish is carried to the young.
Nestlings fledge in 28 days. Young marbled murrelets remain in the nest longer than other alcids and molt into their juvenile plumage before leaving the nest. Fledglings fly directly from the nest to the ocean.
Marbled murrelets are coastal birds that occur mainly near saltwater within 1.2 miles (2 km) of shore. However, marbled murrelets have been found up to 59 miles (80 km) inland in Washington, 35 miles (56 km) inland in Oregon, 22 miles (37 km) inland in northern California, and 11 miles (18 km) inland in central California. Over 90% of all marbled murrelet observations in the northern Washington Cascades were within 37 miles (60 km) of the coast. In Oregon, marbled murrelets are observed most often within 12 miles (20 km) of the ocean. Many marbled murrelets regularly visit coastal lakes. Most lakes used by marbled murrelets are within 12 miles (20 km) of the ocean, but a few birds have been found at lakes as far inland as 47 miles (75 km). All lakes used by marbled murrelets occur within potential nesting habitat.
From southeast Alaska southward, marbled murrelets use mature or old-growth forest stands near the coastline for nesting. These forests are generally characterized by large trees (>32 inches [80 cm] diameter at breast height
Diameter at breast height, or DBH, is a standard method of expressing the diameter of the trunk or bole of a standing tree. DBH is one of the most common dendrometric measurements....
[d.b.h.]), a multistoried canopy, moderate to high canopy closure or an open crown canopy, large snags, and numerous downed snags in all stages of decay. Marbled murrelets tend to nest in the oldest trees in the stand. In Oregon, forests begin to exhibit old-growth characteristics at about 175 to 250 years of age. Moss, on which marbled murrelets nest, forms on the limbs of Douglas-fir that are more than 150 years old.
The only four marbled murrelet tree nests found before 1990 shared the following characteristics: (1) located in a large tree (>47 inches [120 cm] d.b.h.) with an open crown structure, (2) on a moss-covered limb that is camouflaged, partially shaded, and approximately horizontal with a diameter (including associated moss) of at least 14 inches (36 cm), and (3) located within the middle or lower part of a live crown. However, Marshall stated that because of their low aerial buoyancy
marbled murrelets often nest high in the treetops or on steep slopes. Habitat must be sufficiently open to allow for easy flight. All marbled murrelet nests found in Washington, Oregon, and California were located in old-growth trees that ranged from 38 inches (88 cm) d.b.h. to 210 inches (533 cm) d.b.h. with a mean of 80 inches (203 cm) d.b.h. Nests were located high above the ground and had good overhead protection but allowed easy access to the exterior forest. Marbled murrelets may use the same nest in successive years.
Stand size is also important in nest sites. Marbled murrelets more commonly occupy stands greater than 500 acres (202 ha) than stands less than 100 acres (40 ha). However, marbled murrelets may nest in remnant old-growth trees or groves that are surrounded by younger trees. In California, marbled murrelets are usually absent from stands less than 60 acres (24 ha) in size. In Washington, marbled murrelets are found more often when old-growth and mature forests make up over 30% of the landscape. Fewer marbled murrelets are found when clearcut and meadow areas make up more than 25% of the landscape. Concentrations of marbled murrelets offshore are almost always adjacent to old-growth or mature forests onshore, although marbled murrelets may not use the interior of dense stands.
Where large trees are absent in the northern parts of marbled murrelet range, marbled murrelets nest in depressions on the ground, in rock cavities on the ground, or on rock outcrops. Marbled murrelets are both ground nesters and tree nesters where forests and treeless areas meet.
Marbled murrelets forage in the ocean near shore and in inland saltwater areas such as bays, sounds, and saltwater passageways. Some also forage on inland freshwater lakes. Flocks of 50 or more birds have been observed near freshwater lakes. Subadults occur at sea throughout the summer. Marbled murrelets feed within 1,640 feet (500 m) of shore.
Marbled murrelet winter habitat is the same as the nesting and foraging habitat. During the winter marbled murrelets use inland old-growth or mature sites for roosting, courtship, and investigating nest sites. The use of inland lakes during the nonbreeding season occurs in conjunction with visits to nesting areas.
Marbled murrelets feed below the water surface on small fish and invertebrates. Some principal foods include sand lance (Ammodytes hexapterus
), Pacific herring (Clupea haringus
), capelin (Mallotus villosus
), and the invertebrates Euphausia pacifica
and Thysanoessa spinifera
Marbled murrelets do not feed in large flocks as do other alcids, although loose aggregations occur in winter. While feeding during the breeding season marbled murrelets occur in pairs or as single individuals. Subadults feed singly; but in early July, when pairs of adults are still feeding young, mixed flocks begin to form. Marbled murrelets feed during the day and at night.
The Steller's Jay is a jay native to western North America, closely related to the Blue Jay found in the rest of the continent, but with a black head and upper body. It is also known as the Long-crested Jay, Mountain Jay, and Pine Jay...
s (Cyanocitta stelleri
) and common ravens (Corvus corax
) prey on marbled murrelet eggs and nestlings.
Marbled Murrelets and humans
The Marbled Murrelet is considered globally endangered, with some evidence of decline across its range over the last few decades. The biggest threat to the marbled murrelet was long considered to be loss of nesting habitat (old-growth and mature forests) to logging
Logging is the cutting, skidding, on-site processing, and loading of trees or logs onto trucks.In forestry, the term logging is sometimes used in a narrow sense concerning the logistics of moving wood from the stump to somewhere outside the forest, usually a sawmill or a lumber yard...
. Additional factors including high predation rates due to human disturbances and climate-driven changes in ocean conditions are also considered important now.
Scientists at Redwood National Park have established a connection between human presence in marbled murrelet territory and corvid predation of marbled murrelet chicks. Corvid populations, such as Steller's jays, crows, and ravens, are expanding into old-growth forests. Lured by food scraps left by campers and hikers, with increased access aggravated by the patchwork forests created by industrial logging, corvids more frequently discover marbled murrelet nests in areas where these predator species were not previously found.
The populations in Washington, Oregon and California were listed as threatened in 1992 by the U.S. Fish and Wildlife Service due to concerns about loss of nesting habitat
A habitat is an ecological or environmental area that is inhabited by a particular species of animal, plant or other type of organism...
, entanglement in fishing
Fishing is the activity of trying to catch wild fish. Fish are normally caught in the wild. Techniques for catching fish include hand gathering, spearing, netting, angling and trapping....
gear and oil spill
An oil spill is the release of a liquid petroleum hydrocarbon into the environment, especially marine areas, due to human activity, and is a form of pollution. The term is mostly used to describe marine oil spills, where oil is released into the ocean or coastal waters...
s. The remaining populations (Alaska and British Columbia) are currently under review. The species became a flagship species in efforts to prevent the logging of old-growth forests along the Pacific coast from California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
Database entry includes justification for why this species is endangered
- "National Geographic" Field Guide to the Birds of North America ISBN 0-7922-6877-6
- Seabirds, an Identification Guide by Peter Harrison, (1983) ISBN 0-7470-1410-8
- Handbook of the Birds of the World Vol 3, Josep del Hoyo editor, ISBN 84-87334-20-2
- "National Audubon Society" The Sibley Guide to Birds, by David Allen Sibley, ISBN 0-679-45122-6