The marbled murrelet(Brachyramphus marmoratus) is a small seabird from the North Pacific. It is a member of the auk family. It nests in old-growth forests 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 declined in number since humans began logging its nest trees in the latter half of the 19th century. The decline of the marbled murrelet and its association with old-growth forests, at least in the southern part of its range, have made it a flagship species in the forest preservation movement. In Canada (north of 50° North Latitude) and Alaska, the declines are not so obvious because populations are much larger and the survey techniques have not had sufficient power to detect changes.
The marbled murrelet is a small (25 cm), chunky auk with a slender black bill. It has pointed wings and plumage 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. 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.
Marbled murrelets feed below the water surface on small fish and invertebrates. Marbled murrelets often forage in pairs but do not feed in large flocks as do other alcids. Loose aggregations of 500 or more birds occasionally occur in winter. 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.
Marbled murrelets do not breed until they are at least 2 years old. Marbled murrelets nest from mid-April to late September. 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 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 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.
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. Additional factors including high predation rates due to human disturbances and climate-driven changes in ocean conditions are also considered important now.