Brachyramphus marmoratus marmoratus
status: Vulnerable, IUCN Threatened, ESA
range: Canada, USA (Alaska, California, Oregon, Washington)
Description and biology
The marbled murrelet belongs to the family of diving seabirds known as auks (or alcids), which includes species such as puffins, murres, auklets, and guillemoots. The marbled murrelet is small and chunky, with a wingspan of 9.5 to 10 inches (24 to 25 centimeters). It weighs about 10.5 ounces (300 grams). It has webbed feet, a sharp black bill, and pointed wings. Like many other birds, the murrelet grows two sets of feathers each year. In summer, its plumage (covering of feathers) is marbled in shades of dark brown and whitish-gray. In winter, its upperparts are black while its underparts are white.
Murrelets generally feed within 2 miles (3 kilometers) of shore. They prey on small fish such as sandlance, capelin, herring, and smelt. They pursue their prey underwater, diving well below the surface. Steering with their webbed feet, they use their wings like flippers to propel themselves forward. Often, a dive will last no more than 30 seconds. Predators of the murrelet include peregrine falcons and bald eagles.
Marbled murrelets nest primarily in old- growth forests where the trees range from 175 to 600 years old. While most nesting sites are located within 12 miles (19 kilometers) of shore, some have been found up to 50 miles (80 kilometers) away from the ocean. They build their nests on natural platforms underneath an overhanging branch, often at a height more than 100 feet (30 meters) above the ground.
Breeding season lasts from mid-April to the end of August. After a male and female marbled murrelet mate, the female lays one large, spotted, yellowish egg. Both the male and the female incubate (sit on or brood) the egg for about 30 days. After hatching, the nestling or young murrelet stays in the nest for about another 28 days before it fledges (develops flying feathers).
Habitat and current distribution
Marbled murrelets are found near coastal waters, bays, and mountains from Alaska's Aleutian Islands and Kenai Peninsula south along the coast of North America to Santa Barbara County in south-central California. In winter, they leave the northernmost parts of their range and travel as far south as San Diego County, California.
In the mid-1990s, biologists (people who study living organisms) estimated the total North American marbled murrelet population to be 360,000. They also estimated that approximately 85 percent of that population bred along the coast of Alaska.
History and conservation measures
Because marbled murrelets face few natural threats in their environment, they can live as long as 25 years. However, human activities can have a serious effect on the birds. Oil pollution, fishing nets, and habitat loss have all combined to threaten the existence of this bird. It is considered critically endangered in California and Oregon, and threatened in Oregon, Washington, and British Columbia. The species remains abundant in Alaska.
The greatest threat to the marbled murrelet is the loss of its habitat due to the clear-cut logging of old-growth forests. In the past century, more than 95 percent of the old-growth forests along the Pacific coast have been cleared. Very little of the existing old-growth forests is currently protected.
Concern has been raised recently about the number of murrelets killed in gill nets, which are fishing nets designed to catch fish by their gills and drown them; however, the nets end up catching many different aquatic creatures, including murrelets. Studies have reported that 600 to 800 or more marbled murrelets are killed annually in gill nets in Prince William Sound, Alaska, alone.
Since the murrelet feeds close to shore, it is highly vulnerable to oil spills and other types of water pollution. The development of the petroleum industry along the Pacific coast has increased the threat of oil pollution in the murrelet's range.
Conservation efforts on behalf of the marbled murrelet include the Headwaters Murrelet Project, a scientific investigation of the bird in northern California. The project is studying the effect of transferring about 7,500 acres (3,000 hectares) of old-growth forest to public ownership and how that might help the continued survival of the marbled murrelet.