The marbled murrelet is a member of the Family Alcidae, which includes a variety of diving seabirds that feed on fish and other marine organisms. The scientific name of the marbled murrelet is Brachyramphus marmoratus, which means marbled with a short, curved-beaked. Murrelets breed in coastal old growth forests where they make their nests high up in the canopy. These birds inhabit shoreline areas of the north Pacific Ocean, ranging from Alaska to central California, and from Kamchatka, Russia down to Japan.
Until recently, little was known about the breeding behaviour of the marbled murrelet. Investigations of the biology of this atypical seabird, including studies of abundance, distribution and habitat, have been done in the past few years. From these studies it was found that the breeding season lasts from mid-April to late September. Unlike most seabirds, murrelets are solitary breeders that breed inland. The birds' nests are often well hidden, or cryptic, and typically do not appear to be reused in following breeding periods (this may be one of their strategies for eluding predators). The nests are most often constructed in mossy depressions on branches high in the canopy of old growth forests, and the birds do not appear to add any extraneous nesting materials. Female murrelets lay one egg per breeding interval, which means that population growth for these animals is relatively slow. During the breeding season the birds will return to the nest to feed the chicks at dusk and dawn. The birds appear to form strong pair bonds, and breed repeatedly with the same mate throughout their lives.
The first marbled murrelet nest that was ever found was in California, in 1974. In Canada, the first nest was sighted in a Sitka Spruce standing in the Walbran Valley in 1990. As of 1997, 50 nests have been counted in British Columbia coastal forests. Nests are usually found within 40 km from the coast, but some have been found 70 km or more inland. The birds appear to have a preference for nesting in specific kinds of trees. Nests are most commonly found at elevations of 17 - 42 meters in Western hemlock, Mountian Hemlock, Sitka Spruce, Yellow Cedar and Douglas Fir trees that are at least 200 years old. Nests are most often found in trees that range between 300 - 800 years old.
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Why is their population threatened?
There are at least five good reasons why the future of the marbled murrelet may be in jeopardy. The population of these birds is threatened by a combination of both natural and human related factors.
1. Loss of nesting habitat - past and present clear-cut logging, and proposed 80-100 year stand rotations remove all potential nesting sites. The size of trees that murrelets are known to use are not replaced.
2. Gill-netting bycatch - while diving for food, murrelets get caught in the fine mesh of fisheries nets and are drowned.
3. Oil spills and petroleum pollution - toxins from pollution accumulate in the food chain and ultimately poison murrelets and other marine birds.
4. Increase in predator populations - researchers working on the Olympic Peninsula Predator Study have found that most natural mortality results from predation on eggs and nestlings and loss of fledglings that do not make it to sea. These birds also have low reproductive rates, meaning that the population grows slowly.
5. Climate change - El Nino events and global climate change effect ocean productivity and fish abundance, producing decreases in the food supply avalable to the marbled murrelet.
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At the present time, the bulk of the North American marbled murrelet population is located in Alaska, where their numbers reach 270,000. British Columbia holds an estimated 45,000-50,000 birds, located in highest density on the west coast of Vancouver Island. In Washington, murrelet numbers decrease to approximately 5,000 birds that are concentrated in northern Puget Sound; and in Oregon, only 2000-4000 birds remain, mostly in the central coast region. The smallest population of murrelets exists in northern coastal California, where there are only 1400-1700 birds left. The marbled murrelet is currently considered to be endangered in California and threatened in Oregon, Washington and British Columbia.
for a Marbled Murrelet status report (USGS) from 2006, click here
Terms of Endangerment - What do they mean?
The Committee on the Status of Endangered Wildlife in Canada(COSEWIC) is the official organization in charge of designating and listing wildlife species at risk. When a species is determined to be at risk, it is classified into one of the following categories:
Extinct: A species that no longer exits.
Extirpated: A species no longer existing in Canada, but occurring elsewhere.
Endangered: A species facing imminent extirpation or extinction.
Threatened: A species likely to become endangered if limiting factors are not reversed.
Vulnerable: A species of special concern because of characteristics that make it particularly sensitive to human activities or natural events.
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For listings and information on endangered species and how you can help,
visit Environment Canada's
Endangered Species web site
or the World Wildlife Fund - Canada - Conservation website
Conservation in Canada
In Canada, marbled murrelets are protected under the federal Migratory Birds Convention Act of 1917. They are further protected by provincial acts in British Columbia. A recovery plan was established in Canada in 1993 to attempt to raise the status of the marbled murrelet from threatened to vulnerable. Long-term goals of the recovery plan include reducing threats to their nesting habitat and reducing the risks to the birds while at sea.
The marbled murrelet is an excellent example of how marine and terrestrial ecosystems are linked. The health of marine ecosystems is dependent on the health of terrestrial ecosystems. Furthermore, murrelets represent a species that is being affected by human activity in very obvious and quantifiable ways. This gives us the opportunity to attempt to rectify the stresses on their population.
Links to Marbled Murrelet pages:
Dr. Alan Burger's Seabird and Marbled Murrelet Group
Simon Fraser University's Marbled Murrelet Recovery Team
to marine biodiversity index