Brachyramphus marmoratusmarbled murrelet

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Geographic Range

Shoreline regions of the north Pacific Ocean: Western - Japan to Kamchatka, Russia, Eastern- central California to southern Alaska.

Habitat

The general habitat of the Marbled Murrelet is near coastal waters, tide-rips, bays, and mountains. Nesting sites are in higher elevations, exclusively in old growth forests of 175-600 years in age (barring a few ground nests on Alaskan Islands). Nest sites are large, moss covered, horizontal branches with an average height of 45 meters. The sites are often a substantial distance from the coast (Peterson, 1961; Carter and Morrison, 1992; Singer, 1990).

Physical Description

The Marbled Murrelet is a very small, chubby, sea bird that seems to lack a neck. It has a dark brown to black dorsum and a white venter and throat. The nonbreeding plumage includes a strip of white between the back and the wing, thus the name "marbled". The breeding plumage is dark brown dorsally; ventral feathers are white tipped with brown. Males and females are of approximately the same size, 9.5-10" wingspan. Bill length is 13-18 mm; wing length (relaxed) is 120-140mm. The voice of the Marbled Murrelet is a sharp "keer" or lower "kee."

Reproduction

The Marbled Murrelet breeds on mountains near the coast. Breeding season is from mid-April to the end of August. Females have been collected with shelled eggs in their oviducts from April 23 to July 13. The murrelet has single egg clutches. Murrelets may not fledge young until mid-September, based on a 30-day incubation and a 28-day rearing period. Nesting sites are almost exclusively in old-growth forests, yet some have been found in cavities in subalpine areas, and on the ground on islands. Murrelet eggs are yellowish and spotted. The first known nest was found in a rock slide far above the timber line at 1900 ft. on Chicago Island, Alaska, on June 13, 1931. (Peterson,1961; Carter and Morrison, 1992).

Lifespan/Longevity

Behavior

During courtship, the murrelet extends its beak upward in display, calls shrilly, paddles rapidly in unison with its mate for several minutes, and then dives repeatedly. Once the egg is produced, the male and the female murrelet divide the responsibility of incubating the lone egg in the nest. Upon hatching, the nestlings are fed larger prey than that ingested by the parents. The Marbled murrelet can fly up to 100 km one way to the sea to look for food for the young. After the rearing period, murrelet fledglings fly to the sea when they leave their nest. Marbled murrelets occur in loose aggregations in predictable locations near dependable food sources. Groups of one or two birds comprise 63% of all sightings, but aggregations of 100-3197 birds have been reported.

Marbled Murrelets migrate a relatively small distance southward, less than 1000 miles, in the winter months. Members of the Gulf of Alaska population may overwinter in bays of southeastern Alaska and northern British Columbia (Carter and Morrison, 1992).

Communication and Perception

Food Habits

An adult murrelet was observed carrying a fish, presumably for a hatchling. Murrelets eat primarily fish, including Pacific sandlance, Pacific herring, and seaperch. They forage for food solitarily or in pairs, sometimes amongst mixed species feeding flocks (Carter and Morrison, 1992).

Economic Importance for Humans: Positive

Increasing numbers of people are spending considerable sums of money to reach marine bird viewing areas off the coasts of North American States and Provinces. These "nonconsumptive pursuits" (Barry, 1979) contribute significant amounts of money to regional economies. Also, there are indirect commercial benefits. Marine birds play significant roles in their complex ecosystem. Disruption of that ecosystem by the extinction of sea birds could have an adverse affect on the fishing industry. Marine bird excrement, (.12-.24 million tons annually!!) is especially rich in nitrates and phosphates, which phytoplankton, the basis of ocean food pyramids, requires (Berry, 1979).

Economic Importance for Humans: Negative

If additional research finds that the marbled murrelet lives exclusively in old-growth forests and that their numbers decrease proportionally with the decrease in acres of forest, then it could be deemed an indicator species thus a justifiable deterent for further logging operations. The decrease in logging leads to a loss of income and jobs in the logging industry (Carter, Morrison).

Conservation Status

The Alaskan population is estimated at 250,000 birds, centered in south central and south eastern parts of the state, but extending into Bristol Bay and along the Aleutian Islands. This represents the bulk of the North American population. Logging efforts are expanding in the areas of the greatest murrelet population. Continued logging will produce major declines in murrelet numbers. Inland records from British Columbia, Washington, and Oregon suggested the presence of nests in old growth forests, although none had been found prior to 1990. Marbled Murrelet numbers in British Columbia are an estimated 45,000-50,000 birds, with the highest density on the west coast of Vancouver Island. The Marbled Murrelet population of Washington is estimated at 5,000, centered in the northern Puget Sound area. Oregon's population is estimated at 2,000-4,000 birds, located mostly in the central coastal region. There is also a small population of murrelets, (1400-1700 birds) on the north central coast of California.

Threats include mainly the loss of old-growth forests (all locales), some mortality from gill nets (responsible for the annual death of 7.8% of the British Columbia population), and oil pollution (Alaska and Washington). Very little of the existing old-growth forests are currently protected. One locale of substantial old growth forest in British Columbia was expected to decrease 95% in 50 years due to harvest schedules. Four of the five locations where fledglings were found in Washington state have been logged. Of Oregon's old growth forests, 44% is in stands of less than 32 hectares or within 122 meters of a clearcut. This isolation of small patches of forest may decrease reproductive success and increase predation at nest sites. In California, only 4% of the original acreage of Redwood trees is currently protected. This obliteration of habitat could be responsible for the sparse numbers of murrelet in California.

The Marbled Murrelet is considered endanged in California, and threatened in Oregon, Washington, and British Columbia. Its low reproductive rate prevents fast recovery from population decreases. The Marbled Murrelet is one of the few species of alcids whose known and suspected nesting habitat is not protected by federal refuge designation. Several lawsuits have been filed to defer the logging of old-growth forests where murrelets are known or suspected to live. In order to save the habitat of the marbled murrelet there need to be larger forest reserves and/or substantial changes in the logging practices.

Ground searches produced only 15 nest locations up until 1987

Tree searches since then have produced 19 nest locations in old growth forests. Due to the difficulty of locating the nests of these elusive birds, it is necessary to implement plans for further research before the Marbled Murrelet becomes an indicator species such as the spotted owl (Carter and Morisson, 1992).

Other Comments

Closely related species include: (1) Kittlitz's Murrelet, Glacier Bay, Alaska and north. (2) Least Auklet, Aleutian Islands and Bering Sea, ranges do not overlap. (3) Cassin's Auklet, same geographic range. (Peterson, 1961)

Contributors

James Smart (author), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

World Map

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

visual

uses sight to communicate

References

Ainley, D.G. et al 1993. Beached Marine Birds and Mammals of the North American West Coast: A revised Guide to their Census and Identification. U.S. Dept. of Commerce.

Berry, T.W. 1979. Wildlife Research Report, "Social and Economic Values of Marine Birds". United States Dept. of the Interior.

Carter, H.R., Morrison, M.L. 1992. Status and Conservation of the Marbled Murrelet in North America. Western Foundation of Vertebrate Zoology.

Peterson, R.T. 1961. A Field Guide to Western Birds. Houghton Miflin Co. Boston.

Singer, S.W. et al 1990. Discovery an Observation of Two Tree Nests of the Marbled Murrelet. The Condor. The Cooper Ornithological Society.