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Endangered Species:
Marbled Murrelet
About the Marbled Murrelet
Where Murrelets
Occur
Headwaters Forest Project
Desolation Sound Murrelet
Project
Refining the Inland
Survey Protocol
The Effects of Nest Predation
Gill Net Fisheries and Murrelets
Ocean Conditions and Murrelets
MARBLED MURRELET (Brachyramphus marmoratus)
The marbled murrelet, a small seabird which nests in the coastal, old-growth forests of the Pacific Northwest, is listed as a threatened species under the Endangered Species Act. In North America, the birds' range stretches along the Pacific
coast from the Bering Sea to central California, with the largest populations occurring in southeastern Alaska and northern British Columbia.
The murrelet's dependance on old-growth nesting habitat and use of coastal marine feeding areas have brought it into frequent conflict with human economic interests, especially in the southern portion of its range where small, geographically concentrated populations are especially vulnerable to extirpation. However, both natural and human-related factors may be contributing to the species' decline; potential causes include the loss of suitable nesting habitat, accidental death in gill-nets, oil pollution, increases in predator populations, and declines in food supplies due to recent El Nino events.
Since 1993, SEI has worked with a number of partners in order to produce baseline data on murrelet behavior and survival and to develop management options which protect the marbled murrelet. These projects have included at-sea surveys, the development of novel capture and tagging techniques and an inland survey protocol, and studies of nesting, dispersal and survival in Desolation Sound, BC. Other research is investigating the effects of nest predation, gill-net fisheries, and El Nino on marbled murrelet populations. Finally, SEI is continuing to work on the conservation of the murrelets inhabiting California's redwood forests.
Where do Marbled Murrelets Occur?
As mentioned above, marbled murrelets inhabit the pacific coast of North America from the Bering Sea to central California, just south of San Francisco Bay. A closely related species, the long-billed murrelet (B. perdix), occupies similar latitudes along the Siberian coastline and the Japanese archipelago.
In contrast to other seabirds, murrelets do not form dense colonies, and may fly 70 km or more inland to nest, generally in older coniferous forests. They are more commonly found inland during the summer
breeding season, but make daily trips to the ocean to gather food, and have been detected in forests throughout the year. When not nesting, the birds live at sea, spending their days feeding close to shore and then moving several kilometers offshore at night.
In 1993 SEI pioneered the use of aerial surveys along the Oregon coast, finding that most murrelets in the state live off the central and southern coasts. Together with our partners, the Oregon Department of Fish and Wildlife, Marbled Murrelet Study Trust, Menasha Corporation, and NCASI, we have continued this work and expanded our coverage to include Washington and northern California. These at-sea surveys will provide information on where murrelets occur, as well as estimates of their numbers.
Conserving Murrelets in California's Headwaters Forest
Pacific Lumber Company owns some of the last old-growth California redwood stands held in private hands. The Company has agreed a habitat conservation plan (HCP) with the federal and state governments. SEI was instrumental in the development of scientific studies that formed the basis of the agreement. SEI, along with the US Forest Service's Redwoods Sciences Lab, has been studying murrelets in the Headwaters and Pacific Lumber's other holdings, and has played a major role in forming the HCP's murrelet conservation strategy.
Under the HCP, there will be ongoing monitoring of murrelets in the forest and offshore. There will also be a research program, part of which SEI is carrying out. For details on this work, please visit our Headwaters Forest and Marbled Murrelet Population Viability Analysis pages.
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The Desolation Sound Murrelet Project
The Desolation Sound Murrelet Project
In 1997 and 1998, SEI cooperated with researchers from the Canadian Wildlife Service and Simon Fraser University to study the marbled murrelets of Desolation Sound, British Columbia. This program is now capturing and banding many birds every year, providing good estimates of survivorship and a wealth of new scientific information.http://www.sfu.ca/biology/wildberg/species/mamu.html
In addition to using floating mistnets, birds are caught by a new dip-netting technique developed in part by SEI scientists. Using this method, researchers head out at night in small rafts, sneak up on the birds in the water, attract their attention with flashlights, and scoop them up in nets. In 1998, 40 murrelets were captured and fitted with radio tags, leading researchers to 26 active nests, which were monitored to gain information on the birds' reproductive biology and nestling survival.
It has often been noticed that murrelets normally occur in groups of two at sea. We now know that these couples are in fact mated pairs, and that murrelets, unlike other alcid seabirds, are at least relatively monogamous. In addition, it has been shown that, rather than feeding at night, the birds move away from shore, a finding with significant implications for the management of salmon fisheries in the Pacific Northwest.Amazingly, one murrelet first banded in Desolation Sound, was recaptured during our San Juan island surveys (see photos http://www.sei.org/birdshow.html , and section on at-sea surveys below) and subsequently back in Canada. This report http://www.rsl.psw.fs.fed.us/projects/wild/ralph/ralph5.pdf verified speculation that murrelets migrate.
Refining the Inland Survey Protocol
Marbled murrelets are very difficult to detect when not at sea, making it hard to determine whether or not birds are using a given stand of forest. Apparently, this has lead to high rates of false negatives among forest surveys, meaning that occupied stands are often mis-classified as unoccupied, and consequently lost to timber cutting, because no murrelets were found there. False positives are also possible, where forest stands are erroneously thought to hold murrelets. Currently, this problem is addressed by surveying all potential habitat a minimum of twenty times over two consecutive years; both cumbersome and expensive, this approach ties up resources which might be more usefully applied to other murrelet research and conservation projects.
SEI scientists Daniel Grunbaum and Steven Courtney have begun work on redesigning and streamlining the marbled murrelet inland survey protocol. By using mathematical models of surveying techniques in stands with varying rates of detectability and utilization, they have shown how differences in detection probability would lead to surveying biases and have produced statistical estimates of which utilized habitat types would be detected by a given survey protocol.
More recently David Bigger has, using radar, shown that these sorts of errors do occur. These results will be important to any effort to redesign the survey protocol.
Dr. David Bigger is studying murrelets in the Headwaters region of northern California. The overall goal of the program is to determine whether numerical data from inland surveys can be used to determine murrelet densities in forest stands. David is also working on the relative accuracy of radar and audio-visual methods in detecting murrelets. Reports of David's work are available
http://www.sei.org/headwaters/main.html.
Photos of radar equipment in action
Marbled murrelets are killed and eaten by a variety of predators. Adult birds are eaten by falcons and owls, but the biggest threat to the species is thought to be predation on the eggs and chicks while still in the nest. This threat may be getting worse for two reasons. Fragmentation of older forest breeding habitat by timber harvests may make the nests more vulnerable to predators which frequent younger stands or forest edges; additionally, some predators, such as crows and ravens, are becoming more abundant because of food (garbage) provided by humans.
Olympic Peninsula Predator Study:
Directed by SEI biologist John Marzluff, researchers have placed artificial nests containing fake murrelet eggs and chicks high in the forest canopy on the Olympic Peninsula. By monitoring the nests with automatic video cameras and photographic equipment, would-be murrelet predators are caught in the act of raiding the nests, providing information not only on rates of predation, but also on the types of animals responsible. Unsurprisingly, ravens, crows and jays take many eggs; however, unexpected results demonstrated that chicks are eaten by flying squirrels, another interior forest species.
These results, in combination with data on corvid habitat use, argues against the existence of strong predator mediated edge or fragmentation effects in murrelets. However, corvid numbers are definitely increasing, and radio-telemetry studies of ravens show that these predators are commuting many kilometers to feed at town dumps. As rural areas become more developed, it is likely that these human-associated predator species will come into more frequent contact with marbled murrelet populations.
Partners in this project include the University of Washington, NCASI, Rayonier Timberlands, Washington Department of Natural Resources, the US Fish and Wildlife Service, and the US Forest Service.
Oregon Predator Study:
Dr. Marzluff is also studying the ecology of Steller's jays in Oregon. These smaller corvids are thought to be one of the marbled murrelet's main predators. To date, this research has found that the jays are habitat generalists, active in all forest types. However, they may be most abundant in clearings following some harvest practices. This result may be used by our partner, the Oregon Department of Forestry, to develop new harvest guidelines.
Gill-Net Fisheries and Murrelets
There is significant concern among wildlife managers that seabirds may be accidentally caught and drowned in salmon gill-nets, particularly in the heavily utilized waters of Puget Sound. In conjunction with tribal fishermen and the Northwest Indian Fisheries Commission, SEI has undertaken marine surveys to accurately map the distribution of murrelets in critical fishing areas.
In addition, SEI research has shown that the birds stop feeding and move off-shore during the night, making them less vulnerable to entanglement. Tribal fisheries managers have used these data to plan fishing operations which conserve murrelets while still allowing a normal salmon harvest. Other partners in this project include the National Marine Fisheries Service, US Army (Fort Lewis) and members of individual tribes. The Executive Summary of our final report, Seabird Surveys in Puget Sound 1996, is now online.
Ocean Conditions and Murrelets
El Nino and other ocean events may affect the productivity of the sea, since warm water usually produces less food than cold water. Ocean conditions might therefore affect marbled murrelets, which may breed more successfully in areas with higher marine productivity. Dr. Bruce Menge, of Oregon State University, has been monitoring phytoplankton production at numerous sites along the Oregon coast. Some sites show consistently high or low production. Not surprisingly, marbled murrelets appear to be more abundant in those areas with more food, indicating that some areas may be of more importance to the species than others. This information is potentially critical for deciding where to concentrate conservation efforts.
Direct comments, questions or requests for information to Dr. Steven Courtney
