CORVALLIS, Ore. -- A multi-year study of the marbled murrelet, a threatened West Coast seabird that nests as far as 50 miles inland, aims to discover the animal's habitat needs and understand the reasons for the species' ongoing population decline in the Northwest.
In addition to determining the needs of this elusive bird, the study aims to help forest managers on public and private lands balance habitat conservation with timber land management.
The project is possible because of an increase in funding for research in the College of Forestry at Oregon State University provided by the state Legislature in 2015 with broad support from the timber industry and conservation groups. "We are investing in this project because all interests want to know the breeding habitat requirements of the marbled murrelet, so that land management decisions in our productive coastal forests benefit from the best data and science available," said Thomas Maness, dean of the college.
"Managing our forests is not just about producing timber. It's also about habitat. We need to understand where these birds go to nest and the best way to protect this species while actively managing our forests to produce timber revenue that is vital to state and local economies."
The project is managed through the Institute for Working Forest Landscapes at Oregon State and is a joint effort between researchers at the College of Forestry and the Department of Fisheries and Wildlife in the College of Agricultural Sciences.
The research project aims to answer questions about how forests can be managed for both murrelets and timber. "Murrelets prefer mature, late-successional forests, but they may not be restricted to old growth," said James Rivers, professor of animal ecology in the college and the lead scientist on the project.
"The goal of our project is to determine the murrelets' requirements for nesting, to learn more about where the birds are located on the landscape and to understand the factors that influence nest success and their relationship to active forest management."
The long-lived, dove-sized marbled murrelet spends most of its time in coastal waters dining on krill, other invertebrates and forage fish such as herring, anchovies, smelt and capelin. They nest in mature and old-growth forests and typically produce only one offspring per year, if the nest is successful.
Many seabird species, such as common murres, terns and gulls, tend to nest in colonies, but murrelets are comparatively solitary, nesting in the forest and sometimes within small groups. They typically lay their single egg high in a tree on a horizontal limb that is at least 4 inches in diameter, said Rivers.
Globally, marbled murrelets are one of the few seabirds that nest in this fashion. Scientists don't know why the birds have evolved this particular habit. "The end goal for these birds is to be very secretive and quiet so predators don't find their nests and they can produce young," said Rivers.
"We know we have nesting habitat for murrelets throughout our coastal forests. But we don't have large sample sizes of nests. If you look at data along the coast from California to Washington, central Oregon has the highest population based on surveys of birds at sea. The Siuslaw National Forest is in that area, and we think the birds may be going in there to nest."
Only 75 nests have been documented in Oregon since OSU avian ecologist Kim Nelson, a scientist on the project, identified the first one in 1990. "I was on Marys Peak in 1985 when I heard a seabird and wondered what this bird is doing so far from the ocean," said Nelson. She saw murrelets that year at some of her study sites in the Coast Range.
Three years later, she began a series of systematic murrelet surveys funded by the Oregon Department of Fish and Wildlife and the U.S. Forest Service. Progress was slow, since identifying the birds required people to be physically present at specific locations by dawn for extended periods of time and to listen for the birds' smooth, high-pitched call. Nonetheless, they found more than 20 active nests and hundreds of occupied sites throughout the Oregon Coast Range.
In a project funded in the 1990s by the Oregon Department of Forestry and the National Council for the Advancement of Air and Stream Improvement, a forest-products industry research organization, Nelson and other scientists climbed about 5,000 trees in a search for murrelet nests. That study identified an additional 45 nests in Oregon and more in Washington, although most of those nests were not active. "Thus, there is limited information about whether those nests were successful and what factors played a role in any nesting failures that may have occurred," said Rivers.
Along the West Coast, marbled murrelets have been found as far south as Baja California, where they winter, and as far north as the Aleutian Islands. Their populations have been declining by about 4 percent a year in Washington, Oregon and California.
In California, the birds are federally listed as threatened, primarily because of low recruitment of new individuals into the population. The Alaska population is not considered endangered, although population declines have been documented there as well.
The first known murrelet nest was found in the California redwoods in 1974. Based on studies of known nests in the listed range, scientists have found that Steller's jays and other corvids, such as crows and ravens, are the main predators of murrelet nests.
The researchers aim to learn more about how human activities in the forest affect the risk that predators pose to murrelets. Little is known regarding the effects of logging, camping and the presence of garbage dumps on predator numbers and the chances that predators will find and depredate murrelet nests.
Other unknowns about the birds include how long they live (estimated to be 10 to 15 years), the juxtaposition of nesting to foraging areas and whether individual birds shift their primary feeding areas along the coast from one place to another.
To answer such questions, members of the OSU research team have been capturing murrelets on the ocean, tagging the birds with miniature VHF radio transmitters and then tracking where they go. Only adult birds with a "brood patch," a spot with little or no feathers on the breast, are tagged. Such patches indicate that the bird is preparing to breed and incubate an egg.
Last spring, researchers succeeded in capturing and tagging 61 birds. "That was a huge success. We weren't even sure we'd be able to capture birds on the open ocean," said Rivers.
Other research methods include the use of infrared cameras to watch nests 24/7, drone-mounted cameras to search for nests in the forest canopy and a customized audio recorder that can record murrelet calls and help researchers document inland movements.
When the birds are stressed by a lack of food, they have been known to forgo reproduction and not lay any eggs, said Nelson. This year, some of the birds that were captured on the central Oregon coast have been tracked to areas south of Cape Blanco where foraging conditions may be better.
Long-term studies such as this enable scientists to understand how birds adjust to unpredictable ocean conditions, which can influence murrelet behavior from year to year. "We will be able to document rare conditions that might not be detected by a typical two- to three-year study," said Rivers. "Those conditions might have important consequences for the population."
Other scientists on the project include Dan Roby, ornithologist in the Department of Fisheries and Wildlife. In the College of Forestry, participating researchers include Matt Betts, associate professor and specialist in landscape ecology; Joe Northrup, postdoctoral scientist; and Cheryl Horton and Lindsay Adrean, faculty research assistants.
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