“Close up, though, brown becomes sooty brown, brownish black, chocolate, rufous, rusty-buff, light tan, and cinnamon on the bird’s back, head and wings. Brown becomes light brown marbled with soft whites on its throat, flanks and breast.”
— Rare Bird: Pursuing the Mystery of the Marbled Murrelet, by Maria Mudd Ruth
By Nick Houtman
In a small plane high above the Oregon coast last spring, researchers heard the signal they were looking for. The soft ping in their earphones told them that a bird with a tiny transmitter glued to its back was bobbing on the ocean swells below. One of the crew radioed the news to Oregon State University in Corvallis.
It was the first of many signals received from some of the more than 60 birds that had been tagged in hopes of following their movements. Over the following days and weeks, however, things turned quiet. The pings gradually disappeared and with them, at least temporarily, so did the plans to learn more about threats to a creature that has eluded scientists for decades. A few weeks later, the researchers were in for a surprise.
Called “The Enigma of the Pacific” by Canadian naturalist Charles Guiget, the marbled murrelet dines on krill, capelin, anchovies and other small prey at sea. Once she has mated and built up her own reserves, it’s time to nest. She darts inland. And that’s where the fortunes of this dove-sized bird intersect with West Coast forests. Large old trees are thought to be essential for murrelets to nest and raise their young, but murrelet populations are declining, and scientists don’t know if the reduction in older coastal forests is the only bottleneck or if other factors, such as predation or conditions at sea, might be making it harder for the birds to reproduce.
“Murrelets are a species of two worlds,” says Jim Rivers, assistant professor in the College of Forestry and leader of the Oregon Marbled Murrelet Project. “They’re a marine bird. They get all their food from the ocean, but they have this curious behavior of moving inland to nest.” For reasons not fully understood, murrelet populations have declined as much as 90 percent in California, Oregon and Washington. The bird is listed as threatened under the federal Endangered Species Act in all three states.
Along the West Coast, marbled murrelets range as far south as Santa Cruz, California, where they winter, and as far north as the Aleutian Islands. Their populations have been declining by about 4 percent a year.
With funding from the state Legislature, forest ecologists and ornithologists at Oregon State are conducting a long-term, large-scale study to determine what the marbled murrelet needs to survive. In addition, the scientists aim to provide forest managers on public and private lands with information that can be used to balance habitat conservation with timberland management. Leading the project are Rivers and Matthew Betts in the College of Forestry and Kim Nelson and Dan Roby in the Oregon State Department of Fisheries and Wildlife.
Management of Oregon’s productive coastal forests requires a balance between timber production and habitat protection for species such as the marbled murrelet, say leaders in the College of Forestry. The college’s investment in this project spans a range of interests from timber companies to environmental organizations. Decisions benefit from the best data and science available.
Gone to Find Food
Last spring, when the first transmitter signals faded and others failed to show up, the scientists decided to expand their search. They sent planes as far north as the Olympic Peninsula (they were unable to access Canadian air space) and as far south as the San Francisco Bay Area. And that’s when they found signals from the birds they had tagged along the central Oregon coast.
In short, the murrelets had simply picked up and left. Ocean conditions were known to be poor; the cupboard was bare. So the murrelets had gone to find food elsewhere, and the nests that the researchers had hoped to observe never materialized. When the birds are stressed by a lack of food, they have been known to forgo reproduction and not lay any eggs, says Kim Nelson, an ornithologist and wildlife ecologist in the Department of Fisheries and Wildlife and a scientist on the project.
Despite these unexpected findings, the project continues to receive broad support from the timber industry and conservation groups. “The goal of our project is to determine more about the murrelets’ requirements for nesting,” says Rivers, “to learn more about where the birds are located on the landscape and to understand more about the factors that influence nest success and their relationship to active forest management.”
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 a single egg high in a tree in a depression on a horizontal limb that is at least 4 inches in diameter.
“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,” Rivers says. 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.
Marbled Murrelet Facts
Marbled murrelets are known to cruise about 60 miles per hour between their nests and ocean feeding grounds. One bird was clocked by radar at 98 miles per hour.
Home on the Branch
In Oregon, murrelets typically find a large branch, at least 4 inches in diameter, with moss or other substrate to lay their eggs. They do not build a nest.
Marbled murrelets are members of the Auk family, which include puffins, murres and guillemots. All except three species of murrelets nest in colonies along the coast.
What’s in a Name?
Loggers had a different name for the marbled murrelet. They called it a “fog lark,” because of its secretive nature and ventriloquistic dawn calls.
Searching for Murrelets
The first known murrelet nest was found near Santa Cruz in the California redwoods in 1974. In Oregon, only 75 nests have been documented since Nelson 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,” she says. 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, throughout the Oregon Coast Range, they found more than 20 active nests and hundreds of occupied sites.
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.
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. 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.
Drones and Cameras
This past spring, the OSU research team again captured and tagged murrelets with miniature VHF radio transmitters. 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.
Other research methods include the use of cameras to watch nests 24/7, drone-mounted infrared cameras to search for nests in the forest canopy and a customized audio recorder that can pinpoint murrelet calls and help researchers document inland movements.
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,” says Rivers. “Those conditions might have important consequences for the population.”