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Radios Lead Researchers to Nests of Elusive Marbled Murrelets

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captured marbled murrelet
Ready for release: Captured marbled murrelet after processing. Photograph courtesy of Humboldt State University.
It's 2 a.m., about 1 mile off the coast of Redwood National and State Parks in Humboldt County, CA, near the northernmost part of the state. In the pitch-black night, researchers talk quietly while they wait aboard the Coral Sea, a 90-foot-long Humboldt State University research vessel.

Patient waiting is an essential trait for those who study birds, especially "shy," seldom-seen birds. This time, researchers from the U.S. Geological Survey (USGS) and Humboldt State University have waited for an hour before their small talk and dozing between captures are broken by the sound of the two-way radio.

"Coral Sea, this is Orthmeyer in Mobile 1. We have a bird. We're en route."

What Dennis Orthmeyer, USGS research biologist, and the capture team have caught is a marbled murrelet, a seabird about 8 inches long and weighing less than a half-pound. Marbled murrelets feed on small fish and invertebrates in the ocean, using their wings to "fly" through the water. They are unusual among seabirds because they are commonly solitary or found in groups of two or three, instead of the large social groups of many seabirds. Except when these birds nest and raise young, they spend their entire life on the ocean. Even stranger, though, is the fact that these chubby little birds with whirring wings and a fast flight fly inland to nest on high branches of old-growth redwood and Douglas-fir trees.

In 1992, the marbled murrelet was listed as a Federally threatened species in California, Oregon, and Washington, primarily because of the loss of nesting habitat in old-growth forests. In California, the bird is State-listed as endangered. Until this study began in 2001, only a few marbled murrelet nests had ever been found in California. In fact, no marbled murrelet nest had ever been discovered until the 1970s. In 2001, USGS and Humboldt State University scientists found five nests, aided by radios on the birds. This year, the researchers radio-marked an additional 44 birds and continued the search for nests.

capture team on inflatable boat
Capture team: Capture team on inflatable boat heading out in mid-April for capture attempt. Photograph courtesy of Humboldt State University.
This particular murrelet is captured by scientists with many years of experience who used a spotlight and dip net to scoop up the bird as it rode the waves on the ocean where it was spending the night before returning closer to shore to feed at sunrise. Each member of a breeding pair will return to its nest, switching places with its partner before or at sunrise for a 24-hour stint attending the nest. The bird's travel at sunrise or sunset, when coastal fog is most prevalent, caused early loggers in the area to call it the "fog bird."

The capture team carefully transports the bird in a 14-foot-long inflatable boat to the research vessel, where a bird processing line is ready to go.

To keep the captured bird calm, the researchers handle the bird carefully and quickly with gloved and gentle hands, using low lights and talking quietly only when necessary. As soon as the bird arrives at the research vessel Coral Sea, the murrelet is placed in the hands of Humboldt State University seabird biologist Percy Hebert, who examines the bird to determine whether it has a broodpatch—a featherless area on its chest which indicates that the bird is nesting. The bird is then passed to Tom Jenson from the Center for Reproduction of Endangered Species in San Diego for an ultrasound, a technique being developed to discern whether a bird is a male or female, because the marbled-murrelet males and females both look alike.

After this, a measuring team quickly weighs the bird, takes its body measurements, and then draws a small bit of blood for information about sex, genetics, and blood characteristics to identify stress. This blood will be used for baseline information about the species, and in oil spills and other situations where the blood characteristics can be compared. Finally, veterinarian Rick Brown of Humboldt State University attaches a minute radio transmitter—less than half the size and weight of a nickel—to the bird. Then, a short while later, researchers transport the bird by a Zodiac boat to near its capture site, where the bird is released onto the ocean.

Five days later, a California Department of Fish and Game aircraft reports to researchers on the ground that they have located the bird inland from the coast.

The radio provides essential information on the movements, timing of nesting, and habitat of this secretive bird. By tracking the radio signals from these murrelets, biologists have been able to find murrelet nests, which are commonly 200 feet high in old-growth trees.

Knowing the secretive locations of these nests and more about the bird's life history is vital to effectively protecting this unique bird, say Dennis Orthmeyer and Richard Golightly, the two scientists leading this 3-year study of the effects of human disturbance on breeding marbled murrelets.

Orthmeyer, a scientist with the USGS' Western Ecological Research Center, and Golightly, a professor and scientist in the wildlife department at Humboldt State University, Arcata, are pleased because the radios have already led them to five murrelet nests that probably would never have been found through more traditional methods.

After capturing and releasing 23 marbled murrelets last year and 44 this year, the research team is intensively studying the movements and nesting status of the murrelets. Daily ground and airplane crews track the movements of the radioed murrelets on the ocean and inland during the breeding season from April to August.

radio-marked marbled murrelet on nest
Nest located: Radio-marked marbled murrelet on nest. Image from videotape, courtesy of Humboldt State University.
"The scanner is similar to the radio in your car," says Orthmeyer, "and the murrelets are all on different stations. So, if a murrelet signal indicates an inland location during the day, it's at a nest, and ground crews hurry to pinpoint the nest for further study."

Said Golightly, "One of our goals is to provide land managers of Redwood National and State Parks, as well as nearby landowners, with factual information that will enable them to make sound management decisions to help conserve this Federally threatened species. We hope to identify factors that may contribute to successful reproduction and future generations of marbled murrelets."

Since the marbled murrelet is now restricted to small areas of its former range because of the loss of old-growth forests, said Golighty, it is vital that land managers have good science-based information to maintain the successful nesting of the remaining birds.

This team of USGS and Humboldt State University researchers, along with staff from the National Park Service, the Bureau of Land Management, the U.S. Fish and Wildlife Service, and the California Department of Fish and Game, are studying nest locations, different types of habitat necessary for the birds, and general life-history requirements to understand how nesting murrelets respond to human disturbances or other human use of their nesting habitat.

Preliminary results from the first year of the study include the following:

  • All the nests the researchers found were in old-growth trees.
  • Of the five murrelet nests examined, three were probably successful in producing and raising young.
  • At sea, the radio-marked murrelets ranged over the breeding season from the mouth of Humboldt Bay to Brookings, OR, a distance of about 90 miles.

This project is supported by the USGS, Humboldt State University, the National Park Service, the U.S. Fish and Wildlife Service, the Bureau of Land Management, the California Department of Fish and Game, the California Department of Parks and Recreation, and the California Department of Transportation.

Related Web Sites
Western Ecological Research Center
U.S. Geological Survey (USGS), Sacramento, CA
College of Natural Resources and Sciences
Humboldt State University
Center for Reproduction of Endangered Species
San Diego Zoo
Redwood National and State Parks
U.S. National Park Service

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in this issue: Fieldwork cover story:
Gulf of Mexico Gas Hydrate

Tampa Bay Coring

North Carolina Coastal Erosion

Endangered White Abalone

Marbled Murrelets

Research Sediment Core Drilling Proposal

African Dust Microbiology

Outreach Tall Ships

Gulf of Mexico Teacher Workshop

Coastal Louisiana Interview

MRIB Makes Headlines

Meetings U.S. Commission on Ocean Policy

Numerical-Modeling Workshop

Staff & Center News WHFC Employees Farewell

Sound Waves Staff

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