Research

Tuning-in to Migration
by Sarah Warnock, PRBO Conservation Science

In the growing light of a subtropical sunrise, thousands of dowitchers forage in the broad shallows of a cattail marsh on the eastern edge of the Sea of Cortez, in the Mexican state of Sinaloa. Although still early spring, water temperatures will easily exceed 90 degrees Fahrenheit by noon. In just a few weeks, however, these dowitchers—and nearly 1 million other Sinaloa shorebirds—will be wading through ice melt some 5,000 kilometers north on the edge of the Arctic.

Many North American shorebird populations are in decline, due largely to a general reduction in wetland habitat quality and availability throughout the continent. The need for information about which habitats shorebirds use throughout their life cycle has sparked an international team of researchers, land managers, and conservation organizations to work together to learn how stopover, breeding, and wintering sites along the Pacific Flyway are connected.

Over the past 10 years, researchers Mary Anne Bishop, John Takekawa, and Nils Warnock have collaborated with biologists from more than 30 wetland areas to track long-billed dowitchers, western sandpipers, and dunlins from California and Washington to western Alaska. This year, they began working with Mexican biologists Xico Vega and Guillermo Fernandez on a new project to follow radio-marked shorebirds migrating from Mexico.

In Spring 2002, team members from California’s Salton Sea to Alaska’s Yukon Delta sat poised, ready to track 29 long-billed dowitchers and 59 western sandpipers radio-marked in Sinaloa’s Santa Maria Bay. It was a long wait. For several weeks, most of the birds remained at the banding site, but when they left, the birds traveled rapidly, averaging 500 kilometers per day. Most western sandpipers flew north along the Sea of Cortez, through California’s Central Valley, then cut over at San Francisco Bay, where they rested and foraged for several days before continuing up the coast to breeding sites in western Alaska.

Most dowitchers, however, were never heard from again. Despite good coverage of coastal and inland wetlands along the Pacific Flyway, the team found only one—in western Nevada. These dowitchers likely are migrating much further inland than the western sandpipers.

This project will help to define migration and habitat-use patterns of shorebirds and provide a new southern reference point from which to gauge the length of stay in northern wetlands, an important determinant for population estimating. Additionally, the project hopes to highlight the role of Sinaloa’s wetlands as critical habitat for shorebirds. Its coasts and bays remain a premier site for millions of wintering and migrating shorebirds, yet they are largely unprotected. And, environmental pressures are mounting. Water diversion, agrochemical runoff, and an increasing commercial shrimp industry continually threaten these habitats.

Habitat conservation for international migratory species will depend upon the understanding of the biological function of individual sites used throughout the year, as well as upon international partnerships in conservation planning, monitoring, and research.

For more information, contact Nils Warnock, PRBO Conservation Science, 4990 Shoreline Highway, Stinson Beach, California 94970, (415) 868-0371 extension 308, nilsw@prbo.org.

Sinaloa Migration Project Partners

Prince William Sound Science Center
U.S. Geological Survey
PRBO Conservation Science
Simon Fraser University
Pronatura Noroeste-Mar de Cortes
USDA Forest Service
U.S. Fish and Wildlife Service
Pacific Coast Joint Venture
Chase Wildlife Foundation
Goldman Fund
National Fish and Wildlife Foundation

On the Trail of Black Scoters
by Matthew Perry, U.S. Geological Survey and Keith McAloney, Canadian Wildlife Service

The location of breeding and molting areas of some seaduck species is uncertain, and little is known of seaducks' migrational paths and of habitats used during migration, breeding, and molting.

The black scoter is of special concern among the seaducks, because it is both the least common of the three scoter species and the least studied. The Continental Technical Team of the North American Waterfowl Management Plan's Sea Duck Joint Venture recommended that research on this species be conducted to learn more about black scoter movements and to delineate its breeding and molting areas. The team received funding to implant satellite transmitters on this species in Baie des Chaleurs and Restigouche River in New Brunswick, Canada, with the purpose of delineating populations and identifying habitat affinities for staging, breeding, and molting.

A variety of capture techniques was tested in the Restigouche River during April 2002, including the use of net guns, mist netting, and night lighting. Only the latter technique was successful in catching the scoters. For two consecutive nights on the river in early May, researchers captured 13 black scoters: 11 males and 2 females. Scoters, numbering close to 100,000, were at the capture sites courting and feeding and were not too concerned about the lights or the boats. The weather conditions were ideal for catching the birds: a high percentage of cloud cover and light precipitation.

Scientists transported all captured birds to a veterinary hospital where a U.S. Geological Survey veterinarian implanted a 39-gram Platform Transmitting Terminal device into the abdominal cavity of each duck. The transmitter's external antenna was passed through the back of the duck using a surgical catheter. Following surgeries, ducks were monitored for 1 day before being released at the site of capture on the Restigouche River.

Tracking data posted daily on the Internet showed the scoters moving from the Restigouche River for a lengthy stop on the St. Lawrence River. The birds appeared to use the central parts of northern Quebec's boreal forest as breeding areas. Ten of the 11 male scoters eventually went to James Bay for the July molting period. This information will help waterfowl managers to better understand and anticipate problems that black scoters may confront in their movements, and it will enhance scoter monitoring and management capabilities.

For more information, contact Matthew Perry, U.S. Geological Survey, Patuxent Wildlife Research Center, 11410 American Holly Drive, Laurel, Maryland 20708, (301) 497-5622, matt_perry@usgsu.gov, www.pwrc.usgs.gov/resshow/perry/scoters/default.htm, or Keith McAloney, Canadian Wildlife Service, 17 Waterfowl Lane, Sackville, New Brunswick E4L 1G6, (506) 364-5013, keith.mcaloney@ec.gc.ca.

Radios Lead Scientists to Marbled Murrelets Nests
by Catherine Puckett, U.S. Geological Survey

Humboldt State University (HSU) and U.S. Geological Survey (USGS) researchers are conducting a 3-year study of the effects of human-caused disturbance on marbled murrelets.

This small seabird, about 8 inches long and weighing less than a half-pound, feeds on small fish and invertebrates in the ocean, using their wings to "fly" through the water. They are unusual among seabirds because they are often solitary or found in groups of two or three instead of the large social groups of many seabirds. Except for when these birds nest and raise young, they spend their life on the ocean. Even stranger, though, is that these chubby little birds with whirring wings and a fast flight, nest inland 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. In California, the bird is State-listed as endangered. Until this study began 2 years ago, only a few marbled murrelet nests had ever been found in California—in fact, no nests had ever been discovered until the 1970s.

In 2001, USGS and HSU scientists radio-marked 23 birds; in 2002, they marked an additional 44. Researchers captured the murrelets at sea from a Zodiac boat using a spotlight and dip net. The birds spend the night at sea before returning closer to shore to feed at sunrise. Each member of a breeding pair will return to its nest, switching places with its mate before or at sunrise for a 24-hour stint attending the nest.

Scientists transported captured murrelets to the RV Coral Sea, an HSU research vessel, where birds were examined for a broodpatch and underwent an ultrasound exam to determine gender—externally marbled murrelet males and females look alike. A research team weighed the birds, took body measurements, and drew blood to gather information about sex and genetics. Finally, an HSU veterinarian attached a tiny radio transmitter—less than one-half the size and weight of a nickel—to each bird. The birds were then returned and released near their capture sites.

These radio-marked birds have provided essential information on movements, timing of nesting, and preferred habitats. Daily, ground and airplane crews tracked birds' movements on the ocean and inland during the breeding season from April to August. All murrelet nests were found in old-growth trees. Scientists found 5 nests in 2001 and 22 in 2002. Researchers are currently assessing nest success. At sea over the breeding season, the radio-marked birds ranged from Punta Gorda, California, to Newport, Oregon, a distance of about 390 miles.

Since the marbled murrelet is now restricted to small areas of its former range because of the loss of old-growth forests, it is vital that land managers have sound information upon which to base management decisions that affect this threatened bird of the land and sea.

For more information, contact William Boarman, Research Wildlife Biologist, U.S. Geological Survey, Western Ecological Research Center, San Diego Field Station, 5745 Kearny Villa Road, Suite M, San Diego, California 92123, (858) 637-6880, william_boarman@usgs.gov, or Richard Golightly, Professor of Wildlife, Humboldt State University, Department of Wildlife, Humboldt State University, Arcata, California 95521, (707) 826-3952, rtg1@humboldt.edu.

Marbled Murrelet Research Partners

U.S. Geological Survey
Humboldt State University
National Park Service
U.S. Fish and Wildlife Service
U.S. Bureau of Land Management
California Department of Fish and Game
California Department of Parks and Recreation
California Department of Transportation

Planning, Implementation, and Evaluation on the Canadian Prairies
by David Howerter and Michael G. Anderson, Institute for Wetland and Waterfowl Research

Editor: This is the second in a series of articles on the findings of the 8-year Prairie Habitat Joint Venture Assessment Project.

By the mid 1980s the situation seemed bleak. Up to 80% of the landscape across the vast Prairie Pothole Region (PPR)—the heart of duck country—had been converted to agriculture. Ponds were dry over much of the region and duck populations were in decline. In 1986, however, the most ambitious wildlife management plan ever conceived sprang to life with the signing of the North American Waterfowl Management Plan (Plan).

The Plan identified the PPR as the highest priority area for habitat conservation. Much of this vast area lies within the Plan’s U.S. Prairie Pothole Joint Venture and the Canadian Prairie Habitat Joint Venture. The latter joint venture’s conservation goals are to protect and secure 3.6 million acres of wetland and related upland habitats.

Prairie waterfowl managers were immediately challenged to make program decisions without knowing the potential implications of their actions. To help design habitat projects, joint venture partners took advantage of the newly developed Mallard Productivity Model (Model) that was developed by U.S. Fish and Wildlife Service researchers in Jamestown, North Dakota. The Model synthesizes the best available data on mallard ecology into a single package and predicts duck production benefits on critical habitats.

In spite of the Model’s success, many questions remained unanswered. Habitat and population management uncertainties tended to fall into one of four categories, each bringing their own challenges to managers:

Ecological Uncertainty
There are competing hypotheses about the nature of populations or ecosystem dynamics.

Environmental Variation
What managers cannot control is important to often unknown degrees, for instance, annual variation in precipitation in the PPR.

Partial Controllability
Managers cannot fully control the system they are managing. For example, a manager can attempt to affect cover quality by rotating cattle, but outcomes are uncertain.

Sampling Error
Sampling error provides a source of uncertainty when anything in nature is estimated.

All of these uncertainties can undermine management decisions. Given the enormous challenge of restoring waterfowl populations on the prairies, the size of the joint venture’s investment, and the aforementioned uncertainties, the partnership incorporated evaluation as a fundamental component of the joint venture’s management strategy.

Since 1991, the Joint Venture Assessment Team has worked to reduce the uncertainties. By 2000, a study of 27 joint venture project sites had been completed. The team had collected information on 16,000 nests, had completed reproductive histories on 3,600 radio-marked mallard hens, and had collected survival information on 600 mallard broods. Study objectives were to

• evaluate the key hypothesis that duck hatching rates were related to the amount of perennial nesting cover;
• evaluate the effectiveness of various joint venture habitat programs; and
• evaluate the biological assumptions within the Model.

Future issues of Birdscapes will feature findings of this study and reveal how managers have adapted new information and maximized their return on conservation investments. The update to the Plan in 2003 (currently in development) advocates similar approaches to regional planning, implementation, and evaluation in an adaptive framework.

For more information, contact Michael G. Anderson, Director, Institute for Wetland and Waterfowl Research, Ducks Unlimited Canada, P.O. Box 1160, Stonewall, Manitoba, Canada R0C 2Z0, (204) 467-3231, m_anderson@ducks.ca.