Pacific Shorebird Migration Program- Tracking Shorebirds Around the Globe
Biologists from PRBO, USGS, The Global Flyway Network, and other partners are combining efforts to study the global migration patterns of shorebirds in the Pacific Basin.
As of March 17, 2008, the first Bar-tailed Godwits have taken flight from New Zealand to their summer breeding grounds in Alaska. Click here to view live maps.
To answer questions about how long-distance migrating shorebirds use the global landscape, biologists are safely attaching tracking devices to follow their movements. In 2007 and 2008, satellite tracking devices have been attached to Bar-tailed Godwits, Long-billed Curlews. In Summer 2007, Bristle-thighed Curlews in their breeding grounds of western Alaska.
Migration Program Summary
One group of shorebirds of particular conservation concern throughout the Pacific Basin (Fig. 1) includes the godwits and curlews, collectively called the Numeniini. This tribe of shorebirds consists of some of the largest, most charismatic, and far-ranging of the world’s shorebirds. Their annual cycles take them between hemispheres, their migratory flights span continents, and their appearance, behavior, and song have endeared them to humans for millennia. Yet relatively little is known about how individuals of these species, and shorebirds in general, use their global landscape - crucial knowledge for developing and implementing effective conservation strategies.
The Pacific Basin
PRBO Conservation Science (PRBO), the U.S. Geological Survey (USGS), and collaborators in various countries received funding from The David and Lucile Packard Foundation for an international, collaborative study using the latest remote sensing technology to fill key information gaps on how the Numeniini navigate within and across continents. During 2007-2008, four species (Bar-tailed Godwit, Hudsonian Godwit, Bristle-thighed Curlew, and Long-billed Curlews)—representative of the various migration strategies exhibited by the Numeniini—will be fitted with satellite telemetry tags and followed throughout their annual migration cycles throughout the Pacific Basin. For each species, we expect to learn the timing and routes of migration, temporal and spatial use of stopover and staging sites, and habitat needs. This information will not only guide effective conservation efforts for each species but also help scientists and conservation groups better understand the effects of global-scale threats to shorebirds, including habitat destruction, climate change, and the spread of infectious diseases.
Shorebirds, like most populations of water birds, face serious conservation threats primarily due to human-induced changes to their landscape (Terborgh 1989, Page and Gill 1994, Warnock et al. 2001, BirdLife International 2003, Zöckler et al. 2003, Australian Conservation Plan 2005). Habitat destruction, climate change, disease, increases in native and non-native predators, and changes in food supplies are thought to be key factors responsible for troubling downward trends in shorebird populations throughout the world. On a global scale, three times as many populations of shorebirds are declining as are increasing (Zöckler et al. 2003). In North America, almost half of the shorebird species for which adequate data exist (72 species) have suffered significant or apparent population declines (Brown et al. 2001, Morrison and Hicklin 2001). Throughout the East Asian and Australasian flyways, there is an overall lack of population trend data, but for those shorebird populations of known trend, 85% are declining and 9% increasing. Shorebirds inhabiting Oceania have probably suffered the most with 40% of the species (41 species) inhabiting this biome classified as globally threatened or near threatened (Zöckler et al. 2003).
Probably no group of shorebirds is of greater conservation concern than the Numeniini. Worldwide there are 13 species in this group, 12 (92%) that regularly occur within the Pacific Basin and 7 (54%) that breed in North America (Table 1). Globally, 85%, and in the Pacific Basin, 83% of Numeniini have formally been designated as species of conservation concern (Table 1; Brown et al. 2001, Morrison and Hicklin 2001).
Table 1. Range and conservation status of shorebirds in the tribe Numeniini. Shading denotes species commonly occurring within the Pacific Basin; bold denotes species breeding in North America. Taxonomy and systematics follow del Hoyo (1996); conservation status: IUCN (=Wetlands International ), Brown et al. 2001, USSCP (2004), and CSCP (2000).
1 Also one of nine target species for the US Fish and Wildlife Service’s Focal Species Strategy for Migratory Birds (USFWS 2005).
The development of effective conservation strategies for most members of the Numeniini has been problematic, since critical data are missing due to the difficulty in studying these birds. Curlew and godwit populations are generally small and they have some of the most complex migrations among all birds. Their breeding and non-breeding grounds are far removed from each other, ranging from 4,000 to over 11,000 km. Species such as Bar-tailed and Hudsonian godwits may fly over 25,000 km in a single year, using different routes to and from breeding grounds. On their breeding grounds, the Numeniini typically occur in low densities and establish huge, widely dispersed territories.
The primary negative impact on shorebird populations throughout the Pacific Basin has been and continues to be loss and degradation of habitat, particularly habitats in coastal marine environments. For example, the state of California lost 91% of its wetlands between the 1780s and the mid-1980s (Dahl and Johnson 1991), many of these critical to shorebirds (Page and Gill 1994). Along the west coast of Mexico, in the state of Sinaloa, over 21,000 ha of intertidal and mangrove swamps important to shorebirds have been converted to shrimp farms (Ducks Unlimited 2006). Vast amounts of intertidal flats critically important to shorebirds and other migratory waterbirds are still being reclaimed for human endeavors. For instance, in South Korea, annually, 1% of intertidal flats are being reclaimed for human development (Korean Wetlands Alliance 2006). The largest such project, the Saemangeum reclamation project, involves draining 30,000 ha of tidal flats and 10,000 ha of estuarine shallows representing what is arguably the most important shorebird site in South Korea, affecting shorebirds from around the Pacific Basin (Barter 2002, Woodley 2006).
In addition to habitat loss, there is an urgency to understand how global warming affects shorebird habitats, not only on the nonbreeding grounds where sea level rise threatens to inundate areas, but also on breeding areas in the Arctic and sub arctic where unprecedented rates of successional change are occurring on tundra and taiga landscapes. Climate change may also affect the wind systems that migrants use during long flights, potentially impacting their probability of survival, especially for the trans-ocean migrants. The looming specter of avian influenza throughout the Pacific Basin adds another key threat for these birds.
In order to develop effective conservation strategies for Numeniini to combat threats, we must understand how birds use their vast and complex landscape that for an individual may stretch from tundra in the Arctic to grasslands of Argentina. However, we know relatively little about how individual shorebirds move around the globe. Only recently, through improved tagging and tracking technologies, has it become possible to follow birds worldwide. Now, shorebirds the size of godwits and curlews can be tracked through space and time by using solar powered or implanted satellites tags. Such tags or platform transmitter terminals (PTTs) send digital signals to NOAA polar-orbiting weather satellites. The signal is detected and the location calculated by satellite during overpasses that occur every 1-2 hours (Kenward 1987, Samuel and Fuller 1996). Bird-borne PTTs are programmed to transmit for a few hours every 1-7 days, providing one or more locations with a rough accuracy of 1-10 km, thereby allowing for tracking birds anywhere on the earth.
Goals and Objectives
We will use PTT technology to gain previously unattainable data on the movements of Bar-tailed Godwit, Hudsonian Godwit, Bristle-thighed Curlew, and Long-billed Curlew. All four species are of high conservation concern as determined by the US and Canadian Shorebird Conservation plans (Donaldson et al. 2000, Brown et al. 2001), and relatively little is known about how individuals of these species migrate. Additionally, different life history aspects of these species are already under study by members of this proposed research team, so logistic difficulties in working with these species have been worked out and cost sharing with other funding sources is possible. Finally, these species have contrasting migration strategies, ranging from the longest non-stop migration known in birds (the Bar-tailed Godwit), to an intermediate length Pacific Basin oceanic migrant (the Bristle-thighed Curlew), to a relatively short-length interior western North American migrant (the Long-billed Curlew), offering opportunities to study the different physiological strategies these birds undertake to migrate.
Specific study objectives include:
- Determine the migratory routes of Pacific Basin Bar-tailed Godwit, Hudsonian Godwit, Bristle-thighed Curlew, and Long-billed Curlew.
- Identify intermediate stopover areas and estimate the length-of-stay at stopover areas.
- Evaluate inter-relationships of stopover sites around the Pacific Basin.
- Compare migratory strategies of different Numeniini species migrating different distances.
- Begin identifying key threats specific to Pacific Basin populations of Bar-tailed Godwit, Hudsonian Godwit, Bristle-thighed Curlew, and Long-billed Curlew and begin developing conservation frameworks for mitigating these threats.
- Improve public awareness of conservation issues pertaining to Numeniini and other shorebirds through outreach including web pages (e.g. USGS and PRBO web sites), presentations, and publications.
Understanding the migratory movements and breeding and non-breeding ground requirements of these shorebirds will help develop more effective conservation strategies for the threatened Numeniini by giving us a better understanding of how shorebirds move about the Pacific Basin. Satellite data gathered on these large species will also help us understand the movements of some of the small shorebirds for which we often lack movement data (although see Warnock and Bishop 1998, Warnock et al. 2004) such as the Sharp-tailed Sandpiper that appears to follow similar routes as the Bar-tailed Godwit.
Work will be done by an outstanding international, collaborative team of shorebird migration experts. This group has unparalleled experience in large-scale shorebird tracking programs throughout the world, and this proposed work will build on work that has already been done.
Robert Gill, M.Sc. – U.S. Geological Survey, 1011 E. Tudor Rd., Anchorage, AK 99503, Phone: (907) 786-3514
Nils Warnock, Ph.D. – PRBO Conservation Science, 3820 Cypress Dr. #11, Petaluma, CA 94954 (415) 868-0371 x308 nwarnock at prbo dot org
Phil Battley, Ph.D. - Research Fellow, School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand, Phone +64 (0)9 3737599 ext 87277
Brian McCaffery - U. S. Fish & Wildlife Service, Yukon Delta National Wildlife Refuge, P.O. Box 346, Bethel, AK 99559, Phone: (907) 543-1014
Gary Page, M.Sc. - PRBO Conservation Science, 3820 Cypress Dr. #11, Petaluma, CA 94954 , (415) 868-0371 x309
John Takekawa, Ph.D. - USGS Western Ecological Research Center, SFB Estuary Field Station, 505 Azuar Drive, Vallejo, CA 94592 USA tel:707/562-2000;
Daniel Mulcahy, Ph.D., D. V.M., Dipl. A.C.Z.M. - US Geological Survey Alaska Biological Science Center 1011 East Tudor Road, Anchorage, AK 99503, Tel: (907) 786-345
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