Collaborative Approaches to the Study of Shorebird Migration and Conservation in North America.

Program for Regional and International Shorebird Monitoring (PRISM)
Shorebird Research Group of the Americas (SRGA)

Stephen Brown, Manomet Center for Conservation Sciences, Manomet, MA
sbrown@manomet.org

Introduction

The migration ecology of shorebirds presents special problems for conservation, and makes large scale collaborative programs essential. The Shorebird Conservation Plans for the U.S. and Canada led to the development of two major programs addressing shorebird migration and conservation at large spatial scales. The Program for Regional and International Shorebird Monitoring (PRISM) provides a single blueprint for addressing monitoring needs during migration, wintering, and breeding that were identified as critical for shorebird conservation. PRISM has three main components: breeding surveys in arctic, boreal, and temperate regions, migration surveys, and neotropical surveys. Site selection criteria and survey protocols are being developed that will be useful for monitoring efforts throughout the hemisphere.

The Shorebird Research Group of the Americas (SRGA), which also formed from the Shorebird Plans, determined that understanding the causes of shorebird declines would require a coordinated international, multidisciplinary effort. The group recently proposed the Hemisphere Shorebird Project, a collaborative approach to determining limiting factors for representative species through research on a hemispheric scale. This project will weigh the effects of the five most likely causes for declines across the range of several species, including habitat loss, climate change, predation, contaminants, and human disturbance. The SRGA is open to participation by anyone interested in shorebird research, and will be coordinated by an international steering committee.

Both of these programs could have potential application to work on austral migrants through the application of similar collaborative approaches, or modification of protocols developed for hemispheric migrants.

Program for Regional and International Shorebird Monitoring

Jonathan Bart, Brad Andres, Stephen Brown, Garry Donaldson, Brian Harrington, Heather Johnson, Vicky Johnston, Stephanie Jones, R. I. G. Morrison, Michel Sallaberry, Susan K. Skagen, and Nils Warnock

PRISM is a single blueprint for monitoring shorebirds in Canada and the United States, and is based on the Canadian and U.S. shorebird conservation plans (Brown 2001, Donaldson 2001). The goals of PRISM are to:

1. Estimate the size of breeding populations of shorebirds in North America.
2. Describe shorebirds’ distribution, abundance, and habitat relationships.
3. Monitor trends in shorebird population size.
4. Monitor shorebird numbers at stopover locations.
5. Assist local managers in meeting their shorebird conservation goals.

A complete description of PRISM is available on the web at http://wss.wr.usgs.gov/data/document_main.html. Most of this effort in development of PRISM has focused on the primary goal of estimating trend in population size because we believe that is technically the most difficult goal. Bart and Francis (2001) have proposed goals and standards for comprehensive avian monitoring programs. Their general goal, building on earlier work by Butcher et al. (1993), is 80% power to detect a 50% decline occurring during 20 years, using a two-tailed test with the significance level set at 0.15 and acknowledging effects of potential bias. They analyze existing and feasible levels of accuracy for shorebirds and show that relatively few species meet the proposed standard at present but that if the Canadian and U.S. bird conservation initiatives are implemented, the standard will probably be met for most shorebird species breeding regularly in North America. This is the current goal for PRISM analyses.

A three-part approach for estimating trends in population size has been developed:

1. Arctic, boreal, and temperate breeding surveys.
2. Temperate non-breeding surveys.
3. Neotropical surveys.

The rationale underlying this scenario is that trends in population size can best be studied during the breeding season, on the breeding grounds. At this time, populations are stable rather than mobile, surveys are relatively straightforward because the birds are dispersed, and extrapolation from sampled plots to the entire population can be made using standard methods from classical sampling theory. This approach works well in temperate latitudes. In northern areas, where gaining access is difficult and costly, we propose an initial survey on the breeding grounds, to obtain estimates of population size, and then opportunistic data collection from these areas and a comprehensive program of surveys at staging sites, migration areas, and neotropical areas at lower latitudes, where access is reasonably easy, to provide indications of population declines. When such warning signs appear, or at intervals of 10-20 years, the breeding ground surveys can be repeated to get updated population sizes and thus estimates of change in population size. This approach avoids the high cost of annual surveys in remote northern areas but also avoids complete reliance on trend estimates from migration when several sources of bias are possible.

The U.S. Plan suggested that selected subspecies and distinct populations, in addition to all species that breed regularly in the U.S. and Canada, should be included in the monitoring and assessment program. The rationale for this suggestion was that many subspecies, and a few populations, have such different breeding and/or non-breeding ranges that separate management efforts would be needed if they declined. For example, the three subspecies of dunlins in North America winter in different parts of the world, and evidence exists that one (Calidris alpina arcticola) of them may be declining whereas this is not true for the other two. Computing a single species-wide trend for dunlins does not provide managers the information they need. Furthermore, it is relatively straightforward to calculate separate trends for the three subspecies since they spend both the breeding and non-breeding periods in almost completely non-overlapping areas. The same rationale holds for a few distinct populations. For example, small populations of marbled godwits breed near James Bay and in western Alaska. They are separated from the main population by hundreds of kilometers, and certainly each warrant population-specific conservation actions by managers. It thus seems appropriate to identify them as separate taxa in monitoring and assessment program. The U.S. shorebird plan identified 72 species, subspecies, or distinct populations that warrant separate monitoring and assessment efforts. With slight modifications following review by Canadian shorebird specialists, the PRISM list of focal species now covers 74 taxa including 49 species.

Work is underway on many aspects of PRISM, including ongoing arctic surveys and developing approaches to migration surveys. People or organizations interested in collaborating with PRISM should contact Jon Bart, co-chair of the PRISM International Committee, at jbart@usgs.gov.

Hemisphere Shorebird Project Proposal of the Shorebird Research Group of the Americas

Rob Butler, Ron Ydenberg, Garry Donaldson, and Stephen Brown

Pacific Wildlife Research Centre, Canadian Wildlife Service, 5421 Robertson Road, Delta, B.C. V4K 3N2 Canada; Centre for Wildlife Ecology, Department of Biological Sciences, Simon Fraser University, Burnaby B.C. V5A 1S6; Canadian Wildlife Service, Hull, Quebec K1A 0H3, Canada;
Manomet Center for Conservation Sciences, 81 Stage Road, P.O. Box 1770, Manomet, MA 02345 USA

There is ample evidence that many shorebirds counted in censuses in North America have declined in the past two decades but the reasons for the declines are unclear (e.g. Jehl and Lin 2001, Morrison et al. 1994, 2001). Censuses on the eastern seaboard and mid-west showed that 9 of 30 species were significantly declining with most pronounced declines among species with wide non breeding ranges in non-marine habitats (J. Bart, pers. comm.). Trends were most detectable in the north Atlantic and less so in the mid west. The geographic range and number of species reported to have declined in recent decades suggests that a general widespread cause might be at work.

Shorebirds breeding in North America migrate to winter quarters in North, Central and South America, Europe and Asia via traditional migratory routes or ‘flyways’. Many species travel tens of thousands of kilometres each year. Some species migrate in large flocks that assemble at a small number of stop over sites often populated by humans. Others migrate in small numbers stopping at many small sites and some species exhibit both migration behaviours. In nearly every case, shorebirds spend part of their year in habitats altered by large numbers of humans living nearby.

The collective wisdom of shorebird biologists and conservationists from Canada and the United States mostly drawn from North America was compiled through meetings of the Canadian Wildlife Service Shorebird Technical Committee in Quebec City, the Waterbird Society in Lacrosse, Wisconsin in 2002, and at the 7th Annual Western Sandpiper Research Group at Simon Fraser University in 2003. The view of these specialists was that the answer to why shorebirds were declining would require a coordinated international, multidisciplinary effort across the range of a few species which we call the Hemisphere Shorebird Project. Emerging from these discussions were five most likely causes for declines.

Possible causes for declines

1. Climate Change

Snow melt is thought to play an important role in determining the timing of breeding and reproductive success of arctic breeding shorebirds. The Eastern Arctic is showing wider swings in temperature than the western arctic. We predict that nesting success of shorebirds in the eastern arctic has become more variable than shorebirds in the west. We will test this prediction by examining meteorological records of timing of snow melt and air temperature at shorebird nesting areas over the past three decades. We will relate timing of nesting and nesting success in relation to snow melt and summer temperature at 10 sites spread from east to west across the arctic. We will then make an estimate of expected fledging success from archived data of snow melt over the past 30 years. The estimates for the eastern arctic will be entered into population models of recruitment to compare relative population change to actual change seen in counts made on Maritime Shorebird Surveys over the past 30 years.

2. Avoidance of predators

The recovery of birds of prey in North America has resulted in a shift in the migration routes, an avoidance of dangerous stop over sites, and briefer stop over by individual shorebirds at sites that historically held large numbers of shorebirds (Ydenberg et al. 2001, Butler et al. 2003). We predict that shorebirds have become more numerous in non-coastal areas that have fewer birds of prey. We also predict that small, enclosed sites where birds of prey can launch surprise attacks are used by fewer shorebirds now than in the past. Finally we predict that individual shorebirds are spending less time at sites that give an impression that the number of birds has declined.

3. Contamination

The ‘trophic contamination hypothesis’ posits that shorebirds accumulate industrial and urban pollution at stop over sites that are subsequently released in sudden high doses as fat is burned during migratory flights that then disrupt their ability to make migratory decisions. For example, large contaminant doses might hamper refuelling by reducing the satiation signal in shorebirds so that they do not accumulate sufficient fat for migration. In addition, organochlorines deposited on mudflats in the 1970s and 1980s and now buried by sediments are more accessible to long-billed shorebirds that probe deeply for prey than short-billed species that forage at or near the surface. We predict that OC loads will be greater in long billed species than in short billed species. We will compare contaminant levels of birds collected along the migration route and on the breeding ground to determine if contaminant loads differ greatly between flights and sites. Within these samples, we predict that long-billed species will carry greater OC loads than short-billed species.

4. Human Disturbance

This hypothesis posits that human disturbance at stop over sites has reduced the time available for shorebirds to accumulate fat for migration. As a result, the shorebirds stay longer to acquire the fat or depart for places where they can forage undisturbed. We predict that shorebirds at stop over sites with large numbers of people will have lower mass than the same species at nearby undisturbed sites. We also predict that the number of shorebirds has declined more rapidly at sites with high human disturbance than at sites with low disturbance.

5. Habitat Loss and Degradation

This hypothesis posits that the number of potential stop over sites has declined resulting in increased competition for food so that the poorest competitors moved to marginal foraging habitat where they suffered higher mortality than birds in good habitat.

Approach

We will decipher the cause for declines among the highly migratory species of shorebirds by synthesizing existing information from various shorebird networks and assemble teams to fill gaps in our knowledge to complete the synthesis for species in decline. The project would run for five years. The first year would be devoted to the synthesis of existing data, and establishing species networks including the enlisting of contributors. The subsequent years will be used to collect field data to thoroughly investigate the reasons for declines in selected species.

The Shorebird Research Group of the Americas (SRGA) is a collaborative, international, and multi-disciplinary group of biologists interested in researching conservation questions pertaining to shorebirds in the Americas. In the US and Canada, the SRGA advises on shorebird science to the National Working Groups of the USA and Canadian Shorebird Plans (Donaldson et al. 2000, Brown et al. 2000). Participants from other countries will be strongly encouraged and will report nationally according to their own specific needs. Its membership includes individuals from government, university and private organizations. Recent concerns about possible declines in some shorebirds in North America prompted the formation of the SRGA and the development of the following proposal to provide advice on the question of population stability of shorebirds in the Americas. Coordination of this project will be determined through consultation with SRGA partners. The Hemisphere Shorebird Project will be coordinated through the Centre for Wildlife Ecology at Simon Fraser University. Each country will implement the results as they see fit. In the US and Canada, results will be reported through the National Working Groups of the respective Shorebird Plans.

Shorebird researchers recognize that determining the causal factors for declining populations is a high priority for shorebirds but that there are additional research questions that must be addressed to build a solid science foundation on which to base conservation decisions. Thus, the SRGA will adapt to the science needs of the conservation community and address additional questions as priority needs arise.

Please forward comments to the Chair of the SRGA, Rob Butler at rob.butler@ec.gc.ca.

References

Bart, J. and C. Francis. 2001. Quantitative Goals for Avian Monitoring Programs. Manuscript.

Brown, S., C. Hickey, B. Harrington, and R. Gill (eds.). 2001. United States Shorebird Conservation Plan, 2nd Ed. Manomet Center for Conservation Sciences, Manomet, Massachusetts. 70 pp.

Butcher, G. S., B. G. Peterjohn, and C. J. Ralph. 1993. Overview of national bird population monitoring programs and databases. Pages 192-203 in D.M. Finch and P.W. Stangel, editors. Status and management of Neotropical migratory birds: Proceedings of the 1992 Partners in Flight National Training Workshop, 21-25 September, Estes Park, Colorado. U.S. Forest Service Rocky Mountain Forest and Range Experiment Station General Technical Report RM-229.

Clark, C.W. and R.W. Butler. 1999. Fitness components of avian migration: a dynamic model of
Western Sandpiper migration. Evolutionary Ecology Research 1:443-457.

Donaldson, G. D., C. Hyslop, R. I. G. Morrison, H. L. Dickson, and I. Davidson. 2000. Canadian
Shorebird Conservation Plan. Canadian Wildlife Service Special Publication, Ottawa.

Jehl, J. R., Jr. and W. Lin. 2001. Population status of shorebirds nesting at Churchill, Manitoba.
Canadian Field-Naturalist 115: 487-494.

Morrison, R. I. G., C. Downes And B. Collins. 1994. Population trends of shorebirds on fall
migration in eastern Canada 1974-1991. Wilson Bulletin 106:431-447.

Morrison, RIG, Y. Abry, RW Butler, GW Beyersbergen, GM Donaldson, CL Gratto-Trevor, PW Hicklin,
VH Johnston and RK Ross. 2001. Declines in North American shorebird populations. Wader
Study Group Bulletin 94: 39-43.