Symposium Participants: Stephen Brown
PRISM, The Program for Regional and International Shorebird Monitoring
Jonathan Bart 1, 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
Corresponding author: jon_bart@usgs.gov
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:
- Estimate the size of breeding populations of shorebirds in North America.
- Describe shorebirds’ distribution, abundance, and habitat relationships.
- Monitor trends in shorebird population size.
- Monitor shorebird numbers at stopover locations.
- 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 et al. (Submitted) 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:
- Arctic , boreal, and temperate breeding surveys.
- Temperate non-breeding surveys.
- 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.
References
Bart, J., K.P. Burnham, E.A. Dunn, C. Frances and C.J. Ralph. Submitted. Goals and strategies for estimating trends in landbird abundance. Journal of Wildlife Management.
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.
Donaldson, G., C. Hyslop, R. I. G. Morrison, I. Davidson. In Press. Canadian Shorebird Conservation Plan, Special Publication, Canadian Wildlife Service, Ottawa.
