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ix WHY MONITOR SHOREBIRDS? Long-term monitoring of populations is of paramount importance to understanding responses of organisms to global environmental change and to evaluating whether conservation practices are yielding intended results through time (Wiens 2009). The population status of many shorebird species, the focus of this volume, remain poorly known. Long-distance migrant shorebirds have proven particularly difficult to monitor, in part because of their highly migratory nature and ranges that extend into highly inaccessible regions. As migrant shorebirds travel the length of the hemisphere, they congregate and disperse in ways that vary among species, locations, and years, presenting serious challenges to designing and implementing monitoring programs. Rigorous field and quantitative methods that estimate population size and monitor trends are vitally needed to direct and evaluate effective conservation measures. Many management efforts depend on unbiased population size estimates; for example, the shorebird conservation plans for both Canada and the United States seek to restore populations to levels calculated for the 1970s based on the best information available from existing surveys. Further, federal wildlife agencies within the United States and Canada have mandates to understand the state of their nations’ resources under various conventions for the protection of migratory birds. Accurate estimates of population size are vital statistics for a variety of conservation activities, such as prioritizing species for conservation action and setting management targets. Areas of essential habitat, such as those designated under the Western Hemisphere Shorebird Reserve Network, the Important Bird Areas program of BirdLife International and the National Audubon Society, or Canada’s National Wildlife Areas program, are all evaluated on the basis of proportions of species’ populations which they contain. The size, and trends in size, of a species ’ population are considered key information for assessing its vulnerability and subsequent listing under the U.S. Endangered Species Act and the Canadian Species at Risk Act. To meet the need for information on population size and trends, shorebird biologists from Canada and the United States proposed a shared blueprint for shorebird monitoring across the Western Hemisphere in the late 1990s; this effort was undertaken in concert with the development of the Canadian and U.S. Shorebird Conservation Plans (Donaldson et al. 2000, Brown et al. 2001). Soon thereafter, partners in the monitoring effort adopted the name “Program for Regional and International Shorebird Monitoring” (PRISM). Among the primary objectives of PRISM were to estimate the population sizes and trends of breeding North American shorebirds and describe their distributions (Bart et al. 2002). PRISM members evaluated ongoing and potential monitoring approaches to address 74 taxa (including subspecies ) and proposed a combination of arctic and FOREWORD Contribution of Arctic PRISM to Monitoring Western Hemispheric Shorebirds Susan K. Skagen, Paul A. Smith, Brad A. Andres, Garry Donaldson, and Stephen Brown STUDIES IN AVIAN BIOLOGY NO. 44 Bart and Johnston x Efforts prior to Arctic PRISM to estimate population size based primarily on wintering and migration surveys were unable to determine the relative distribution of breeding shorebirds between Alaska versus Canada for widely dispersed species. Establishing the relative responsibility borne by Canada and the United States for a particular species’ conservation was therefore difficult. Interpretation of results from surveys that varied in proportional coverage of birds along different flyways may have provided misleading perspectives for shorebirds such as the Semipalmated Sandpiper, a species currently under consideration for listing by the Committee on the Status of Endangered Wildlife in Canada. Historically , 75% of all Semipalmated Sandpipers were thought to migrate through the Bay of Fundy based on comparisons of total counts at this site during migration with counts on the wintering grounds. It was assumed that these birds bred in the eastern arctic, suggesting that Canada had the lead responsibility for conservation of both breeding and migrating Semipalmated Sandpipers. Recent surveys in areas that previously lacked coverage are now revealing a new perspective on Semipalmated Sandpiper distribution. At sites surveyed to date, densities are much higher in the western regions than in eastern areas. Although much of the species’ range remains to be surveyed , it seems that a large fraction of the population likely breeds in Alaska and may therefore use inland migration routes where they will not be exposed to environmental threats operating in the Bay of Fundy. Moreover, results to date suggest that the population size of Semipalmated Sandpipers is much larger than once believed. The Bay of Fundy may be used by a smaller fraction of the species than once thought, yet it is still of critical importance to southbound...

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