64 



Birds — Old Liviiifi Resources 



report). Given the substantial loss of wetlands 

 throughout all western states except Alaska 

 (median loss of 37%; Page and Gill 1994) and a 

 similar loss of native grasslands (Knopf 1994), 

 it is likely that other species of temperate-breed- 

 ing shorebirds for which we have no trend data 

 have also suffered population declines. 



Shorebirds breeding throughout the remote 

 and sparsely populated Polar Domain have been 

 least affected by loss of breeding habitats. Most 

 of these species, however, are dependent on 

 wetlands and other greatly altered habitats out- 

 side this region during winter and migration. 

 Information from long-term studies in Europe 

 suggests that populations of Arctic-breeding 

 shorebirds can be affected by conditions on the 

 wintering grounds as well as by those on the 

 breeding grounds (Goss-Custard and Moser 

 1988; Moser 1988). Arctic breeders such as the 

 buff-breasted sandpiper, upland sandpiper, and 

 American golden-plover winter primarily in 

 grassland habitats of the pampas in South 

 America. These habitats have been virtually 

 eliminated by agricultural development (Bucher 

 and Nores 1988: Blanco et al. 1993). The bris- 

 tle-thighed curlew, unique among shorebirds 

 because of its tlightlessness during moll (Marks 

 1993), is threatened by problems associated 

 with increasing human populations on winter- 

 ing grounds in Oceania, including the introduc- 

 tion of mammalian predators (Marks et al. 

 1990; Gill and Redmond 1992). 



Surfhirds {Aphizci virgata) and 

 bjack tumstones (Arenaria 

 melanocephakt). 



In long-term studies of shorebirds nesting at 

 Prudhoe Bay on Alaska's North Slope between 

 1981 and 1992. considerable annual variation in 

 nesting density and nest success has been found 

 in several species of shorebirds (D. Troy. Troy 

 Ecological Associates and British Petroleum 

 Exploration, unpublished report). Much of this 

 variation has been attributed to predation and 

 environmental factors such as snow cover and 

 temperature at the start of the breeding season. 



However, among eight species of intensively 

 monitored shorebirds. only dunlin (Calidris 

 alpiiui articola) have exhibited a general, but 

 not significant, downward trend in nesting den- 

 sity over this 10-year period. 



Detecting Future Trends 



To conserve the tremendous biodiversity of 

 our shorebird resources in western North 

 America, we suggest a two-tiered monitoring 

 program that addresses trends in both habitat 

 axailability and shorebird population size. In 

 this program we should: 



• Identify and map the current geographic extent 

 and quality of breeding, staging, and wintering 

 habitats important to shorebirds, particularly 

 those species with relatively small populations or 

 restricted habitat requirements; 



• Monitor the extent and quality of these habitats, 

 evaluating them at periodic intervals; 



• Develop cooperative, international programs to 

 monitor trends in shorebird populations; 



• Monitor a representative sample of shorebird 

 populations and evaluate trends in comparison 

 with changes in critical habitats; and 



• Establish cooperative, international agreements to 

 protect critical breeding, staging, and wintering 

 habitats, with priority given to those species with 

 low numbers, specific habitat requirements, and 

 immediate threats. 



Recently developed technology and conti- 

 nental habitat mapping now provide the tools to 

 identify and map the cuirent extent of wetlands 

 and other habitats important to shorebirds of 

 western North America. By coupling this with 

 cuiTent information on shorebird distribution 

 and habitat requirements, we will be able to 

 identify areas critical for shorebirds. The same 

 technology can be used to monitor changes in 

 these habitats over time. 



Several existing programs can be adapted or 

 modified to provide reliable information on 

 trends in size of several shorebird populations. 

 Each species needs to be evaluated individually 

 to determine where it could be monitored most 

 cost-effectively — breeding grounds, staging 

 areas, or wintering grounds. Programs such as 

 the International Shorebird Survey. Breeding 

 Bird Survey, and Christmas Bird Count can be 

 used to coordinate efforts of large numbers of 

 volunteers to simultaneously collect informa- 

 tion on several species of shorebirds. For many 

 other species like the snowy plover, buff-breast- 

 ed sandpiper, and bristle-thighed curlew — of 

 particular concern or difficult to monitor with 

 these programs — specific surveys need to be 

 designed and repeated periodically to effective- 

 ly monitor population trends. 



