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50 STATE OF THE ESTUARY SHOREBIRDS long-billed dowitchers. Small included dunlin, Western sandpiper, and least sandpiper. CONTEXT In winter, the mudflats that ring the Estuary shimmer with thousands of peeps and plovers, plucking away at worms, tiny clams, and other critters in the ooze. The Estuary is a site of hemispheric importance for migratory shorebirds that overwinter here. Over one million WINTERING shorebirds, including SHOREBIRD year-round residents, use the intertidal A B U N DA N C E mudflats, marshes, SAN FRANCISCO and saline ponds of B AY the Estuary each year . . S TAT U S . . (>300,000 birds in win- Fair to Poor ter). Species of shore- . . . .T R E N D . . . . birds using the Estuary Mixed in the non-breeding season vary greatly in .....BENCHMARK..... Derived from average body size and abun- abundance dance; their migratory 2006-2008 pathways and breeding ground locations vary as well. The variety among wintering shore- birds make them a good measure of the condition of San Francisco Bay’s intertidal wetlands and saline ponds. INDICATOR The indicator measures the abundance of 2015 Marbled godwit. Photo. Rinus Baak, USFWS shorebirds per hectare during the winter. Scientists selected nine common, wintering, migratory shorebird species, representing three groups based on body size and breed- ing distribution, as indicators for intertidal mudflats, salt marshes, and saline ponds in the north, central, and south regions of the Estuary. Large shore- birds included American avo- cet, willet, and marbled godwit. Medium-sized included black-bellied plover, and short- and Photo: Rick Lewis The benchmark derives from the average abundance of each group in each Bay region from early winter surveys conducted 2006- 2008. The indicator score is based on differ- ence in density relative to the benchmark and the degree of certainty in density estimates. The 2006-2008 makes a good benchmark because it represents the state of shorebird populations just prior to a period of substan- tial change in wetlands in San Francisco Bay brought about by large-scale restoration of saline ponds to tidal marshes. STATUS & TRENDS The status of large and medium shorebirds is poor; small shore- birds are fair. Non-breeding shorebird pop- ulations of different species and size groups are changing in different ways in abundance