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If you’ve ever wondered how many shorebirds winter in San Francisco Bay, a report released last fall has the statistics.  

The San Francisco Bay Bird Observatory, in partnership with other nonprofits and two federal agencies, counted 343,000 of them in a three-day period in November 2008. The census was conducted when high tides had forced the birds off the mudflats, concentrating them at roosting sites on higher ground. SFBBO’s report compared those numbers with those from the two previous years; the composite picture shows a reassuring amount of stability and one potentially troubling negative trend. 

For each of the three years, three of every ten birds counted were western sandpipers. Counts for this species were remarkably consistent, ranging from 102,005 to 103,179. Runners-up in abundance were the dunlin (29 percent of the total), least sandpiper (12 percent), American avocet (8 percent), and willet (6 percent). Seventeen other species were recorded; snowy plovers and Wilson’s snipe, whose habits and habitats are not conducive to the high-tide method, were not included. 

Some interesting distributional patterns emerge from the data. The Central Bay, including the Berkeley, Albany, and Richmond shorelines, had the highest numbers of “rockpipers,” shorebirds that forage on rocks and riprap: black oystercatchers, black turnstones, surfbirds, and spotted sandpipers. San Pablo Bay and southern San Francisco Bay led other regions in the total count, but each had a different assemblage of species. Semipalmated plover, killdeer, American avocet, greater yellowlegs, and dunlin had their highest counts in San Pablo Bay; black-bellied plover, black-necked stilt, lesser yellowlegs, long-billed curlew, marbled godwit, ruddy turnstone, red knot, western and least sandpipers, and dowitchers were most numerous in the South Bay, including the salt ponds. 

The trend for black oystercatchers, a steady increase from 2006 through 2008, is consistent with my sense that there are more of these striking creatures around than there used to be, at least in the East Bay. Greater yellowlegs, spotted sandpipers, black turnstones, surfbirds, sanderlings, least sandpipers, and dunlins also had their best year in 2008. It’s interesting that half the species on this list are rocky-shoreline specialists. 

Long-billed curlew numbers held steady across the three-year period. The largest North American shorebird, the grassland-nesting curlew has lost considerable grassland habitat and was listed as a California Species of Special Concern until last year. Some nest in the Klamath Basin and Modoc Plateau regions, although it’s not clear where this population spends the winter. 

On the other hand, semipalmated plover numbers have trended downward. Why would this mudflat-foraging species be declining while other birds with similar habitat preferences are stable or increasing? As of 1999, at least, no continent-wide decreases in the plover’s wintering and migratory populations had been reported. Maybe the low counts in 2007 and 2008 were anomalies. 

The species whose trajectory raises a warning flag is the red knot, a chunky short-billled midsized sandpiper. Never common as a wintering bird in San Francisco Bay, its numbers fell from 671 in 2006 to 130 in 2008. Fall counts from 1988 to 1993 averaged 1698. The species may be in trouble throughout its range. Conservationists have been concerned for some time about its rufa subspecies, which stops off at Delaware Bay on its northward migration to fatten up on horseshoe crab eggs. The unregulated harvesting of horseshoe crabs for bait has clearly had an impact on rufa knots. 

The knots that spend the winter here belong to the subspecies roselaari, which nests in northwestern Alaska and Siberia’s Wrangel Island and winters along the Pacific coast of the Americas and in the southeastern United States. A few years ago, U.S. Geological Survey biologist Robert Gill told me that spring staging flocks on the Yukon and Copper River deltas had decreased from about 100,000 in the ’70s and ’80s to a few tens of thousands. Russian observers have reported a comparable decline in Siberia. The Alaskan Shorebird Conservation Plan, finalized in 2008, estimates the global roselaari population as less than 50,000.  

Another shorebird specialist, Brian Harrington, has called red knots “a potential early barometer of the effects of climate change on highly migratory and vulnerable species,” in part because they concentrate in only a handful of wintering and stopover areas. If the decline of roselaari is real, it could reflect environmental changes anywhere along the bird’s intercontinental route. 

In any case, kudos are due to the SFBBO folks and their associates for counting the seemingly uncountable flocks. Like it or not, the Bay is changing; restoration efforts in the South Bay and elsewhere are racing the rising tides. It’s good to have a well-documented baseline for shorebird populations, among many other things. 

If you’ve ever wondered how many shorebirds winter in San Francisco Bay, a report released last fall has the statistics.  

The San Francisco Bay Bird Observatory, in partnership with other nonprofits and two federal agencies, counted 343,000 of them in a three-day period in November 2008. The census was conducted when high tides had forced the birds off the mudflats, concentrating them at roosting sites on higher ground. SFBBO’s report compared those numbers with those from the two previous years; the composite picture shows a reassuring amount of stability and one potentially troubling negative trend. 

For each of the three years, three of every ten birds counted were western sandpipers. Counts for this species were remarkably consistent, ranging from 102,005 to 103,179. Runners-up in abundance were the dunlin (29 percent of the total), least sandpiper (12 percent), American avocet (8 percent), and willet (6 percent). Seventeen other species were recorded; snowy plovers and Wilson’s snipe, whose habits and habitats are not conducive to the high-tide method, were not included. 

Some interesting distributional patterns emerge from the data. The Central Bay, including the Berkeley, Albany, and Richmond shorelines, had the highest numbers of “rockpipers,” shorebirds that forage on rocks and riprap: black oystercatchers, black turnstones, surfbirds, and spotted sandpipers. San Pablo Bay and southern San Francisco Bay led other regions in the total count, but each had a different assemblage of species. Semipalmated plover, killdeer, American avocet, greater yellowlegs, and dunlin had their highest counts in San Pablo Bay; black-bellied plover, black-necked stilt, lesser yellowlegs, long-billed curlew, marbled godwit, ruddy turnstone, red knot, western and least sandpipers, and dowitchers were most numerous in the South Bay, including the salt ponds. 

The trend for black oystercatchers, a steady increase from 2006 through 2008, is consistent with my sense that there are more of these striking creatures around than there used to be, at least in the East Bay. Greater yellowlegs, spotted sandpipers, black turnstones, surfbirds, sanderlings, least sandpipers, and dunlins also had their best year in 2008. It’s interesting that half the species on this list are rocky-shoreline specialists. 

Long-billed curlew numbers held steady across the three-year period. The largest North American shorebird, the grassland-nesting curlew has lost considerable grassland habitat and was listed as a California Species of Special Concern until last year. Some nest in the Klamath Basin and Modoc Plateau regions, although it’s not clear where this population spends the winter. 

On the other hand, semipalmated plover numbers have trended downward. Why would this mudflat-foraging species be declining while other birds with similar habitat preferences are stable or increasing? As of 1999, at least, no continent-wide decreases in the plover’s wintering and migratory populations had been reported. Maybe the low counts in 2007 and 2008 were anomalies. 

The species whose trajectory raises a warning flag is the red knot, a chunky short-billled midsized sandpiper. Never common as a wintering bird in San Francisco Bay, its numbers fell from 671 in 2006 to 130 in 2008. Fall counts from 1988 to 1993 averaged 1698. The species may be in trouble throughout its range. Conservationists have been concerned for some time about its rufa subspecies, which stops off at Delaware Bay on its northward migration to fatten up on horseshoe crab eggs. The unregulated harvesting of horseshoe crabs for bait has clearly had an impact on rufa knots. 

The knots that spend the winter here belong to the subspecies roselaari, which nests in northwestern Alaska and Siberia’s Wrangel Island and winters along the Pacific coast of the Americas and in the southeastern United States. A few years ago, U.S. Geological Survey biologist Robert Gill told me that spring staging flocks on the Yukon and Copper River deltas had decreased from about 100,000 in the ’70s and ’80s to a few tens of thousands. Russian observers have reported a comparable decline in Siberia. The Alaskan Shorebird Conservation Plan, finalized in 2008, estimates the global roselaari population as less than 50,000.  

Another shorebird specialist, Brian Harrington, has called red knots “a potential early barometer of the effects of climate change on highly migratory and vulnerable species,” in part because they concentrate in only a handful of wintering and stopover areas. If the decline of roselaari is real, it could reflect environmental changes anywhere along the bird’s intercontinental route. 

In any case, kudos are due to the SFBBO folks and their associates for counting the seemingly uncountable flocks. Like it or not, the Bay is changing; restoration efforts in the South Bay and elsewhere are racing the rising tides. It’s good to have a well-documented baseline for shorebird populations, among many other things.