Bird lovers count San Francisco bay's shorebirds
By the time the tide rolled over the mud flat near the northern rim of San Pablo Bay, the long-billed curlews were among the last still feeding.
The rising water forced the smaller birds to stop, but the curlews, the largest North American shorebird with a long down-curving bill, could still stab into the mud to pull up a juicy morsel.
Eight of them were busy doing just that, packing calories to fuel their long flight next spring back to Alaska.
"The more they can fatten up here, the more successful they're going to be breeding in the Arctic," said Julian Wood, a biologist at PRBO Conservation Science who on a recent day was out counting shorebirds for an annual survey. "It's all connected."
Avocets and black-necked stilts live here year-round, but the rest of the bay's shorebirds breed in Alaska and make their way down the West Coast to spend the winter here, he said. An estimated 1 million shorebirds live or winter around the San Francisco Bay, making it the most important habitat on the West Coast for migrating shorebirds, according to Wood.
This month, more than 100 biologists and trained volunteers fanned out around the bay to count them.
In the Napa-Sonoma Marshes State Wildlife Area, Wood peered through a tripod-mounted scope and ticked off the shorebirds on a distant mud flat -- 54 marbled godwits, 123 black-bellied plovers, 1,240 dunlins (a kind of sandpiper), 69 western sandpipers.
Then a truck passed by on State Route 37, its loose tarp making a "pop, pop, pop" sound in the distance. Hundreds of birds rose into the sky, briefly interrupting the count.
"It sounds vaguely like a shotgun blast," said Wood. "It doesn't take a lot to scare these guys, especially with the tide getting high. They're getting restless."
The high tide makes these marshes ideal for counting birds. The mudflats ringing the bay itself were underwater, so the birds came across State Route 37 to continue feeding on exposed mud for as long as they could.
"That's what makes San Francisco Bay such a great place for birds," Wood said. "At any given time, they can find foraging habitat."
The fledgling survey started in the early 1990s and restarted five years ago after a long hiatus. The surveys are done by PRBO Conservation Science, a Petaluma-based science and conservation advocacy group, and the San Francisco Bay Joint Venture, a partnership of public and private entities dedicated to restoring more wetlands around the bay.
Bird researchers hope the surveys will help them identify trends in the shorebird population. Based on the limited information gathered to date, they say shorebird populations overall appear to be stable.
But the surveys have detected a shift in bird numbers from the South Bay and Central Bay to the North Bay since the early 1990s.
That might be due to previous marsh restorations in the North Bay, Wood said. As the South Bay salt pond restorations continue to develop, more birds might later shift back south. That is why bird advocates want to continue and even expand the surveys.
"Hopefully, we can keep it going so we can get a sense of what's going on," said Christina Sloop, science coordinator for the San Francisco Bay Joint Venture.
This year, the survey was expanded to include six sites in Southern California, more than 10 in the Central Valley and 11 estuaries in Mexico, according to PRBO Conservation Science.
Next year, the organization hopes to expand the surveys to South America.
Source: Mercury News