This article is from the source 'nytimes' and was first published or seen on . It last changed over 40 days ago and won't be checked again for changes.

You can find the current article at its original source at https://www.nytimes.com/2019/11/12/science/caspian-terns-san-francisco-bay.html

The article has changed 2 times. There is an RSS feed of changes available.

Version 0 Version 1
A Silicon Valley Disruption for Birds That Gorge on Endangered Fish A Silicon Valley Disruption for Birds That Gorge on Endangered Fish
(7 days later)
DON EDWARDS SAN FRANCISCO BAY NATIONAL WILDLIFE REFUGE, Calif. — If you took a short kayak trip a few years ago to tiny islands nested in former salt ponds near Silicon Valley, you would have found plastic bird decoys all over. With their snowy white bodies, black crowns and sharp red bills, the decoys looked like real Caspian terns, a graceful migratory bird the size of a large crow.DON EDWARDS SAN FRANCISCO BAY NATIONAL WILDLIFE REFUGE, Calif. — If you took a short kayak trip a few years ago to tiny islands nested in former salt ponds near Silicon Valley, you would have found plastic bird decoys all over. With their snowy white bodies, black crowns and sharp red bills, the decoys looked like real Caspian terns, a graceful migratory bird the size of a large crow.
The goal of those doppelgängers was to lure terns to breed on the islands, and, in doing so, prevent endangered salmon and trout living hundreds of miles to the north from vanishing.The goal of those doppelgängers was to lure terns to breed on the islands, and, in doing so, prevent endangered salmon and trout living hundreds of miles to the north from vanishing.
The Columbia River Basin on Oregon’s northern border was once one of the most productive salmon habitats in the world. But commercial fishing and the construction of dams over the last two decades have contributed to the decline of wild salmonids by 95 percent. The fish are protected under the Endangered Species Act. But that doesn’t stop traveling terns, which are themselves protected under the Migratory Bird Treaty Act, from eating the salmon and undermining their recovery. The Columbia River Basin on Oregon’s northern border was once one of the most productive salmon habitats in the world. But commercial fishing and the construction of dams over the last two centuries have contributed to the decline of wild salmonids by 95 percent. The fish are protected under the Endangered Species Act. But that doesn’t stop traveling terns, which are themselves protected under the Migratory Bird Treaty Act, from eating the salmon and undermining their recovery.
“It’s a very difficult situation, given the competing interests,” said Alex Hartman, a wildlife biologist with the U.S. Geological Survey’s Western Ecological Research Center in Dixon, Calif.“It’s a very difficult situation, given the competing interests,” said Alex Hartman, a wildlife biologist with the U.S. Geological Survey’s Western Ecological Research Center in Dixon, Calif.
Dr. Hartman is part of a federal effort to bring these fowl and fish back into balance. The goal: Getting more terns to breed farther south and eat herring, sardines and other fish in the protected bay. And while it’s not expected that all of the birds will settle for San Francisco Bay, the effort could point the way toward limiting the terns’ annual northward migration while still preserving their numbers.Dr. Hartman is part of a federal effort to bring these fowl and fish back into balance. The goal: Getting more terns to breed farther south and eat herring, sardines and other fish in the protected bay. And while it’s not expected that all of the birds will settle for San Francisco Bay, the effort could point the way toward limiting the terns’ annual northward migration while still preserving their numbers.
Caspian terns — which migrate north from Mexico and Central America in search of nesting sites along coastal California up through Canada — are no strangers to the San Francisco Bay Area. During the 1980s and 1990s, more than 1,000 breeding pairs nested every summer on tidal islands and levees in the bay’s southern reaches. But in the 2000s, the birds’ numbers declined 36 percent. Biologists blamed loss of bare ground nesting habitat to tidal marsh restoration efforts, as well as a rise in predatory California gulls.Caspian terns — which migrate north from Mexico and Central America in search of nesting sites along coastal California up through Canada — are no strangers to the San Francisco Bay Area. During the 1980s and 1990s, more than 1,000 breeding pairs nested every summer on tidal islands and levees in the bay’s southern reaches. But in the 2000s, the birds’ numbers declined 36 percent. Biologists blamed loss of bare ground nesting habitat to tidal marsh restoration efforts, as well as a rise in predatory California gulls.
Over the same time period, nearly 9,000 bird pairs — the largest known Caspian tern colony in the world — nested on the beaches of Rice Island on the Oregon side of the Columbia River estuary. There, they gorged on the river’s most valuable residents, young salmon and trout. To reduce the carnage, the U.S. Army Corps of Engineers and federal fisheries biologists plotted a gentle relocation.Over the same time period, nearly 9,000 bird pairs — the largest known Caspian tern colony in the world — nested on the beaches of Rice Island on the Oregon side of the Columbia River estuary. There, they gorged on the river’s most valuable residents, young salmon and trout. To reduce the carnage, the U.S. Army Corps of Engineers and federal fisheries biologists plotted a gentle relocation.
Before the 1999 breeding season, the teams erected rows of black fabric fences and stakes with flapping streamers to successfully shoo terns from Rice Island.Before the 1999 breeding season, the teams erected rows of black fabric fences and stakes with flapping streamers to successfully shoo terns from Rice Island.
“The birds don’t like nesting in areas where they feel boxed in,” said Daniel Roby, a wildlife biologist at Oregon State University.“The birds don’t like nesting in areas where they feel boxed in,” said Daniel Roby, a wildlife biologist at Oregon State University.
The scientists enticed these Rice Island terns 17 miles closer to the Pacific Ocean, to East Sand Island, where they could dine on anchovies and herring rather than salmon and trout.The scientists enticed these Rice Island terns 17 miles closer to the Pacific Ocean, to East Sand Island, where they could dine on anchovies and herring rather than salmon and trout.
To lure the birds, Dr. Roby and his team set out 400 fake Caspian terns on East Sand Island and played audio recordings of real tern colonies every spring and summer between 1999 and 2001. Other biologists had used this technique a decade earlier to restore Arctic and common tern populations in Maine.To lure the birds, Dr. Roby and his team set out 400 fake Caspian terns on East Sand Island and played audio recordings of real tern colonies every spring and summer between 1999 and 2001. Other biologists had used this technique a decade earlier to restore Arctic and common tern populations in Maine.
“Terns in general respond very successfully to social attraction,” said Stephen Kress, founder of the National Audubon Society’s Seabird Restoration Program and a pioneer of the technique. The birds like being with each other so much, he said, that they will flock en masse to new breeding spots.“Terns in general respond very successfully to social attraction,” said Stephen Kress, founder of the National Audubon Society’s Seabird Restoration Program and a pioneer of the technique. The birds like being with each other so much, he said, that they will flock en masse to new breeding spots.
That happened quickly at East Sand Island, Dr. Roby said. “Once the birds found the colony site and started nesting, they didn’t need much more encouragement.”That happened quickly at East Sand Island, Dr. Roby said. “Once the birds found the colony site and started nesting, they didn’t need much more encouragement.”
By 2001, the entire Rice Island colony of terns had relocated, and their diets plunged from 83 percent salmon and trout to 30 percent. Even so, the relocated birds still ate 5.5 million of the threatened fish each year, enough to impair their recovery.By 2001, the entire Rice Island colony of terns had relocated, and their diets plunged from 83 percent salmon and trout to 30 percent. Even so, the relocated birds still ate 5.5 million of the threatened fish each year, enough to impair their recovery.
Encouraged by the terns’ attraction to East Sand Island, biologists broadened the plan to seven other sites hundreds of miles away in Oregon and California. Starting in 2008, the U.S. Army Corps of Engineers created new islands suitable for nesting at each site and teamed with Bird Research Northwest, a collaboration between biologists and federal agencies, to use social attraction to coax terns farther away from the Columbia River.Encouraged by the terns’ attraction to East Sand Island, biologists broadened the plan to seven other sites hundreds of miles away in Oregon and California. Starting in 2008, the U.S. Army Corps of Engineers created new islands suitable for nesting at each site and teamed with Bird Research Northwest, a collaboration between biologists and federal agencies, to use social attraction to coax terns farther away from the Columbia River.
“That’s the greatest value of social attraction,” said Dr. Kress, “keeping away all eggs from being in one basket.”“That’s the greatest value of social attraction,” said Dr. Kress, “keeping away all eggs from being in one basket.”
Some new islands built within lakes in inland Oregon did attract terns. But in drought years, the lakes got too shallow and birds didn’t nest at those sites. Drops in water levels reduced the numbers of fish for terns to eat, and coyotes and other animals could easily cross to the islands to prey on tern eggs and chicks.Some new islands built within lakes in inland Oregon did attract terns. But in drought years, the lakes got too shallow and birds didn’t nest at those sites. Drops in water levels reduced the numbers of fish for terns to eat, and coyotes and other animals could easily cross to the islands to prey on tern eggs and chicks.
Those problems didn’t exist in San Francisco Bay, the only coastal site chosen to entice terns away from East Sand Island. Once used for salt harvesting, the 30,000-acre Don Edwards National Wildlife Refuge now supports a mosaic of restored tidal marshes and salt ponds managed for waterfowl and shorebirds.Those problems didn’t exist in San Francisco Bay, the only coastal site chosen to entice terns away from East Sand Island. Once used for salt harvesting, the 30,000-acre Don Edwards National Wildlife Refuge now supports a mosaic of restored tidal marshes and salt ponds managed for waterfowl and shorebirds.
“We actively maintain water levels in the managed ponds year-round,” said Rachel Tertes, a biologist at the refuge. “They’re never dry.”“We actively maintain water levels in the managed ponds year-round,” said Rachel Tertes, a biologist at the refuge. “They’re never dry.”
The California Department of Fish and Wildlife, along with other partners, constructed mud islands within these managed ponds in 2010 for birds, like snowy plovers, stilts and avocets. In 2014, the Army Corps of Engineers modified five of those islands to make them hospitable to Caspian terns, which create small hollows in gravelly ground for their nests.The California Department of Fish and Wildlife, along with other partners, constructed mud islands within these managed ponds in 2010 for birds, like snowy plovers, stilts and avocets. In 2014, the Army Corps of Engineers modified five of those islands to make them hospitable to Caspian terns, which create small hollows in gravelly ground for their nests.
In 2015, Dr. Hartman suited up in a life vest and hip waders and ferried a kayak full of plastic birds to the islands. There, he and his team placed nearly 400 dummy terns, as well as solar-powered patio speakers that played the birds’ mating and nesting calls.In 2015, Dr. Hartman suited up in a life vest and hip waders and ferried a kayak full of plastic birds to the islands. There, he and his team placed nearly 400 dummy terns, as well as solar-powered patio speakers that played the birds’ mating and nesting calls.
Then, they waited.Then, they waited.
“We didn’t know if it was going to work,” Hartman said. “We hoped it would.”“We didn’t know if it was going to work,” Hartman said. “We hoped it would.”
The Caspian terns took notice within a month. That year, 224 bird pairs nested on two of the islands. By 2017, that number doubled, the scientists reported in the journal Global Ecology and Conservation in October.The Caspian terns took notice within a month. That year, 224 bird pairs nested on two of the islands. By 2017, that number doubled, the scientists reported in the journal Global Ecology and Conservation in October.
The quick success surprised Cheryl Strong, a former wildlife biologist at the refuge. “I thought maybe we’d get a handful in the first year, and another handful in the second year,” she said. “But a lot of birds came in right away.”The quick success surprised Cheryl Strong, a former wildlife biologist at the refuge. “I thought maybe we’d get a handful in the first year, and another handful in the second year,” she said. “But a lot of birds came in right away.”
On average, 211 baby terns were born each year, the researchers estimated.On average, 211 baby terns were born each year, the researchers estimated.
After the 2017 breeding season, the scientists removed the plastic dummies and speakers, but Caspian terns kept returning to the area on their own. In 2018, 472 pairs nested on the same two islands. According to a survey conducted by biologists early in this year’s nesting season, 380 Caspian terns were seen on the islands, and more were likely to arrive to nest.After the 2017 breeding season, the scientists removed the plastic dummies and speakers, but Caspian terns kept returning to the area on their own. In 2018, 472 pairs nested on the same two islands. According to a survey conducted by biologists early in this year’s nesting season, 380 Caspian terns were seen on the islands, and more were likely to arrive to nest.
The San Francisco Bay tern re-population hasn’t yet made much of a dent in the numbers of terns eating salmon and trout in the Columbia River Estuary. Numbers and colors on leg bands attached to the birds by biologists show that many terns in the refuge came from other spots around San Francisco Bay. Just a handful came from northern Oregon.The San Francisco Bay tern re-population hasn’t yet made much of a dent in the numbers of terns eating salmon and trout in the Columbia River Estuary. Numbers and colors on leg bands attached to the birds by biologists show that many terns in the refuge came from other spots around San Francisco Bay. Just a handful came from northern Oregon.
But Caspian terns aren’t fully dedicated to particular nesting sites, and are amenable to moving. With colonies expanding, scientists anticipate the birds themselves would function as the plastic decoys had, luring more terns to the new grounds at Don Edwards.But Caspian terns aren’t fully dedicated to particular nesting sites, and are amenable to moving. With colonies expanding, scientists anticipate the birds themselves would function as the plastic decoys had, luring more terns to the new grounds at Don Edwards.
As the 2019 nesting season ended, staff at the refuge cleared the artificial islands of pesky weeds poking through the pebbly ground. They are waiting for the spring arrival of new tern flocks, hoping that they’ll keep coming back year after year, for the sake of the salmonids up north.As the 2019 nesting season ended, staff at the refuge cleared the artificial islands of pesky weeds poking through the pebbly ground. They are waiting for the spring arrival of new tern flocks, hoping that they’ll keep coming back year after year, for the sake of the salmonids up north.
“We’ve provided safer places for terns to nest,” said Ms. Strong. “Having more colonies and successful nesting sites, no matter what, is going to be better for the birds.”“We’ve provided safer places for terns to nest,” said Ms. Strong. “Having more colonies and successful nesting sites, no matter what, is going to be better for the birds.”