‘Climate Endangered’ Least Terns Thrive In Northern California, But For How Long?

Last fall, Audubon Society scientists released a report surveying habitat for 588 bird species across the United States and Canada, and concluding that 314 of those birds had a “very high” chance of losing significant habitat due to climate change by 2080. Of 314 species tagged with “significant” climate concern, 126 were classified as “climate endangered” — in danger of potentially losing over half of their current range by 2050. In this occasional series, Bay Nature sets out to see what that report means on the ground in the Bay Area.

Click here for part one, which looked at the popular black oystercatcher.

ith the roar of traffic zooming ahead on the highway and the incessant chatter of birds behind, Dave Riensche slams the door of his field truck shut and gazes out at the half-acre, manmade island off the Hayward Regional Shoreline that hosts the densest population of endangered California least terns on the West Coast.

Riensche, a wildlife biologist with East Bay Regional Park District, studies these birds, a subspecies of the least tern found only along the California coast and northern Mexico’s Baja California. The birds have been listed as federally endangered since 1970, and have had annual population surveys conducted since 1974. In that first year only 582 breeding pairs were found. Now the number has risen to more than 4,500 pairs in recent years as a result of protective measures such as fencing and predator control.

Riensche guides us to a spot to view the colony floating just 35 metres away. With binoculars and spotting scope in hand, we saw many tern parents sitting on nests, which is a testament to the prolific number of eggs being laid this year. Says Riensche, “It’s like you’re at a movie theater and there’s popcorn – you’d walk by an egg and the chick would just poke through, boom, boom, boom.”

The California least tern, with a jet black head, gray body, and erect tail feathers, is a rare species in the Bay Area that’s more common in southern California and the Baja Peninsula. Least terns winter off of South America’s Pacific coast, then return to the north to nest on the water in both coastal and inland areas. The Hayward colony, and a companion colony in Alameda, represent – for now – the farthest northern extent of the bird’s breeding range.

Which raises, for Riensche, a question: “The majority of California least terns are in southern California, so how come the two northern colonies in Alameda and Hayward are doing so well?”

And a possibly related question: how long can they keep doing well?

The answer to this question remains ambiguous. Audubon’s climate report forecasts an 82 percent decline in current summer range by 2080, but it also notes that creative wildlife managers and the tern’s natural adaptability could keep the bird around. For now the terns are thriving at the northern limits of their range, Alameda and Hayward. Their success lies in the fledgling per pair ratios, which are high at these two sites. There are more total nesting spots along the Southern California coast, but the ratio is nowhere near the same.

For Riensche and Northern California, at least, there are some reasons for optimism: nesting colonies like the ones in Alameda and Hayward are well protected from human disturbance and development, two of the main causes of the tern’s decline so far. The Hayward colony’s floating island is closed to the public. Riensche has developed a suite of interesting tactics for keeping predators away, like traps, and speakers that play least tern mating calls, a shrill whistling kideek kideek.

That just leaves the slower-building – but less obviously solvable — problem of sea level rise. “Everything is subject to sea level rise,” Riensche says. “If sea level rises, the island is in major peril.”

There already is erosion of 1-2 feet per year on the bay side of the island, he says. But for now, the Hayward colony has reached its carrying capacity every year for the past three years – although in 2012, when Alameda’s colony had a significant decrease in nesting success, the Hayward colony was able to absorb an additional 100 birds.

The climate threat is also, perhaps, an opportunity. As the state gets warmer, new territory might open up. Terns seem to be moving farther north into California, perhaps to escape predation and to find more inland nesting habitat; terns have already been sighted in Sacramento.

And Riensche has his own plans for the Hayward island: rip-rap, better predator fencing, dredging a moat so foxes and raccoons can’t get at the young birds. There is also the danger of chicks falling into the water and drowning due to nesting too close to the edge as well as rising sea levels.

“We want to keep these birds surviving, no matter what,” Riensche says.

The Black Oystercatcher Gets ‘Climate Endangered’ Status — But It’s Complicated

ane Hart stakes her vigil almost daily at Lookout Point near the Cliff House. She sets and tunes her Swarovski spotting scope to maximum viewing capability, and scans the shoreline and out onto Seal Rocks for one of California’s most familiar seabirds. A former teacher turned fervent birder and Golden Gate Audubon volunteer, Hart has been watching a breeding pair of black oystercatchers on the rocks for the last 4 months. Despite a number of studies conducted in the northern part of their range, from the Aleutian Islands to Oregon, there hasn’t been much research done on black oystercatchers in California and Baja. So the Audubon Society set out to learn more, and when the group asked Hart to participate in a study of the species’ nesting and breeding habits, she jumped at the chance. Now, most mornings you’ll find her on the high rocks above the crashing waves, watching the birds fish and nest, listening for the piercing whee-wee-wee-wee the birds use to defend their territory and attract mates, taking notes on their movements and activities.

With a stark black nape leading down to a dark brown body, a bright orange bill, and that piercing alarm call, the black oystercatcher is a popular sight in the Bay Area. They can be spotted scanning their rocky intertidal ecosystems from above, diving into the surf to pry their favorite prey-mussels, chitons, and limpets-from the adhesive havens of the rocks below. Although migratory in other parts of its range, the black oystercatcher is unique for being the only seabird in the Bay Area that does not migrate. They instead stay year-round in bowl-shaped cavity nests on rocky coastal cliffs and intertidal zones.

Climate change isn’t kind to range-limited animals that live near oceans. Audubon’s 2014 climate report predicts the black oystercatcher’s winter and summer range could shrink considerably – and quickly, with changes evident perhaps by as soon as 2020. By mid-century, the range might shift northward up the Pacific Coast, into Oregon and Washington, which could mean an even higher risk of extinction for the Bay Area population.

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ut the birds seem comfortable enough for now: for the last four years 80-100 Northern California oystercatcher nests have been tracked annually, with Mendocino, Madrone, Morro Bay, Monterey, and Redwood Regional chapters of Audubon California harboring successful breeding populations. The first Audubon population assessment of black oystercatchers in California, published in 2011, showed nesting sites ranging from coastal San Luis Obispo north to coastal Humboldt County.

Audubon’s climate report listing of the black oystercatcher is mainly for three reasons: there aren’t that many of them left on the Pacific Coast, they don’t have high breeding success, and most of all, they’re shorebirds, completely dependent throughout their lives on the rocky intertidal habitat for food and shelter — and the shoreline is moving with sea level rise. Researchers at Point Blue conducted a vulnerability analysis of birds in the Bay Area in 2008, with the black oystercatcher coming out near the top of the list as the most vulnerable.

But big-picture models can’t necessarily capture the nuance of an individual species, and in the case of the oystercatcher, there’s quite a bit of nuance. Audubon California Marine Program Director Anna Weinstein, who with more than 150 shorebird biologists in 2011 conducted the first survey of the black oystercatcher’s distribution and abundance in California, said that there’s still basic information to find. “There’s a lot of work to be done, more than you would think for such a charismatic bird,” she says. “We’ve only collected baseline information — distribution, abundance, breeding success.”

In an article in Marine Ornithology in 2014, Weinstein and her colleagues suggested, in fact, that Northern California had more black oystercatchers than previously thought, and also might be a valuable climate refuge for the birds. Black oystercatchers’ northern nesting sites tend to be closer to the water, and so face a high risk of inundation, while California and Southern Oregon have a marine terrace that provides nesting sites higher above sea level – offering protection, somewhat, against sea level rise.

The 2011 survey also estimated the number of black oystercatchers in the state at around 4,000-6,000, considerably higher than previous estimates. Audubon’s annual Christmas Bird Count has shown a stable global population, and an increase in black oystercatchers in both the Bay Area and California.

“Yet,” the paper concludes, “even if this is the case, the species is highly vulnerable to decline given the gravity of the threats faced by this species and all shorebirds.”

Changes in intertidal habitat, as well as warming and acidifying oceans, could affect the food the birds rely on. Human disturbance is also a threat, which is why Audubon is trying to run an outreach campaign to keep visitors away from the birds. “People have been very responsive,” Weinstein says. “They’ll say, ‘Oh, I didn’t know that I was driving the bird away from its nest by trying to get closer to it.’ They actually listen, and then begin to realize their impact, which is crucial.”

People want to save what they are familiar with and what they love, and the black oystercatcher is a familiar and beloved flagship species in the Bay Area.

“They have a chance,” Weinstein says. “These birds are tough, they’re survivors that chase away predators such as ravens and red-tailed hawks, and I have a sense that they will prevail and adapt to climate change. They are a bird for today’s world.”

What’s Living in the Antioch Dunes National Wildlife Refuge? Plenty, Still.

ith the metallic clanking of Amtrak’s San Joaquin as it whooshes by and the acridity of gypsum floating through the air, it is sometimes hard to remember the conservation importance of Antioch Dunes National Wildlife Refuge. A mere 55 acres in size, Antioch Dunes is one of the smallest refuges in the United States. At first glance the landscape looks like a large vacant lot that is located next to gypsum drywall factory.

But this large empty lot is the first wildlife refuge in the country to be dedicated exclusively to the conservation of insects and plants, and a home to three endangered species-the Antioch Dunes evening primrose, Contra Costa wallflower, and Lange’s metalmark butterfly.

The Antioch Dunes National Wildlife Refuge. (Photo by Dan Rademacher)

About 50 volunteers were allowed into the refuge on July 25 to spend the morning searching and cataloguing species of all kinds, as part of a citizen science bioblitz sponsored by the U.S. Fish and Wildlife Service and Nerds for Nature. The opportunity was a rare one, as the refuge is open to the public only once a month for docent-led tours.

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For Carmen Minch, an outdoor recreation planner for the San Francisco Bay National Wildlife Refuge Complex, the day was as much a chance to remind people about the value of protecting the dunes as it was a scientific opportunity.

“It’s vitally important to have local people seeing what’s literally in their backyards,” Minch said. It is my hope that events like this will help to show people that nature is all around them, they just have to look for it. Sure, there aren’t any sexy animals here, but they still play just as important a role.”

Many of the bioblitzers hailed from the East Bay, particularly Concord, Livermore, Martinez, and Antioch. Kenneth Brosas, a teenager who had moved recently to Antioch from the Philippines, said he was determined to learn the lay of the land.

“I’m here wanting to learn more about North American wildlife and familiarize myself with the nature of my community while I’m here,” he said.

Kay Kirby, on the other hand, has lived in Antioch all her life. Out tracking animals and plants with her grandson Colin, she says for her the Antioch Dunes have always evoked a sense of reverence and beauty. She painted the dunes, with paintbrush and with memories, 40 years ago. She said she has always had a special place in her heart for the evening primrose.

The critically endangered primrose was one of the highlights of the bioblitz, recorded in 21 different locations by 11 different observers. Most of the sightings were found in the deeply thistled interior of the refuge.

The Antioch Dunes evening primrose. (Photo by Robyn Boothby, US Fish and Wildlife Service)

The species scoring the most observations was the harlequin cabbage bug, which is anything but endangered and is a pest to farmers and growers alike. For the entire day, 28 different iPhone-wielding observers added 637 observations for 111 species-not bad for a seemingly empty lot.

USFWS biologist Susan Euing also spotted a small patch of Antioch Dunes buckwheat growing in a clump near the edge of the embankment facing the river. Although wild buckwheat (Eriogonum nudum) is found throughout the West Coast, the Antioch Dunes variety grows only in the wildlife refuge, and serves as the primary host plant for the endangered Lange’s metalmark butterfly. First discovered in 1933 and described in 1938, the Antioch Dunes buckwheat began to decline rapidly as its native dunes habitat was being depleted to make bricks to rebuild San Francisco after the 1906 earthquake.

The butterfly was placed on the Endangered Species list in 1976 in the first major listing of insect species following the passage of the Endangered Species Act in 1973. In 1977, entomologist Richard Arnold began the first serious collection and survey of the species in Antioch, providing the majority of research about the butterfly today.

The participants of the bioblitz didn’t see the butterfly, which is in its cocoon phase. But the sighting of its host plant offered at least a reminder, and a hope, that the Lange’s metalmark will live for another season.