Petaluma Profile: Bird ecologist sounds the alarm about disappearing shorebirds
Scott Jennings is trying to understand the declining numbers of migrating shorebirds at Tomales Bay.
Jennings, an avian ecologist from Petaluma, has worked at Audubon Canyon Ranch since 2016. The nonprofit is an environmental conservation organization founded in 1962 in Marin County.
Audubon Canyon Ranch works to protect herons, egrets, waterbirds, and shorebirds in the region. The group’s research goal is to better understand what’s happening to the bird population and determine if conservation efforts need to be stepped up, and if so, how.
“If you happen to be on Tomales Bay at the right time and place, it can seem like there are quite a few shorebirds around,” Jennings said. “But just 30 years ago there were almost three times as many.”
Many people know Tomales Bay for its oysters and for kayaking. But it is also an important wintering destination for migrating shorebirds. The 15-mile-long tidal estuary, formed by the San Andreas Fault, is part of the Pacific Flyway, a chain of habitats that migrating birds use as stopovers or wintering grounds along the west coast of the Americas.
“The birds connect various landscapes along this route,” Jennings said. “The connections between all these species and the different landscapes they travel through are really fascinating and beautiful to me.”
In Tomales Bay alone, dozens of species of shorebirds have been spotted. Many of them travel astonishingly long distances to winter in Tomales Bay or along the west coast of North and Central America. Each summer, some fly to the Arctic tundra. Others navigate their way to particular locations between the Rockies and the Sierra and Cascade ranges where they breed and nest.
“These birds have a tremendous capacity to time the seasons and travel great distances to find food and raise their young,” Jennings said, full of admiration.
In the wintertime, maybe you’ve seen plovers that scuttle back and forth as if chasing the waves on sandy beaches or dunlin that soar in unison in big flocks over the water.
“Some of the shorebirds are tough to tell apart so people just lump them all into one group called ‘peeps,’ because they resemble the marshmallow candies,” said Jennings,
With the help of volunteers, scientists at Audubon Canyon Ranch have been counting the shorebird populations for decades, building invaluable long-term data-sets. This is not as easy as it might seem. Imagine identifying and counting thousands of very similar-looking birds that are often found together and are constantly on the move.
“Every winter, we have up to 15 teams of one to three observers, each going out to assigned sections of likely shorebird habitat along Tomales Bay,” Jennings said, describing the tightly orchestrated counts he helps organize between November and February.
After studying vertebrate ecology and conservation biology at UC Santa Cruz, Jennings took a position as a field biologist and Avian Ecologist at Petaluma’s Point Blue Conservation Science. He earned his masters degree at Oregon State University, where his graduate work looked at food sources and survival of Adélie penguin chicks.
When Jennings is not counting birds, he is crunching numbers, analyzing the data researchers have collected. Even after accounting for rainfall that can impact where shorebirds forage, or predators that sometimes eat them — and for the 2008 restoration of parts of the Tomales Bay estuary — the graphs Jennings’ team have produced show a steep decline in most of the shorebird species they’ve been monitoring.
“In Tomales Bay, the shorebird population is down by 66%,” Jennings said. “In terms of numbers, the biggest losers were dunlin and western sandpipers.”
Both these species travel long distances to breed in the Arctic tundra during the summer. The San Francisco Bay, including Tomales Bay, is the largest estuary on the West Coast and is internationally recognized as a biodiversity hotspot. But this status has done little to protect migratory habitats, which are rapidly being degraded by development, industrial operations, and recreational activities.
“These migration paths are subject to a whole range of landscape changes that humans have made,” Jennings said.
Although local restoration efforts in Tomales Bay may have helped some bird species, so far, they’ve done little to stop the overall decline of migrating shorebirds. Conservation of migratory birds is particularly challenging, Jennings explained, because they travel such long distances with so many threats along the way.
“Ecology is complex. Effective conservation of local birds must be linked with regional/global efforts,” Jennings’ team reported recently in the journal “Ornithological Applications,” noting that isolated, relatively small habitat projects in single locations might not be enough to reverse overall negative population trends.
“There has to be regional and continent-wide collaboration on conservation efforts,” he said, “to improve habitat availability and quality across the entire range of these migratory species, if we are to reverse the negative trends.”