How DNA could help save California’s pheasants

SAN JOSE, Calif. - Startled, large flocks of pheasants burst into flight, exploding with colorful fuss and flutter from thickets of wild grass and fallen leaves.

But this was decades ago, when California’s autumnal landscape was a mosaic of fallowed fields, diverse crops and weedy stubble — and the handsome birds were abundant, including in the Bay Area.

Now the inconceivable is happening: Pheasants are vanishing.

To understand why, the state’s wildlife biologists are taking tiny tissue samples from the tongues of hunted birds in California wildlands, hoping that a map of the species’ genetic diversity will help explain their loss, and suggest a solution.

Birds were sampled at seven refuges. Since November 2023, the scientific team has collected an estimated 330 to 350 samples; when the study wraps up after pheasant hunting season ends, it hopes to have a total of 400 samples.

Increasingly isolated from each other because of fragmented habitats, the birds may be suffering from dangerous inbreeding. Or perhaps wild birds are breeding with weaker farm-raised and released birds, creating less resilient offspring.

Prized game animals, “they were so common at one time, and part of a long-standing traditional hunting heritage in California,” said Ian A. Dwight, principal investigator at the California Department of Fish and Wildlife.

Their loss is part of a larger emptying out of our skies. Nearly one-third of wild birds in the United States and Canada have vanished since 1970, according to a comprehensive study in the journal Science by a team of scientists from seven research institutions in the United States and Canada.

To study the pheasants, the wildlife department is sending staff to hunting “check stations” in the most rural swaths of the state, where game is inspected.

A small tissue sample — the size of a pencil eraser — is cut from each bird’s pale red tongue, a muscle that is rich with genetic material. This does not harm the meat or feathers, which are of interest to hunters. The sample is placed in a protective vial and stored at a CDFW facility to be later shipped to the University of Nebraska lab of Robert Wilson, an expert in the genetics of game birds.

Analyses will show whether the birds have long stretches of DNA where both copies of a gene are identical, indicating that they share a recent ancestor and are inbred. Gene variation is critical to a species’ healthy reproduction and immunity to disease.

The study could also reveal to what degree, if any, birds are the offspring of domestic and wild mixing.

Naturalists love their iridescent plumage.

“They are a delight for the eyes,” said Kirsten Holmquist of Sunnyvale, Calif., who in 2023 spotted a male bird posing on the side of a levee at the Sunnyvale Baylands. “The male has such a rich profusion of color. The female has a lovely complex pattern.”

Native to China, pheasants were imported in the late 1800s by the then-California Fish Commission.

By 1912, the species was well-established in alfalfa fields and pastures of California, including Santa Clara, San Mateo, Alameda and Contra Costa counties. Historical records describe a massive flock of 150 birds near Morgan Hill and a smaller flock between Berryessa and Milpitas, according to William Bousman of the Santa Clara Valley Bird Alliance.

Even as orchards replaced grain fields, there remained ample habitat, writes Bousman. The population of the species, which is related to other game birds like wild turkey and California quail, likely peaked from the 1930s to 1950s.

Even in the early 1980s, “the birds were quite common in the Palo Alto Baylands, Sunnyvale ponds and other bayfront areas that were less traveled and grassy,” said Bird Alliance director Matthew Dodder. “Since then, they have had a steady decline.”

Surviving birds can sometimes be spotted in some of the seasonal wetlands and grasslands of the San Francisco Bay Area, such as Harvey Marsh in Sunnyvale Baylands Park, East Palo Alto’s Ravenswood Preserve, Fremont’s Coyote Hills Regional Park and along eastern Contra Costa County’s Suisun Bay.

What happened? In addition to urbanization, widespread stocking of the birds for hunting has slowed or stopped, said Dodder.

And the intensity and efficiency of California agriculture has increased.

Farmers no longer let land stand idle, so there’s less brush for birds’ shelter and food. Every pocket of land is put to use, eliminating the hedgerows between parcels, according to a 2016 study by a team led by Peter Coates of the U.S. Geological Survey’s Western Ecological Research Center in Dixon.

Rice is replacing cereal grains like wheat and barley, and pheasants can’t nest in flooded rice fields, according to the study. Increasingly popular nut tree orchards don’t provide a vegetative understory.

Finally, new harvesters are ultra-efficient, so seed isn’t scattered. Modern mowing leaves little stubble. And new state regulations prohibit post-harvest burning, so fields are blanketed with weed-killing herbicide.

All of these factors are creating smaller islands of suitable habitat, shrinking and isolating bird populations, Dwight said. Hunting is considered an insignificant factor in reducing numbers, because only males are shot.

“Pheasant populations are becoming more and more fragmented,” said Taylor, who is coordinating the National Wild Pheasant Conservation Plan, a blueprint for restoring populations.