In the late 1800s, California introduced red foxes for hunting and fur farms; at Seal Beach, they drove light-footed Ridgway's rails down to just 5 pairs in 7 years

In the marshes of Southern California, a small, shy bird has been fighting for survival for more than a century. The light-footed Ridgway’s rail is rarely seen, but its story shows how one human decision made generations ago can still impact an ecosystem today. According to a 2020 species review by the U.S. Fish and Wildlife Service, citing a 1994 California Department of Fish and Game report, non-native red foxes introduced in California in the late 1800s eventually drove the rail's population at the Seal Beach National Wildlife Refuge down to just five breeding pairs within seven years.

A shy marsh bird most people have never heard of

The light-footed Ridgway’s rail is a chicken-sized bird with a curved bill and gray-brown feathers that blend into coastal marsh grass. It lives in the cordgrass and pickleweed marshes that fringe the coast from Santa Barbara down through San Diego and into Baja California, Mexico. It was designated a federally endangered bird on March 8, 1969, and was listed as a state endangered species in California on June 27, 1971. The bird is rare even today. The federal review estimated its statewide population at 308 breeding pairs in 2019, down from 656 pairs in 2016.


From hunting trend to ecological trap

Red foxes are not native to most of the California lowlands. Researchers Jeffrey Lewis, Kevin Sallee and Richard Golightly detailed how these foxes came to be in a study published in The American Midland Naturalist. Foxes were introduced into the state in the late 1800s for sport hunting and fur farming. Some got away. Some were deliberately released by fur farmers or pet owners who no longer wanted them. In the years that followed, the foxes spread out through the Sacramento and San Joaquin valleys, the San Francisco Bay area, and eventually the coastal plains of Southern California.

The red fox is a cunning, opportunistic predator. By the time the foxes reached the marshes, they found easy prey among ground-nesting birds like the rail. The eggs and chicks of the rail, tucked into low nests of woven marsh grass, were poorly defended against a fox that could simply walk in and take them. That same research links increases in red fox populations in California to declines in several other native birds, including the California least tern and the snowy plover.

Five pairs left in just seven years

Nowhere was this more evident than at the Seal Beach National Wildlife Refuge in Orange County. The federal review documents that red foxes arrived at Seal Beach and in seven years reduced the light-footed Ridgway's rail population to just five breeding pairs. For a small and geographically isolated population, that number is near the border of local extinction. Wildlife managers then responded with a coordinated removal effort targeting the non-native foxes. The results were significant: the rail population at Seal Beach rebounded to 65 pairs by 1993, a roughly thirteenfold recovery after the predator pressure was removed.

Why coyotes are part of the solution

Interestingly, the fox problem at Seal Beach never stayed solved by trapping alone. A 2012 U.S. Fish and Wildlife Service conservation plan for the refuge found that red fox numbers there have stayed under control largely because coyotes re-established themselves in the area. That sounds strange because coyotes are predators too, but ecologists have seen this pattern before.

In a widely cited paper in the journal Nature, ecologists Kevin Crooks and Michael Soulé described a process they called "mesopredator release." Removing top predators such as coyotes can leave smaller predators such as foxes, raccoons, and skunks unchecked, allowing their populations to increase to the detriment of ground-nesting birds. Their research on fragmented habitat in Southern California found that when coyotes hung around, they kept smaller predators in line and native bird diversity fared better. In Seal Beach, the return of coyotes seems to have done much the same, indirectly protecting the rail by keeping fox numbers down.

Where things stand for the rail today

The light-footed Ridgway's rail remains listed as endangered. The federal review in 2020 recommended no change in status, stating that predation and loss of habitat from development, sea level rise, and shrinking marsh acreage continue to threaten the bird's survival. Refuge managers continue active predator control programs against other threats such as feral cats and crows at several sites including Point Mugu, Seal Beach, Kendall-Frost, and the San Diego National Wildlife Refuge Complex. Since 2001, a captive breeding program has released more than 550 rails back into the wild, according to the most recent count in the review.

This chapter of the story is a reminder of how a choice made for sport or fashion over a century ago can reverberate through an ecosystem for generations. On one refuge, removing an invasive predator helped this small secretive marsh bird claw back from the brink. But its full recovery depends on protecting the fragile strip of coastal marsh where it lives.