The Life and Times of the California Clapper Rail

California Clapper Rail 2

This story was originally published in the 1991 Summer issue of Tideline, the newsletter of the San Francisco Bay National Wildlife Refuge Complex newsletter. As of 2014, the California Clapper Rail has been renamed Ridgway's Rail.


Out in the salt marsh, amidst the tracts of pickleweed and dense stands of cordgrass along meandering tidal sloughs, stalks the secretive California clapper rail.  Described by Arthur Cleveland Bent in 1926 as "a product of the Golden State [which] never wanders far from the Golden Gate," the California clapper rail is a hallmark of our bayshore wetlands.  Its presence certifies the health of the salt marsh, just as the presence of a red-legged frog is indicative of a healthy pond, or a caged canary singing deep in a coal mine certifies the health of the subterranean air.

In the past, thousands upon thousands of California clapper rails foraged, mated and nested in the extensive marshes along San Francisco Bay.  They flourished here for good reason.  Salt marshes contain everything that these birds require - abundant food, nesting sites and cover are available, and few terrestrial predators venture far into the tidal wetlands.

Life Cycle

Clapper rails build nests low in the marsh, near tidal sloughs.  Picklweed, cordgrass, gumplant and other nearby marsh plants make up the nests, which are constructed on the marsh floor and hold a half dozen or more eggs.  The nests are hard to see, because they are built beneath the vegetative canopy, which hides them from some predators.

However, other predators still find the nests, and eat the eggs within.  Norway rats, native racoons, red foxes and feral cats consume, in some studies, almost half of the population's total production of eggs each year.

Other eggs may be lost due to San Francisco's Bay's high contaminant levels. Mercury and selenium become lethal at high concentrations and have been found in clapper rail eggs.  Studies are underway to determine whether damage has been done to our rail population as a result of embryo mortality caused by these and other heavy metals.

High tides destroy nests and kill more eggs.  Adult rails are known to construct "brood nests" on floating platforms of stems and stalks, which help keep their young hatchlings above water during six-and seven-foot tides.  Tidal flooding is more frequent, and of longer duration near sloughs, which are low in elevation and therefore most prone to inundation by high tides.  However the survival benefits of nesting close to the sloughs are important , and outweigh the hazards of being flooded.

The sloughs are essential foraging areas for adult and young rails.  Biologists have identified the marsh animals usually eaten by clapper rails, and most are common along tidal sloughs.  Mussels, spiders, clams, shore crabs, amphipods and other salt marsh invertebrates compose the bulk of the birds' diet.  Locating close to tidal sloughs makes hunting more efficient.   It also makes escape from predators more likely.

The networks of  sloughs become avenues of escape for the vulnerable, flightless chicks.  Unlike the broad, flat expanses of pickleweed, sloughs offer twists, turns, and shadows, thus making evasion more possible.  Despite this, young clapper rails still fall prey to predators.

Adult rails are eaten too, picked off from above from harriers, hawks, falcons, and ravens.  No one knows how long clapper rails live.  One thing is certain; as predation increases in intensity, life expectancy drops accordingly.

Even with predation, flooding and other hazards of life in the salt marsh, California clapper rails have flourished here since the birth of the Bay and the development of the extensive salt marshes.  First noted by field crews with the Pacific Coast Railroad Survey in 1850, California clapper rails have been recorded along the Bay in marshes located in San Francisco, San Mateo, Santa Clara, Alameda, Contra Costa, Solano, Napa, and Sonoma counties.

Other studies have shown that California clapper rails also once occurred in Elkhorn Slough near Monterey Bay, in Morro Bay, Tomales Bay, and Humboldt Bay.  In short, many areas with prime salt marsh in central and northern California have supported California clapper rails.  Tragically, most of the salt marsh is gone now.  Loss of the marsh has meant loss of the rails.

Population Status

In 1970 the California clapper rail was listed as "endangered" on the U.S. Endangered Species List.  Filling and diking of historic marsh habitat had reduced the numbers to the point that extinction was considered imminent.  A 1971-1975 census of the birds showed that the population, which had at one time numbered in the tens of thousands, had dropped to about 4,000.  Another census, conducted between 1981 and 1986, used better, more accurate methods which resulted in a more realistic estimate of population size.  Scientists surveyed 45 marshes and counted a maximum of 1300 birds.

More recent studies have demonstrated a severe drop in numbers.  In 1990 the estimate for the entire population of California clapper rails was 500 birds.

Going . . .Going . . . Going . . .?

The California clapper rail has never really had much of a chance.  Beginning in the days of the Gold Rush, clapper rails were harvested by the thousands.  They were served from silver chafing dishes on Nob Hill as well as from iron stew pots in Angels Camp.  But hunting, by itself, rarely exterminates a thriving population.  In the case of the California clapper rail, overhunting was followed by grievous habitat loss.

The Gold Rush brought thousands of immigrants to the Bay Area, and filling of the Bay began.  Salt marshes have since been dredged, diked and bulldozed, until less than 10 percent of the original wetlands survive.  Species such as the California clapper rail, which are utterly dependent upon salt marsh habitat, were imperiled.

Overhunting, pollution and habitat loss have been decimated the population, making the clapper rail one of California's most endangered species.  Recently, another factor has entered this dismal picture:  a non-native subspecies of the red fox has established itself in the Bay Area, and is making short work of the remaining clapper rails.  A proven rail eater, the red fox prowls through the marsh bolting down too many of the endangered birds.  It may use the sloughs - the rails' network of escape routes - as avenues of entry into nesting territory.No one knows how the fox got here.  It may be descended from escaped game farm animals, or from released pet foxes brought in from the midwest.  Regardless of its reason for being here, its effect on the rail population has been terrible.  Unlike most native terrestrial predators, it does range far into the marsh where it devours clapper rails.  and it is becoming more and more abundant each year.  The future looks very grim.

The Future:  Survival or Extinction?

What will happen to this endangered species?  Is it doomed to extinction?  Will other vulnerable species disappear as well?  Wildlife biologists with the U.S. Fish and Wildlife Service, the National Audubon Society and other agencies and organizations are trying to save it.  They know that the best way to help any species survive is to reverse the trends that have brought it to the brink of extinction in the first place.  

The California clapper rail has been protected from hunting since the early 1900s.  Whereas during the 1890s five thousand rails could be legally killed in a single week, none can be hunted today.  Over-harvesting is a problem of the past.

Habitat, however, is still a serious problem.  Though wetlands can no longer be "developed" without a permit accompanied by damage mitigation measures, there is very little salt marsh left.  Most of what remains is composed of isolated, relict strips and patches.  Clapper rails may not be able to traverse wide, inhospitable sections between the few surviving areas of prime marsh, and therefore may not find mates.

Pollution remains a serious threat.  Field studies to determine sources and concentrations of metals, organochlorines and other contaminants have been underway for several years.  Much needs to be done to assess the nature of pollutants in the Bay, in order to attack that problem in an intelligent manner.

The red fox and other terrestrial predators will continue to ravage the defenseless clapper rail population unless they are effectively managed.  Fewer than 500 California clapper rails exist today, and the number continues to decline.  Natural predators and high tides cause enough harm; the rail population cannot afford to have many of its members be devoured by non-native predators that are increasing their numbers, expanding their range, and devastating their helpless prey.

Agencies responsible for the quality of San Francisco Bay and its resident creatures are dedicated to doing everything necessary to save the California clapper rail.  As responsible citizens, we must support their efforts.  As caretakers of our natural heritage, we can do no less.