Sensitive Bird Species Nesting at Bolsa Chica

Bolsa Chica is used by many nesting bird species, including some sensitive species that only nest at a limited number of sites in California.  The Restoration Project expanded the available nesting sites through the construction of Nest Site 1, Nest Site 2, and Nest Site 3.  North Tern Island and South Tern Island are two nesting sites in Inner Bolsa Bay that were already heavily used prior to the restoration.  The five nesting sites can be seen in this map.

Jump to species profiles for the following birds:

  California Least Tern

  Western Snowy Plover

  Elegant Tern

  Black Skimmer

  Belding's Savannah Sparrow

  Light-footed Clapper Rail (not currently known to nest at Bolsa Chica)

SPECIES PROFILES

California Least Tern (Sternula antillarum browni) - State and Federally listed Endangered Species

  Species Profile Written by Dr. Charles Collins for the US Fish and Wildlife Service

Unfrequented sandy beaches close to estuaries and coastal embayments had traditionally served as nesting sites for the California least tern. Primarily due to coastal development and intense human recreational use of beaches, the least tern was denied suitable nesting areas and was listed as Endangered with extinction in 1970. A few least tern nesting areas are on beaches (such as, Tijuana Estuary, Naval Amphibious Base-Coronado, Santa Margarita River mouth, Huntington and Venice Beachs). The majority of nesting areas are on manufactured (inadvertently and intentionally) substrates or fills. Since 1970, nesting sites have been recorded from San Francisco Bay to Bahia de San Quintin, Baja California. The nesting range in California has apparently always been widely discontinuous, with the majority of birds nesting in southern California from Santa Barbara County south through San Diego County.

This exclusive fish-eater typically feeds mostly on topsmelt, northern anchovy, and jacksmelt. Feeding is carried out both in the calm waters of narrow estuaries or large bays and for a short distance (i,e., usually within 3 kilometers off beaches in the open ocean. Their hovering and plunging habits are conspicuous.

The California least tern is migratory, usually arriving in its breeding area by the last week of April and departing again in August. Least terns are colonial nesters but do not nest in as dense a concentration as other tern species. Minimum breeding age is 2 years. The nest of the California least tern is a simple scrape or depression in the sand and one to four eggs are laid, usually two. There is one breeding season, from May through August and only one brood is raised. However, the birds will renest if eggs or chicks are lost. Re-nesting attempts after initial failures, and 2-year-old birds nesting for the first time, often occur from mid-June to early August. Parents continue to feed fish to their young even after they are strong fliers.

The least tern is vulnerable to a long list of predators, some of which are very abundant in urban environments, such as feral cats and dogs, crows, and American kestrel. To protect least tern nest sites from disturbance, ground access is typically controlled by fences or other obstructions. Nest site management requires these three elements to improve least tern reproductive success: protection from disturbance, management of predators, and surface preparation where weeds or excessive plant growth is a problem.

At the time of listing as Endangered, the least tern breeding population was estimated to be about 600 pairs. The Statewide breeding population has increased considerably in just the last five years and has exceeded 4,500 pairs since 2000.

When the Bolsa Chica nesting islands were created in 1978, the least tern began nesting on the north island. When elegant terns, then black skimmers, began nesting on the north island, the least tern was crowded off of it and began nesting on the south island. In recent years, least tern nesting success at Bolsa Chica has been very poor, largely due to predators and the relatively small suitable area for nesting.

Western Snowy Plover (Charadrius alexandrinus nivosus), Federal Threatened Species 

  Species Profile Written by Jack Fancher, US Fish and Wildlife Service

The western snowy plover is a sparrow-sized, white and tan colored shorebird with dark patches on either side of the neck, behind the eyes, and on the forehead. The coastal western snowy plover population is defined as those individuals that nest adjacent to or near tidal waters and includes all nesting colonies on the mainland coast, peninsulas, offshore islands, adjacent bays, and estuaries. The breeding range of the western snowy plover extends along coastal beaches from the southern portion of Washington State to southern Baja California, Mexico.

The breeding season of the western snowy plover extends from March 1 through September 15. Generally, 3 eggs are laid in a nest that consists of a shallow depression scraped in sandy or saline substrates. Some nests are lined with plant parts, small pebbles, or shell fragments. The female usually incubates the eggs for an average of 27 days. Snowy plovers will renest after loss of a clutch or brood. Snowy plover chicks are precocial and leave the nest within hours of hatching in search of food. The tending adult provides danger warnings, thermoregulation assistance, and guides the chicks to foraging areas, but does not provide food to their chicks. Broods rarely stay in the immediate area of the nest. Young birds are able to fly within approximately 31 days of hatching. Double brooding and polyandry have been observed and snowy plover females may leave very young chicks to find another mate, leaving the male to care for the brood. Western snowy plover adults and young forage on invertebrates along intertidal areas, along beaches in wet sand and surf cast kelp, in foredune areas of dry sand above the high tide, on salt pans, and along the edges of salt marshes and salt ponds. The snowy plover is primarily a run and glean type of forager.

Poor reproductive success resulting from human disturbance, predation, and inclement weather, combined with permanent or long-term loss of nesting habitat to urban development and the encroachment of introduced beachgrass, has led to the decline in active nesting colonies as well as an overall decline in the breeding and wintering population of the western snowy plover along the Pacific coast of the United States. In southern California, the very large human population and the resultant beach recreation activities by humans have precluded the western snowy plover from breeding on historically used beach strand habitat. As a result of these factors, the Pacific coast population of the western snowy plover was Federally listed as Threatened with extinction in 1993.

There are only a handful of snowy plover breeding locations currently used in southern California. The more well used locations include Bolsa Chica, Camp Pendleton, Batiquitos Lagoon, Naval Amphibious Base-Coronado, and Tijauna Estuary. Snowy plover nesting use at Bolsa Chica is reported in detail in the annual reports.

At Bolsa Chica, the western snowy plover reproductive success has varied between poor and very good. Typically, between 30 and 40 adults are present during breeding season. In some years, half or more nests were destroyed by egg stealing predators, such as crows which are very abundant in the adjacent urban area. The use of mini-exclosures on nests reduced nest loss. However, plover chicks are very vulnerable to avian chick predators found at Bolsa Chica, such as American kestrel and loggerhead shrike. Bolsa Chica continues to be an important snowy plover breeding area in southern California.

Elegant Tern (Thalasseus elegans), CDFG Species of Special Concern 

  Species Profile Written by Dr. Charles Collins for the US Fish and Wildlife Service

The Elegant Tern is one of the group of crested terns and has the longest crest of all. Their slender yellow-orange bill appears to droop slightly at the tip. The adult in summer plumage has a black cap with long nuchal crest. The under parts may have a pink tinge, which in such cases is diagnostic in comparison with other more red- billed Terns. Some have darker central primaries contrasting with paler surrounding ones. The adult in winter (basic) plumage has a white head merging diffusely with black mask from the eye to the nape. Elegant Terns possess a black loral triangle in front of the eye, which passes directly into the post-ocular mask. Thus the eye is not isolated by white. Only at a close range is a narrow white eye ring visible.

The Elegant Tern has the most restricted breeding distribution of any tern in North America. It is currently found in only five colonies in North America: Isla Rasa and Isla Montague, in the Gulf of California, Mexico, and the San Diego saltworks, Bolsa Chica, and Pier 400 Terminal Island, in southern California.

Departure from southern California nesting colonies begins in late August or early September. This is often preceded by an influx of birds from other colonies, presumably in Mexico. Many range north in late summer and autumn, commonly to San Francisco and Humboldt Bay. They are much less common further north, but may reach Oregon and western Washington during El Niño years. Although some linger until November/December, most depart south in early fall to winter in coastal Ecuador, Peru, and Chile where a few remain throughout the year. Elegant Terns occur as vagrants to east Texas and the Atlantic coast. Restricted to littoral marine habitat, Elegant Tern migrations are restricted to coastal marine waters.

In southern California, Elegant Tern foraging occurs primarily >8 km from the colony. They can be found foraging in most bays and protected areas of north San Diego County: including, but not limited to, the mouth of the Santa Margarita River, Oceanside Harbor, Buena Vista Lagoon, Agua Hedionada Lagoon and San Elijo Lagoon, south to La Jolla Cove and Mission Bay. They are typically found foraging singly or in groups of two or three. Elegant Terns are, at times, also found foraging in the outer evaporating ponds of the San Diego Bay saltworks. The diet of the Elegant Tern consists entirely of fish, the bulk of which are caught in marine waters. Those nesting at the San Diego saltworks consumed northern anchovy, topsmelt, bay anchovy, jacksmelt, jack mackerel, and long-jawed mudsuckers. Northern anchovies made up 86.8 % of their diet in 1981 and 35% in 1995. At Bolsa Chica from 1993 to 2001, and Terminal Island from 1998, 2000 and 2002, 56.4% of identified prey were northern anchovy and 13.1% were pacific sardines. Pipefish of 2-3 species made up an additional 13.5% and topsmelt, California grunion, Pacific saury and jack mackerel were also taken in smaller amounts (< 7%). Year to year variation was noted particularly the ratio of northern anchovy to pacific sardine with higher numbers of anchovy being taken in colder water years.

Elegant Terns court and form pairs while still on migration and away from the nesting colony. In general, courtship and copulation do not occur at the nesting colony nor do the birds assemble in large numbers more than a few days prior to commencement of egg laying. They arrive at the nesting grounds and then continue courtship and pair formation in small groups or flocks called “clubs” close to but not at the nesting colony. Elegant Terns are highly colonial nesters; large groups of pairs dig shallow nest scrapes and lay eggs in one 24-hour period, with about 10 nests per square meter. At this density, nests are only 30-32 cm apart (measured from center to center) in a compact hexagonal pattern. At the San Diego saltworks, Elegant Tern egg laying commences on or about 19 April and extends through 10 June with the peak of nest initiations occurring during the week of 10 May. Nest initiation dates at Bolsa Chica and Terminal Island are about one to two weeks later than this. Elegant Terns prefer small, isolated, and undisturbed islands in Mexico. They nest in the presence of other breeding gull or tern species. Nests may have small twigs, bones, clam and snail shells that are within reach of a sitting tern pulled in to partially line the nest or they may simply be unlined shallow scrapes in the ground where they most often lay a single egg; two egg clutches are regular but it is not always sure that these are not the result of two females laying in the same scrape. During incubation and chick brooding periods the terns defecate while on the nest, and by the end of the season the substrate of each nesting group has a honeycombed white “pavement” of fecal material. Some of the diverse nesting habitats reported include; sandy and marshy coastal islands, sandy islets in salt lakes. At Bolsa Chica and Terminal Island they nest on the bare sandy substrate. Incubation times range between 23 and 27 days. Most chicks remain in the nest for about four days before becoming ambulatory and joining other chicks to form a dense moving creche. Young exhibit an extraordinarily long period of dependence on their parents, extending well over six months post fledging.

Although Elegant Terns breed at five different sites in North American, three of which are found in southern California, possibly 90 to 97% of the world population of this tern breeds on Isla Raza, Mexico.

The San Diego population has increased from approximately 30 pairs in 1959 to over 800 pairs in 1981. No nesting occurred at the Salt Works in 1990, but breeding was reestablished in 1991, with 250 pairs of Elegant Terns producing approximately 200 chicks. Nesting decreased at the Salt Works between 1993 and 1997 but between 312 and 427 pairs of Elegant Tern nested there in 1993, and only80 pairs were estimated to be present in 1994 and there were only two nesting attempts in 1997. The nesting population again surged in 2003 with perhaps as many as 10,000 pairs nesting there.

In Orange County, Elegant Terns were common post-breeding migrants until 1983, when birds began to remain at Bolsa Chica throughout the spring and early summer. Their numbers increased until 1987 when 31 pairs nested (largely unsuccessfully). Bolsa Chica is now an established breeding colony and contained up to 4,000 pairs in 1995 and 1996. Smaller numbers have nested there in recent years, mostly due to the growth of the Terminal Island colony and/or disturbance at Bolsa Chica.

In 1998, a large cohort of Elegant Terns bred at Terminal Island in the Los Angeles Harbor. The nesting area is a portion of a 15-acre nesting site provided for Least Terns and enclosed with three-foot high chick fencing. Many of these terns nesting at Terminal Island in 1998 were originally from the Bolsa Chica colony and were expected to move back there when the site was developed by the Port of Los Angeles. However, from 2000 to 2002, they successfully nested principally in two locations within the designated nesting site for Least Terns and may continue to nest here despite adjacent areas at Terminal Island having been developed for port facilities. By 2003 the total southern California population of Elegant Terns had increased to 10,000-12,000 of which 10,000 returned to breed in the San Diego saltworks largely abandoning both Bolsa Chica and Terminal Island where the bulk of the population had bred in recent years. This sudden shift was reversed in 2004 when large numbers (>10,000 pairs) of Elegant Terns nested at Terminal Island and another 1300 at Bolsa Chica. Local water conditions may have influenced this shift in colony location. Birds banded t Bolsa Chica and Terminal Island have been recovered in the other nesting colonies further substantiating a high degree of inter-colony movement from year to year within southern California. To date, no banded bird from one of the Mexican breeding colonies has been recovered in any of the southern California colonies. More distant recoveries of Elegant Terns banded at Bolsa Chica include individuals overwintering or in migration in El Salvador (2) Costa Rica (1) and Colombia (1).

Elegant Terns are found throughout the eastern Pacific coastal region, a region that is the epicenter of El Niño events. As such, they are subject to large-scale climatic changes that impact local food resources as seen in a variety of other seabird species including locally nesting Least Terns. Growth studies performed before, during, and after the El Niño event of 1998 showed no significant impact on Elegant Tern chick growth suggesting that this species is adapted to periodic climatic shifts and short-term changes in availability of their principal prey. They may only be affected by the most severe of these climatic events.

Even so, their limited breeding range and small number of breeding colonies is cause for some caution and has resulted in the Elegant Tern being listed as a Bird Species of Special Concern in California.

Black Skimmer (Rhynchops niger), CDFG Species of Special Concern 

Bolsa Chica Update  Post-restoration, several hundred Black Skimmers have been observed during the nesting season on the created Nest Site 1.  The birds have nested there each year, although the number of nests or fledglings has not been quantified.  The skimmers are believed to have reduced the reproductive success of the western snowy plover and California least tern due to predation and trampling, respectively.

  Species Profile Written by Dr. Charles Collins for the US Fish and Wildlife Service           

The Black Skimmer is unmistakable within its range. Its unusual voice, bill, and feeding behavior make it truly unique. The adult in breeding plumage is black above and white below with a white tail. The basal half of the laterally compressed bill is bright red with the distal half black. The lower mandible extends 2-3 cm beyond the upper, which is hinged and can be freely elevated and clamped shut. The wings are long and narrow.. The feet of Black Skimmers are bright red-orange and webbed. Their tail is short and is square or slightly forked

In the eastern U.S. skimmers are almost exclusively coastal; nesting on barrier beaches, shell banks, spoil islands, and salt marshes from Massachusetts and Long Island, NY, along the Atlantic and Gulf coasts to s. Mexico with isolated colonies on the . Yucatan Peninsula. In Florida, skimmers frequently occur inland, sometimes in large numbers, and have bred near Belle Grande in south.-central Florida and at Lake Okeechobee.

During the last three decades, Black Skimmers have become increasingly common along the southern California coast. The first Pacific coast record was in 1962 at the Santa Ana River mouth. Six years later they were observed at the Salton Sea and bred there in 1972. Until they began nesting at the San Diego saltworks in 1976, they were an irregular visitor to coastal southern California. Their breeding range expanded northward along the Pacific coast with breeding established at Bolsa Chica in 1985, Upper Newport Bay in 1986 and Terminal Island in 1998. They have continued to breed in most years at the Salton Sea and a small group (< 10 pairs) has bred irregularly in south San Francisco Bay since 1994. They have also bred in Batiquitos Lagoon since 1995. In addition to southern California the western population of Black Skimmers breeds south to Nayarit, Mexico.

Post-breeding Black Skimmers disperse from their breeding colonies but many over-winter in southern California. Winter roosts have typically been at Santa Barbara, Long Beach, Seal Beach and Mission Bay in San Diego. Typical winter roosting areas are located on public beaches, even those with a lot of human activity, or estuarine sand bars where they frequently associate with gulls and, occasionally, terns and shorebirds. Black Skimmers banded at Bolsa Chica and Upper Newport Bay have been noted at all of these wintering areas as well as in Ensenada and Bahia San Quintin in Baja California. A single individual was observed in winter far to the South near Mazatlan in coastal Mexico. Many color banded individuals from Salton Sea colonies have also been seen at the several coastal wintering sites.

Black Skimmers are highly nocturnal. Although they can occasionally be seen foraging in the daytime the bulk of their feeding activities and chick provisioning takes place from dusk to dawn. Skimmers forage mainly in tidal waters of bays, estuaries and lagoons but also utilize rivers, and salt marsh pools, creeks, and ditches; such habitats tend to concentrate small fish. They feed preferentially under low wind conditions when the water surface is smooth. They typically glide low over the water with their lower mandible slicing the surface of the water. When the mandible contacts a fish or other object, the maxilla clamps down while the head and neck tuck downward and back, securing the prey. Fish are then turned and swallowed headfirst or carried crosswise in the bill to the nest. There is much controversy over the foraging habitat of skimmers, with little information available on major food items; however, observed prey has been primarily small fish in range of 3-12 cm length (rarely up to 20 cm). The types of fish caught seem to depend on the region and local availability. At Bolsa Chica in 1995-1996 northern anchovy (23.6%) was the most commonly taken prey. Topsmelt (15.0%) California sardine (11.6%), California grunion (5.3%), California killifish (3.6%), mosquitofish (6.2%) and shadow gobies (8.6%) were also regular prey items. At the San Diego saltworks in 1995-1998 California sardine (20.9%) and topsmelt (16.8%) were the most abundant prey species with jacksmelt (3.0%), California grunion (6.8%), California halfbeak (8.6%), California killifish (6.8%), arrow goby (4.1%), Shadow goby (5.8%) and longjaw mudsuckers (3.9%) also recorded. The diversity of prey items taken is a reflection of the equally diverse foraging habits of Black Skimmers.

Most Black Skimmer breeding colonies are found on beaches, or sand islands, particularly in coastal southern California. In other parts of their range they utilize sand bars, dredge spoil islands, or salt marshes where they will nest of mats of dead vegetation. Proximity to Caspian Terns and other tern species is an important feature of skimmer colonies in southern California. During nest building, mates take turns scraping, using exaggerated sand-kicking posture (neck, head, bill, and tail elevated) with alternate foot strokes that throw sand backwards. Birds rotate in the scrape to create a saucer-shaped depression, similar to resting scrapes used throughout the year. The depression takes only a few minutes to create, but the process of nesting may involve several scrapes and nest showing behavior, requiring 5-7 days between onset of nest “building” and laying No material is added to the nest. Eggs are mainly ovate to elongated, crème-colored and blotched with varying amounts of black that blends well with the sandy environment. Egg laying begins 7 to 10 days the after first nest scrapes, appear. Eggs are laid in 1-2 day intervals with a typical clutch size of 3-4 eggs. Incubation period can be as short as 21-23 days but can last 23-25 days in areas of disturbance.

Post-breeding and wintering flocks in southern California regularly contain color-banded individuals from breeding colonies at the Salton Sea. Some of these have also been noted to remain and breed at Bolsa Chica, Upper Newport Bay and the San Diego Saltworks. There appears to be a lot of movement between wintering groups even within a single winter season. Black Skimmers seen in Santa Barbara have been seen within a few days in Long Beach and, later on, back in Santa Barbara. The same is true of birds in Mission Bay and Long Beach. In other cases marked individuals appear to remain at one wintering site all winter and also return to it in subsequent years. Some Black Skimmers show a degree of natal philopatry, returning to breed in their natal colonies; they breed for the firs time when two years old. Others have moved to different southern California colonies to breed and have been recorded at more than one colony in a single breeding season. One of the individuals which colonized San Francisco Bay had been banded earlier at Bolsa Chica.

Los Angeles Harbor is the northernmost nesting location for Black Skimmers in southern California. In 1998 and 1999, Skimmers nested on an area of newly deposited dredge fill. Black Skimmers initiated 10 nests in 1998 but none were successful. In 1999, they used another site adjacent to an area where Caspian Terns were also nesting. The skimmers initiated approximately 170 nests here in 1999, but productivity was poor, primarily due to high chick mortality and predation by gulls. In 2000, they again attempted nesting on the new fill area, this time within the 15-acre nesting site provided for Least Terns. They nested late in the Least Tern nesting season (late July), initiating approximately 115 nests but produced no fledglings, and most nests were abandoned by mid-August. There was no evidence of gull predation but high chick mortality and abandonment may have been due to frequent visits by Peregrine Falcons. Such late season nesting of Black Skimmers has frequently occurred at other nesting colonies, and may involve more pairs than earlier breeding attempts so not all can be attributed to re-nesting by birds which failed in an earlier nesting.

At Bolsa Chica, in 2003 and possibly in earlier years as well, late season predation of pre-fledging chicks by Peregrine Falcons may have caused nest abandonment and termination of breeding that season. They have been negatively impacted by nest predators (avian and terrestrial) at several of their breeding sites. When breeding in association with the larger and more aggressive Caspian Terns they may gain some protection from potential predators. However there is some disadvantage to nesting jointly with the large colonies of Elegant Terns. The large crèches of Elegant Tern chicks wander over their nesting colony and seem to disturb Black Skimmers tending eggs or small chicks. Trampling of smaller Black Skimmer chicks appears to have been an extra source of mortality. Black Skimmer reproduction was enhanced at Bolsa Chica in years when low fencing was used to keep the Elegant Tern chick crèches away from skimmer nests.

Their limited breeding range in southern California and most of their breeding being limited to only 3-4 colonies has resulted in the Black Skimmer being listed as a Bird Species of Special Concern in California.

Belding's Savannah Sparrow (Passerculus sandwichensis beldingi) State Listed Endangered Species 

  Species Profile Written by Jack Fancher, US Fish and Wildlife Service

The Belding’s Savannah sparrow is one of four subspecies of Savannah sparrows that is otherwise widely distributed and occur in a variety of habitat types, including grassland, high-elevation meadow, and marshes. The Belding’s Savannah sparrow is unique in that it represents one of only two wetland-dependant avian species endemic to coastal salt marshes in southern California. This species is a year-round resident of these salt marshes, and is therefore reliant upon these habitats to meet all of its life history requirements. This race ranges along the southern California coast from Santa Barbara County (Goleta Slough) in the north into Baja California, Mexico (near El Rosario) in the south.

The Belding’s Savannah sparrow is a small brown sparrow with fine streaking on the head and face, a pale beige to white belly, and often shows a dark central breast spot. As with most ground dwelling species, this bird is inconspicuous and blends well with its environment. The most distinguishing characteristic is the yellowish color of the lores (area between the bill and eyes).

The main factors that influence the long-term survivability of this subspecies are the health and security of its habitat. In southern California, the long-term protection of coastal salt marsh habitat is closely tied to ownership and use of the land. Threats of salt marsh habitat loss or degradation have slowed but continue. Other threats include problems associated with human trespassing, pets within the marshes, encroachment from adjacent human activities, and habitat degradation.

This subspecies was listed as endangered by the State of California in 1974 due to the development, degradation, and fragmentation of coastal salt marsh habitat as numbers of Belding’s Savannah sparrows decreased dramatically.

Because of the secretive nature of this sparrow, it can be difficult to obtain accurate population estimates. Given the right habitat conditions, territory size may be small and breeding pairs may occur in relatively high concentrations. Census techniques consist of searching for territorial males in suitable habitat during the breeding season (late March through early July). Territorial behavior is ascertained through detection or observation of singing, scolding, aerial chases, nest-building, feeding young, or extended perching of individuals or presumed mates perching together in an area.

The Belding’s Savannah sparrow population in California increased from 1,084 pairs in 1973, 1,610 pairs in 1977, 2,274 pairs in 1986, 1,844 pairs in 1991, 2,350 pairs in 1996, and 2875 pairs in 2001. However, statewide censuses of Belding’s Savannah sparrows reveal wide fluctuations in local population sizes, with local extinctions occurring in some years. The population at Bolsa Chica has been more regularly censused and the population has been fluctuating between 100 and 250 breeding pairs.

Light-footed Clapper Rail (Rallus longirostris levipes) State and Federal Endangered Species 

  Species Profile Written by Jack Fancher, US Fish and Wildlife Service

The light-footed clapper rail is a hen-sized marsh bird that is long-legged, long-toed, and approximately 14 inches long. It has a slightly down-curved beak and a short, upturned tail. Males and females are identical in plumage. The cinnamon breast contrasts with the streaked plumage of its grayish brown back and gray and white barred flanks.

The light-footed clapper rail uses southern California coastal salt marshes, lagoons, and their maritime environs. The birds nest in the lower intertidal zone of coastal salt marshes where dense stands of cordgrass (Spartina foliosa) are present. They also build nests in pickleweed (Sarcocornia pacifica). Light-footed clapper rails have also been known to reside and nest in freshwater marshes, although this is not common. They require shallow water and mudflats for foraging, with adjacent higher vegetation for cover during high water .

Light-footed clapper rails inhabit coastal marshes from the Carpinteria Marsh in Santa Barbara County, California, to Bahia de San Quintin, Baja California, Mexico. It is believed that most salt marshes along the coastline at one time supported clapper rails. However, recent census data indicate that less than 50 percent of the coastal wetlands in California are currently occupied. Southern California’s largest subpopulation of light-footed clapper rails, located in the Upper Newport Bay, has been stable since 1980. In contrast, the second and third largest subpopulations at Tijuana Marsh and Seal Beach NWR have been dramatically affected by major environmental disturbances. Very small populations of clapper rails are prone to local disappearance.

Very limited evidence exists for intermarsh movements by light-footed clapper rails. This subspecies is resident in its home marsh except under unusual circumstances. Within marsh movements are also confined and generally of no greater spread than 1,320 feet. Minimum home range sizes for 9 clapper rails that were radio-harnessed for telemetry at Upper Newport Bay varied from approximately 0.8 to 4.1 acres. The larger areas and daily movements were by first year birds attempting to claim their first breeding territories.

Light-footed clapper rails forage in all parts of the saltmarsh, concentrating their efforts in the lower marsh when the tide is out, and moving into the higher marsh as the tide advances. Foraging activity is greatest in the early morning, while vocalizing shows a strong peak just before dark. Activities are also tide-dependent. The rails are omnivorous and opportunistic foragers, and rely mostly on salt marsh invertebrates.

The pair bond in light-footed clapper rails endures throughout the season, and often from year to year. Nesting usually begins in March and late nests have usually hatched by August. Nests are placed to avoid flooding by tides, and in dense enough cover to be hidden from predators and to support the relatively large nest. Females lay approximately 4-8 eggs, which hatch in 18-27 days. Both parents care for the young; while one forages, the other adult broods the chicks. By the age of two days, chicks will accompany adults on foraging trips, however, adults have been observed feeding fully grown chicks of at least six weeks of age within 80 feet of their incubation nest.

Destruction of coastal wetlands in southern California has been so extensive that many estuaries where light-footed clapper rails were once abundant have been reduced to remnants. Although salt-marsh habitat loss, degradation, and fragmentation are the leading threats to light-footed clapper rails, they are also threatened by disturbance, diseases, contaminants, and predation by non-native red foxes, feral cats, crows, and some hawks or owls. The light-footed clapper rail was federally listed as endangered in 1970. It remains one of California’s birds most endangered with extinction.

The light-footed clapper rail has two nearby concentrations of breeding birds: Anaheim Bay (Seal Beach NWR) and Upper Newport Bay. Bolsa Chica has not supported breeding clapper rails in more than a century, due to the loss of tidal influence and cordgrass. Transient individuals, probably from Anaheim or Newport Bay are occasionally seen at Bolsa Chica, however.  A video of a clapper rail seen at Bolsa Chica was shot in August 2009. 

The restoration was designed to greatly benefit clapper rail by providing breeding habitat in the tidally influenced areas.  Cordgrass was transplanted in the Full Tidal Basin and Muted Tidal Basins in 2007 and 2009 and is expected to spread to a density capable of supporting breeding clapper rails within five years of transplant.

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