California clapper rail
FWS Focus

Overview

The California clapper rail (Rallus longirostris obsoletus) is one of the largest rails (family Rallidae), measuring 13-19 inches from bill to tail. It is characterized by its hen-like appearance, a long, slightly downward-curving bill, olive-brown upper parts, a cinnamon-buff colored breast, dark flanks crossed by white bars and white undertail coverts which are often exposed when the bird is agitated.

Characteristics
Overview

California clapper rails occur almost exclusively in tidal and brackish marshes with unrestricted daily tidal flows, adequate invertebrate prey food supply, well-developed tidal channel networks, and suitable nesting and escape cover to provide habitat during extreme high tides. Their current distribution is restricted to the San Francisco Bay Estuary (U.S. Fish and Wildlife Service 2013, 2020).  

Clapper rails are secretive and difficult to observe (U.S. Fish and Wildlife Service 1984). Rails prefer to walk or run over other forms of locomotion, and they swim well (Sibley 1955. Ripley 1977, Todd 1986). When flushed, they normally fly only a short distance before landing (Zucca 1954). Clapper rails are at least seasonally monogamous, and defend overlapping year-round territories (Zembal et al. 1989, Albertson 1995, Garcia 1995). Both sexes share in incubation, which lasts from 18 to 29 days (Taylor 1996).

Lack of extensive blocks of tidal marsh with suitable structure structure
Something temporarily or permanently constructed, built, or placed; and constructed of natural or manufactured parts including, but not limited to, a building, shed, cabin, porch, bridge, walkway, stair steps, sign, landing, platform, dock, rack, fence, telecommunication device, antennae, fish…

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is the ultimate limiting factor for the species’ recovery (U.S. Fish and Wildlife Service 2013). Non-native mammalian predators are a significant threat to the species, (Albertson and Evens 2000) and vulnerability to predation is exacerbated by reduction of clapper rail habitat to narrow and fragmented patches close to urban edge areas that diminish habitat quality. Levees provide artificial access for terrestrial predators and displace optimal cover of high marsh vegetation. Although Bay-wide invasion of exotic Spartina alterniflora (smooth cordgrass) and its hybrids with the native S. foliosa may threaten California clapper rails in future decades, hybrid Spartina currently provides habitat for the rail, and eradication of exotic hybrid Spartina is a current threat (Casazza et al. 2016, U.S. Fish and Wildlife Service 2020). Contaminants, particularly methylmercury, are a significant factor affecting viability of California clapper rail eggs (Ackerman et al. 2012, Casazza et al. 2014). Low genetic diversity is an increasing concern for the species, with Wood et al. (2017) documenting low contemporary gene flow among the regional marshes and significantly high genetic relatedness among individuals within marshes. Anticipated sea level rise presents a severe threat in the long term, especially in the central and south San Francisco Bay, where opportunities for landward migration of habitat are absent (U.S. Fish and Wildlife Service 2103, Zhang and Gorelick 2014, Rosencranz et al. 2018, Thorne et al. 2018, Thorne et al. 2019).

Taxonomy Note: Based on the work of Maley and Brumfield (2013), the American Ornithologist’s Union (AOU) Committee on Classification and Nomenclature accepted in its 55th Supplement to the AOU Check-list of North American Birds (Chesser et al. 2014), revisions to the specific assignments under the genus Rallus. Among those changes, the species R. obsoletus (Ridgway’s rail) and R. crepitans (Clapper rail) were split from R. longirostris, and R. longirostris was deleted.

The AOU Check-list of North American Birds has not addressed subspecies treatments since its 5th edition was published in 1957. Rather, the AOU refers to the listing of the Birds of North America by the Cornell Lab of Ornithology for subspecies treatments. In its subspecies treatments for R. obsoletus (Eddelman and Conway 2018), the Cornell Lab of Ornithology included a change from California clapper rail (Rallus longirostris obsoletus) to California Ridgway’s Rail (Rallus obsoletus obsoletus).

Until a time when the USFWS formally adopts the taxonomic and nomenclature changes described above, the USFWS maintains the use of California clapper rail (Rallus longirostris obsoletus) as used in this species profile.

Ackerman, J. T., C. T. Overton, M. L. Casazza, J. Y. Takekawa, C. A. Eagles-Smith, R. A. Keister, and M. P. Herzog. 2012. Does mercury contamination reduce body condition of endangered California clapper rails? Environmental Pollution, 162:439-448. http://dx.doi.org/10.1016/j.envpol.2011.12.004

Albertson, J. D. 1995. Ecology of the California Clapper Rail in South San Francisco Bay. M. S. thesis, San Francisco State Univ.

Albertson, J.D., and J. Evens. 2000. California clapper rail in: Olofson, P.R. (ed.). Baylands Ecosystem Species and Community Profiles: life histories and environmental requirements of key plants, fish, and wildlife. Goals Project (Baylands Ecosystem Habitat Goals), San Francisco Bay Regional Water Quality Control Board, Oakland, California.

Casazza, M. L., M. A. Ricca, C. T. Overton, J. Y. Takekawa, A.M. Merritt, and J. T. Ackerman. 2014. Dietary mercury exposure to endangered California Clapper Rails in San Francisco Bay. Marine Pollution Bulletin, 86:254-260. http://dx.doi.org/10.1016/j.marpolbul.2014.07.009

Casazza, M.L., C.T. Overton, T.D. Bui, J.M. Hull, J.D. Albertson, V.K. Bloom, S. Bobzien, J. McBroom, M. Latta, P. Olofson, T.M. Rohmer, S. Schwarzbach, D.R. Strong, E. Grijalva, J.K. Wood, S.M. Skalos, and J. Takekawa. 2016. Endangered species management and ecosystem restoration: finding the common ground. Ecology and Society, 21(1):19. http://dx.doi.org/10.5751/

Chesser, R.T., R.C. Banks, C. Cicero, J.L. Dunn, A.W. Kratter, I.J. Lovette, A.G. Navarro-Sigüenza, P.C. Rasmussen, J.V. Remsen, Jr., J.D. Rising, D.F. Stotz, and K. Winker. 2014.  Fifty-fifth Supplement to the America Ornithologists’ Union Check-list of North American Birds.  The Auk, 131:CSi–CSxv. DOI: 10.1642/AUK-14-124.1

Eddleman, W.R. and C.J. Conway. 2018. Ridgway's Rail (Rallus obsoletus), version 2.1. In The Birds of North America (P. G. Rodewald, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bna.ridrai1.02.1

Maley, J.M. and R.T. Brumfield. 2013. Mitochondrial and next-generation sequence data used to infer phylogenetic relationships and species limits in the clapper/king rail complex.  The Condor, 115(2):316-329. DOI: 10.1525/cond.2013.110138.

Rosencranz, J.A., K.M. Thorne, K.J. Buffington, C.T. Overton, J.Y. Takekawa, M.L. Casazza, J. McBroom, J.K. Wood, N. Nur, R.L. Zembal, G.M. MacDonald, and R.F. Ambrose. 2018. Rising Tides: Assessing Habitat Vulnerability for an Endangered Salt Marsh-Dependent Species with Sea-Level Rise. Wetlands. Published online December 4, 2018. https://doi.org/10.1007/s13157-018-1112-8. 16 pp.

Thorne, K., G. MacDonald, G. Guntenspergen, R. Ambrose, K. Buffington, B. Dugger, C. Freeman, C. Janousek, L. Brown, J. Rosencranz, J. Holmquist, J. Smol, K. Hargan, and J. Takekawa. 2018. U.S. Pacific coastal wetland resilience and vulnerability to sea-level rise. Science Advances, 4:eaao3270. 11 pp.

Thorne, K.M., K.A. Spragens, K.J. Buffington, J.A. Rosencranz, and J. Takekawa. 2019. Flooding regimes increase avian predation on wildlife prey in tidal marsh ecosystems. Ecology and Evolution, 00:1-12.

U.S. Fish and Wildlife Service. 2013. Recovery Plan for Tidal Marsh Ecosystems of Northern and Central California. U.S. Fish and Wildlife Service, Sacramento, California. xviii + 605 pp.

U.S. Fish and Wildlife Service. 2020. Five-year review: California clapper rail (Rallus longirostris obsoletus). San Francisco Bay-Delta Fish and Wildlife Office, Sacramento, California. 33 pp.

Wood, D.A., T.D. Bui, C.T. Overton, A.G. Vandergast, M.L. Casazza, J.M. Hull, and J.Y. Takekawa.  2017. A century of landscape disturbance and urbanization of the San Francisco Bay region affects the present-day genetic diversity of the California Ridgway’s Rail (Rallus obsoletus obsoletus). Conservation Genetics, 18:131-146. DOI 10.1007/s10592-016-0888-4.

Zhang, H. and S.M. Gorelick. 2014. Coupled impacts of sea-level rise and tidal marsh restoration on endangered California clapper rail. Biological Conservation, 172:89-100.

Scientific Name

Rallus longirostris obsoletus
Common Name
California clapper rail
FWS Category
Birds
Kingdom

Location in Taxonomic Tree

Identification Numbers

TSN:

Characteristics

Characteristic category

Habitat

Characteristics
Habitat

Throughout their distribution, California clapper rails occur within a range of tidal and brackish marshes (Harvey et al. 1977). In the south and central San Francisco Bay, and along the perimeter of San Pablo Bay, rails typically inhabit tidal marshes dominated by Sarcocornia pacifica and Spartina foliosa, especially where significant habitats exist that are accessible during high tide. Spartina dominates the lower marsh zone (marsh plain) throughout the south and central Bay (DeGroot 1927, Hinde 1954, Harvey 1988). Sarcocornia dominates the middle and sometimes upper marsh zone throughout the south and central Bay, with Distichlis spicata, Jaumea carnosa, Frankenia salina (alkali-heath), and others mixing with occasional Sarcocornia in the high marsh zone. Grindelia stricta var. angustifolia occurs along the upper edge of tidal sloughs throughout the entire San Francisco Bay Estuary. The marshes of Humboldt Bay, Morro Bay and Elkhorn Slough historically have not supported Spartina. Vegetation at these locations has been dominated by Sarcocornia pacifica and Distichlis spicata (U.S. Fish and Wildlife Service 2013).

Rail foraging and refugial habitat encompasses the lower, middle and high marsh zones, as well as the adjacent transitional zone. Lower and middle marsh zones provide foraging habitat at low tide. Small tidal channels (i.e., first- and second-order) with dense vegetation covering the banks are particularly important habitat features (Keldsen 1997, Garcia 1995). These provide important foraging habitat and hidden routes for travel in close proximity to nesting habitat. Within tidal marshes in portions of north San Francisco Bay, the abundance of California clapper rails is positively correlated with channel density or the total length of channel per unit area of marshland (Garcia 1995, Evens and Collins 1992, Collins et al. 1994, Foin et al. 1997). Keldsen (1997) found that rails prefer locations with a greater number of tidal creeks, Grindelia shrubs and higher elevations. However, high tide conditions result in increased predator pressure on rails in a high marsh zone that has already been reduced by decades of developmental pressure. Sea level rise is expected to increasingly threaten California clapper rail tidal marsh habitat extent and condition (U.S. Fish and Wildlife Service 2013, Zhang and Gorelick 2014, Rosencranz et al. 2018, Thorne et al. 2018, Thorne et al. 2019).

Collins, J., J. Evens, and B. Grewell. 1994. A synoptic survey of the distribution and abundance of the California clapper rail (Rallus longirostris obsoletus) in the northern reaches of the San Francisco Estuary during the 1992 and 1993 breeding season. Draft Technical Report to California Department of Fish and Game, Yountville, CA. 36 pp.

DeGroot, D.S. 1927. The California clapper rail: its nesting habitats, enemies, and habitat. Condor 29:259-270.

Evens J., and J.N. Collins. 1992. Distribution, abundance, and habitat affinities of the California clapper rail (Rallus longirostris obsoletus) in the northern reaches of the San Francisco Estuary during the 1992 breeding season. Final report to California Department of Fish and Game, Yountville, CA. Avocet Research Associates, Point Reyes, CA. 26 pp.

Foin, T.C., E. J. Garcia, R.E. Gill, S.D. Culberson, and J. N. Collins. 1997. Recovery strategies for the California clapper rail (Rallus longirostris obsoletus) in the heavily-urbanized San Francisco estuarine ecosystem. Landscape and Urban Planning 38:229-243.

Garcia, E.J. 1995. Conservation of the California clapper rail: An analysis of survey methods and habitat use in Marin County, California. M.Sci. Thesis, University of California, Davis. 135 pp.

Harvey, T.E. 1988. Breeding biology of the California clapper rail in south San Francisco Bay. Transactions of the Western Section of the Wildlife Society 24:98-104.

Harvey, H.T., H.L. Mason, R. Gill, and T.W. Wooster. 1977. The marshes of San Francisco Bay: their attributes and values. Report to San Francisco Bay Conservation and Development Commission.

Hinde, H. 1954. The vertical distribution of salt marsh salt marsh
Salt marshes are found in tidal areas near the coast, where freshwater mixes with saltwater.

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phanaerogams in relation to tide levels. Ecol. Monogr. 24:209-225

Keldsen, T.J. 1997. Potential impacts of climate change climate change
Climate change includes both global warming driven by human-induced emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century humans have had an unprecedented impact on Earth's…

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on California clapper rail habitat of south San Francisco Bay. M.S. Thesis, Colorado State University.

Rosencranz, J.A., K.M. Thorne, K.J. Buffington, C.T. Overton, J.Y. Takekawa, M.L. Casazza, J. McBroom, J.K. Wood, N. Nur, R.L. Zembal, G.M. MacDonald, and R.F. Ambrose. 2018. Rising Tides: Assessing Habitat Vulnerability for an Endangered Salt Marsh-Dependent Species with Sea-Level Rise. Wetlands. Published online December 4, 2018. https://doi.org/10.1007/s13157-018-1112-8. 16 pp.

Thorne, K., G. MacDonald, G. Guntenspergen, R. Ambrose, K. Buffington, B. Dugger, C. Freeman, C. Janousek, L. Brown, J. Rosencranz, J. Holmquist, J. Smol, K. Hargan, and J. Takekawa. 2018. U.S. Pacific coastal wetland resilience and vulnerability to sea-level rise. Science Advances, 4:eaao3270. 11 pp.

Thorne, K.M., K.A. Spragens, K.J. Buffington, J.A. Rosencranz, and J. Takekawa. 2019. Flooding regimes increase avian predation on wildlife prey in tidal marsh ecosystems. Ecology and Evolution, 00:1-12.

U.S. Fish and Wildlife Service. 2013. Recovery Plan for Tidal Marsh Ecosystems of Northern and Central California. U.S. Fish and Wildlife Service, Sacramento, California. xviii + 605 pp.

Zhang, H. and S.M. Gorelick. 2014. Coupled impacts of sea-level rise and tidal marsh restoration on endangered California clapper rail. Biological Conservation, 172:89-100.

Wetland

Areas such as marshes or swamps that are covered often intermittently with shallow water or have soil saturated with moisture.

Characteristic category

Food

Characteristics
Food

The clapper rail is an omnivore with a relatively broad feeding niche. Animal matter has been consistently emphasized as a major component of the diet (Moffitt 1941, Heard 1982, Zembal and Fancher 1988). Food items found in California clapper rails' stomachs include introduced ribbed horse mussel (Ischadium demissum), spiders (Lycosidae spp.), clams (Macoma balthica), yellow shore crabs (Hemigrapsus oregonensis), amphipods (shrimp-like crustaceans), Nereis vexillosa (a polychaete worm) and striped shore crab (Pachygrapsus crassipes; Williams 1929, Applegarth 1938, Test and Test 1942, Varoujean 1972). Rails occasionally have been seen capturing and consuming rodents, particularly during higher tides; small birds are also occasionally taken (Spendelow and Spendelow 1980, Jorgenson and Ferguson 1982).

Applegarth, J.H. 1938. The ecology of the California clapper rail in the south arm of the San Francisco Bay. M.Sci. Thesis, Stanford University, Palo Alto, CA. 153 pp.

Heard, R.W. 1982. Observations on the foods and food habits of clapper rails from tidal marshes along the east and gulf coasts of the United States. Gulf Resource Report 7:125-135.

Jorgenson, P.D., and H.L. Ferguson. 1982. Clapper rail preys on savannah sparrow. Wilson Bulletin 94:215.

Moffitt, J. 1941. Notes on the food of the California clapper rail. Condor 43(6):270-273.

Spendelow, J.A., and H.R. Spendelow, Jr. 1980. Clapper rail kills birds in a net. J. field Ornithol. 51(2):175-176.

Test, F.H., and A.R. Test. 1942. Food of the California clapper rail. Condor 44:228.

Varoujean, D.H. 1972. A study of the California clapper rail in Elkhorn Slough, 1972. Report for Calif. Dept. of Fish and Game. 9 pp.

Williams, L. 1929. Notes on the feeding habits and behavior of the California clapper rail. Condor 31:52-56.

Zembal, R., and J. M. Fancher. 1988. Foraging behavior and foods of the light-footed clapper rail. Condor 90:959-962.

Characteristic category

Behavior

Characteristics
Behavior

Clapper rails are secretive and difficult to observe (U.S. Fish and Wildlife Service 1984). Rails prefer to walk or run over other forms of locomotion, and they swim well (Sibley 1955. Ripley 1977, Todd 1986). When flushed, they normally fly only a short distance before landing (Zucca 1954).

Clapper rails are active for 75 to 90 percent of the day. Activity peaks in the early morning and late evening (Zembal and Massey 1983, Zembal et al. 1989), when rails forage in the marsh vegetation. Rails often roost at high tide during the day (Zembal et al. 1989).

They exhibit strong territorial defense, particularly during the late winter and early breeding seasons (Williams 1929, Albertson 1995, Garcia 1995). Territoriality weakens during extreme high tides when cover is limited, and during the post breeding season (U.S. Fish and Wildlife Service 2013). Clapper rails generally exhibit strong site fidelity (Albertson 1995).

A banding study in the mid-1980s revealed movement of rails in the south Bay of about 500 m (1,641 ft) from the original capture site (U.S. Fish and Wildlife Service 2013). Longer distance dispersal has also been documented, with a female rail moving 2.1 kilometers (1.3 miles) over three days (Albertson 1995) and a male rail moving 44.8 kilometers (27.8 miles) over 43 days (Casazza et al. 2008).

A 1991-1992 radiotelemetry study in south San Francisco Bay indicated an average home range of 4.7 hectares (11.6 acres) and an average core use area of 0.9 hectare (2.2 acres) (Albertson 1995).

Albertson, J. D. 1995. Ecology of the California Clapper Rail in South San Francisco Bay. M. S. thesis, San Francisco State Univ.

Casazza, M.L., C.T. Overton, J.Y. Takekawa, T. Rohmer, and K. Navarre. 2008. Breeding behavior and dispersal of radio-marked California clapper rails. Notes in Western Birds, 39:101-106.

Garcia, E.J. 1995. Conservation of the California clapper rail: An analysis of survey methods and habitat use in Marin County, California. M.Sci. Thesis, University of California, Davis. 135 pp.

Ripley, S.D. 1977. Rails of the world. David R. Godine, Publisher. Boston, MA.

Sibley, C.G. 1955. The responses of salt-marsh birds to extremely high tides. Condor 57(4): 241-242.

Todd, R.L. 1986. A saltwater marsh hen in Arizona: A history of the Yuma clapper rail (Rallus longirostris yumanensis). Final Rept. Arizona Game and Fish Dept., Fed. Aid Proj. W-95-R, Phoenix, AZ.

U.S. Fish and Wildlife Service. 1984. Salt marsh harvest mouse and California clapper rail recovery plan. Portland, OR.

U.S. Fish and Wildlife Service. 2013. Recovery Plan for Tidal Marsh Ecosystems of Northern and Central California. U.S. Fish and Wildlife Service, Sacramento, California. xviii + 605 pp.

Williams, L. 1929. Notes on the feeding habits and behavior of the California clapper rail. Condor 31:52-56.

Zembal, R., and B.W. Massey. 1983. The light-footed clapper rail: Distribution, nesting strategies, and management. Cal-Neva Wildl. Trans. 1983:97-103.

Zembal, R., B.W. Massey, and J.M. Fancher. 1989. Movements and activity patterns of the light-footed clapper rail. J. Wildl. Manage. 53:39-42.

Zucca, J.J. 1954. A study of the California clapper rail. Wasmann Journal of Biology 12(2):135-153.

Characteristic category

Physical Characteristics

Characteristics
Size & Shape

The California clapper rail is one of the largest species of the genus Rallus, measuring 32-47 centimeters (13-19 inches) from bill to tail (Ripley 1977).

Ripley, S.D. 1977. Rails of the world. David R. Godine, Publisher. Boston, MA.

Weight

Males generally weigh 300-350 grams (0.66-0.77 pound) and females 248-301 grams (0.55-0.66 pound; Taylor 1996).

Taylor, P.B. 1996. Clapper Rail in: Hoyo et al. (eds.). Handbook of the birds of the world. Vol. 3. Lynx Edicions. Barcelona.

Color & Pattern

The clapper rail has a hen-like appearance, with a long, slightly downward curved orange bill, a reddish brown breast, black and white barred flanks, and white undertail feathers. Juveniles have a paler bill and darker plumage, with a gray body, black flanks and sides, and indistinct light streaking on flanks and undertail feathers. Downy young are black with dark legs (Eddleman and Conway 1998).

Eddleman, W.R., and C. J. Conway. 1998. Clapper rail (Rallus longirostris) in: A. Poole and F. Gill, (eds.). The birds of North America. No. 340. The Birds of North America, Inc., Philadelphia, PA.

Sound

Clapper rails have a wide variety of calls, although few are commonly heard. All calls are variants on a single note, with differences due to changes in intensity, pitch, note length and interval between notes. Massey and Zembal (1987) grouped clapper rail vocalizations into eight calls, of which four are commonly heard: clapper, kek, kekburr and agitated kek. The clapper is the basic species call, serving as a territory pronouncement and for mutual mate recognition. Both sexes clapper year-round, with daily peaks at dawn and dusk (U.S. Fish and Wildlife Service 2013).

 

Massey, B.W., and R. Zembal. 1987. Vocalizations of the light-footed clapper rail. J. Field Ornithol. 58(1):32-40.

U.S. Fish and Wildlife Service. 2013. Recovery Plan for Tidal Marsh Ecosystems of Northern and Central California. U.S. Fish and Wildlife Service, Sacramento, California. xviii + 605 pp.

Characteristic category

Lifecycle

Characteristics
Lifecycle

The breeding period of the California clapper rail is prolonged. Pair bonding and nest building are generally initiated by mid-February. Nesting may begin as early as late February or early March (Evens and Page 1983) and extend through July in the south Bay, and into August in the north Bay (DeGroot 1927, U.S. Fish and Wildlife Service unpubl. Data in U.S. Fish and Wildlife Service 2013). There appears to be a break in nesting between mid-May through late June in the north Bay, a period that corresponds to the highest summer tides (Evens and Page 1983). Two peaks in nesting activity occur, a greater peak between mid-April and early May and a lesser peak between late June and early July (DeGroot 1927, Applegarth 1938, Gill 1972, Harvey 1988). The second nesting peak has been interpreted as attempts by late nesters (DeGroot 1927), second attempts after initial nesting failures (Gill 1972), or second broods (Wilbur and Tomlinson 1976).

Applegarth, J.H. 1938. The ecology of the California clapper rail in the south arm of the San Francisco Bay. M.Sci. Thesis, Stanford University, Palo Alto, CA. 153 pp.

DeGroot, D.S. 1927. The California clapper rail: its nesting habitats, enemies, and habitat. Condor 29:259-270.

Evens, J., and G.W. Page. 1983. The ecology of rail populations at Corte Madera Ecological Reserve: with recommendations for management. Report by the Point Reyes Bird Observatory. Stinson Beach, CA. 62 pp.

Gill, R., Jr. 1972. South San Francisco Bay breeding bird survey, 1971. Calif. Dept. Fish and Game, Wildlife Management Branch Administrative Report 72-6. Sacramento, CA. 69 pp.

Harvey, T.E. 1988. Breeding biology of the California clapper rail in south San Francisco Bay. Transactions of the Western Section of the Wildlife Society 24:98-104.

U.S. Fish and Wildlife Service. 2013. Recovery Plan for Tidal Marsh Ecosystems of Northern and Central California. U.S. Fish and Wildlife Service, Sacramento, California. xviii + 605 pp.

Wilbur, S.R., and R.E. Tomlinson. 1976. The literature of the western clapper rails. Wildl. Res. Rpt. No. 194, U.S. Fish and Wildlife Service, Washington, DC.

Lifespan

The only estimates of annual adult California clapper rail survivorship are relatively low, ranging from 0.49 to 0.52 (Albertson 1995). These are similar to survival estimates reported for the Yuma subspecies (Eddleman 1989). Increased predation occurs during extreme winter high tides, probably due to increased movement of rails at this time when little cover is available (Albertson and Evens 2000). Adult survivorship has been suggested as the key demographic variable associated with survival of clapper rail populations (Foin et al. 1997).

Albertson, J. D. 1995. Ecology of the California Clapper Rail in South San Francisco Bay. M. S. thesis, San Francisco State Univ.

Albertson, J.D., and J. Evens. 2000. California clapper rail in: Olofson, P.R. (ed.). Baylands Ecosystem Species and Community Profiles: life histories and environmental requirements of key plants, fish, and wildlife. Goals Project (Baylands Ecosystem Habitat Goals), San Francisco Bay Regional Water Quality Control Board, Oakland, California.

Eddleman, W.R. 1989. Biology of the Yuma clapper rail in the southwestern U.S. and northwestern Mexico. Final Rept., Intra-Agency Agreement No. 4-AA-30-02060, U.S. Bur. Reclam., Yuma Proj. Office., Yuma, AZ.

Foin, T.C., E. J. Garcia, R.E. Gill, S.D. Culberson, and J. N. Collins. 1997. Recovery strategies for the California clapper rail (Rallus longirostris obsoletus) in the heavily-urbanized San Francisco estuarine ecosystem. Landscape and Urban Planning 38:229-243.

Reproduction

Clapper rails are at least seasonally monogamous, and defend overlapping year-round territories (Zembal et al. 1989, Albertson 1995, Garcia 1995). Males perform most of the nest building (Meanley 1985). Rails frequently build several nest platforms, but use only one for incubation (Applegarth 1938, Gill 1972, Wilbur and Tomlinson 1976). Nests must be built at an elevation that protects the bowl from complete inundation during high tides (Evens and Collins 1992, Collins et al. 1994).

Egg-laying often begins prior to completion of the nest (Eddleman and Conway 1998). Both sexes share in incubation, which lasts from 18 to 29 days (Taylor 1996). Eggs are approximately 45 millimeters (1.77 inch) in length, and light tan or buff-colored with cinnamon-brown or dark lavender spotting concentrated at the broader end. Clutch size ranges from 5 to 14 eggs (DeGroot 1927, Gill 1972). Hatching is generally synchronous, but eggs may hatch one to several days apart (U.S. Fish and Wildlife Service 2013). After hatching, adults remain with the chicks for up to five to six weeks (Applegarth 1938, Meanley 1985).

Several studies from across the species’ range from 1988 through 1999 (Harvey 1988, Foerster et al. 1990, Schwarzbach et al. 2006) demonstrate nest success (the rate of nests having at least one egg hatch) of 32% to 56%, hatching success (the rate of eggs hatched per total eggs laid) of 19% to 41%, and a predation rate of 30% to 39%. Normal hatching success of other clapper rail eggs can be much higher (Kozicky and Schmidt 1949).

Albertson, J. D. 1995. Ecology of the California Clapper Rail in South San Francisco Bay. M. S. thesis, San Francisco State Univ.

Applegarth, J.H. 1938. The ecology of the California clapper rail in the south arm of the San Francisco Bay. M.Sci. Thesis, Stanford University, Palo Alto, CA. 153 pp.

DeGroot, D.S. 1927. The California clapper rail: its nesting habitats, enemies, and habitat. Condor 29:259-270.

Eddleman, W.R., and C. J. Conway. 1998. Clapper rail (Rallus longirostris) in: A. Poole and F. Gill, (eds.). The birds of North America. No. 340. The Birds of North America, Inc., Philadelphia, PA.

Garcia, E.J. 1995. Conservation of the California clapper rail: An analysis of survey methods and habitat use in Marin County, California. M.Sci. Thesis, University of California, Davis. 135 pp.

Gill, R., Jr. 1972. South San Francisco Bay breeding bird survey, 1971. Calif. Dept. Fish and Game, Wildlife Management Branch Administrative Report 72-6. Sacramento, CA. 69 pp.

Meanley, B. 1985. The marsh hen: A natural history of the clapper rail of the Atlantic coast salt marsh salt marsh
Salt marshes are found in tidal areas near the coast, where freshwater mixes with saltwater.

Learn more about salt marsh
. Tidewater Publ., Centreville, MD.

U.S. Fish and Wildlife Service. 2013. Recovery Plan for Tidal Marsh Ecosystems of Northern and Central California. U.S. Fish and Wildlife Service, Sacramento, California. xviii + 605 pp.

Zembal, R., B.W. Massey, and J.M. Fancher. 1989. Movements and activity patterns of the light-footed clapper rail. J. Wildl. Manage. 53:39-42.

Geography

Characteristics
Range

California clapper rails were historically abundant in all tidal and brackish marshes in the San Francisco Bay vicinity (Cohen 1895), as well as in all of the larger tidal estuaries from Marin to San Luis Obispo counties in California. They are now restricted almost entirely to the marshes of the San Francisco Bay Estuary, where the only known breeding populations occur (U.S. Fish and Wildlife Service 2013, 2020).

Cohen, D.A. 1895. The California clapper rail. Oologist 12(11):171-173.

U.S. Fish and Wildlife Service. 2013. Recovery Plan for Tidal Marsh Ecosystems of Northern and Central California. U.S. Fish and Wildlife Service, Sacramento, California. xviii + 605 pp.

U.S. Fish and Wildlife Service. 2020. Five-year review: California clapper rail (Rallus longirostris obsoletus). San Francisco Bay-Delta Fish and Wildlife Office, Sacramento, California. 33 pp.

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