Publications:

Literature Review

California black rail

Laterallus jamaicensis

USFWS: No status
CDFG: Threatened

Background

Distribution, Abundance and Trends. Historically, black rails occurred along the Pacific coast from Bahia San Quintin in Baja California to San Diego, Los Angeles and north to San Francisco. Inland, these rails occurred from the delta of the Colorado River north to the central valley of California and on to eastern Oregon marshlands. Today the coastal and inland wetlands are greatly reduced from their historic range. A desert strong hold for this species appears to be along the lower Colorado River where over a hundred birds have been observed repeatedly during censuses in recent years. Black rails are known to occur within the Salt Creek watershed of the Dos Palmas region, both in the wetlands in the Dos Palmas Springs area at and at the mouth of Salt Creek. No accurate numbers are available. There is also a record from the Whitewater delta area at the north end of the Salton Sea. Appropriate management of both Dos Palmas and the Whitewater delta could expand existing habitat for this species.

Black rails are birds of dense coastal and inland marsh habitat. Based on radio telemetry data gathered on the lower Colorado River, black rails selected habitat dominated by California bulrush, Scirpus californicus and three square bulrush S. americanus. They either avoided cattails Typha domingensis or utilized cattail habitat in proportion to its availability. However, nests were often constructed of cattail leaf blades, even though cattails were rarely the dominant vegetation type surrounding the nest. Preferred habitat sites had a shallow water depth of <2.5 cm, with 25% of the substrate covered in water. They preferred areas closer to the shoreline than would have been expected in random distribution.

Home range size in appropriate habitat along the lower Colorado River varied from 0.43 to 0.55 ha. depending on sex and time of year. The birds are resident year-round. The home range sizes described above are three to four times smaller than those described for the eastern black rail, and may result from more stable water levels than found in tidal habitats. The rails were found to be entirely diurnal in their activity.

Black rails are omnivorous, eating both invertebrates and bulrush seeds. Predators include house cats, short-eared owls, northern harriers, great blue herons and great egrets.

Threats and Limiting Factors. Threats to the black rails' continued occurrence within the Plan area include water diversions that reduce marsh habitat, including the lining of the earthen Coachella canal above Dos Palmas; habitat modification for flood control at the Whitewater River delta; tamarisk infestations which degrade and dry up marsh habitat; and predation from exotic bullfrogs. Even with appropriate habitat management practices, the black rail population within the Plan area is small and will probably require immigration from habitats outside the area being addressed in this conservation plan to maintain long-term viability.

Special Considerations. California black rails are often found in association with Yuma clapper rail habitat. Conservation measures for one species will benefit the other, however, additional information is needed on how these two species partition the habitat.