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Literature Review

Yuma clapper rail

Rallus longirostris yumanensis

USFWS: Endangered
CDFG: Threatened

Background

Distribution, Abundance and Trends. Yuma clapper rails are and have been restricted to the region of the lower Colorado River, the Colorado River delta, and appropriate habitats surrounding the Salton Sea and in the Whitewater River north of the Sea. There are rare records for this species in marshland habitat along the eastern shore of the Sea of Cortez. Within this historic range, appropriate habitat along the lower Colorado River and delta areas has been severely reduced through water diversions and salt cedar infestations. The Plan area is at the northern edge of the Yuma clapper rail distribution. There are records from the Whitewater River delta and upstream, in scattered locations, for approximately 10 miles along the Whitewater River channel, and from two agricultural drains on the west side of the Salton Sea. The Salton Sea and Whitewater River habitats are potentially impacted due to chemical contaminants, salt cedar infestations, and flood control channel maintenance. The Yuma clapper rail occurs at the Salton Sea State Recreation Area at the mouth of Salt Creek. The Yuma clapper rails occur within the Dos Palmas marshland complex in unknown numbers. The Dos Palmas area may have particular importance in that it may be one of the few occupied sites throughout this bird's entire range that is relatively free of chemical contaminants. Both Dos Palmas and the Whitewater River delta/Salton Sea could, if managed appropriately, provide additional habitat to what already exists there. The population size of Yuma clapper rails within this area is not known, nor are the trends in its population numbers known, but it is likely that this population will require immigration from occupied habitat to the south to maintain long term viability.

Yuma clapper rails are found in marsh habitats of cattails Typha domingensis and bullwhip/California bulrush Scirpus californicus. In habitats found along and adjacent to the lower Colorado River, these rails selected some combination of cattails and bulrush for breeding. There was a post-breeding shift at some sites concurrent with a rise in water level, to higher elevation willows, arrowweed and salt cedar dominated habitats. Common reed Phragmites communis was also used as habitat, but usually occurred in areas too dry for breeding and foraging. Water depth appears to be an important habitat character, with average preferred depths varying from 6.5 cm to 20 cm depending on the study site In deeper water a residual mat of decaying vegetation was important to allow the rails to have access and use throughout their home range. The rails also preferred habitat edges and generally less dense habitat to facilitate the birds' mobility and access. Home ranges for male birds were found to average 7.7 +/- 5.9 ha, and for females 9.9 +/- 9.6 ha.

Threats and Limiting Factors. Water diversions, salt cedar infestations, habitat manipulation for flood control and chemical contamination (the last two pertain primarily to the Whitewater delta) are the primary threats to Yuma clapper rails within the Plan area. Another potential threat is the lining of the Coachella Canal; leakage from the Coachella Canal currently provides a portion of the water supply to rail habitat at the Dos Palmas Preserve/ACEC. The canal lining may also be a threat to the water supply in Salt Creek. There are small amounts of Yuma clapper rail habitat in the Plan area, and it is unknown whether the habitat areas are large enough to sustain a viable population. Additional surveys are needed as part of Plan implementation to determine patch sizes and whether they are adequate to sustain a viable population. There are opportunities for habitat restoration and enhancement in the Plan area.

Special Considerations. California black rails are often found in association with Yuma clapper rail habitat. Conservation measures for one species will benefit the other.