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I I I I I I I I I I I I I I I I I I I BIOLOGICAL OPINION Status of the Species The Yuma clapper rail is the only subspecies of clapper rail known to regularly inhabit freshwater marshes; in Mexico it also inhabits brackish marshes. Clapper rails are associated primarily with dense marsh vegetation, but high densities also occur in some moderately dense cattail/bulrush marshes. They may also occur in dense reed and even sparse cattail/bulrush, but in reduced numbers. Habitat edges between marshes and terrestrial vegetation are important, but the main factors determining habitat use are the annual range of water depth and the existence of residual mats of marsh vegetation (Eddleman 1989). Most individuals remaining through winter are found in tall, dense cattail/bulrush stands; however, some occur in flooded saltcedar and willow stands. The most productive clapper rail areas consist of a mosaic of uneven-aged marsh vegetation interspersed with open water of variable depths (Conway et al, 1993). Habitat requirements of the Yuma clapper rail include freshwater or brackish stream sides and marshlands associated with heavy riparian and wetland vegetation (Grinnell and Miller 1944). Openings within the wetland, especially channels with flowing water are also important (Todd 1971, Tomlinson and Todd 1973, Cornelius 1972). A variety of water level conditions are encountered by Yuma clapper rails on the Colorado River, ranging from nominally stable levels in unconnected backwaters to unpredictably unstable levels in wetlands connected to the river. Rosenberg et al. (1991) believe that artificial marshes behind backwater levees compare favorably with natural marshes as habitat. Life History Nesting. Nesting behavior commences by February; nesting begins in mid-March and runs through early July, with most eggs hatching during the first week of June. There is no evidence of more than one brood per season, despite the long breeding period (Eddleman 1989). Both adult s care for the eggs and young. Clutch size is usually six to eight eggs. Young are precocial and follow the adults through the marsh within 48 hours of hatching. Adults lead the young to productive feeding areas where they quickly learn to feed on their own. Young clapper rails experience high mortality from predators, usually within their first month of life. Surviving clapper rails of other subspecies fledge in 63-70 days. Nest bowls are built in three major microhabitats, the base of living clumps of cattail or bulrush, under wind thrown bulrush, or on the top of dead cattails remaining from the previous year's growth. Mature cattail/bulrush stands provide materials for nest building and cover for their nests. Sometimes they weave nests in the forks of small shrubs that lie just above moist soil or above water that is up to two feet deep (Thelander 1994). Food Habits. The preferred prey of the Yuma clapper rail is the crayfish, predominantly Procambarus clarki (Todd 1986), which is not native to Arizona. Crayfish comprises up to 95% of the rail's diet by volume (Ohmart and Tomlinson 1977). The rails will also take isopods, aquatic and terrestrial beetles, damselfly and dragonfly nymphs, earwigs, grasshoppers, spiders, freshwater shrimp, freshwater clams, leeches, plant seeds and small fish. Using data from Ohmart and Tomlinson (1977), Rosenberg et al. (1991) state that crayfish, like the rails themselves, are 69