Yuma Clapper Rail Survey Along Lower Colorado River at Topock Gorge, 2004. Final Report

摘要

The Yuma clapper rail (Rallus longirostris yumanensis) was listed endangered on 11 March 1967 by the Secretary of Interior pursuant to the Endangered species Act of 1966 (US Dept. of Interior 1968). California listed the Yuma clapper rail rare in 1971 (Leach and Fisk 1972). In 1978, Arizona classified the Yuma clapper rail as group 3, similar to the federal status of endangered (AZ Dept. of Game and Fish Commission 1978). In 1996, personnel from the Resources Management Office of the Lower Colorado Region, U. S. Bureau of Reclamation (Reclamation) began to conduct surveys for the presence of the Yuma clapper rail in Topock Gorge within the U.S. Fish and Wildlife Services (USFWS) Havasu National Wildlife Refuge (HNWR), along the lower Colorado River. Surveys were conducted at the request of staff at HNWR. In 2001 and 2002, Reclamation conducted Yuma clapper rail surveys in Topock Marsh, just upstream of Topock Gorge, within HNWR. The USFWS resumed surveys at Topock Marsh in 2003. Reclamation conducts these surveys in accordance with the Biological and Conference Opinion on Lower Colorado River Operations and Maintenance Lake Mead to Southerly International Border (USFWS 1997), which required that surveys be performed to continually track the population of Yuma clapper rails in order to maintain a minimum breeding population of 700-1000 on the lower Colorado River (USFWS 1983).