8031

• UCREFRP Catalog Number: 8031
• Author: U.S. Department of the Interior.
• Title: Fish and Wildlife Service Final Biological and Conference Opinion on Lower Colorado River Operations and Maintenance - Lake Mead to Southerly International Boundary.
• USFW Year: 1997.
• USFW - Doc Type: \
• Copyright Material: NO

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

result of the habitat loss and mortality/dispersal of flycatchers on the San Pedro River, the
unprotected Roosevelt Lake breeding group is now Arizona's largest.

Yuma Clapper Rail

Listing History

The first list of rare and endangered wildlife published by the Service (USFWS 1966) included the
Yuma clapper rail (Rallus longirostris yumanensis). It was listed in the Federal Register on March
11, 1967 (32 FR 4001) as endangered under the Federal endangered species legislation enacted in
1966 (Public Law 89-669) without critical habitat. The State 0 f California listed it as rare in 1971
and later redesignated it as threatened (Thelander 1994). The State of Arizona is proposing to
include this species on its list of "Wildlife of Special Concern in Arizona" (AGFD, in prep.). The
Yuma clapper rail was listed as an endangered species because of the low numbers of birds
detected and the loss of breeding habitat on the LCR resulting from channelization and dredging
projects.

Species Description

The Yuma clapper rail is a chicken-shaped marsh bird with a long, down-curved beak:. Both sexes
are slate brown above, with light cinnamon underparts and barred flanks. This subspecies is
slightly lighter in color and slightly thinner than other clapper rails. Fully grown, the bird measures
14 to 16 inches long, Rarely visible in the dense marsh vegetation it inhabits, it can be detected
by its call. While other rail species are vocal year round, the Yuma clapper rail is nearly silent
in winter.

The taxonomic status of the Yuma clapper rail was clarified with field work beginning in 1970.
Forty-one clapper rails were collected in selected areas of the LCR and coastal areas of the Sea of
Cortez in Mexico. Three separate and distinct subspecies were identified, including R. I.
yumanensis, based on plumage and wing configurations and distribution patterns (Banks and
Tomlinson 1974).

Distribution and Abundance

The Yuma clapper rail is an uncommon to fairly common summer resident and breeder between
February and September, north to Topock Marsh. It is more secretive and, possibly, less
numerous in winter (Rosenberg, et al. 1991). Until recently, most of the population was thought
to retreat to Mexico during the winter. Telemetry studies, however, indicate that over 70% of the
breeding population winters along the LCR (Eddleman 1989).

Breeding population centers are Mittry Lake, West Pond Imperial NWR, Bill Williams River

67