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

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BIOLOGICAL OPINION

Status of the Species

these types of effects will continue to adversely affect critical habitat.

The result, in 1996, of the human activities in the area is the near extinction of the bony tail chub,
and the imminent loss of the last large razorback sucker population. Efforts to rejuvenate the aging
bony tail chub and razorback sucker populations in Lakes Mohave and Havasu and similar programs
in the Upper Basin are critically needed to forestall the extinction of these species in the wild.
These efforts are providing time in which to address the larger problems, but old age is decimating
the wild populations. The young fish from the hatchery and pond programs are, although
surviving, all within the same age range. Without successful recruitment, limited ability to recover
these fish exists. Without natural habitats, recruitment may be limited to captured wild larvae and
hatchery production, an alternative that does not represent long-term recovery. These fish still do
have the capacity to restore their own numbers if the situation allows for recruitment. Protecting
the remaining constituent elements of critical habitat and providing management to restore degraded
conditions may increase the opportunity for recruitment into these populations.

Southwestern Willow Flycatcher

Listing History

The Service included the southwestern willow flycatcher on its Animal Notice of Review as a
category 2 candidate species on January 6, 1989 (USFWS 1989). This flycatcher was proposed
for listing as endangered, with critical habitat, on July 23, 1993 (USFWS 1993b). A final rule
listing the southwestern willow flycatcher as endangered was published on February 27, 1995
(USFWS 1995). The listing became effective on March 29, 1995. Following the review of
comments received during the public comment period, the Service deferred the designation of
critical habitat, invoking an extension on this decision until July 23, 1995. A moratorium on
listing actions under the Act passed by Congress in April, 1995, required the Service to cease wor k
on the designation of critical habitat. The moratorium has since been removed, but under the
Service I s priority system, completion of the critical habitat package has been delayed until high
priority listing packages have been completed. The States of California and New Mexico also list
the southwestern willow flycatcher as endangered (CDFG 1992, NMDGF 1988). The State of
Arizona considers the southwestern willow flycatcher a Species of Special Concern (AGFD 1996).

Species Description

The southwestern willow flycatcher is a small passerine bird (Order Passeriformes; Family
Tyrannidae) measuring approximately 15 centimeters (cm) (5.75 inches) in length from the tip of
the bill to the tip of the tail and weighing only 11 grams (0.4 ounces). It has a grayis h-green back
and wings, whitish throat, light gray-olive breast, and pale yellowish belly. The eye ring is faint
or absent. The upper mandible is dark, the lower is light yellow grading to black at the tip. As
its name implies, it is an insectivore typically perching on a branch and making short direct flights,

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