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

Table 5. Nest predation and brood parasitism rates documented for the southwestern willow
flycatcher across its range I.

Location Pre-1993 1993 1994 1995
S. Fork Kern River (Kern Co., CA)
% nests parasitized2 50 - 80 38* 16* 19*
% nests depredated 33 - 42 37 47 34
San Luis Rey River (San Diego Co. CA) * * 0* 0*
% nests parasitized 28 5
% nests depredated
Colorado River (Coconino Co., AZ)
% nests parasitized ~50 100 44 100
% nests depredated 30 78 0
Verde River (Yavapai Co., AZ)
% nests parasitized 100 50 extirpated
% nests depredated 100 50
Little Colorado River (Apache Co., AZ)
% nests parasitized 22 0
% nests depredated 33 28
Rio Grande (Socorro Co., NM)
% nests parasitized 20 66
% nests depredated 40 60
Gila River (Grant Co., NM)
% nests parasitized 16 - 27
% nests depredated 45

I Sources: Sogge and Tibbitts (1992), Sogge et aI. (1993), Brown (1988), Griffith and Griffith (1994), Mayard 1994,
Muiznieks et aI. (1994), Sogge and Tibbitts (1994), Cooper (1995), (W.Haas, San Diego Nat'l History Mseum, pers.
comm.), Skaggs (1995), Sogge (1995a), Sogge et aI. (1995), Spencer et aI. (1995), Whitfield and Strong (1995).

2 Proportion of nests containing at least one brown-headed cowbird egg.

* Brown-headed cowbird control program implemented.

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