Southwestern Willow Flycatcher (Empidonax trailli extimus)

 SWFL Fledgling, Wikieup, AZ

SWFL Fledgling, Wikieup, AZ

The Southwestern Willow Flycatcher (SWFL) is a migratory songbird which arrives in summer at a limited number of breeding site across the Southwestern United States. 

LISTING STATUS

Federally Endangered (USFWS)

CA State Endangered (CDFW)

VOCALIZATIONS

SWFL are known for their distinctive "fitz-bew" call that both sexes produce throughout the breeding season. Males often mew from conspicuous perches in varying rates throughout nest stages. Contact wits and twitters are common between a mated pair. 

Suitable BREEDING Habitat

Breeding SWFL are riparian obligates, typically nesting in relatively dense vegetation near surface water. Nests are typically built within a dense tree or shrub that is ≥ 3 m tall (with or without a higher overstory layer), has dense twig structure, and contains dense live green foliage (Allison et al. 2003). SWFL have shown some habitat adaptability as shown by utilizing both native and non-native different dominant plant communities, size and shape of breeding grounds, and canopy structure and height (USFWS 2014). Hydrological conditions can be extremely dynamic within their breeding habitat, oscillating between saturated to dry conditions even within the same breeding season; thereby causing nest placement to be extremely important when site selecting. 

BREEDING

Male SWFL begin arriving on breeding grounds in early May and immediately start establishing territories prior to the arrival of the females a few weeks later. Females choose the nest site and build a compact cup built of fine grass and soft plant material that is typically placed in the crotch of thin branches. The female lays 3-4 eggs and general performs all incubation duties. Chicks hatch between 12-13 days after the onset of full time incubation and fledge between 12-15 days old. SWFL will readily re-nest after a failed nest attempt but only occasionally attempt a second brood after a successful nest. They typically remain on their territory through early August and then begin migrating back south to wintering grounds in southern Mexico, Central America, and northern South America. 

SURVEY REQUIREMENTS

The current survey protocol divides the SWFL breeding season in to three survey periods: May 15-31, June 1-14, and June 25-July 17. A total of three surveys, one visit per period, are required in order to determine presence/absence for non-project related surveys. For project related surveys,  a total of five surveys are required in order to determine presence/absence. One visit must occur within survey period one and two visits each in the remaining periods.

To conduct protocol surveys for SWFL the surveyor must posses both a state bird letter permit and federal recovery permit for this species. The USFWS requires a written 15 day notification prior to the initiation of surveys and a 45-day letter report summarizing the findings. 

CONSERVATION STATUS

Formerly a common summer resident throughout California, SWFL have been extirpated as a breeding bird from most of its former range (Garrett and Dunn 1981). Previously, its breeding range extended wherever extensive willow riparian tracks occurred but now only small, scattered populations remain (Riparian Joint Venture 2004). The primary cause of decline of this species is attributed to the combined pressure of riparian habitat removal and increasing pressure from Brown-headed Cowbird parasitism (Garrett and Dunn 1981; Unitt 2004). 

The Willow Flycatcher was listed as state endangered in 1991, federally listed as endangered on February 27, 1995. On February 4, 2013, the USFWS designated 1,227 stream miles as critical habitat. The USFWS released their 5 year review of the species in late 2014 determining the species continues to face "a high degree of threat, has a high potential for recovery, is a subspecies, and experiences conflicts development, particularly from impacts associated with aquatic and riparian habitats" (USFWS et al. 2014). 

DOCUMENTS/LINKS

USFWS SWFL Species Profile

USFWS 5-Year Review

USGS Techniques and Methods 2A10: A Natural History Summary and Survey Protocol for the Southwestern Willow Flycatcher

SDNHM Bird Atlas Species Account

REFERENCES

Allison, L. J., C. E. Paradzick, J. W. Rourke, and T. D. McCarthey. 2003. A characterization of vegetation in nesting and non-nesting plots for Southwestern Willow Flycatchers in central Arizona. Studies in Avian Biology. 26:81-90. 

Garrett, K. and J. Dunn. 1981. Birds of southern California: status and distribution. Los Angeles Audubon Society. 408 pp. 

McKernan, R.L., and Braden, G. 2002. Status, distribution, and habitat affinities of the Southwestern Willow Flycatcher along the Colorado River-Year 6, 2001. Biol.Sci. Div., San Bernardino County Mus., Redlands, CA.

Riparian Joint Venture. 2004. The riparian bird conservation plan: a strategy for reversing the decline of riparian associated birds in California. California Partners in Flight. http://www.prbo.org/calpif/pdfs/riparian.v-2.pdf. 

Rosenberg, K. V., R. D. Ohmart, W. C. Hunter and B. W. Anderson. 1991. Birds of the lower Colorado River valley. Univ. of Arizona Press, Tucson. 

Sogge, M.K., Ahlers, Darrell, and Sferra, S.J., 2010, A natural history summary and survey protocol for the Southwestern Willow Flycatcher: U.S. Geological Survey Techniques and Methods 2A-10, 38 p.

Unitt, Philip. 2004. San Diego County Bird Atlas. San Diego Natural History Museum. San Diego, CA.

USFWS and Arizona Ecological Services. Southwestern Willow Flycatcher 5 Year Review: Summary and Evaluation. August 15, 2014.Phoenix, AZ.