The southwestern willow flycatcher (Empidonax traillii extimus) is a small bird that breeds in dense riparian habitats across the southwestern United States. It is one of four subspecies of the willow flycatcher and is distinguished by its distinctive call and habitat preferences. Properly identifying the southwestern willow flycatcher is important because it is an endangered species under the Endangered Species Act.
Physical Description
The southwestern willow flycatcher is a small passerine bird, measuring approximately 5.5 to 6 inches in length with a wingspan of 8 to 10 inches. It has an olive-gray upper body, whitish throat, light olive breast, and pale yellowish belly. There are two white wingbars visible when the wings are outstretched. The eye ring is faint or absent. The upper mandible is dark, while the lower mandible is light. The tail is not strongly forked.
Overall the southwestern willow flycatcher looks very similar to other subspecies of willow flycatcher. Distinguishing physical features include its somewhat paler plumage, longer bill, and relatively longer wings compared to other subspecies. However, these subtle physical differences make visual identification challenging for non-experts. The most reliable identification method is by the bird’s unique vocalizations.
Call Description
The primary song of the southwestern willow flycatcher is a sneezy “fitz-bew” or “fitz-bewheee.” It is often described as sounding like “fitZA-veer.” The song has an upward inflection and emphasis on the first and last syllables. It is repeated every few seconds, so a singing male may sound like it is repeatedly sneezing.
Other common call notes include a “whitt” contact call and a sneezy “be-dah” alarm call. The various calls are higher-pitched and more nasal compared to other subspecies of willow flycatcher. In addition, the southwestern willow flycatcher has a smaller song repertoire overall.
Being able to distinguish the unique vocalizations of the southwestern willow flycatcher is the most reliable way to identify the bird in the field. With practice, the sneezy, nasal song can be readily distinguished from other species. Several online recordings are available for training purposes.
Geographic Range
The southwestern willow flycatcher breeds in riparian habitats across the southwestern United States, primarily southern California, southern Nevada, southern Utah, Arizona, and western New Mexico. Its wintering range includes southern Mexico, Central America, and northern South America.
Areas with large populations in the US include the Rio Grande in New Mexico, the Colorado River system in Arizona and California, the Gila River in Arizona and New Mexico, Owens Valley and Kern River in California, Virgin River in Nevada and Utah, and other large river systems or wetlands.
Knowing you are within the southwestern willow flycatcher’s breeding range during spring and summer increases the probability of a sighting. Use range maps to determine if you are within a suitable region.
Breeding Habitat
Southwestern willow flycatchers breed in dense riparian habitats along rivers, streams, or wetlands. Typical vegetation includes thickets of willows, tamarisk, Russian olive, buttonbush, cottonwoods, and alders. The habitat generally has dense vegetation in the understory and canopy layers.
Preferred nesting sites have trees and shrubs around 10 feet or more in height, dense foliage down to ground level, high canopy cover, and often standing or slow moving water nearby. The nests themselves are neatly constructed cups positioned in a fork or on horizontal branches in small trees or shrubs.
Searching for the southwestern willow flycatcher in dense riparian thickets within its known breeding range provides the highest probability of sighting the species. Be attentive for its unique call within these preferred habitats.
Migration Stopovers
During spring and fall migration, southwestern willow flycatchers use many of the same riparian habitats for stopover sites to rest and refuel. Migration peaks in May and early June during spring, and August through September during fall.
Some key stopover sites include the Colorado River in Arizona and California, the Rio Grande and Gila River in New Mexico, the Kern and Owens Rivers in California, and scattered oases, canyons, and drainages throughout the Southwest.
Stopping over at known migrant hotspots during peak migration periods provides an opportunity to detect passing southwestern willow flycatchers by their vocalizations among the dense vegetation.
Similar Species
The southwestern willow flycatcher looks very similar to other willow flycatcher subspecies. It can also be confused with other Empidonax flycatchers where their ranges overlap, especially the western wood-pewee (Contopus sordidulus) and gray flycatcher (Empidonax wrightii).
In the field, listen for their distinctive calls. The “fitz-bew” of the southwestern willow flycatcher sounds distinct from the descending “fee-bee-o” of the western wood-pewee. The gray flycatcher has a harsh, scraping “waa-cheer” call. With practice, the southwestern willow flycatcher’s sneezy song is identifiable.
When to See Them
The southwestern willow flycatcher breeds in the southwestern U.S. from late April through early September before migrating to its wintering grounds.
The best chances to detect the flycatcher are during territory establishment and pair formation in May and June. Males sing actively and frequently throughout this period. Nesting activity peaks in June and July, with a second wave late July through August.
Conduct surveys between dawn and early afternoon when the birds are most actively singing. Avoid cold, excessively windy, or wet weather.
Survey Protocols
Standardized survey protocols have been developed by the USFWS to detect southwestern willow flycatchers and determine breeding status. The surveys involve multiple site visits during the breeding season and playing recorded calls to elicit responses.
Four survey visits should be conducted from May 15 to July 17 at each survey area. The site visits should be spaced at least 5 days apart and survey the same location each time.
During each survey, the recorded southwestern willow flycatcher call is played and responses noted. All detected southwestern willow flycatchers are mapped and monitored for breeding activity like nesting or feeding young.
Proper permits from state and federal wildlife agencies are required to conduct official protocol surveys. But birders can still use tapes or smart phone apps to play the call during personal surveys.
Population Trends
Historically, the southwestern willow flycatcher bred throughout riparian systems of the American Southwest but declined sharply in the 20th century. By the 1990s, there were just several hundred breeding pairs left.
Habitat loss from river flow regulation, groundwater pumping, land use conversion, and livestock grazing contributed to the declines. Introduced tamarisk provided new nesting habitat but also led to population fragmentation.
The southwestern willow flycatcher was federally listed as endangered in 1995. Conservation efforts since have helped stabilize populations in some core breeding areas but recovery is still needed rangewide.
Continued monitoring provides data on population trends over time and gauges the success of conservation actions. The public can assist by reporting southwestern willow flycatcher sightings to resources like eBird.org.
Why Identifying Them is Important
Correctly identifying southwestern willow flycatchers is important for the following reasons:
- They are an endangered species – Accurate identification allows appropriate conservation plans and habitat protections to be implemented under the Endangered Species Act.
- Monitors population trends – Systematic surveying and monitoring provides data on population sizes and trends over time in response to conservation efforts and threats like climate change.
- Guides management plans – Knowing key sites and population densities helps target appropriate habitat restoration and management, water resource planning, and other actions.
- Allows ecological research – Proper identification enables studies on topics like migration routes, nesting ecology, survival rates, food resources, and effects of habitat changes.
- Informs species status assessments – Reliable distribution and abundance data aids periodic reviews on whether to uplist, downlist, or delist the species under the Endangered Species Act.
In summary, correctly identifying the southwestern willow flycatcher contributes significantly to conservation and management of this endangered bird throughout its range. Misidentification would compromise these efforts.
Identification Tips Summary
Here are key tips for identifying a southwestern willow flycatcher:
- Listen for its distinctive “fitz-bew” or “fit-bewheee” song – the most reliable identification clue.
- Look for small passerine birds in dense riparian thickets within the southwestern range.
- Note pale plumage, faint eye ring, and habitat during breeding season of May to early September.
- Conduct surveys during peak activity in early morning using call playback recordings.
- Distinguish sneezy song quality from similar Empidonax flycatchers like gray flycatcher.
- Be aware of key migration stopover sites during spring and fall passages.
- Learn the standardized survey protocols and get proper permits if conducting formal surveys.
- Report sightings to track populations trends and guide conservation efforts.
Following these tips will help birders and biologists reliably detect the southwestern willow flycatcher and contribute towards protecting this endangered species.
Conclusion
In conclusion, identifying the southwestern willow flycatcher relies heavily on recognizing its unique vocalizations, especially the sneezy “fitz-bew” song. Search in dense riparian habitats within its breeding range during spring and summer activity periods. Distinguish it from look-alike species by call, plumage, range, and habitat. Learn the standard survey protocols if interested in formal monitoring programs. Accurate identification of this endangered flycatcher enables proper protections under law and informs management plans to aid the species’ recovery.