The Southwestern Willow Flycatcher (
Empidonax trailii extimus) - also known as Traill's Flycatcher - is an endangered bird in the
Tyrannidae family. A small bird - usually a little less than 6 inches in length, including tail - it has conspicuous light-colored wing bars but lacks the conspicuous pale eye-ring of many similar
Empidonax species. Overall its body is brownish-olive to gray-green above, with a whitish throat, pale olive breast, and yellowish belly. It's bill is relatively large, with a completely pale lower mandible. Both sexes are alike. True to its name, it feeds primarily on flying insects, collecting them by
sallying (flying out short distances from perch) and, to a lesser extent, hovering and gleaning. It's also been known to eat a few berries and seeds. They are best identified by vocalizations - a liquid, sharply whistled
whit! or a dry
sprit; its song is a sneezy
witch-pew or
fitz-bew. While perched, it characteristically flicks its tail slightly upward. The flycatcher is a summer breeder within its range in the United States (Arizona, California, Colorado, Nevada, New Mexico, Texas and Utah). It is gone to wintering areas in Central America by the end of September. Nest territories are set up for breeding, and there is some site fidelity to nest territories.
Empidonax trailii extimus arrives on breeding grounds in late April to early May. Nesting begins in late May and early June, with fledging from late June to mid-August. Typically lay 3-4 eggs per clutch, laid at one day intervals and are incubated by the female for about 12 days. Young birds fledge 12-13 days after hatching. Typically only raise one brood per year; however some pairs will raise a second brood, or renest after a nest failure. For nesting, requires dense riparian (the interface between land and a river or stream) habitats with microclimatic conditions dictated by the local surroundings. Saturated soils, standing water, or nearby streams, pools, or cienegas are a component of nesting habitat that also influcences the microclimate and density of the vegetation component. Habitat not suitable for nesting may be used for migration and foraging. Loss and degradation of these dense riparian habitats are the primary habitat threat to the flycatcher. Historically, water developments that altered flows in the rivers and streams were the primary threat. Now, with riparian areas limited and re-growth difficult due to changes in flows, fire is a significant risk to remaining habitats. Human disturbances at nesting sites may result in nest abandonment.
