(Southwest) Willow Flycatcher (Empidonax traillii extimus)

Distribution

Breeding: Willow Flycatchers are widespread across the United States and southern Canada; the distinct Southwestern Willow Flycatcher (E. t. extimus) breeds in southern California, Arizona, New Mexico, extreme southern portions of Nevada and Utah, extreme southwest Colorado, and western Texas. Now extirpated from most of its former California range.

Winter: From Nayarit and southwestern Oaxaca, Mexico south to Panama and northwestern Colombia.

Breeding habitat

The breeding site must have a water table high enough to support riparian vegetation, and are usually within close proximity (less than 20 yards or 18 meters) of water or very saturated soil in the form of large rivers, smaller streams, springs, or marshes. An important characteristic of the habitat appears to be the presence of dense vegetation, usually throughout all vegetation layers present, e.g. dense growths of willows, seepwillow, or other shrubs and medium-sized trees. There may be an overstory of cottonwood, tamarisk, or other large trees, but this is not always the case.

Conservation status

Overall, the Willow Flycatcher is a common and widespread species, with populations stable or increasing in the East, but declining in most western regions. The southwestern subspecies (E. t. extimus) is of highest conservation concern and is listed as an endangered species. This population is highly restricted to riparian forest stands and is greatly reduced from its historical Distribution. Many efforts are underway to identify and monitor important populations of this subspecies, as well as to determine its precise habitat and area requirements.

Description

Male: Closely resembles the other races of Willow Flycatcher, and several other species of the Empidonax genus, particularly the closely related Alder Flycatcher (Empidonax alnorum). Roughly the size of a small sparrow, the Willow Flycatcher is overall greenish or brownish gray above, with a white throat that contrasts with a pale olive breast. The belly is pale yellow. Two white wing bars are visible, an eye ring is faint or absent. The bill is two-toned, with the upper mandible dark, the lower mandible light.

Female: Same as adult male.

Juvenile: Little information. Similar to adults, but tend to show buffier wing bars, more yellow on the belly, and slightly more color in the upperparts. These differences fade rapidly.

Note: As the Empidonax flycatchers are renowned as one of the most difficult groups of birds to distinguish by sight alone, the most reliable way to distinguish the Willow Flycatchers from other similar flycatcher species is not to rely upon its appearance, but rather through its distinct song.

Vocalizations

Songs: A harsh, burry RITZ-bew, RRRITZ-beyew, or rrrEEP-yew, often alternating among these variations, sometimes merely a strong rrrIP. Usually rough and low with emphatic rising ending.

Calls: Call a thick, liquid whit.

Foraging strategy

Sits and waits on a relatively open perch, like an exposed tree limb, and hawks after flying insects; also gleans insects from foliage while hovering. Occasionally pounces on insects on the ground.

Diet

Almost exclusively insects, but will eat berries or seeds during certain times of year.

Behavior and displays

• Most of available time spent sitting or singing, only small amounts of time foraging, flying, at the nest, defending territory, or in courtship.

• Territorial disputes among males frequent before nesting begins, and intruding males may occasionally be attacked by both members of a territorial pair.

• Agonistic behaviors include “tail-flick” and “crest-raise,” also extending breast feathers, flicking wings, flying at other flycatchers to replace them on their perch, and chasing conspecifics.

• Physical contact is rare.

• Advertising song is important in pair-bond establishment and reinforcement. Posture during song is upright, with head thrown back, tail flicked upward, and chest thrown outward.

• In-flight bathing occurs by diving to water surface.

Courtship

• Pairs and trios engage in vigorous sexual chase during courtship and territorial establishment.

Nesting

Nest Site: Primarily in thickets, especially of willow, though other shrubs or trees are used, near slow streams, standing water, or seeps. Nest placed in a fork or on a horizontal limb of shrub.

Height: Average height 24 feet (7.5 meters), but populations of E. t. extimus may place nests much higher.

Nest: Female weaves nest of forb stems, plant fibers, pine needles, shreds of bark, and dry grasses; outside may contain lichens, paper, cocoons, and shredded grass. Cup is lined with feathers, hair, rootlets, and finer materials.

Eggs: 3–4, occasionally 5, creamy white or buff eggs are dotted, blotched with brownish to blackish irregular spots about large end, often in a loose wreath. Southwestern clutches may be smaller than average.

Incubation period: Female incubates for 12–15 days.

Nestling period: Female broods young, both adults feed, but female plays the major role. Typically direct flight to the nest with food, or to twig near nest. Young leave nest at 12–15 days.

Fledgling period: Nestlings may move some distance from nest for short intervals, only to return to nest. For the first few days fledglings often huddle together on the same perch remaining near the nest for 3–4 days, then follow adults through territory until 24–25 days.

Broods: Single brooded.

Cowbird Parasitism: May incur a high rate of cowbird parasitism.

Notes

• Song is entirely innate; females sometimes sing territorial song.