The Willow Flycatcher (Empidonax traillii) is associated with willow bushes and other deciduous shrubs in open habitats across North America.
The Willow Flycatcher breeds in a variety of shrubby habitats across North America. Its habitat preferences are well documented for eastern North America, the southwestern United States and the Pacific Northwest. Typically, upland sites supporting a mixture of shrubs including willow, hawthorn and rose are preferred. In Alberta, the Willow Flycatcher has historically occupied relatively dry, upland, shrub dominated sites. During surveys in Alberta in 1999, Willow Flycatchers were found in shrubby wetlands, road and rail ditches, and brush around lake margins. The species also occurred in the mesic habitats typical of Alder Flycatchers. The surveys provided no evidence that dry, upland habitats currently support any Willow Flycatchers.
As their name would suggest, willow bushes are an integral part of the Willow Flycatcher's habitat. The average height of the willows in Willow Flycatcher territories is about 2 metres and the bushes are often densely packed.
The Willow Flycatcher is a small flycatcher (140 millimetres long, and weighing approximately 11 grams) in the family Tyrannidae, with a medium-dark, brownish olive to grayish olive back and head, two light wing-bars and light underparts with a brownish olive breast band and slight yellow wash to the vent. The Willow Flycatcher is insectivorous and catches insects on the wing.
The only reliable method of identifying Willow Flycatchers in the field is by their songs. This is especially critical when trying to distinguish the visually identical Willow and Alder Flycatchers. Both male and female Willow Flycatchers sing. The standard advertising song of the Willow Flycatcher is "afitz-bew". It will also emit a sharp, dry "whit" as well as a "zbew". Many sources have noted that the Willow Flycatcher begins to vocalize much earlier in the day than other bird species within the same habitat. In Alberta, vocal displays are often performed from tall spruce trees that offer an unobscured view of the bird's territory. Where spruce is not present, bare willow branches are often used and in some sites Willow Flycatchers use overhead powerlines as perches. These display perches are also used to initiate foraging sallies.