Each of the four genealogical subdivisions of Empidonax is characterized by a different type of nesting habitat, as indicated on the tree by the color-coded bars at the base of each major branch. Members of the same branch may differ somewhat in habitat as well, but such differences are not as profound as the differences among branches. In most cases, within-branch differences in habitat are related to differences in range.

The Acadian Flycatcher, the only living member of Branch 1, is the only species that nests in the hot and humid forests of the southeastern United States. Its favored nesting areas tend to be rather moist, as in the bottomland hardwoods of the coastal plain or the very damp forests of the Appalachian coves.

The yellowish birds of Branch 2 have the most distinctive habitat. They nest in cool, damp, shady forests. There are exceptions (e.g., lava tubes), however, that indicate it may be nest sites, rather than the type of forest, that is the true cause of this association. They place their nests of moss on protected ledges. Moss and protected ledges are more likely to be found in damp forests than elsewhere.

Branch 3 birds are restricted to damp thickets. These are usually thickets of alder (Alnus) in the case of the Alder Flycatcher and willow (Salix) in the case of the Willow Flycatcher. Climate seems to have little to do with the choice of nesting locality, as the Willow Flycatcher is found in both subalpine meadows and desert riparian areas in Arizona. Populations that nest in the desert lowlands are, however, in a different subspecies from those nesting at higher elevations. See the Willow Flycatcher page for the details.

Branch 4 species nest in a variety of habitat types, and some occur in side-by-side territories if their preferred habitats are contiguous. Despite these differences, the nesting habitats of these species are more similar to each other than to habitats of the other three branches. All can be classified loosely as sunny openings in woodlands. The most derived of these are the nesting habitats of the Hammond's and Gray Flycatchers. Hammond's prefers rather damp forests and often comes into contact with the Cordilleran or Pacific-slope Flycatcher. The Gray Flycatcher needs bare ground, and often nests in Big Sagebrush (Artemisia tridentata) stands. Otherwise it is found in open pine woodland.

Except for the Hammond's-Dusky-Gray trio, within-branch differences in habitat are often correlated with non-overlapping ranges. See the Biogeography Section for graphic demonstration of this fact. Click here to continue the story of Empidonax evolution with a look at nest placement.