Like Dusky Flycatcher, Hammond’s Flycatcher is a hard to identify Empidonax flycatcher of western mountains. Both species winter in western Mexico and both species occur in many of the same mountain ranges.
Hammond’s prefers evergreen forests while Dusky is more of a deciduous forest species. While Dusky may be found in brushy mountain slopes and aspen glades, Hammond’s is a bird of spruce and fir forests. The overall ranges are similar, but Hammond’s is especially prevalent in the Sierra Nevada range and occurs more in the coastal ranges, while Dusky is somewhat more prevalent in drier ranges to the east. This difference is noticeable when the maps for the two species are compared directly; watch for the bright signal for Hammond’s along the Pacific slope.
The migrations of the two species are interesting to compare as well. In fall, Hammond’s moves noticeably later, with the STEM map retaining a signal on into October. Dusky Flycatcher, by comparison, is clearly on the move in August and by mid-September its occurrence has become low enough that it fades from view by mid-September. The spring timing is more similar, with both species returning in April, but it seems that Hammond’s makes an earlier and more noticeable push through the southwestern deserts (note Arizona and especially southeastern California), while Dusky makes its first significant showing in breeding areas. Perhaps this is because some Hammond’s have father to travel (breeding much farther into Canada than Dusky) and consequently they are more likely to make stopovers than Dusky. Both species winter in small numbers in southeast Arizona, and that signal, though faint, can be seen during portions of the winter.