Hammond's flycatcher (Empidonax hammondii) is a small insect-eating bird. It is a small Empidonax flycatcher, with typical length ranging from 4.7- 5.5 inches. The name of this bird commemorates William Alexander Hammond who was the surgeon general of the US Army. Hammond collected bird specimens for Spencer Fullerton Baird. Hammond's flycatchers have grayish-olive upperparts, darker on the wings and tail, with whitish underparts; they have a conspicuous white eye ring, white wing bars, a small bill and a short tail. The breast is washed with grey and the sides of the belly with yellow. Female usually have a shorter, wider bill compare with male's.[4] Immature are similar to adults, but have broader wing bars and are more buff. Hammond's flycatchers have been recorded in the COSA in April and May.