adult; no sexual dimorphism (California, USA; 2006-07-30)

Pacific-slope Flycatcher
Empidonax difficilis

Native Range: North America

Notes: this is one in a large group of small-sized Empidonax flycatchers that constitute a "sibling-species" complex, meaning that the species are nearly impossible to tell apart from one another in the field by plumage and morphology alone; instead, identification to a particular species relies on a combination of clues including habitat, subtle plumage features, behaviors in some cases, and especially the species' distinctive songs (which originally gave biologists the bes thint that multiple species were present).

tear-shaped buffy eye-ring; crested look (California, USA; 2006-07-30)

dorsal view; olive-yellow body (California, USA; 2006-07-30)

wide flycatcher-type bill; strong wingbars (California, USA; 2007-04-22)

usually perches in low branches... (California, USA; 2007-04-22)

in the forest understory (California, USA; 2006-07-30)

heads-on view (California, USA; 2006-07-30)