170 Field Museum of Natural History — Zoology, Vol. IX. 



Family TYRANNID^- Flycatchers. 



* GROUP 1. Wing, 2.13 to 2.37 inches long. 



Bill, broad and flattened, with numerous small black bristles at 

 base of upper mandible; tip, with small but distinct hook; tarsus, 

 rounded, not flattened and sharp at the back as in the Vireos. 



^ Top of bill. Side of bill. 



First primary shorter than fifth; bill, with small hook at tip, 

 flat and wide at base; back, olive green; belly, not yellow, or only 

 faintly tinged with yellow; eye ring, whitish. Empidonax ■minimus. 



Least Flycatcher. 



See No. 215. 



Back, olive green; belly, clear yellow. Empidonax flaviventris. 



Yellow-bellied Flycatcher. 



See No. 212. 



GROUP 2. Wing, 2.37 to 2.75 inches long. 



First primary, about as long as fifth; under mandible yellowish 



white; throat, dull white; breast and belly, dull white, tinged with 



pale yellow; back, olive green. Empidonax virescens. 



Green-crested Flycatcher. Acadian Flycatcher. 



See No. 213. 



Under mandible, yellowish white; throat and under parts, yellow 

 or greenish yellow; back, olive green. Empidonax flaviventris. 



Yellow-bellied Flycatcher. 



See No. 212. 



* For directions for measurement, see page 21. 



