FAMILY TYRANNIDAE 531 



rami and basal third of gonys buffy white ; narrow cutting edges of 

 maxilla and mandible dull yellowish white; rest of bill black; tarsus, 

 toes, and claws on inner and outer anterior toes, brown ; claws on 

 central anterior toe and on hind toe, fuscous. 



Measurements. — Males (10 from Chiriqui, Veraguas, and Cerro 

 Campana, western Province of Panama), wing 47.0-51.5 (49.7), 

 tail 33.2-39.2 (36.6), culmen from base 10.1-12.5 (11.9), tarsus 

 15.4-16.5 (15.9) mm. 



Females (10 from Chiriqui, Veraguas, and Cerro Campana, west- 

 ern Province of Panama), wing 43.2-46.5 (44.6), tail 28.0-35.3 

 (31.8), culmen from base 11.2-12.2 (11.6), tarsus 14.2-16.1 

 (15.1) mm. 



Resident. Found on the Pacific slope in forested areas in the 

 upper Tropical Zone from 450 to 1525 meters, from western Chiriqui 

 through Veraguas and Code to Cerro Campana in the western sector 

 of the Province of Panama ; ranges also to the upper Tropical Zone 

 from 750 to 900 meters on Cerro Azul ; in Darien to 900 meters on 

 Cerro Sapo ; on Cerro Pirre from 750 meters to the lower Subtropical 

 Zone at 1580 meters; on Cerro Mali from 575 meters on the base to 

 the upper Tropical Zone at 1430 meters. 



They are encountered regularly from undergrowth near the ground 

 to the lower tree crown, in undisturbed forest, and are adapted to 

 change, as they come regularly to second growth where this has at- 

 tained fair size. At rest they perch quietly with the body held erect. 

 As they are so small, it may be difficult then to see them, since the 

 smallest leaves may hide them. Males have a low song that may be 

 represented by the syllables weet chee si-loo, often given with the 

 syllables in reverse order. The more common call, that often at- 

 tracts attention, is a rattling, steely note given usually by the males, 

 and possibly may be restricted to them. In this sex, the trachea is 

 thin-walled and considerably enlarged, the swelling beginning im- 

 mediately below the larynx on the upper end, and tapering distally 

 to terminate at the syrinx. In calling, the crest may be elevated, and 

 the feathers of cheeks and upper neck erected. As stated, this call 

 appears to be confined to the males. In females the trachea is small 

 and of normal form. It should be noted that because of the thin 

 wall the trachea shrinks appreciably after preservation in alcohol, so 

 that while still enlarged it appears smaller than in life. 



Skutch (Publ. Nutt. Orn. Club, no. 7, 1967, pp. 90-92), in obser- 

 vations on the Pacific slope of southern Costa Rica, recorded males 

 calling persistently from the middle of January to May, scattered 



