182 



BIRDS OF THE REPUBLIC OF PANAMA PART 4 



(44.0), culmen from base 13.8-14.8 (14.4), tarsus 16.2-17.5 (17.0) 

 mm. 



Resident. This race is endemic to Isla Coiba, where I found it to be 

 common in January and February 1956, ranging in leafy cover from 

 low second-growth thickets near the shore to the summits of the tallest 

 forest trees in the interior of the island. Invariably they moved about 

 among the twigs and leaves in unceasing activity in pursuit of tiny in- 

 sects, often so high above the ground that I could barely detect their 

 tiny forms. The slender body, with long, narrow tail held at an angle 

 above the back, and their quick, nervous movements, mark them even 

 when the gray and white plumage is not clearly seen. I found them in 

 pairs, and near breeding at this season. On January 21 one male was 

 much excited by my squeaking, and came to perch within 4 m of me 

 while it sang repeatedly a series of high-pitched notes of the usual 

 gnatcatcher quality mingled with beautifully clear, warbling phrases of 

 much louder sound that would have graced the gifted song of a mock- 

 ingbird. 



Eisenmann (with E. S. Morton) on October 8-11, 1965, found this 

 species more numerous on Isla Coiba than anywhere else in Panama. 

 They also found it on nearby Isla Coibita. The vocalizations heard on 

 Isla Coiba in October were neither musical nor noticeably nasal. Birds 

 heard singing on Isla Coiba by Ridgely in early April 1976 seemed to 

 him to vocalize like mainland birds. 



POLIOPTILA SCHISTACEIGULA Hartert: Slate-throated Gnatcatcher, 

 Cazajejen Gargantigris 



Polioptila schistaceigula Hartert, 1898, Bull. Brit. Orn. Club, 7, p. 30. (Cachabi 

 [=Cachavi], 500 ft, Esmeraldas, Ecuador.) 



Small, slender; dark slaty gray, except lower belly to undertail co- 

 verts, which are white. 



Description. — Length 97-102 mm. Adult (sexes alike), crown, back, 

 and undersurface from throat to chest dark slaty gray; base of lores 

 faintly white; upper throat lightly spotted white; broken eye-ring 

 white; upper tail coverts slightly lighter gray; wings and tail black, 

 outer two pairs of rectrices slightly tipped white; lower belly to under- 

 tail coverts, underwing coverts, and inner web of underside of all but 

 outer three primaries edged white. 



A male collected at the Peluca Hydrographic Station in Colon on 

 February 27, 1961, had the iris reddish brown; maxilla and extreme 

 tip of mandible black; rest of mandible neutral gray; tarsus and toes 

 dark neutral gray; claws black. The tongue spots were tiny and incon- 



