FAMILY SYLVIIDAE 



181 



the mouth of the Rio Tuquesa on the Rio Chucunaque, as well as from 

 Cana and Jaque. There is a recent sight report of a pair on Rey in the 

 Pearl Islands on February 11, 1970 (Ridgely, 1976, p. 279). Beyond 

 Panama this race ranges north to Guatemala and probably south to 

 adjacent northwestern Colombia. 



I found a fully grown young bird at Jaque on April 13, 1946, so the 

 nesting season in Panama may begin in February as it does in Costa 

 Rica (Skutch, Pac. Coast Avif., no. 34, 1960, p. 34). On March 13, 

 1948, I collected a pair in near breeding condition at La Cabuya, Her- 

 rera. Along the Chepo Road in the Province of Panama, Major Gen- 

 eral G. Ralph Meyer found a pair building a nest on March 18, 1944; 

 the nest contained 1 egg on March 26, and 1 from the full clutch of 3 

 eggs was collected on April 9. Bond and de Schauensee reported a male 

 with testes enlarged that was collected at Garachine, Darien, on April 

 24, 1941. On May 26, 1912, E. A. Goldman collected a female at Cana, 

 Darien, with an egg almost ready to lay. 



Most of what is known of this race's breeding biology comes from 

 Skutch (op. cit. pp. 43-56). He found 6 nests, which ranged in height 

 from 2 to 8 m off the ground. The nest is built by both male and female 

 and closely resembles the lichen covered cup-shaped nest of the North 

 American Blue-gray Gnatcatcher (P. caerulca). The clutch was either 

 2 or 3, and the eggs white, finely speckled all over with brown. An 

 egg obtained by Major General Meyer measured 14.4x11.7 mm. The 

 males assisted in incubation, a habit shared with P. caerulca and P. 

 melanura, and also with Ramphocaenus, but rare in tropical passerines 

 as a whole. After a 13-day incubation period the young hatch entirely 

 devoid of down. They are brooded regularly for at least the first 5 days 

 and are fed entirely on insects. The length of the nestling period and 

 the extent to which young are cared for thereafter are not known. 



POLIOPTILA PLUMBEA CINERICIA Wetmore 



Polioptila plumbea cinericia Wetmore, 1957, Smiths. Misc. Coll., 134(9), p. 80. 

 (Isla Coiba, Panama.) 



Characters. — Similar to P. b. superciliaris, but dorsal surface, in- 

 cluding the wings, decidely darker gray; lower foreneck and breast 

 grayer (instead of white as in superciliaris); sides darker gray; bill 

 averaging broader. 



Measurements. — Males (9 from Isla Coiba), wing 46.2-49.7 (48.5), 

 tail 41.8-46.3 (44.1), culmen from base 13.0-14.9 (14.0), tarsus 16.6- 

 17.8 (17.2) mm. 



Females (6 from Isla Coiba), wing 45.1-47.4 (46.6), tail 41.9-45.3 



