FAMILY UIRUNDINIDAE 



39 



Measurements. — Males (10 taken in breeding season, March to May 

 in southern Arizona) , wing 104.5-111.5 (108.6), tail 45.3-50.0 (47.5), 

 culmen from base 8.5-10.8 (9.7), tarsus 10.2-11.2 (10.6) mm. 



Females (10 taken in breeding season, April to June, in Baja Cali- 

 fornia, southern California, and southern Arizona), wing 100.2-107.4 

 (104.4), tail 42.9-48.7 (46.3) , culmen from base 9.1-10.7 (9.9), tarsus 

 10.2-11.5 (10.9) mm. 



Winter migrant from the north, found locally from December to 

 March along the lower channels of the larger rivers. Recorded from 

 specimens in western Colon (Rio Indio, Chilar) and the northern Canal 

 Zone (above Gamboa, near Juan Mina). 



This is the form that breeds in the western United States and 

 southwestern Canada. The series of 12 specimens taken in Panama 

 from small flocks during January, February, and March in 1952, 1955, 

 and 1961 includes 9 females and 3 males. 



In 1952, in February and March, I found these swallows abundant 

 along the lower course of the Rio Indio in western Colon, in small 

 flocks that fed over the water and the adjacent shore. In the main they 

 ranged apart from the scattered pairs of the resident race uropygialis, 

 which were more common farther inland along the river. 



STELGIDOPTERYX RUFICOLLIS UROPYGIALIS (Lawrence) 



Cotyle uropygialis Lawrence, Ibis, ser. 1, vol. 5, no. XVIII, April 1863, p. 181. 



(Atlantic slope, Canal Zone, Panama.) 

 Stelgidopteryx ruficollis decolor Griscom, Proc. New England Zool. Club, vol. 11, 



Dec. 14, 1929, p. 69. (Divala, Chiriqm.) 



Characters. — In general like the northern migrant races, but throat 

 and upper foreneck rufous; darker above; rump slightly to definitely 

 paler than back, shading from light gray at base of feathers to nearly 

 white at tips; breast, sides, flanks, axillars, and underwing coverts light 

 grayish brown; carpal edge of wing barred rather indistinctly with dull 

 white; center of lower breast yellowish white; abdomen and undertail 

 coverts white, in some tipped with black. Immature, with back, wing 

 coverts, and tertials edged (in part indistinctly) with dull cinnamon; 

 rump, sides, and flanks tinged with cinnamon. 



In a female, taken at El Llano, eastern Province of Panama, Febru- 

 ary 3, 1962, the iris was wood brown; bill, tarsus, and toes black. In 

 another of the same sex from Puerto Armuelles, Chiriqui, February 7, 

 1966, the iris was dark brown, tarsus and toes fuscous, claws black. 



Measurements. — Males (10 from Canal Zone, eastern Province of 



