FAMILY IIIRUNDINIDAE 



17 



ward, merge gradually into the large population (hypopolia) of Alaska. 

 Intermediates from Oregon have been described as a distinct race, 

 aprophata, with the "lower parts paler, and forehead more buffy (less 

 clearly whitish)" (Petrochelidon albifrons aprophata Oberholser, Sci- 

 entific Publications Cleveland Museum, vol. IV, no. 1, 1932, p. 6). In- 

 dividual variation is such that this proposed additional race may not be 

 distinguished with certainty, especially in winter migrants. 



PETROCHELIDON PYRRHONOTA HYPOPOLIA Oberholser 



Petrochelidon albifrons hypopolia Oberholser, Canadian Field-Nat., 1920, vol. 33, 

 no. 5, p. 95. (Fort Norman, Northwest Territories.) 



Characters. — Forehead white; size larger. 



Measurements. — Males (10 from Alaska and MacKenzie), wing 

 112.7-116.1 (114.1), tail 45.7-51.7 (49.2), oilmen from base 9.0-10.9 

 (9.8), tarsus 12.4-14.2 (13.3) mm. 



Females (10 from Alaska and MacKenzie), wing 110.5-115.5 

 (113.1), tail 47.1-53.9 (50.4), oilmen from base 9.1-10.6 (9.7), tarsus 

 12.4-15.0 (13.6) mm. 



Migrant from the north, abundance uncertain. At the Cienaga Santo 

 Domingo, eastern Province of Panama, below La Jagua, on March 30, 

 1949, when a flock of 100 or more Cliff Swallows circled near, I shot 1 

 and the others disappeared. The bird taken was extremely fat and also 

 of maximum size, with the wing measuring 116.5 mm. It agrees fully 

 in this with the population of northern Alaska and northwestern Can- 

 ada, and is identified as the race nesting in that area. It is the only 

 definite record of this subspecies from Panama that I have seen. 



PETROCHELIDON PYRRHONOTA TACHINA Oberholser 



Petrochelidon hmifrons tachina Oberholser, Proc. Biol. Soc. Washington, vol. 16, 

 February 21, 1903, p. 15. (Langtry, Texas.) 



Characters. — Forehead light to fairly dark buff (varying from dull 

 buffy white to dull brown) . Size small. 



Measurements. — Males (10 from Chihuahua, Guanajuato, and 

 Texas), wing 100.0-105.1 (102.5), tail 42.8-45.7 (44.3) culmen from 

 base 8.4-9.9 (9.3), tarsus 11.8-12.6 (12.0) mm. 



Females (10 from Texas and New Mexico), wing 101.3-104.7 

 (103.0), tail 42.6-47.6 (45.2), culmen from base 8.4-9.9 (9.1), tarsus 

 11.2-12.2 (11.9) mm. 



Migrant from the north. Abundance uncertain. 



On February 26, 1956, I collected a female, at Las Lajas, near the 



