212 U. S. NATIONAL MUSEUM BULLETIN 217 



On June 3, holes were started by one group of about 50 swallows 

 along a section of bank, and in a few days there were 30 or 40 holes 

 under construction within a stretch of 50 feet. This particular group 

 seemed to swarm together as they flew in their unbelievably swift 

 banks and turns, giving the impression of social organization in the 

 pattern of flight. Many other holes were started in the bank in front 

 of the village and scattered or concentrated groups of holes were 

 formed in many banks exposed by the rapid fall of the river. The 

 swallows are adept at selecting banks which do not disintegrate, as in 

 many places they do during the summer by thawing and drying. The 

 swallows also selected nest sites in firm but early-drying sandy loam. 

 The construction of holes was still in progress on June 15. It is 

 obviously a laborious operation for such small birds with their slight 

 equipment for digging. 



A recorded first arrival (Bent, 1942) in Fairbanks, May 14, pre- 

 cedes the arrival at Old Crow by two weeks. Alfred Gross (Bent, 

 1942) refers to an account, written for him by Frank L. Farley, of 

 a large migratory flight of bank swallows passing northward over 

 the Athabaska River about 125 miles northwest of Edmonton on 

 May 11. Since they are reported to be rare west of the Cas^de and 

 Coast Eanges (Munro and Cowan, 1947), it is presumed that the 

 northward migration travels through the Mackenzie Valley. 



The Indians name this bird Shai tso ve. 



Petrochelidon pyrrhonota hypopolia Oberholser 



Males Female!^ 





Weight 



Fat 



Testes 



Weight 



Fat 



Eggs 



Date 



(!7.) 





(mm.) 



(g.) 







June 10 



30.2 



MF 



7x10, 10x10 









June 14 



27.0 



MF 



9x11, 8x8 



30.1 



MF 



1 in oviduct, 1 broken follicle, brood 

 patch 



June 14 









30.0 



F 



1 in oviduct, 2 broken follicles 



June 23 





MP 



6x9, 7x8 









Jimel7 













5 fresh eggs, 4 slightly incubated 

 eggs 



A single cliff swallow was noticed on the evening of May 25. During 

 the next day their number increased, and on May 27 was twice that 

 of the approximately 50 tree swallows which had arrived in the village 

 10 days earlier. The arrivals at once set about examining the mud 

 nests remaining from last year under the eaves of buildings. Many 

 old nests had been destroyed, but those most nearly intact were first 

 claimed and their reconditioning was begun. These did not suffice 

 for all the swallows, and work was gradually started on badly broken 

 nests and at new positions. The construction was a laborious op- 

 eration, and often the instinctive engineering was frustrated by the 



