370 University of California Publications in Zoology. [Vol. 7 



and circled about through the pines, soon returning, however, 

 and continuing their erratic flight over the water. 



■ Seventeen individuals were seen circling over the broad 

 Leonard Creek flats (6000 feet) in a manner resembling that of 

 a gyrating flock of turkey vultures. As a rule the nighthawk 

 moves its wings slowly. Its principal call-note, which may be 

 rendered by the syllables "squee-awk!" is uttered immediately 

 after it makes three short wing-beats. The process of "boom- 

 ing" is as follows. The nighthawk, being high in the air, sets 

 its wings and dives rapidly earthward. When it reaches a point 

 ten or fifteen feet from the ground it suddenly catches itself, 

 the operation producing a most peculiar and indescribable 

 buzzing or whistling sound, which constitutes the ' ' boom. ' ' This 

 note is in a measure analogous to the explosive sound made by 

 the Anna hummer as it reaches the lowest point in its nuptial 

 flight. After producing the boom the nighthawk remounts to 

 something like its original height, repeating the maneuver only 

 at irregular intervals. 



Eggs were discovered June 25, on Thousand Creek. 



Three specimens (nos. 9160, 9308, 9309) were secured. 



Aeronautes melanoleucus (Baird) 



White-throated Swift 



Noted flying about the cliffs of Little High Rock Caiion. 

 They were seen entering crevices, so may have been nesting. No 

 specimens taken. 



Selasphorus platycerus (Swainson) 

 Broad-tailed Hummingbird 



Distribution. — Hummingbirds presumably of this species 

 were noted as follows: at Big Creek Ranch, May 18 and 20; at 

 intervals in the vicinity of the head of Big Creek; and at 

 Leonard Creek Ranch, where they were buzzing in and out 

 among the trees of the large poplar windbreaks. 



Habits. — On July 1 a single specimen (no. 9082) was taken 

 on a meadow at an altitude of 8000 feet. It was feeding about 

 iris, which was blooming on the mountain meadows at this time. 



