256 BULLETIX 17 6, UNITED STATES NATIONAL MUSEUM 



Coiirtshij). — The courtship of the black swift and apparently copu- 

 lation also are accomplished on the wing. Mr. Rathbun (1925) says: 



Black Swifts appear to mate in June. There is no sign that this has taken 

 place when they arrive in May, as then the birds are always seen in com- 

 panies and not in pairs as is subsequently often the case. But soon after they 

 have become distributed in colonies about the region and begin to make the 

 daily flight to and from the lower country, indications of mating are seen. 

 All may be gliding about when suddenly — iierhaps from a far height, a Swift 

 will dash at one beneath, this followed by erratic flight actions on the part of 

 both and their disappearance in the distance. This dive I have seen made 

 with such speed that the eye could scarcely foUow it, and during the time thpt 

 the birds are darting and twisting about it is a common thing for them to 

 descend almost to the ground. 



He says, in some notes sent to me : "On one occasion the latter part 

 of June, I saw a pursuit by one black swift after another that lasted 

 a full 15 minutes. This was the longest of any we ever observed, and 

 we have seen many of them." 



Nesting. — The honor of discovering the first nest of the northern 

 black swift belongs to A. G. Vrooman (1901), who relates the historic 

 incident as follows : 



On the morning of June 16, 1901, I, with a companion, started out with the 

 intention of taking a few sets of Cormorants' eggs on the cliffs a few miles 

 west of Santa Cruz, California. On reaching the locality, I noticed a pair of 

 Black Swifts flying about over the cliffs, much lower than they usually fly. 

 One bird rose high in the air and struck off in a bee line, at the rate of a mile 

 a minute. I then resumed my search for the Cormorants, which I found on 

 the face of the cliff, where shore line turns sharply inland and about where the 

 Swifts had been seen. * * * 



After moving my ladder a little, I proceeded to reach out and down for a 

 more distant set of Baird's Cormorant eggs when suddenly, right from inider 

 the pole and not more than three or four feet from my han^, a Black Swift 

 flew out and down toward the water and passed around the angle toward the 

 ocean. It did not rise above the cliff, in the immediate vicinity, as my com- 

 panion above the cliffs did not see it at all, though I called to him to watcb 

 if it came above. 



I then moved my ladder a little closer and went down farther so that my face 

 was about a foot and a half from the egg which the Swift had just left. It was 

 placed on a shelf or crevice in the lower edge of a projection standing out 

 perhaps four or five feet from the main wall and about ninety feet from the 

 breakers below. This crevice was four or five inches high, five or six inches 

 deep, and about twenty inches long, very narrow at one end, and about thirty 

 feet from the top of the cliff, twenty feet of which is earth sloping back to 

 the level laud above. This portion of the cliff was wet and dripping constantly, 

 causing tufts of grass to grow here and there, where there was earth enough 

 to support the roots. It was just behind one of these tufts of grass, in a slight 

 depression in the mud, formed no doubt by the bird, that the egg was laid. 

 I did not disturb the egg or nest, not going nearer than a foot and a half, 

 intending to return a week later to get possibly a full set, which I did, but 

 found things just as I had left them a week before and no Swifts were in 

 sight. I took the egg, and pealed off the nest, grass and all, and have it in my 

 collection. 



