268 BULLETIN" 17 6, UI«riTED STATES NATIONAL MUSEUM 



plunges and hurried upward flights. The long, narrow wings at 

 times 'twinkle' rapidly, or when the bird is sailing, are either held 

 uplifted over the back or curved downward with the tips well below 

 the body. The tail is very slightly forked but in flight it is con- 

 stantly spread and appears fan-shaped w^hen the bird makes a sudden 

 turn." 



I can find no evidence that the northern black swift has ever been 

 seen perching on a tree or wire, or resting on the ground ; its regular 

 resting places seem to be the steep, rocky walls, often dripping with 

 moisture, such as they choose for nesting sites. Though their feet 

 are small and light, they have very sharp claws, and are able to 

 cling to the rough surface for long periods. Mrs. Michael (1926) 

 has seen them clinging to the wet walls behind the Vernal Falls and 

 near it. "From the distance of fifty yards the birds appeared to 

 stick as limpets do to the wet rocks of a sea shore." But, on closer 

 examination, she found that "they were not sticking to the wall as 

 limpets, but their bodies were held slightly away from the wall, with 

 not even their tails touching." With one bird, she noted that "his 

 strong toe nails were hooked to some tiny support and his entire tar- 

 sus rested firmly against the w^all, thus holding his body and tail 

 free." Later (1933) she saj^s of a young black swift that she had in 

 captivity: "When climbing up a sheer surface the swift used its 

 wings, feet, tail and sharply hooked bill. When in repose it lay flat 

 on its belly in the manner of a poor-will. * * * The legs seemed 

 to have swivel joints, and it was strange to see the bird reach up 

 its foot between the body and wing to comb its back and crown 

 feathers." 



Voice. — There is not much to be said about the voice of the black 

 swift. All observers agree that it is generally a silent species; its 

 note is seldom heard, except during the mating season and on its 

 breeding grounds. Mr. Rathbun (1925) writes: 



During its spring migration and shortly following, a period when the birds are 

 associated in numbers, we have watched them for long spaces of time and 

 always a perfect silence seemed to prevail among them. And this apparently is 

 the case until the time comes when by their actions they show that they are 

 mating. Even now their chatter-like note is but seldom heard, although in- 

 variably it is given at the time when one dashes at another, and this often 

 proves the case when a pair may happen to fly in close company. During the 

 midsummer we have heard their rapid notes as the birds passed in flight near 

 the close of day, and in the autumnal migration when rarely one would make 

 a quick dash at another. But these instances are uncommon and the species 

 can properly be regarded as quite silent, being very different in this respect 

 from the Chaeturine Swifts whose shrill twitterings are so frequent as they fly 

 about. And the chatter of the Black Swift somewhat resembles that of the 

 smaller ones ; it being as rapid, but smoother in quality and more rolling, in 

 fact rather pleasing to hear. 



