260 BULLETIN 17 6, UNITED STATES NATIONAL MUSEUM 



The latest nesting record comes from Albert Ervin Thompson 

 (1937), who found a nest "near the western boundary of General 

 Grant National Park in Fresno County, California, in the Transition 

 Life Zone at an elevation of five thousand two hundred feet above 

 sea level in the Sierra Nevada Mountains." He says further : 



The narrow mountain gorge in which the nest was found is forested with tall 

 •sugar and yellow pines, white fir, incense cedar, and giant sequoia, and, because 

 of a steep slope to the northwest, receives very little direct sunlight except during 

 a brief portion of the afternoon. At other times only random shafts of light 

 find their way among the trees. 



The nest was built in a hollow of a granite wall, sheltered by an overhanging 

 projection of rock. It was about six feet above the bed of a mountain brook and 

 not more than twelve feet removed from a rushing cascade that boiled down a 

 chute from a cliff above. Because of the smoothness of the sheer face of the 

 rock, the situation was inaccessible to snakes and small mammals. The nest 

 was formed by moist mossy material, imbedded in a natural growth of the same 

 plant. Seeping water and spray from the waterfall kept the site continiially 

 moist. For this reason the nest was at first mistaken for that of a water ousel. 

 One egg was laid, but after it hatched the young bird mysteriously disappeared, 

 perhaps devoured by an enemy. 



Eggs. — The single ^gg of the northern black swift is usually, in the 

 six specimens that I have examined, elliptical-ovate in shape, though 

 some are nearly elliptical-oval. The shell is smooth but without 

 gloss. They are dull, pure white in color, but one is somewhat nest- 

 stained. The measurements of 34 eggs average 28.(5 by 19.0 milli- 

 meters; the eggs showing the four extremes measure 31.5 by 18.3, 

 28.0 by 20.6, 24.5 by 19.5, and 28.5 by 17.8 millimeters. 



Young. — Nothing seems to be known about the period of incuba- 

 tion or to what extent the two sexes assist in incubation and the feed- 

 ing of the young, though it seems to be assumed that the female does 

 most of the brooding and feeding. All observers seem to agree that 

 the young swift is fed at infrequent intervals, mainly early in the 

 morning and late at night. Mr. Michael (1927) says: "Most young 

 birds receive food every few minutes, but here we find young birds 

 that go for hours without food. Raking the sides all day long, the 

 old swifts probably return in the evening to pump their young full of 

 concentrated nourishment." Many hours of patient watching yielded 

 very little information on this point, but on August 15 — 



at 12 : 30 an old bird arrived. She flew up the canyon and alighted directly on 

 the edge of the nest. Clinging here with her tail appressed and one long wing 

 spread out across the surface of the wall she apparently pumped food into the 

 young bird. She appeared to fairly stuff the young one, pumping food into him 

 ten times in twenty seconds with but slight pauses between times. At first 

 the young one was very eager and squirmed with delight while being fed. Soon, 

 however, he was full and had to be coaxed to take the last two or three helpings. 

 When through feeding her young one, the mother bird crawled iip onto the 

 nest and the young one squirmed and twisted until his head was quite snuggled 



