352 ANIMAL LIFE IX THE YOSEMITE 



P^'rom the Big Trees auto road above El Portal, on the morning of 

 April 27, 1916, several White-throated Swifts and Violet-green Swallows 

 were seen coursing about together over the Merced Canon. Both species 

 exhibited skill in their aerial evolutions, but the swifts were the more 

 daring. Tliej" would dart downward, almost vertically, with such velocity 

 that one would think they must be dashed to earth. Yet they checked their 

 flight with apparent ease, and then circled lightly or sailed upward on 

 set wings. Once three swifts swept past within a couple of yards of the 

 observer, going at such high speed that their stiff-feathered wings made 

 a distinct swishing sound as they cut through the air. On two occasions 

 one swift was seen to pursue and grapple with another, as if to mate, 

 and then the two went tumbling over and over, downwards through the 

 air for a couple of hundred feet or more, to break apart and take opposite 

 courses just before they reached the ground. 



Black-chinned Hummingbird 

 Archilochus alexandri (Bourcier and Mulsant) 



Field characters. — Male with chin non-iridescent black, bordered immediately below 

 by a narrow iridescent purplish collar; back and top of head dark iridescent green; 

 flanks greenish. (See pi. 46c.) Female with top of head and back bronzy green; under 

 surface grayish, with faint buffy tinge on flanks; no rufous or greenish tinge on sides; 

 ends of outer tail feathers wedge-shaped. 



Occurrence. — Summer visitant locally at lower altitudes on both sides of the Sierra 

 Nevada, Eecorded at Snelling, Dudley (6 miles east of Coulterville), El Portal, and 

 Mono Lake Post Office. 



The Black-chinned Hummingbird is a foothill species, found in the 

 summertime along the beds of canons and adjacent lower slopes. A male 

 was seen at Snelling on May 28, 1915, perched on a dead willow stub in 

 the tangled river-bottom vegetation ; and on May 2, 1916, another was 

 seen in growths of yerba santa on the hillside above El Portal. At Mono 

 Lake Post Office a male was seen feeding at the blossoms of a wild currant, 

 during a snowstorm on May 23, 1916, seemingly unmindful of the state 

 of the weather. Three days later another was seen sitting on a barbed 

 wire fence. Later in the season (June 30), at the same place, four were 

 seen, one of which was driving a Green-backed Goldfinch away from the 

 hummer's favorite perch on a willow twig near an irrigating ditch. 



At Dudley, on Smith Creek, 6 miles east of Coulterville, according to 

 Mr. Donald D. McLean, this hummingbird does not arrive until the middle 

 of June. Nesting there takes place, therefore, rather late in the season. 

 Three nests have been found, all on the ranch, close to the house. On 

 July 14, 1920, a nest containing 2 fresh eggs, which the female was begin- 

 ning to incubate, was found situated 4i/2 feet above the ground on a 



