SWALLOWS 499 



siderable. Moreover, work must be suspended at frequent intervals in 

 order that the birds may hunt for food. 



The Cliff Swallow arrives in the western part of the Yosemite region 

 some time in March, but the birds there do not begin nesting until early 

 May. This delay is probably due to the relative paucity of insect life 

 in April as compared with the plenty in May and June. When the adults 

 arrive they can find sufficient forage for themselves, but at that season 

 there is not enough to enable them to feed a brood of young. Hence they 

 delay until the food supply is adequate for the increased needs of nesting 

 time. East of the mountains, near Williams Butte, in 1916, the birds 

 returned for the season on April 27. 



Barn Swallow. Hirundo erythrogaster erjrthrogaster Boddaert 



Field characters. — Body size about that of a Linnet but tail and wings much longer 

 and slenderer; tail deeply forked, with the outermost feathers very narrow toward tips 

 (pi. 46e). Upper surface of body iridescent dark blue; forehead and under surface 

 of body light reddish brown; chest with a dark band, not often complete. Voice: A 

 series of twittering notes. 



Occurrence. — Common summer visitant locally at low altitudes both east and west of 

 Sierra Nevada. Eecorded from Snelling and near Lagrange eastward to Bower Cave, 

 12 miles east of Coulterville ; also, east of mountains, in neighborhood of Mono Lake. 

 Chiefly near smooth flowing water; local distribution controlled largely by availability 

 of suitable nesting sites such as low bridges. Usually in pairs, at most in small 

 companies. 



The general range of the Barn Swallow in the Yosemite region is 

 practically the same as that of the Cliff Swallow, but as the nesting 

 requirements of the two species are different, their local distribution is 

 not the same. While the Cliff Swallow must have an expanse of wall, either 

 of rock or board, and nests in colonies, the Barn Swallow prefers to live 

 more apart and places its solitary nest on a beam beneath a bridge. Thus 

 the Cliff Swallow is to be found in considerable numbers in a few localities, 

 whereas small numbers of the Barn Swallow are found in many places 

 through the lowland and foothill districts. By reason of its choice of nest 

 site the Barn Swallow is often associated with the Black Phoebe. 



The Bam Swallow differs conspicuously from all its fellows in the 

 possession of a deeply forked tail (pi. 46e), This, in flight, is the most 

 easily noted field character. When the bird is perched on a wire or twig 

 the observer sees four points of feathers projecting backward from its 

 body ; these comprise the tips of the elongated and narrowed wings and 

 the long outermost tail feathers. The six species of swallows found in 

 the Yosemite section exhibit little difference in skill of flight, yet the 

 Barn Swallow, with its attenuated tail, seems to us to be slightly more 

 adept and certainly more graceful in its aerial coursing than its square- 

 tailed relatives. 



