SWALLOWS 501 



The Tree Swallow resembles the Violet-green Swallow in general plan 

 of coloration and in habits, but it does not range so high altitudinally as 

 does the latter species, nor was it anywhere so abundant. We found the 

 Tree Swallow in May and June along the lower reaches of the Merced 

 and Tuolumne rivers west of the foothills, and in the neighborhood of 

 Mono Lake, beyond the Sierras. 



The Tree Swallow is, perhaps, more prone to perch than other swallows. 

 A pair will be seen a good deal of the time sunning themselves on twigs 

 of the dead tree in which their nesting site has been chosen. The nest 

 is hidden as a rule within an old woodpecker hole in some tree standing 

 at the edge of quiet water. 



Northern Violet-green Swallow. Tachycineta thalassina lepida Mearns 



Field characters. — Body size slightly less than that of Linnet or Junco; wings long 

 and pointed, when closed reaching an inch beyond the slightly notched tail. Whole 

 under surface of body, and sides of rump, pure white (pi. 46/) ; upper surface of body 

 intense green, with violet tinge on rump discernible at short range. Voice: A plaintive 

 tsee or che, sometimes repeated to form a twitter. 



Occurrence. — Common summer visitant to Upper Souoran and Transition zones on 

 west slope of Sierra Nevada; also at east base of mountains. Recorded from Pleasant 

 Valley and near Lagrange eastward to floor and walls of Yosemite Valley and to near 

 Chinquapin; also in vicinity of Mono and Walker lakes; seen in migration near Wash- 

 burn Lake. Forages in the open, roosting and nesting in hollow trees or in rock 

 crevices. Often in loose flocks while foraging. 



Of the six species of swallows found in the Yosemite section the North- 

 ern Violet-green Swallow is the one most likely to be seen by the summer 

 visitor to the region. During the warmer months of the year it is common 

 in Yosemite Valley (the only swallow regularly there, indeed), and it is 

 plentiful in the blue oak belt of the western foothills. It occurs in some 

 numbers east of the mountains in the same season, and it was observed at 

 Washburn Lake in the fall. 



In a general way the Violet-green Swallow resembles the Tree Swallow. 

 Both species have pure white underparts and dark backs, and both nest 

 in natural cavities of trees; but the Violet-green Swallow shows con- 

 spicuous white patches on the sides of the rump (pi. 46/). Sometimes the 

 white feathers of these patches curl up so as to completely cover the rump, 

 at least in side view, while again a dark space may show between the two. 

 The pure white under surface readily distinguishes the present species 

 from the remaining swallows found in the region. 



In Yosemite Valley, and at certain places in the foothills, the Violet- 

 green Swallow and the White-throated Swift may be seen together and 

 the characteristics of the two may be compared closely. The swallow is 



