Tree-Swallow 419 



p. 15 ; Tresz 81, p. 287 ; Allen & Brewster 83, p. 160 ; Morrison 88, 

 p. 73 ; Cooke 97, pp. 19, HI, 217 ; Rockwell 08, p. 175 ; Henderson 09, 

 p. 238. 



Description.— Male — Above, including the sides of the head and neck, 

 metallic steely-blue ; wmgs and tail dusky black without much gloss, 

 below pure white ; iris brown, bill black, legs horny. Length 5-25 ; 

 wing 4-65 ; tail 2-15 ; culmen -25 ; tarsus -45. 



The female resembles the male, but is usually rather duller in colour 

 and slightly smaller — wing about 4-5. A young bird is uniform dark 

 mouse-grey above and beneath white, shaded across the chest with 

 pale greyish-brown. 



Distribution. — Breeding tliroughout North America from Alaska 

 and Labrador, south to California and Virginia ; in winter from Soiith 

 Carolina and the Gulf states to the Bahamas and tlnrough Mexico 

 to the Guatemala highlands. 



The Tree- Swallow is a rather uncommon summer resident in Colorado, 

 breeding from the plains to about 10,000 feet in the mountains, chiefly 

 in the latter. Dennis Gale found a good many nests about Ward at 

 10,000 feet in Boulder co., and Aiken noticed it breeding at Mosca 

 Pass at about the same elevation. It arrives in April, breeds in June 

 and departs in September. 



The following are recorded localities : Boulder co. (Gale), South 

 Park (Allen), El Paso co. (Allen & Brewster), Fremont co. (Aiken), 

 Twin Lakes (Scott), Crested Butte (Warren), Grand Jmiction, rare 

 (Rockwell), San Juan (Drew), and Fort Lewis (Morrison). 



Habits. — ^The Tree-Swallow is not quite so swift and 

 agile on the wing as some of the other Swallows, and it 

 is also rather quarrelsome, frequently contending wdth 

 the Violet-green and ousting it away from its nesting- 

 places. It builds its nest in hollow trees, very frequently 

 makmg use of the nesting-site of the Woodpecker, and 

 often driving its rightful owner out. Dennis Gale found 

 a good many nests on Jim Creek and near Ward in 

 Boulder co. ; most of these were in Sapsuckers' holes 

 in aspens ; in one case another Woodpecker, the Rocky 

 Mountain {Dryohates v. monticola) had already laid its 

 eggs when the Swallows appropriated the hole and built 

 a nest above the Woodpecker's eggs. The nest is formed 

 of a foundation of grass stems with a lining of feathers. 



DD 2 



