Tree-Swallow 419 
p. 15; Tresz 81, p. 287; Allen & Brewster 83, p. 160; Morrison 88, 
p. 73 ; Cooke 97, pp. 19, 111, 217 ; Rockwell 08, p. 175 ; Henderson 09, 
p. 238. 
Description.—Male—Above, including the sides of the head and neck, 
metallic steely-blue ; wings 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 throughout North America from Alaska 
and Labrador, south to California and Virginia ; in winter from South 
Carolina and the Gulf states to the Bahamas and through 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 Junction, 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 with 
the Violet-green and ousting it away from its nesting- 
places. It builds its nest in hollow trees, very frequently 
making 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 (Dryobates 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 
