SWALLOWS 
299 
food on the wing and can often be seen sweeping over ponds, slightly 
furrowing the still surface as they drink. They are skilful nestmakers and 
build a remarkable variety of forms, .from bottle-necked structures of 
kneaded mud to holes tunnelled in earth banks. 
Economic Status. Flying insects constitute almost the entire food of 
the swallows. Sailing high or low in the air as food results justify, the 
swallows attack many winged insects which are otherwise almost un- 
molested. Over grain fields and about barnyards where insect-eating birds 
are few the swallows congregate and give efficient assistance to the agri- 
culturist. Their dirt is sometimes objectionable when they nest in num- 
bers under the eaves of residences. It is well in such cases to provide 
suitable nesting sites for them elsewhere about the farm buildings where 
they can congregate without offence. 
615. Violet-green Swallow, l’hirondelle vert-violet. Tachycineta thalassivia. 
L, 4*75. Plate XLV A. Solid white below from throat to undertail-coverts, and extending 
over face to include cheeks. Above: head to rump a rich velvety bottle green, washed 
with violet-bronze; rump and tail glossy, dark violet. Female similar but duller. Juvenile 
has the violet and green colours above replaced by ashy brown. 
Distinctions. Adult birds, or those with any indication of the violet and green above, 
are unmistakable. Juveniles with their pure white underparts can be mistaken only for 
the Tree Swallow. Sometimes differentiation between them may be difficult without 
specimens for comparison. The Violet-green is distinctly smaller and the brown of the 
upperparts is generally greyer and less brownish. 
Field Marks. With its black-appearing back and upperparts and pure white under- 
parts, to be mistaken only for the Tree Swallow. It has two excellent marks for field 
distinction, however. The cheeks are clear wiiite, giving a white face that is not apparent 
in the Tree Swallow, and in flight a sharp white spot show's on either side of the dark rump. 
The only other similar bird having such white rump-spots is the White-throated Swift, 
so far found in Canada only in the lower Okanagan Valley, a true swift and not a 
swallow. Note distinctions under family (page 269). 
Nesting. Nest in crannies of high perpendicular cliffs, frequently in holes in trees and 
occasionally in bird-houses or about buildings. Nest of grasses with feathers when pro- 
curable. 
Distribution. Western North America. In Canada, British Columbia north through 
central Yukon. Probably adjoining foothills in Alberta. 
SUBSPECIES. The form of northern North America is the Northern Violet-green 
Swallow (I’Hirondelle vert- violet du Nord) Tachycineta thalassina lepida. 
One of the loveliest of the swallows. Its distinctive violet and green 
colours can rarely be discerned in life and to the eye it flashes in the sun 
in contrastive black and white. It is seen to best advantage in the narrow, 
steep mountain valleys of the interior, skimming close to the lower ground 
or high up in the blue in flocks that weave in and out amongst themselves 
in complicated pattern. Their nests may be up a steep mountain face, 
so high that only a white spot on the rocks at the entrance to a community 
niche marks the spot, and from the ground below the birds can hardly be 
distinguished with the naked eye as they enter or leave; even powerful 
glasses may leave the observer in doubt as to whether the moving specks 
are swallows high up or flies lower down. The species will nest in boxes 
about the house when such cliffs are not immediately available. 
614. Tree Swallow, white-bellied swallow, l’hirondelle bicolore. Irido - 
procne bicolor. L, 5-90. Plate XLV B. Pure white below, from throat to tail-coverts. 
Above, solid steely black. Juveniles have iridescent black replaced by sooty brown. 
Distinctions. The adult uniform steely black above, and pure white below, is unmis- 
takable in eastern Canada. Except from the Violet-green Swallow in British Columbia, 
juveniles can be distinguished by the purity of their white underparts and absence of any 
