272 
MICROPODIIFORMES 
in its winter quarters or confused with closely allied forms. The swift 
spends much time on the wing and seldom comes to rest except in a chimney 
or hollow tree. In the autumn, before migration, great numbers gather 
together and at evening seek the shelter of some ample chimney where 
they pass the night. They may be seen just before dusk flying about in 
complicated patterns near the chosen chimney, and as the sun sets, circling, 
until, as they throw the wings straight up over the back and drop fluttering 
into the stack, one rapidly following another, they appear to pour in like a 
miniature maelstrom. The birds cling to the perpendicular walls of the 
chimney by hundreds, in masses like lumps of soot. Occasionally one with 
insecure hold drops a few feet, loosening, as it does so, others below; there 
is a momentary flutter of wings and a small chorus of fine, sharp chippings 
until they find new holdings and settle for the night. 
424. Vaux’s Swift, le martinet de vaitx. Chaetura vauxi. L, 4-15. A small 
swift of even, sooty brown colour, lightening slightly on throat, breast, and rump. Like 
the Chimney Swift but smaller. 
Distinctions. Its extremely small size (wing, 4-50 or under), faintly pale underparts, 
and the tail spines (Figure 388c) will separate it easily from the big Black Swift, the only 
species it is likely to be confused with in British Columbia. Its possible occurrence in 
western Alberta makes it necessary to differentiate it from the Chimney Swift; size is the 
best distinction, but the rump and uppertail-coverts are slightly lighter than the back, 
instead of being of the same colour. 
Field Marks. The characteristic regular bow of the forward wing outline (f igure 
388e), rapid, even, and continuous beats, alternating with a long, sweeping sail, and general 
torpedo-like body outline, with dense, dark coloration, will distinguish this as a swift. 
In the eastern Prairie Provinces this species is not to be expected. In British Columbia 
it is to be confused only with the Black Swift, which is a much larger bird, and tiie White- 
throated, which is very local and strongly marked with white. Near the mountains in 
Alberta it may be taken for the Chimney Swift, from which it can be separated only by 
its smaller size. Swifts in this locality should be very carefully identified. 
Nesting. In communities in hollow cottonwoods, and similar trees, occasionally in 
buildings, water tanks, etc. 
Distribution. Western North America. In Canada, interior valleys of southern 
British Columbia and on the coast as far north as southern Alaska. 
This bird is somewhat local in British Columbia and its distribution is 
largely determined by the presence of suitable hollow trees. Though 
much like the eastern Chimney Swift, it has not followed the example of 
that species in using chimneys for nesting. 
Subfamily — Micropodinae. Typical Swifts 
This subfamily is chiefly Old World in distribution and is represented 
in Canada by but one species of very rare or local occurrence. The tail 
is spineless. The feet are thick, fleshy, and more or less flattened. The 
single species here considered is easily recognized by its white throat and 
breast. 
425. White-throated Swift, le martinet a gorge blanche. Aeronautes saxatalis. 
L, 6-75. Nearly as large as the Black Swift, but with extensive white throat, breast, and 
line down abdomen, tips of secondaries, and a patch on each side of the rump. 
Distinctions . The only Canadian swift with decided white patches. 
Field Marks. The characteristic regular bow of the forward wing outline, rapid, even, 
ami continuous wing beat, alternating with long, sweeping sail and general torpedo-like 
body outline will distinguish this as a swift. The white throat and breast, and the white 
spots on either side of the rump will identify it as this species. The Violet-green Swallow 
associates with it and has similar white spots beside the rump, but the flight action is that 
of a swallow instead of a swift. 
