In flight (and they are seldom seen at rest) the bold pattern of black and white is unmistakable distinction. They are the fleetest of our small birds and even in the rarified air of their lofty performances they need no supercharger. Only hardy naturalists glimpse these sprites of the high canyons and mountains of the west.
NEST: glued to cliff or cave sides; built of vegetable fibre, lined with a few feathers.
EGGS: 4 or 5; pure white.
From southern British Columbia and southern Alberta, east to the Black Hills and Western Nebraska; south to Lower California.