If you live in the eastern part of the United States, perhaps you have watched the sooty-black colored chimney swifts darting over the housetops or disappearing in large numbers into some unused chimney at dusk.

Chimney swifts roost inside unused chimneys by clinging to the inside walls with their sharp toenails and using their short, spiny tail to prop them up.

Chimney Swift

They rarely perch on branches because their feet and legs are small and weak, and cannot support them well.

The chimney swifts build its nest by gluing small twigs to the chimney wall with a glue-like saliva from its beak.  Some nests are almost entirely made up of saliva, and look like half-saucers made of milky glass.

In some countries, men sometimes collect nests and make a soup from them.

During the day, swifts are almost always in the air, flying with a bat like flight.  They like to fly in large groups, capturing insect food while flying.  They almost always return at dust to the chimney where they live in large numbers. – Dick Rogers