Swift

The swift is a bird in the family Apodidae. It is in the order Apodiformes with treeswifts and hummingbirds. The swift is very good at flying. It spends all of its time in the air.
The scientific name for the swift ("apus") comes from the Ancient Greek word απους, "apous" which means "without feet". This is because swifts have very small, weak feet. Swifts use their feet to hold on to vertical places (for example, the wall of a house, or a cliff). Swifts do not want to land on the ground. It is often thought that if they land on ground, they cannot fly up again, but that is not true. They can take off but with difficulty.
Description.
Swifts are small birds. They can fly very well and very fast. Some swifts can fly at 514m per second. If a swift needs to fly very fast, it can fly at 60m per second for a short amount of time. When catching insects, they fly in a series of swoops, changing direction rapidly as they pursue the prey. 
Swifts have long, curved wings. The wings are in the shape of a sickle or boomerang. They have a forked tail. This means it looks like a V shape. 
Swifts can be seen all over the world. They like to live in warmer places and they migrate every year. For example, Swifts fly to Europe in the spring and summer. When it gets cold at the start of autumn, the Swifts fly to Africa where it is warmer.
Nests.
Swifts make their nests in a corner between two walls. For example, near the roof of a house, or in an area between rocks in a cave. They use mud and saliva (spit) to make a cup-shaped nest. 
There are some swifts which only use saliva to make their nests. These swifts are in the genus "Aerodramus". In Asia, people take the nests and use them to make bird's nest soup. This soup is very popular in China.