Why do swifts spend so much of their lives in the air?

Swifts are extraordinary birds that rarely come down except to nest. Their long, narrow wings and streamlined bodies make them superb fliers, allowing them to spend huge amounts of time chasing insects in the air. They can feed on the wing, drink in flight, and adapt to a life where the sky is effectively their habitat. Some studies have shown that certain swifts can remain airborne for months during migration and nonbreeding periods. Their lifestyle is one of the most extreme examples of aerial specialization in birds.