Not just swift, but with the stamina to be in the air for 10 months without landing…
How do they sleep and fly? No one is sure but do it they must…they are already known as some of the fastest fliers on the planet, migrating from Europe (where they nest) to Africa every year, eating large quantities on insects along the way. Anyone who has seen them ducking and diving chasing bugs through the air column can attest to their speed and dexterity, and their height above the ground is a good indicator of air pressure, since insects fly higher when it rises. It had long been suspected that they spent most of their time airborne due to an absence of roosting areas in Africa, but scientists have now confirmed this by fitting them with tiny tracking devices and following the movements of 19 individuals throughout two years as they moved from Sweden to Central Africa, via Spain and across the Sahara.
deepintheshadyglen