This thread has given me a brand new appreciation for birds, which I previously cared very little about. Now Crows are one of my favorite animal, and I just heard about this today on the radio.
Check out this article about common swifts. Make sure you read the very last line of the article, even though it's not about Swifts.
http://www.npr.org/sections/thetwo-w...onths-straight
Scientists have long suspected that the common swift remains airborne for extraordinary amounts of time during its annual migration.Now, a team of scientists in Sweden has proved that these birds fly for tremendously long periods of time. They affixed data loggers onto a total of 19 of the master fliers in 2013 and 2014, and recaptured the birds months or years later. Researchers found that the birds can spend almost their entire 10-month nonbreeding period on the wing.