I assumed that they must come down to nest, of course, but this quote > They mate on the wing. And while young martins and swallows return to their nests after

I assumed that they must come down to nest, of course, but this quote > They mate on the wing. And while young martins and swallows return to their nests after their first flights, young swifts do not. As soon as they tip themselves free of the nest hole, they start flying, and they will not stop flying for two or three years, bathing in rain, feeding on airborne insects, winnowing fast and low to scoop fat mouthfuls of water from lakes and rivers. really made it sound like they don't touch the ground at all for two or three years. I suppose this is possible if they only feed on insects, don't need to land to sleep, and can rest their bodies while flying. EDIT: I found an article which supports the idea that they might stay aloft for months on end (https://doi.org/10.1016/j.cub.2016.09.014 https://doi.org/10.1016/j.cub.2016.09.014). They do land, just for very short periods of time and less than 1% of their time outside breeding season.