How frigatebirds cross entire oceans without ever needing to rest
"Allowing air currents to do the work of lifting them makes frigatebirds' flight hugely efficient. The heart rate monitors Weimerskirch and his colleagues attached to the birds showed that they didn't flap their wings at all while gaining altitude — the energy costs of ascending thousands of feet in the air were the same as when they were sitting still."Aeronautical engineers: what's it take to develop long-range flight vehicles that are this efficient? Graphite wings/fuselage?