Science
How does an albatross fly for hours without flapping?
- It rides wind gradients over waves
- It glides downhill
- It uses thermals
The answer is It rides wind gradients over waves. Dynamic soaring - harvesting energy from the difference in wind speed.
Dynamic soaring - it harvests energy from the fact that wind moves faster higher up. The bird climbs into the wind, gaining height at the cost of speed, turns at the top, dives back down across the wind gradient and regains the speed with interest, then repeats. It is extracting energy from the difference in air speed between wave-top and ten metres up, which means it can cross oceans at almost no metabolic cost.
The numbers are extraordinary. A wandering albatross has a wingspan around three and a half metres, the largest of any living bird, and a locking mechanism in the shoulder that holds the wing extended without muscular effort. Tracked birds have covered several thousand kilometres in a fortnight and circled the Southern Ocean; heart-rate measurements show flying costs them barely more than sitting.
They also live extremely long and breed extremely slowly - a chick every two years, first breeding around ten, and pairs that stay together for decades. Wisdom, a Laysan albatross banded in 1956, was still laying eggs in her seventies. That life history is why longline fishing has been so damaging: a bird taking a baited hook is drowned, the population cannot replace losses quickly, and most albatross species are now threatened. Simple measures - weighted lines, streamers, setting at night - have cut the bycatch enormously where they are used.