That is very interesting. I always assumed sea birds used combination of wing in ground effect [1] and the lift of wind hitting the front of waves to cover long distance, but this explanation makes much more sense for birds crossing oceans.

[1] https://www.youtube.com/watch?v=vkVVnx70FgI

Edit: It just occurred to me that the albatross is in some way surfing the wind in much the same way a surfer pumps along a wave to generate speed.