Albatrosses have for years been known to use the flight pattern of leeward dives, windward climbs to move around, which is what this paper describes. Those two movements are the only things you need to gain energy when there is wind shear, so I don't see any reason that this isn't an evolutionary adaption. Birds using this technique use less energy when moving around, which is a clear benefit.

I've noticed that most people who have trouble grasping evolution are making two mistakes: they tend to look from a given adaption back in into time for a rather simple linear path to describe the adaption, and they don't grasp the shear number of iterations that occurred and the massive number of random adaptions that failed.

Soaring flight seems pretty easy to evolve to me. Any soaring ability will be an advantage to a bird, who can use less energy to fly. This just takes it to an extreme. Each little step along the way provides an advantage, which is exactly the kind of situation that evolution is able to take advantage of.

At a broad level, one mechanism that's fairly well documented is selecting more for gliding-oriented versus flapping-oriented wing and muscle structure, which may coevolve with behavior and habitat. I do agree that there are a lot of evolutionary explanations that are more like "it's plausible that it'd be this" than actually proven, though.

It can be an instinct; an innate behavior that is not learned, such as a bear preparing for hibernation, or certain birds migrating in fixed patterns. When animals display these specific behaviors even in the absence of instruction from their parents or other members of their species, then it must be genetic, even though it's probably not known how that would work specifically.

The accusation of a "just-so story" is made against a claim of how an adaptation came about. But that's not happening here, they just state that it is an evolutionary adaptation, without a theory of how it was acquired.

I see "instincts" as being a cover term rather than an explanation. It's another way of saying animals just know how to do stuff.

You'll just have to accept that there can be a solid scientific concept without an explanation. Gravity is another example.

http://en.wikipedia.org/wiki/Baldwin_effect ?