I have observed seabirds at the point at the end of my road. The wind is side shore, the birds are trying to move along the coast to their roost which is directly into the wind. They will fly at an angle either up down or sideways at around 45 degrees to the wind, then sometimes straight into the wind until they lose momentum then off at an angle gaining speed, straight into the wind for a moment then off the wind gaining speed. Makes me think about sailing upwind and the physics of it.

They go left, right, up down and every angle in between but always forward.

Ive seen it done on a yacht before to good effect whilst racing, A quick turn upwind (past sails filling position) then back off the wind before all momentum was lost. It was certainly a less costly move than doing another two tacks to get to the mark. I wonder how much distance you could take if you carved upwind like you would coming up to fast tack, then pushed the board back off wind consistently?

I'd read years ago how albatross can go downwind without flapping their wings and was very surprised to find one going upwind when I was out off the local beach. It was going upwind better than I was, barely putting in a flap every now and then. Sailing is taking advantage of a discontinuity in the velocity of two fluids. We use water and air, the boundary is pretty distinct. And we can have a fin continuously in the water and a sail continuously in the air. An albatross makes use of the velocity profile in the air. It can't really stick one wing in the low and slow air and the other wing in the faster higher air so it has to alternate. Dipping in the higher air for a while and the lower air for a while. Relying on momentum to connect the two. I suppose you can imagine sailing by alternatively putting down the centreboard for 5 seconds then hoisting the sails for 5 seconds and using momentum to keep things moving in between?