What this calculation shows is what glide ratio Godwit must have if it spends 1/3 of its body weight very efficiently to gain altitude and reaches destination in completely calm air. By the looks of it it doesn’t have this glide ratio, and I doubt it spends 1/3 of its weight only gaining altitude.
So it means that it must gain altitude and, perhaps, travel speed by alternative means, most likely using updrafts and riding winds.
So it means that it must gain altitude and, perhaps, travel speed by alternative means, most likely using updrafts and riding winds.