Feeding against the wind
Imagine you’re a bird, nice warm feathers, but you’re not that large. Because you’re small, you have a large surface to body ratio, meaning you’re cooling down quickly. This means you’ve got to keep on eating, to make sure you’ve got enough fuel to keep yourself warm. Even when there is a near gale, you have to keep on feeding. Head against the wind (otherwise the wind will mess up your nice plumage), and preferably with a group.
Well, these Knots are doing exactly that.