By being able to move just a tiny group of feathers a bird can effectively turn, rise, stop, and pivot in the air without drastically reducing speed. If every bird had to fly at high speeds all the time they would likely be crashing, missing landings, or dropping out of the sky because of the drag needed to move their entire wing. These feathers are incredibly important for control, without them a bird would have to be flying at high speed all the time in order to control their movements.
Alula feather full#
Using those tiny feathers allows the bird to ascend or descend without creating the massive amounts of drag present in full wing movement. When a bird slows down they pull out their alula and create a small gap between the alula and the wing’s surface, this small gap gives the bird a greater angle of attack, creating lift. If you’re flying slowly you can’t move your whole wing, too much drag is created and the bird will just fall, that’s where the alula come in! Typically that’s how you’ll see the alula, closed against the wing because typically birds are flying pretty fast, as a result a slight change in wing movement can cause their bodies to ascend and descend fast enough not to need alula, but what about when they slow down? In this position the feathers are most aerodynamic, reducing any drag to allow the bird to pick up speed. When not in use the Alula will lay flush against the edge of the wing and pressed against the wing’s surface. They may look like nothing but those tiny feathers are key when it comes to controlling flight. There can be anywhere from 2 to 6 alula depending on the species! Alula feathers, sometimes known as ‘winglets’ or 'the bastard wing’, are those small feathers that sort of resemble miniature primaries on the top side of the wing.
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