From John Henson
This little American Kestrel came flying straight at me, and for a split second I wasn't sure if I was about to get the shot or get buzzed!
They're tiny, unbelievably fast, and almost impossible to predict. Capturing one head-on like this takes a little luck, a lot of patience, and complete trust in your autofocus.
Those little nubs sticking out of our bird friend's wings here are something very special. Those are the alulae, also called "bastard wings", and they are the birds equivalent of thumbs, with 3-5 flight feathers on them.
This may seem somewhat insignificant, but they serve a very important purpose. They are so important that we humans stole the idea.
I'm no aviation expert, so perhaps someone may be able to provide more details, but the alulae are used during takeoff, landing, and certain aerial maneuvers where the main wings no longer produce enough lift, what would be called a "stall" in an aircraft. It basically keeps them from just dropping out of the air when they're moving too slowly to maintain adequate air passing over the wings.
I've seen various citations for them being on all flighted birds, all birds, and all birds with the exception of hummingbirds. ๐คช
As you hinted in your other comment, there are avian dinosaurs and some other prehistoric birds not related to modern birds with them, so now there is the thought that alulae are another form of convergent evolution.
I found a research paper on their evolution that seems interesting that I'll have to read today.
It's a cool bit of anatomy we often don't notice, but it seems a very crucial bit of kit for birds, so it's totally worth learning about!
Wow, TIL!
Also impressive how efficient the bastards must be, given how small they seem in those examples.
It doesn't sound like it takes much to get the job done. Not that I understand it, but they create vortices that then direct the air currents where they need to go.
It usually happens so fast and while the bird is in motion we don't see it with our eyes in real time, but searching "[bird_name] landing" got me plenty of results if you wish to see the bastard wings of a particular bird. I tried to find ones on ostriches, but didn't see anything I could be totally positive were alulae.