What is a wing claw?
Wing claws are a remnant from the evolutionary past. The claws were needed to help early birds to climb trees. Functional wing claws persist in many species today including the Ostrich and the Hoatzin. There are 12 species of birds today that have wing claws, including emus, swans, ostriches, and ducks.
Below: Wing claw on a red hybrid chicken.
Wing claws were needed as early birds were not good flyers and needed to climb up and then glide down from tree to tree. They may have also had some defensive uses. Over time the bones and claws have reduced in size as they were no longer needed and for the most part have gone.
Wing claws are one or in some cases two of the hand bones that protrude through the skin of the bird. It may just be a pointy bit of bone that sticks out of the skin or there may be a nail that grows out from the end. Some of my Muscovy ducks had the full claw.
What are wing claws on domestic poultry?
Wing claws in chickens and other poultry is a small curved claw that sticks out from the last joint on the wing. Not all poultry has wing claws and some birds have it but they are not always visible.
Below: A small wing claw hidden under the feathers.
Natural selection has decreased the size of the claw over time as they have become unnecessary. Indeed in some birds they have disappeared altogether.
The wing claw is a actually "carpal spur" and not technically a "claw," many people might consider it to be a claw. It does look like a claw and the alula near the carpal joint often sticks out, and can be quite sharp. I have been painfully poked by it a few times.
Do chickens have wing claws?
Some chickens have visible wing claws that protrude through the skin. Some birds have wing claws that are not big enough to poke through the skin and are just a stub of bone under the skin.
I'm convinced quite a few chickens have them but people never notice as they are small and obscured by the feathers.
Below: A wing claw on a Silkie.
I have seen wing claws more often in broiler chickens mostly I suspect because you see them all without their feathers when processing. I'm not sure you would define them all as wing claws but from a practical standpoint, there is a "claw like" structure that I see on many of my birds at slaughter.
Do ducks have wing claws?
I had never noticed whether my ducks had wing claws or not but on closer inspection while sitting with a Muscovy duckling in my lap, I noticed a rather large claw on each wing.
I rounded the whole batch up and had a look at the wings of the other ducklings. The Indian runner ducks had no wing claws at all and the Muscovies had around 75%. I hadn't ringed them so I was not able to deduce whether they all had the same parents or not.
Below: This is what you get for not wearing gloves when clipping a Muscovy wings! One got me with its claw.