Legs bend, toes curl?

[lightsoutcalls]

I threw this out on the biology sub-forum as well...
My understanding about the physical function of a turkey's leg is that when the bird sits down (legs bend) the toes automatically curl.  As I understand, this is related to the length of the tendons in the turkeys leg.  This helps hold the bird on the roost when he sits down.  If this is true, it would mean that it is physically impossible for the bird to have curled toes when his legs are in a straight position.  
I've seen a lot of birds mounted in a roost position with straight legs and curled toes.  It has me questioning if I understand the anatomy of the turkey correctly???

[lightsoutcalls]

When they lift their legs to walk, the same motion is happening as when they sit down... the leg is bending.  It is just happening as a reverse process -  the foot is coming up to the body rather than the body lowering towards the foot. 

[TRKYHTR]

We are talking about the tendons in the leg/foot. Tendons are connective tissue that attaches muscle to bone. When a turkey is standing some of the tendons are more loose. there are some tendons that also curl the toes. So they are able to work when the opposite tendon is loose. When a turkey bends down the tendon that curls the toe gets tight and curls it. The reason it is able to curl when the turkey is standing is because the muscle is curling the toe pulling the tendon tight. Hope that makes sense.

TRKYHTR