Question About Big Bird's Hands

[D'Snowth]

This is something I've been observing for years, and I see that given their distinct design that Big Bird's hands seem to keep their shape remarkably well, particularly more recent versions of the puppet - if you look at earlier Big Bird puppets, you can see wrinkles and creases in his hands. So, I'm curious to know if Big Bird's hands any sort of an inner shell, like maybe a very thin foam or something, that helps the hands keep their shape so well?