Grebes - bizarre behaviour

[Dinusaur]

On Oct 29, I visited Colonel Sam Smith Park and took some photos of the water birds including grebes, buffleheads, swans, American coots, Scaup, Gadwalls and many other. While looking at the photos on my computer I noticed that some of the grebes had one of their legs sticking out at the rear. Initially I thought it might be due to some deformity. Later online research revealed that this is actually deliberate and is called 'foot-shipping'. Grebes do that to warm their feet in sunlight; sometime they even fold it back inside their wings to keep them warm. Here are some photos; if you look carefully at the last photo you will notice that one of the legs is indeed tucked under its wings.






Here's a link to a nice article on this behaviour. Don't know why this is only specific to Grebes. May be their body anatomy allows it, however, what do the others (e.g. ducks) do when their feet get cold?
http://www.featheredphotography.com/blog/2012/10/07/western-grebes-a-bizarre-behavior-finally-explained/