Birds have two legs but some species commonly stand on just one leg, usually to rest or warm the other one.  

Recently, when an immature Eagle flew to an Elm tree, it perched and then raised its right leg and tucked the foot under the lower breast feathers for a time.  At that moment, the air temperature was hovering near zero. 

The Eagle had no problem repositioning itself on the small limb and leaned a bit to the left to adjust its center of gravity and balance, as Canada Geese are seen doing while standing on ice.

Most bird legs have little feathering to protect the underlying tissu...