How do birds regulate their body heat?

http://birding.about.com/od/birdingbasics/a/howbirdskeepwarm.htm

well they put there feathers around there head

If they are in a group they will huddle together to gain warmth from each other when its cold, if they get too hot they will lay and spread out opening their feathers so they can let air cool the...

yes

Yep, the heat is transferred via convection when fluid flow is involved, which is primarily blood flow. For example, you hands are cold, then warm blood flow helps to warm them up. That's convection....