bird is conductor or insulator ?

Insulators often contain pockets of trapped air like feathers on a bird and fur on animals to keep them warm.

 

The birds think that their feather are the good insulators, even the Penguins! 

Down is a very good insulator, for it entraps lots of air compared to its own weight. 

With any thermal insulator, what we are buying is still air, because for practical purposes, air is the best insulator.