Conduction is very rapid if the temperature difference is large. This is why a cold water bath makes us feel cold all over very quickly and why it is not advisable to lick a frozen object. Convection occurs when heat is carried away by the movement of the air. It takes a lot of food to sustain life in a cold environment. Birds, with their high body temperature and high metabolic rate eat more food, ounce for ounce, than most other vertebrates, shrews being the exception.
Birds tend to be very active much of the time.
Flying requires seven times more energy than resting. Many birds migrate thousands of miles, twice a year. Long distance migrants, like Eared Grebes, will double their weight at stopover sites like the Great Salt Lake before continuing their migration. Fat is an excellent fuel and most birds are very efficient at converting excess food to fat. Acclimatization is the term given to the changes, in behavior and body structure, that occur during continuous or repeated exposure to hot or cold environments.