Answer:
The author shows that just as we need fuel to heat our homes in winter, chickadees need fat on their bodies to keep warm in winter. Body fat is the fuel, so they eat large amounts of food.
Step-by-step explanation:
Body fat is fuel that the chickadee's body uses to keep warm, all that fat is consumed by the body itself during the night, making the chickadee spend the day eating as much fatty food as it can find. The author shows that this fat is consumed just like the fuel we use to heat ourselves, having the same effect on this bird.