Birds are often small with high energy needs and for this reason they can digest food very quickly. This high digestive rate helps young birds grow to maturity quickly and migrating birds to put on the fat reserves that make their long flights possible. Carnivores can digest whole small animals over several hours while fruit can take less than 45 minutes to pass completely through the system. The pancreas secretes insulin thus regulating blood sugar levels. Because of this speedy metabolism, small birds need to eat far more regularly than larger ones, and need to stock up well before the long winter nights when foraging is not possible for many hours and keeping warm burns up a lot of energy.
Food is taken in at the mouth.
Birds do not chew their food, though it may be broken up or crushed by the bill in the process of being obtained. Birds do not have the soft palate that we have which enables us to swallow in our traditional manner. From here the food continues its journey through the bird by means of peristaltic contractions. The oesophagus is basically a muscular tube which draws the bird's food further into its body. Note that some birds have quite functional salivary glands and in birds which feed mainly on small insects or seeds this saliva is used to glue the insects or seeds into a sticky ball for ease of swallowing.