Chapter 5 - Fuelling migration

Abstract

This chapter is concerned mainly with the body reserves that birds accumulate for migration: with the amount of reserve accumulated in relation to the length of migratory flight, the resulting rise in body weight and change in body composition, the energy content of different body reserves (fat, protein and carbohydrate) and the strategies taken to acquire the reserves. Such strategies include lengthening of feeding periods to give greater daily food intake, enlargement of gut and change of diet (in many birds involving an emphasis on fruit) and reduction of other energy-demanding activities. Some large birds, such as arctic-nesting geese, accumulate enough body reserve in wintering areas, not only to fuel the spring migration but also for egg production and incubation. This enables such birds to start breeding before food becomes plentiful in breeding areas.