DIFFERENCES IN THE FORAGING OF JUVENILE AND ADULT BIRDS: THE IMPORTANCE OF DEVELOPMENTAL CONSTRAINTS

Juvenile birds differ from conspecific adults in their diet and methods of prey capture and prey handling. Juvenile-adult differences in foraging result from (1) immaturity of the beak, skeleto-muscular and neurological systems and (2) the time required to learn foraging skills. These conclusions are largely based on field observations. More experimental studies to assess the relative importance of the various constraints are needed.
Juvenile birds appear to be under strong selection to reach adult form and function as rapidly as possible. Remaining differences between juveniles and adults are largely attributable to constraints. In contrast to many other taxa there are few examples in which juvenile-adult differences in foraging have been accentuated by selection on the juvenile behaviours.