European honey buzzard
The flight feathers of adults and juveniles can differ considerably in length, particularly among the raptors. Juveniles tend to have slightly longer rectrices and shorter, broader wings (with shorter outer primaries, and longer inner primaries and secondaries) than do adults of the same species. However, there are many exceptions. In longer-tailed species, such as swallow-tailed kite, secretary bird and European honey buzzard, for example, juveniles have shorter rectrices than adults do. Juveniles of some "Buteo" buzzards have narrower wings than adults do, while those of large juvenile falcons are longer. It is theorized that the differences help young birds compensate for their inexperience, weaker flight muscles and poorer flying ability.