Alternative origins for flight in birds

Three origins for flight in birds are discussed in terms of adaptive scenar ios. The discovery of feathered but flightless dinosaurs in China suggests that many of the adaptations in birds, currently considered as components o f flight, might better be considered as requirements for the success of fea thers and the development of feathers may well have been a more important e vent in bird evolution than the development of flight. The existence of an array of potential ancestors with feathers and the success of large groups of birds without volant representatives suggest that flight might have evol ved more than once.