The function and evolution of the tail streamer in hirundines

摘要: The morphology of a bird’s tail may result from compromises between aerodynamic efficiency, phylogenetic constraints and selection for non-aerodynamic characteristics, such as mate attraction. A good example trait shaped by trade-offs efficiency reproductive benefits mediated through female preference is the streamer barn swallow. Here we use standardized task to measure impact manipulated lengths on maneuvering flight in swallow sand martin, closely related species that lacks streamer. Our results show has role flight. However, outer feather approximately 12 mm (9–20%) longer than optimum Furthermore, addition artificial streamers enhances maneuverability even at small lengths, thereby implying have evolved via natural increased performance. therefore suggest initial elongation functional explanation terms choice become associated with this trait, promoting development costly handicap.