The energetic cost of short flights in birds

Many small birds perform short flights, for which takeoffs, ascents and des cents form a targe component of the total flight time and which are charact erised by low airspeeds. Using the doubly-labelled water technique, zebra f inches Taeniopygia guttata engaging in repeated short flights were found to expend 13.65 kJ more than 'non-flying' controls, which equated to a flight expenditure of 27.8 times their basal metabolic rate. This is over three t imes the predicted flight expenditure derived from existing aerodynamic mod els. These data were used to determine a coefficient (0.11) for converting the mechanical power derived from aerodynamic models into metabolic power. An equation is presented, based on body mass, which can be used to predict the costs of short flights in ecological and behavioural studies of birds.