ENERGETIC CONSEQUENCES OF COORDINATING WINGBEAT AND RESPIRATORY RHYTHMS IN BIRDS

The coordination of ventilatory and locomotor rhythms has been documen ted in many birds and mammals. It has been suggested that the physiolo gical significance of such coordination is a reduction in the cost of ventilation which confers an energetic advantage to the animal. We tes ted this hypothesis by measuring the external work required to ventila te birds mechanically during simulated flight. Patterns of wing motion and breathing were produced in which the relationship between wing mo tion and breathing was in phase and out of phase with the relationship seen during normal flight. Differences between the energetic costs of in-phase versus out-of-phase synchronization were particularly large (26%) in instances where locomotion and respiration frequency were syn chronized at one breath per wingbeat. The saving (9%) obtained from in -phase versus out-of-phase coordination at the 3:1 coordination ratio seen normally in free-flying Canada geese was smaller but still suppor ted the hypothesis that there is a significant net saving obtained fro m reducing the mechanical interference between locomotion and ventilat ion by locomotor-respiratory coupling.