Fig. 3. The metabolic power of starlings during flight in a wind tunnel calculated using DLW (squares, N=30 flights by 4 birds), heat transfer modelling (crosses, N=20 flights by 4 birds) and mask respirometry excluding the estimated additional cost of carrying the respirometry mask and tube (circles, N=45 flights by 2 birds; data from Ward et al., 2001, 1998).