Variation in energy intake and basal metabolic rate of a bird migrating in a wind tunnelWingbeat frequency and the body drag anomaly: Wind-tunnel observations on a thrush nightingale (Luscinia luscinia) and a teal (Anas crecca)How body water and fuel stores affect long distance flight in migrating birdsFlight costs and fuel composition of a bird migrating in a wind-tunnelEnergy expenditure in relation to flight speed: whay is the power of mass loss rate estimates