Relationships between heart rate and the rate of oxygen consumption of flying and walking barnacle geese (Branta leucopsis) and bar-headed geese (Anser indicus)

We tested the hypotheses that the relationship between heart rate (fH) and the rate of oxygen consumption ((O(2))) differs between walking and flying in geese and that fH and (O(2)) have a U-shaped relationship with flight speed. We trained barnacle geese Branta leucopsis (mean mass 2.1 kg) and bar-headed geese Anser indicus (mean mass 2.6 kg) to walk inside a respirometer on a treadmill and to fly in a wind tunnel with a respirometry mask at a range of speeds. We measured fH and (O(2)) simultaneously during walking on the treadmill in five individuals of each species and in one bar-headed goose and four barnacle geese during flight in the wind tunnel. The relationships between fH and (O(2)) were significantly different between flying and walking. (O(2)) was higher, and the increment in (O(2)) for a given increase in fH was greater, for flying than for walking geese. The relationship between fH and (O(2)) of free-living barnacle geese during their natural migratory flights must differ from that measured in the wind tunnel, since the fH of wild migratory birds corresponds to values of (O(2)) that are unrealistically low when using the calibration relationship for our captive birds. Neither fH nor (O(2)) varied with flight velocity across the range of speeds over which the geese would fly sustainably.