Oxygen resaturation during post dive recovery in a diving bird Aythya fuligula: implications for optimal foraging models

The rate of oxygen uptake at the surface between dives was measured for four tufted ducks, Aythya fuligula, during bouts of foraging dives to a depth of 1.8 m. The ducks surfaced into a respirometer box after each dive so that the rate of oxygen uptake ((V) over dot O-2) could be measured. (V) over dot O-2 decreased over time at the surface and there was a particularly rapid phase of oxygen uptake for approximately the first 3 s. The specific shape of the oxygen uptake curve is dependent upon the duration of the preceding dive. The uptake curve after longer dives was significantly steeper during the first 3 s at the surface than after shorter dives, although (V) over dot O-2 after the first 3 s was not significantly different between these two dive duration bins. Thus, the mean total oxygen uptake (VO2) was higher after surface periods following longer dives. Due to the high (V) over dot O-2 during the initial part of the surface period, the curve associated with longer dives was statistically biphasic, with the point of inflection at 3.3 s. The curve for shorter dives was not statistically biphasic. The birds may increase their respiratory frequency during the first 3 s after longer dives, producing the increased (V) over dot O-2, which would enable the birds to resaturate their oxygen stores more rapidly in response to the increased oxygen depletion of the longer submergence time.