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Ancel, A, Starke LN, Ponganis PJ, Van Dam R, Kooyman GL.  2000.  Energetics of surface swimming in Brandt's cormorants (Phalacrocorax penicillatus Brandt). Journal of Experimental Biology. 203:3727-3731. AbstractWebsite

The energy requirements of Brandt's cormorants (Phalacrocorax penicillatus) during surface swimming were measured in birds swimming under a metabolic chamber in a water flume. From the oxygen consumption recordings, we extrapolated the metabolic rate and cost of transport at water speeds ranging from 0 to 1.3 ms(-1). In still water, the birds' mean mass-specific rate of oxygen consumption ((V)over dot(O2),) while floating at the surface was 20.2ml O-2 min(-1) kg(-1), 2.1 times the predicted resting metabolic rate. During steady-state voluntary swimming against a how, their Po, increased with water speed, reaching 74 mi O-2 min(-1) kg(-1) at 1.3 ms(-1), which corresponded to an increase in metabolic rate from 11 to 25 W kg(-1). The cost of transport decreased,vith swimming velocity, approaching a minimum of 19 J kg(-1) m(-1) for a swimming speed of 1.3 m s(-1) Surface swimming in the cormorant costs approximately 18% less than sub-surface swimming. This confirms similar findings in tufted ducks (Aythya fuligula) and supports the hypothesis that increased energy requirements are necessary in these bird diving to overcome buoyancy and heat submergence.

Ancel, A, Kooyman GL, Ponganis PJ, Gendner JP, Lignon J, Mestre X, Huin N, Thorson PH, Robisson P, Lemaho Y.  1992.  Foraging behaviour of emperor penguins as a resource detector in winter and summer. Nature. 360:336-339.   10.1038/360336a0   AbstractWebsite

The emperor penguin (Aptenodytes forsteri), which feeds only at sea, is restricted to the higher latitudes of the antarctic sea-ice habitat1-3. It breeds on the winter fast ice when temperatures are -30-degrees-C and high winds are frequent3. Assuming entirely the task of incubating the single egg, the male fasts for about 120 days in the most severe conditions. When it is relieved by the female around hatching time, the distance between the colony and the open sea may be 100 km or more4,5, but where emperors go to forage at that time or during the summer is unknown. The polynias are areas of open water in sea-ice and during winter, with the under-ice habitats at any time of the year, they are among the most difficult of all Antarctic areas to sample. Here we monitor by satellite the routes taken by emperor penguins for foraging and compare them with satellite images of sea-ice. Winter birds walking over fast ice travelled up to 296 km to feed in polynias, whereas those swimming in light pack-ice travelled as far as 895 km from the breeding colony. One record of diving showed that although most dives are to mid-water depths, some are near the bottom. Obtaining such detailed information on foraging in emperor penguins means that this bird now offers a unique opportunity to investigate the Antarctic sea-ice habitat.