Magellanic Penguins Spheniscus magellanicus commuting through San Julian Bay; do current trends induce tidal tactics?

The behaviour of Magellanic Penguins Spheniscus magellanicus commuting betw een their foraging areas and breeding areas in San Julian Bay, Argentina wa s studied to examine whether tidal rip currents affected travelling pattern s. Although there was no apparent relationship between departure and arriva l patterns and the state of the tidal cycle, birds travelling against the c urrent dived for longer periods and had shorter rests on the surface than b irds travelling with the current. In addition, birds swimming against the c urrent hugged the banks of tidal rivers much more closely than did birds sw imming with the current, thus reducing the magnitude of the current against which they had to swim. In cases of extremely high current speeds, birds t ravelling upstream walked. Models regarding the energetics of movement indi cate that the strategies adopted by Magellanic Penguins can result in subst antial energy savings.