Nascimento says they're mostly Magellan penguins migrating north from Argentina, Chile and the Falkland Islands in search of food in warmer waters.
He said Tuesday that autopsies done on several revealed their stomachs were entirely empty -- indicating they likely starved to death.
Scientists are investigating whether strong currents and colder-than-normal waters have made it tougher for the penguins to hunt the fish and squid they normally feed on.
