first victims – Adelie penguins (who don’t see well in the dark)

The Adelie penguin is regarded as an “indicator” species, an animal so delicately attuned to its environment that its survival is threatened as soon as something goes wrong. So as temperatures rise, Adelies are among the first to feel the effects, early victims of the devastating worldwide changes that scientists expect if the warming persists and intensifies.

But the die-offs scientists are seeing in the warmest areas of Antarctica are expected to spread as temperatures continue to rise. If the warming continues,Adelie researcher David Ainley said, the Adelies ultimately will go extinct — though it might take hundreds of years. The reason is simple, he said: “Penguins don’t see well in the dark.”
Chicago Tribune, 1 Jul 2007

see also – first victim