Many predators, including penguins, have evolved ways to dispose of mercury. The chemical builds up in feathers that the birds regularly molt in large quantities. Sontag, now a polar researcher ...

The occasion was summer in the Southern Hemisphere—egg-laying season, the time when penguins, so agile and quick in the water, clumsily come ashore to molt, find a partner, and with luck produce ...

Birds fly while penguins swim and dive. Penguins molt all their feathers at once, instead of replacing a few feathers at a time. They can also walk upright like humans. So why are penguins an ...