Watch This Time-Lapse Video That Reveals Patterns in Penguin Huddles

We don’t give emperor penguins enough credit. Yes, they look pretty silly, but they’re incredibly hardy animals. They’ve adapted to survive temperatures 40 degrees below zero—and their babies can do the same. Penguin chicks born in the bitter Antarctic winter are fluffy, hungry, and tough as nails.

One secret to the penguins’ survival is the huddle. Thousands of birds converge on a single point on the ice and crowd together, threading their beaks and wings into the gaps like commuters on a packed train in Tokyo. But as this time-lapse video from PBS shows, what looks like a static clump of birds is actually a constantly moving and highly organized system.