The world’s oldest penguin has celebrated her 37th birthday with a cake made of fish and ice. Humboldt penguin Spneb has lived at Paradise Park zoo, in Hayle, Cornwall, since 1988.

Ahead of Earth Day, a sneak peek for National Geographic's The Secrets of the Penguins is revealed. Watch it here!

For "Earth Day", the National Geographic documentary series "The Secret World of Penguins", produced by Oscar winner James ...