Blue-footed boobies are brilliant fishers. They fly above the sea, spot fish near the surface, and then fold their wings back and plunge into the water like an arrow — sometimes from a height of 30 metres — hitting the water at up to 100 km per hour. A special arrangement of air sacs under the skin cushions the impact so they do not get hurt.
The blue colour of their feet comes from the fish they eat, which contain a pigment called carotenoid. The brighter and bluer the feet, the healthier the bird — which is why females prefer males with the brightest feet when choosing a mate. The feet are a window into how healthy a bird is.
Both parents take turns keeping the eggs warm — not by sitting on them, but by covering them with their big, warm feet! Because the colour of their feet fades when they are unwell or not eating well, their feet also act as a health signal to their partner. If the feet start to fade, it might mean one bird needs to eat more fish.
Boobies nest on the ground among rocks. Chicks hatch covered in fluffy white down and grow quickly, begging noisily for food. The word 'booby' comes from the Spanish 'bobo', meaning silly or clown — early sailors found the birds' fearlessness around humans rather ridiculous and gave them the nickname that stuck.