PHOTO COMMENTS

A BIRD’S BEAK, THE PERFECT TOOL

Text and photos: Alberto Hurtado

Birds are beings designed to fly. To conquest the sky, they had to lose weight. They replaced reptilian scales with feathers and their teeth with a light tool: the beak. This occurred 140 million years ago. Since then, beaks have evolved, adapting to the requirements of each species.

Although the basic structure of the beak is similar in all birds, there is a variety of shapes. The most widespread and versatile, such as that of warblers and thrushes, is sharp and fairly long, allowing them to pick up a great variety of food, from invertebrates to fruit. Other more specialised beaks require a specific diet. Raptors, for example, have curved beaks for killing and, generally, tearing their prey. Many ducks and geese have broad beaks to catch the vegetal matter on which they feed. Most herons have a long pointed beak for fishing. Waders have a wide variety of ways to probe for food at different depths in mud or sand; in some cases they have sensitive beaks with a flexible tip, which allows them to detect and seize prey despite not seeing it.

The most specialised beaks are probably those of flamingos and pelicans. The former feed with their beak fully immersed in the water. Water is sucked in through the partly opened bill and it is squeezed out again by its wide tongue. Then, a row of spines or lamellae along the edge of the bill filter out the food within. Pelicans in turn have articulated bones on both sides of their lower jaw. As the bird pushes its beak underwater to trap a fish, water resistance forces these bones to bow out, creating a large pouch which fills with water. As the bird lifts its head, the pouch contracts, forcing out the water but, hopefully, retaining the fish.