Sulidae – Boobies & gannets

These seabirds have air sacs under their skin to cushion their bodies against the impact of breaking the water’s surface

These birds are specialized marine hunters found across tropical and temperate seas worldwide, often forming large, noisy colonies on cliffs, islands, and sometimes even flat ground. Their colonies are usually located on offshore islets free of land predators, which provides a safer environment for raising their young.

Physiologically, boobies and gannets are built for life at sea and in the air. They possess muscular legs and strong, webbed feet that aid in powerful swimming and diving. Their sleek and streamlined bodies allow them to cut through water with minimal resistance. This hydrodynamic design is essential for their hunting technique, which involves high-velocity plunges from heights of up to 30 meters (98 feet) into the ocean to catch fish and squid. Upon spotting a school of fish from the air, they fold their wings back and dive into the water with astonishing precision and speed, penetrating the ocean’s surface to depths of 15 to 25 meters (49 to 82 feet).

Sulidae’s feathers are kept waterproof by a special oil produced in their preen glands. This oil not only provides buoyancy and prevents their feathers from becoming waterlogged but also serves as a defense against parasites. Uniquely adapted nostrils that close during the dive help prevent water from entering their respiratory system. This adaptation, along with their ability to breathe through their mouths, is crucial for their survival in aquatic environments.

Their vision is another remarkable adaptation; it is as acute underwater as it is in the air, allowing them to adjust their trajectory and speed as they chase their prey underwater. They are known to consume their catch below the surface to avoid theft by other birds, a behavior known as kleptoparasitism, which is common among seabirds.