While birds are commonly associated with flight, a remarkable group of avian species has evolved to master the underwater world. These diving birds exhibit unique adaptations, allowing them to plunge into aquatic environments and navigate depths with agility to find food.
Diverse World of Diving Birds
Many bird families include species capable of diving beneath the surface. Penguins, found primarily in the Southern Hemisphere, are perhaps the most recognized, having foregone flight for an aquatic existence. Cormorants, distributed globally, are known for their deep diving abilities. Loons, also called divers, inhabit freshwater lakes in North America and northern Eurasia, migrating to coastal marine environments for winter. Grebes are widely distributed freshwater birds, though some species move to marine habitats in winter. Diving ducks, including eiders, long-tails, and mergansers, can submerge for extended periods to forage. Auks, such as puffins, are seabirds primarily found in the Northern Hemisphere, spending much of their lives at sea.
Built for the Depths
Diving birds possess specialized physical and physiological adaptations enabling their aquatic prowess. Unlike most birds with hollow, air-filled bones for flight, penguins have dense, solid bones that reduce buoyancy, helping them submerge and withstand pressure at depth. Their wings have transformed into stiff, flipper-like structures, and their leg bones are also dense. Many diving birds feature webbed feet, which act as powerful paddles for propulsion underwater. Streamlined bodies further reduce drag, allowing efficient movement through water. Plumage also plays a role; while some diving birds, like cormorants, have feathers that become waterlogged to aid in diving by reducing buoyancy, others have highly waterproof feathers. Physiologically, these birds can slow their heart rate (bradycardia) and restrict blood flow to non-essential organs, conserving oxygen during prolonged dives. Emperor penguins, for instance, can slow their heart rate from around 70 beats per minute to as low as 10 beats per minute while diving.
Mastering the Dive
Birds employ different techniques to enter and navigate the water. Pursuit divers, such as penguins, loons, and cormorants, propel themselves underwater using their webbed feet or wings. Penguins use their flipper-like wings to “fly” through the water, while loons and cormorants primarily use their feet. These birds often dive from the surface of the water. Plunge divers, including gannets and kingfishers, use gravity and momentum, spotting prey from the air before diving headfirst into the water at high speeds. Gannets can dive from heights up to 45 meters, reaching speeds of up to 24 meters per second without injury. Their narrow, pointed beaks and neck musculature are adapted to reduce impact forces upon entry. Brown pelicans also perform spectacular plunge dives, hitting the water with enough force to stun fish below the surface.
Life Below the Surface
The primary purpose of these underwater excursions is foraging. Diving birds hunt a variety of aquatic prey, including fish, crustaceans, and mollusks. Kingfishers, for example, have sword-like beaks ideal for catching small fish, shrimp, or tadpoles. Cormorants are highly efficient at catching fish and have been observed to use rocks as tools to open the shells of prey. Different species exhibit varied dive capabilities in terms of depth and duration. Emperor penguins are among the deepest diving birds, capable of reaching depths over 500 meters (1,800 feet) and remaining submerged for up to 32.2 minutes. While Atlantic Puffins typically dive to 50 feet, they are capable of reaching 200 feet and can hold their breath for up to one minute. Cormorants can dive to depths of 45 meters (150 feet) and stay underwater for several minutes.