Seabirds are a diverse group of birds, from small storm petrels to large albatrosses, uniquely adapted to marine environments. They have evolved various physical and behavioral traits to thrive in the ocean’s challenging conditions. Their diets are as varied as the birds themselves, reflecting their specific habitats, foraging grounds, and specialized adaptations for acquiring food.
Primary Food Sources
Seabirds primarily consume marine organisms, with fish often forming a significant portion of their diet. Many species target small, schooling fish like capelin, sandeel, herring, and sprats, which are abundant in various ocean regions. Larger seabirds, such as gannets and cormorants, can also prey on larger fish, including cod.
Marine invertebrates are another major food source. Squid and various crustaceans, including krill, shrimp, amphipods, and copepods, are commonly consumed. Smaller seabirds, like the least auklet, specialize in feeding on zooplankton, tiny marine animals drifting in the water column. Some seabirds are opportunistic feeders, supplementing their diets with carrion, such as dead fish or marine mammals, or human refuse.
Diverse Feeding Strategies
Seabirds employ various methods to secure their food, each suited to different prey types and ocean conditions. Surface feeding is common, where birds seize prey directly from the water’s surface while flying or swimming, or dip their heads into the water. This can involve surface seizing, where prey is grasped, or dipping, where only the bill or head enters the water.
Plunge diving involves birds plummeting from the air into the water, using momentum to reach prey below the surface. Gannets and boobies are well-known plunge divers, often diving from considerable heights to capture fish. Pursuit diving requires birds to actively chase prey underwater, propelling themselves with wings (e.g., penguins, auks) or feet (e.g., cormorants, loons). Some seabirds also engage in filter feeding, straining small organisms like zooplankton. Another strategy is kleptoparasitism, where birds like frigatebirds and skuas steal food from other birds.
Dietary Adaptations of Seabird Groups
Different seabird groups exhibit specialized adaptations aligning with their diets and feeding strategies.
Albatrosses
Albatrosses, with their impressive wingspans, are primarily surface feeders and scavengers, often consuming cephalopods like squid, fish, and carrion. Their large olfactory systems and varied beak shapes aid in locating food across vast oceanic distances.
Penguins
Penguins are flightless birds that excel as pursuit divers, using their powerful, paddle-like wings to propel themselves through water in pursuit of fish, squid, and krill. Their streamlined bodies, dense feathers, and spiny tongues help them efficiently catch and hold slippery prey underwater.
Gulls
Gulls are generalist feeders, known for their adaptability and opportunistic diets that include fish, marine invertebrates, carrion, and human refuse. They employ various feeding methods, from surface feeding and shallow plunge dives to dropping hard-shelled prey onto rocks.
Puffins
Puffins are adept at both plunge and pursuit diving, primarily targeting small schooling fish. Their small, stiff wings are highly effective for underwater propulsion, allowing them to “fly” through the water. They possess specialized backward-pointing spines on their tongue and the roof of their mouth, which enable them to hold multiple fish crosswise in their bill during foraging trips to feed their young.