Earth is a marine planet. Ninety-seven percent of our planet’s water is in oceans that cover 71 percent of Earth’s surface. Marine animals of all kinds have evolved to fill and take advantage of the vast ecosystems the oceans provide. Tiny zooplankton to huge sharks and mammals such as whales are all marine animals—and so are many kinds of birds.
Seabirds are marine birds. They are birds adapted to life at sea, living and feeding in an ocean environment. Compared to songbirds and other land-based birds, seabirds live longer and take more time to reach breeding age. As an example, Laysan Albatrosses can live 50 years or more and aren’t mature adults until age 5 or sometimes much later.
Most seabirds nest and raise young in colonies on small islands surrounded by ocean or on shoreline cliffs. Summer months living in breeding colonies are often the only months some seabirds come to land. Seabird pairs have fewer young than land birds, usually just a single clutch a year. While many seabirds lay a single egg, that lone hatchling is taken care of for a long time. A guillemot chick, for example, fledges and leaves the colony with its father, staying with him for its first several months at sea. Shuttling between summer breeding colonies and winter feeding grounds often means undertaking long yearly migrations. Arctic Terns have one of the longest migrations of any animal on Earth, flying as much as 55,000 miles a year. That’s the equivalent of flying between New York and Los Angeles 15 times.
Some seabirds are adapted to lives spent hundreds of miles from land. Albatrosses and kittiwakes may fly for weeks or even months without landing, sleeping and feeding on the wing while over the ocean. Seabirds can drink seawater, sleep floating on water or even while flying, and feed from the ocean. Many marine birds are able to live without fresh water thanks to salt-excreting glands. Some seabirds, like petrels and kittiwakes, feed on squid, crustaceans, and other macroplankton, as well as small fish near the surface. Gannets and pelicans plunge down deep into water to catcher larger fish. Other seabirds, such as cormorants and guillemots, essentially fly underwater, pumping their wings as they pursue prey beneath the surface. Eider and other sea ducks feed on what’s living underwater on rocks, including clams, snails, and other mollusks, as well as aquatic plants.
In general, taxonomy doesn’t define a seabird as much as its adaptations to living at sea and feeding in ocean waters. Most have robin- to crow-sized bodies, but some can be as large as a goose and have a wing span of six feet. The wings attached to those bodies vary greatly in length and shape. Soaring seabirds such as frigatebirds and albatrosses have long thin wings, while underwater swimmers like puffins and penguins have stouter paddle-like wings. With a few exceptions, seabirds have a plumage of densely packed waterproof feathers over an insulating layer of down. Puffins, penguins, and other seabirds that dwell in cold ocean waters also have an insulating layer of fat. This combination of feathers and fat keeps seabirds dry and warm. Most seabirds have webbed feet for surface paddling and/or or steering while diving and swimming underwater. Seabirds generally aren’t as colorful as land birds. Most are mixtures of white, gray, and black, with some color on their legs and bills. The white underside of many seabirds hides them from prey below, and grayish bodies camouflage well with sea and sky.
Ocean animals, including seabirds, pose unique challenges for conservationists. Many migrate and travel across state and national borders, crossing international waterway boundaries and moving from one ocean to another within a year. While many nesting and colony areas are safeguarded, whose responsibility is it to protect seabirds when they’re in open waters? When seabirds die from eating plastic trash, fishing line, or get accidently caught in fishing gear, whose fault is it? The short answer is all of us. Overfishing, oil spills from tankers and offshore rigs, water pollution and ocean trash, development on nesting sites, and the effects of climate change like melting sea ice and sea level rise all create problems for seabirds. In Florida, toxins from an unusually widespread and long-lasting “red tide”—a naturally occurring algae (Karenia brevis)—have severely impacted seabirds and other marine life. Nutrients from a wide variety of human activities are entering the Gulf of Mexico and increasing the intensity and duration of algal blooms. Nearly 100 species of marine birds are in trouble, making seabirds the most threatened group of birds on the planet.
Photos: (t to b) Jean Hall; Walker Golder; Sandy Flint/Audubon Photography Awards.