Sea BirdsThe Santa Barbara Channel, with its oceanside rim of unpopulated islands surrounded by dense, food-rich forests of giant kelp, is a natural haven for seabirds. More than sixty species of marine birds feed in the waters of the Channel Islands National Marine Sanctuary during part of the year. 11 species are known to breed here.
Seabirds spend most of their lives on or near the ocean. They have special adaptations that make their seafaring existence possible. To keep their bodies warm, they are fully feathered. Well-developed oil glands waterproof the feathers, which trap air around their bodies to insulate them from the cold. Unlike terrestrial bird species, seabirds can drink seawater. Their nasal glands act as a second pair of kidneys by helping to filter salt from the blood before it enters the brain. The excess salt is excreted through the nostrils or the roof of the mouth.
Compared with their terrestrial relatives, seabirds are generally larger but less colorful, with plumage that is mostly white, black, brown and gray. Their monochromatic coloration seems to provide a predatory advantage; they may not be as noticeable to the fish upon which they prey.
Unlike shorebirds, which only wade into the water, seabirds are able to swim in order to catch their food. Some, such as the cormorant, grebe and scoter, use their webbed feet to propel themselves underwater in pursuit of fish. Other swimmers use their short, narrow wings like flippers for underwater locomotion. Gulls, terns and pelicans use a different strategy: They dive from above, plunging from the air to overcome their buoyancy, and put their webbed feet to work when lifting off the ocean surface. Some seabirds engage in a more sedentary technique. They settle onto the water and seize passing prey with their bills. Storm-petrels feed from the surface by ducking into the Water and sifting out plankton.
Most seabirds do not possess legs that work well on land; they may stagger clumsily when the need to walk arises. Gulls are an exception, for they seem to function equally well on land and sea. This gives them a feeding advantage because, as scavengers, they can use discarded food and other garbage for sustenance.
Finding food in the marine environment is no easy job. The task of incubating and rearing chicks successfully is so strenuous that it requires the cooperation of both parents. Thus seabirds are almost invariably monogamous. Most mate with an individual of similar age and if they breed successfully, tend to stay together for life. Mating is no shotgun affair among these animals. Through courtship displays, they size up the quality of their mate. Females may examine the territory secured by a potential mate. Male common terns sometimes carry fish around in their bills to display their foraging prowess.
Seabirds have relatively low breeding rates and are thus slow to recover from catastrophes, such oil spills, that affect the marine environment on which they depend. The sight of oiled seabirds lying on fouled beaches is a haunting image. Seabirds are sensitive to contaminated water because oil renders their waterproofing ineffective and hampers their ability to float. A bird's feathers overlap like shingles to repel water. When they are functioning property, the water runs over them, the bird stays warm and is able to float. When oil contaminates the feathers, they become matted down and water begins to penetrate this now worthless shield.
Of all the islands that lie within sanctuary boundaries, San Miguel has the most diverse and abundant concentration of breeding seabirds. Nine species have formed colonies there. The largest colony of Xantus' muffelets lives on Santa Barbara Island along with the only colony of black storm petrels in the United States. Anacapa Island and Santa Barbara Island have the only permanent rookeries in California for the endangered California brown pelican.
The recent history of the brown pelican is one of the success stories of the Federal Endangered Species Program. It shows that intervention on behalf of an imperiled species can be successful. As recently as the 1960s, the Anacapa Island breeding colony of California brown pelicans faced an uncertain future. Pelican eggs had begun to appear with thin or nonexistent shells and by 1969 not one of the thousands of eggs laid on Anacapa produced a live bird. Scientists linked the problem to DDT - a highly toxic pesticide - which flowed into Santa Monica Bay via the Los Angeles sewer system. Once in the Bay, it contaminated the fish on which pelicans feed. In pelicans, the chemical played havoc with the reproductive process by rendering the eggshells useless.
In the early 1970s, both the state and federal governments declared the brown pelican "endangered." DDT was banned in 1972. Oil exploration near pelican breeding grounds was prohibited and people suspected of killing the birds were prosecuted. The fight for protection has led to a dramatic recovery. In fact, the U.S. Fish and Wildlife Service has considered changing the status of the brown pelican to "threatened," a step down on the critical list of species that may not make it.