Marine Birds

Webbed Feet

Many seabirds have webbed feet, which is an adaptation for swimming.

Brandt's Cormorant

Blue-footed booby

Heron

Feathers

All birds have two types of feathers:

• Down feathers (closest to the skin, provide warmth)
• Contour feathers (larger feathers that cover the body - used for flight

Aquatic birds also have powder feathers, which repel water and protect the down feathers. These feathers are even fuzzier than the down feathers which allows them to trap more heat.

Powder

feathers

Powder

feather

Salt Glands

Marine birds get rid of the excess salt in their bodies by using their salt glands.

These glands are located in their head and drain through their nostrils.

Water Conservation

Marine birds conserve the water in their bodies by excreting uric acid which is a concentrated form of urine.

Seagulls

Puffins

Water Conservation

Marine birds conserve the water in their bodies by excreting uric acid which is a concentrated form of urine.

Seagulls

Puffins

Buoyancy

Most birds contain fatty deposits and thin light bones that decrease their overall density. In addition, these birds possess oil glands near their tails that secrete an oily substance called preen. They rub their beaks in preen and spread it on their feathers, which not only waterproofs their feathers, but forms a barrier that seals a thin layer of air between the skin and the feathers to keep them warm.

Preening

Buoyancy is further increased by the presence of many air sacs located within the thorax, abdomen and long bones of the legs and wings. The air sacs store fresh air and are connected to the lungs by a series of tubes that supply the lungs with fresh air whenever birds exhale or inhale. Thus, most marine birds (except for cormorants and frigate birds) float easily on the ocean’s surface, where they often feed and rest.

Buoyancy

Diving

Sea birds reduce their buoyancy by exhaling air from their lungs and air sacs and by squeezing out air from under their feathers by pulling their plumage close to their body.

When they dive, their heart rate slows and oxygen is released from the hemoglobin to supply the brain.

Birds that swim extensively underwater, such as cormorants and penguins have thicker and heavier bones than other birds; and penguins further increase their ability to remain submerged by not having air sacs.

Body Heat

The body temperature of most birds fluctuates between 103 - 106°F. To keep their bodies warm, many birds insulate themselves with trapped air under their feathers. Birds often are seem grooming their feathers, adding new preen and removing old preen by scraping their feathers with their beaks.

One of the most cold-tolerant groups of birds is the penguins. The emperor penguin, for example, easily endures temperatures of below -80°F. The primary adaptation that enables penguins to maintain their internal temperature is a thick layer of blubber under their skin.

Emperor penguin

Senses

Sight - most important sense

Sight is the most important sense to marine birds. Diving birds such as gannets have excellent binocular vision, which enables them to perceive fish swimming deep in the water.

Terns have eyes that are equipped with polarizing filters that allows them to see small fish swimming in the water.

Birds that obtain food by diving possess eyes that focus underwater, however in air these birds are nearsighted.

All birds are equipped with a semi-transparent third eyelid called a nictitating membrane. Some diving birds, such as ducks, have a transparent window in the nictitating membrane, which protects their eyes while allowing them to see underwater.

Nictitating membrane

Senses

Hearing, Smell and Taste

Hearing and smell do not appear to be vital to most marine birds. Although birds hear higher frequencies than humans do and their nasal passages are well developed, marine birds locate food primarily by sight.

However, mating pairs of penguins and several other marine birds recognize each other by sound and terns call to each other during migratory flight.

Taste is the least developed sense in marine birds. Birds have no teeth, very few taste buds and swallow their food quickly without chewing or tasting it.

Eating

Sea birds feed on small fish, squid, krill, egg masses, carrion and drifting garbage.

They often dive below the surface of the water to secure a meal.

Nesting

Although many birds remain at sea for the major part of their lives, all marine birds must return to shore to breed and nest.

Auks

Seychelles seabirds

Competition for food and living space among coastal birds is reduced by specific adaptations that enable them to feed on different foods, nest in different places and remain active at different times of the day.

Wading Birds

• Their stilt-like legs allow then to search in shallow water for food.
• Their snake-like neck enables them to strike at small fish and insects in the water.
• The length of their neck, beak and legs determines where and what types of food a particular species eats.

More Wading Birds

One of the most unusual feeding adaptations is found in the Flamingo. They lower their heads upside down, scooping a mouthful of food and water into their hooked beaks. Then they push out the water through the edges of their closed beaks with their tongues, thus straining food before swallowing it.

Terns & Skimmers

Skimmers

• When searching for food, skimmers fly close to the water’s surface and place their oversized lower bill 5 to 6 cm into the water.
• When their bills touch a small fish, their tails and wings drop to slow them down and they swallow the fish whole.
• Skimmers locate their food by feel and touch because they cannot see the water when they feed.
• Possess a vertical pupil which allow them to feed at night

Skimmers

Frigate Birds

• Frigate birds are unusual because they never swim, float or in any way enter the water.
• They must return to shore each day to rest; however, they are quite capable of flying far out to sea and returning to shore by evening.
• They pluck flying fish from the air, grab small fish and squid from the surface.
• They harass other birds into vomiting their catch, when they then devour.

Frigates