MARINE BIRDS

Lecture Notes -

Marine birds living at the seashore or far out to sea have become secondarily adapted to the ocean. They possess webbed feet and salt glands that empty into their nose, excrete nitrogenous wastes as insoluble uric acid to conserve water, feed on fish, squid garbage carrion etc. and must return to shore to nest. They are plentiful where food is abundant (upwellings, salt marshes etc.) Competition is reduced between species because of specific adaptations enabling them to

1. Stilt-legged birds Long legs help bird search shallows for food. Herons and egrets wade salt marsh waters, where sand pipers are found along the beaches. The length of the neck, beak, and legs determines where and what types of food are available. examples: heron and egret ...strike at small fish and insects, grasping it into their beaks and swallow their catch head first (won't lodge in throat. Others/probe in sand or mud to search for worms/insects ...flamingos lower their heads upside down scooping a mouthful of food and water into their hooked beaks and use their tongue as a plunger, pushing the water out straining the food.

2. Terns and skimmers (Sterna hirundo and Rynchops nigra) Long-pointed wings and a forked tail enabling them to hover over the water using keen eyes with polarizing filters to see small fish swimming in the water. The black skimmer flies close to the waters surface and places its oversize lower bill 2 inches into the water and when their bills touch a small fish, ( their eyes are positioned so they can't see the water...touch is needed) their tails and wings drop to slow them down...the impact is enough to cause the skimmers head to bend backward and at this point the fish is swallowed whole. Their eyes are the only gulls that possess a vertical pupil (like a cat) which enable them to fly at twilight and dark when other birds can't. The elongated mandible of the beak makes it impossible for adult skimmers to feed while standing near the shore (young skimmers possess a more traditional beak while developing).

3. Gulls ( Larus sp.)There are 43 species of gulls and their survival depends on their lack of specialization...they feed on anything along the shore, serving as useful scavengers. They are currently endangering tern populations by competing with them by building their nests in sandy dune area formerly occupied by the terns. They forage for their food in water and land, and often pick up clams fly up about 40' and drop them onto the street breaking them open and then rushing to eat it.

4. Cormorants (Phalacrocorax) Usually seen swimming low over the water searching for schools of fish...when located, they settle into the water and make repeated surface dives, using their webbed feet to swim underwater. Its long neck and pointed beak help it probe among blades of sea grass and rock crevasses as it chases small fish. It consumes hundreds of small fish per day because of its high metabolic rate and are used by Asians to catch fish...a ring is placed around the long neck to prevent the bird from swallowing the fish and are trained to dive from fishing boats into a school of fish. They are fed fish small enough to fit past the neck ring and become dependent on their captors. They are often tethered on lines used to pull them back into the boats. the fish are then expelled from the esophagus and crop by gentle prodding. (crop stores food the birds gulp down rapidly)

5. Brown Pelicans (Pelecanus occidentalis) A big bird with a large pouch below its bill which it uses to catch fish. They live in large colonies and when fish are located, they plunge into the water with their bills open, bob to the surface with the pouch filled with a gallon of sea water and fish. By pushing their heads against their necks, the bird expels the seawater through grooves on their bills.

6. Frigate Birds (Fregatta) Found throughout the tropics and capable of flying far out to sea, and beautiful soaring flight that can out maneuver almost any bird but it cannot settle on the water. they never swim, float or enter the water and must return to shore at the end of the day to rest. They dive toward the water plucking flying fish out of the air, and grabbing small fish and squid from the surface while only wetting the tips of their beaks. They also harass other birds into vomiting their catch and feed on this.

7. Pelagic Birds Many seabirds spend almost their entire life beyond sight of the shore and these are pelagic birds. (return only to breed). Included are Puffins and albatrosses, sooty shearwaters (migrate 20,000 miles) and storm petrels and gannets.

8. Penguins

Adaptations

Ecological importance

Vital components of marine food web, feeding on and adding to the water droppings to fertilize surface water to stimulate growth of marine plants. Birds are attracted to certain areas and leave guano. Industry.

NAME FOOT&/OR GROUP FEEDING UNUSUAL CHARACTERISTIC

 

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