Sea Birds. Copyright 2012 LessonSnips

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1 Sea Birds There are hundreds of species of birds that rely on various aspects of an ocean habitat for survival and these are typically called sea birds or marine birds. Most sea birds like the albatross, penguins, pelicans, and cormorants live on the open sea and come to land for reproduction. Another category of birds are called shore birds. These species basically remain on land and feed on sea creatures and insects that live on the shoreline edge of the ocean, the tidewater area. Examples of shore birds include sandpipers and oystercatchers. Other birds such as sea gulls are adapted to a life that is equally at home on land or on the ocean. Pelagic Zone Sea birds like the albatross inhabit the pelagic zone of the ocean, commonly called the open sea. The pelagic zone is defined by what it is not; it is the ocean that is not near the coastline and it is not near the ocean floor (bottom). There is no definition for how many miles from shore the pelagic zone begins; where it begins depends on the ocean depth. The pelagic zone is further subdivided by the amount of light reaching a certain depth of water. The epipelagic zone from the surface to about 200 meters receives sunlight; the mesopelagic zone is the twilight area between 200 and 1000 meters; the bathypelagic zone is the midnight zone of darkness from 1000 to 4000 meters; and the deepest zones are the abyssopelagic and hadopelagic. Sea birds generally feed on sea creatures that inhabit the epipelagic zone. Researchers have determined that wandering albatross feed in bathypelagic zone; that means that they are capable of diving and withstanding the pressure of being under more than 3,000 feet of water. Adaptations Sea birds are adapted to living in a salt water environment that would be deadly to other creatures. A primary adaptation is the ability to excrete excess salt from the body through a salt gland. The sole function of the salt gland is to rid the body of unneeded salt. The salt gland is located on a sea bird s head as part of its nasal cavity.

2 A sea bird s feathers, called plumage, are also adapted for a life at sea. With a few exceptions, sea bird feathers are waterproof. Sea birds possess a thick layer of under feathers called down feathers which provide warmth from the cold open sea. However, the plumage of various species must also be streamlined to support diving for food and flying long distances across the open water. Sea birds tend to have more feathers than land-based species. In fact, sea birds wings are adapted for extremely long flights. Sea birds will migrate long distances, some even thousands of miles, in order to reach their designated land breeding grounds. Sea birds that need to fly long distances have evolved the ability to glide as a means of conserving energy. Sea birds that rely on diving skills for catching prey have shorter wings. Like freshwater birds, sea birds have webbed feet that aid in efficient swimming. Sea birds nest and reproduce in colonies that are located on land. Certain flocks or species have established colonies on particular islands in the ocean and return to the same location every year. Some pairs even return to the same nest site year after year. Gathering in a huge flock is an effective means of maintaining the species. Sea birds can find a mate within the colony instead of seeking a partner in the open ocean. Many sea birds are clumsy when they walk on land because they are streamlined for a life on the ocean. Gathering in large colonies for the time they spend on land in order to reproduce is another defense mechanism. A large colony provides greater security for vulnerable eggs and newly hatched chicks. However, any degradation of the habitat of the ancestral nesting site, like pollution from human sources, puts an entire species at risk for extinction. Feeding Sea birds have different feeding patterns depending on the species and their preferred diet. Species of sea birds that feed on krill and plankton while they float on the surface of the ocean filter the water in a manner similar to whales. However, most surface-feeding sea birds eat while flying, either skimming the surface with their bills or simply snatching prey or floating debris from the water s surface. Many sea birds dive for prey that is below the surface of the water using a technique called pursuit diving. Pursuit divers begin their dive from the surface of

3 the water. Some birds such as puffins, members of the auk family, have stiff wings that are designed to propel the bird through the water while diving. Some auks are capable of diving 500 feet in search of food. Loons have streamlined bodies designed for diving but they propel themselves downward with their webbed feet. Plunge divers like pelicans begin their dive from the air. This technique uses the momentum developed by the descent through the air to propel the bird downward through the water. Adult pelicans can plunge dive from a height of 70 feet above the surface of the water.

4 Circle True or False after analyzing each of the following statements. 1. True False Examples of sea birds include albatross, penguins, pelicans, and cormorants. 2. True False The pelagic zone of the ocean is adjacent to the tidewater area. 3. True False Species of sea birds regularly feed in the abyssopelagic and hadopelagic ocean zones. 4. True False The salt gland is located on a sea bird s head as part of its nasal cavity. 5. True False Sea birds tend to have more feathers than land-based species. 6. True False Sea birds that need to fly long distances have evolved the ability to glide as a means of conserving energy. 7. True False Sea birds that are good pursuit or plunge divers are also streamlined for walking on land. 8. True False Islands in the ocean are the preferred nesting site for some species of sea birds. 9. True False Sea birds that are pursuit divers begin their dive from the air. 10. True False Plunge diving uses the momentum developed by the descent through the air to propel a sea bird downward through the water.

5 Answers 1. True 2. False 3. False 4. True 5. True 6. True 7. False 8. True 9. False 10. True