Exploring Our Fluid Earth

What is a Bird?

Birds (class Aves) are a group of vertebrate animals with feathers and toothless beaked jaws (Fig. 5.34). They have wing-shaped forelimbs, four-chambered hearts, and hard bony skeletons. Birds reproduce sexually and lay hard-shelled eggs in nests protected by the parents. They occur on all seven continents including Antarctica and can survive a wide variety of environmental conditions ranging from the tropics to the poles.

 

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Fig. 5.34. (A) Mandarin duck (Aix galericulata)

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Image courtesy of Adrian Pingstone, Wikimedia Commons

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Fig. 5.34. (B) Single-wattled cassowary (Casuarius unappendiculatus)

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Image courtesy of Quartl, Wikimedia Commons

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Fig. 5.34. (C) Mexican violetear hummingbird (Colibri thalassinus)

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Image courtesy of Mdf, Wikimedia Commons

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Fig. 5.34. (D) Common kingfisher (Alcedo atthis) eating a tadpole

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Image courtesy of Pierre Dalous, Wikimedia Commons

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Fig. 5.34. (E) Green-headed tanager (Tangara seledon), Ubatuba, Brazil

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Image courtesy of Lars Falkdalen Lindahl, Wikimedia Commons

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Fig. 5.34. (F) Bald eagle (Haliaeetus leucocephalus) catching fish

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Image courtesy of Jason Mrachina, Flickr

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Many bird species live in aquatic environments. Familiar examples from freshwater habitats include ducks, geese, and swans. Other bird groups rely heavily on freshwater resources. America’s national bird, the bald eagle (Haliaeetus leucocephalus), feeds primarily on fish.

 

There are approximately 470 species of marine birds, or seabirds, on Earth (Fig. 5.35). These species live in coastal marine habitats and on islands. All marine birds rely primarily on ocean resources for food and habitat.

 

Fig. 5.35. (A) White-tailed tropicbird (Phaethon lepturus), Warwick Parish, Bermuda

Image courtesy of Kansasphoto, Flickr

Fig. 5.35. (B) King penguins (Aptenodytes patagonicus), Possession Island, Crozet Islands

Image courtesy of franek2, Panoramio

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Fig. 5.35. (C) Buller's albatross (Thalassarche bulleri) Tasmania, Australia

Image courtesy of J.J. Harrison, Wikimedia Commons

Fig. 5.35. (D) Pied oystercatchers (Haematopus longirostris), Hobart, Tasmania, Australia

Image courtesy of J.J. Harrison, Wikimedia Commons

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Evidence of Common Ancestry and Diversity

Today biologists consider birds to be a type of reptile (Fig. 5.22 A). The most recent fossil and phylogenetic evidence indicates that modern birds are actually a subgroup of upright-walking dinosaurs (Fig. 5.22 B). While other dinosaur groups faced extinction around 66 million years ago, birds survived and diversified dramatically. There are approximately 10,000 known bird species today.

 

Fig. 5.22. (A) Phylogenetic tree of all vertebrate animals

Image by David Lin, adapted from image by Petter Bøckman, Wikimedia Commons

Fig. 5.22. (B) Phylogenetic tree illustrating the evolutionary relationships among different reptile groups (shaded in blue)

Image by David Lin, adapted from image by Jacek FH, Wikimedia Commons

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Like other reptiles, all birds are amniotes. Birds lay hard-shelled eggs containing amniotic sacs (Fig. 5.36). Marine bird eggs often have a camouflage pattern, an adaptation that reduces losses to egg-eating predators.

 

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Fig. 5.36. (A) Greater painted-snipe (Rostratula benghalensis) egg

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Image courtesy of Didier Descouens, Museum of Toulouse

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Fig. 5.36. (B) Camouflaged eggs in Eurasian oystercatcher (Haematopus ostralegus) nest, northern Norway

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Image courtesy of Bjørn Christian Tørrissen, Wikimedia Commons

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Fig. 5.36. (C) Emu (Dromaius novaehollandiae) egg

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Image courtesy of Shuhari, Wikimedia Commons

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Also like other reptiles, all birds are tetrapods. The typical walking front limbs of other tetrapods have evolved into wings in birds. Birds stand and walk on their rear limbs. Wings allow most bird species to fly. Most marine birds can flap their wings and lift off from the ground. However, some birds are flightless. Penguins and some other marine birds use their streamlined wings to swim underwater. Large flightless birds like the ostrich, emu, and cassowary have small stubby wings. These wings are examples of vestigial structures or structures that have lost their original function during evolution. They are used to regulate body temperatures and to maintain balance while running.

 

Marine Birds

Many groups of birds are adapted to living in or near water. Ducks, geese, swans, herons, and flamingos are all familiar examples of freshwater birds. Marine birds not only need adaptations to survive in saltwater, but also often far away from land. The most common marine birds fall within four large groups: penguins, tubenoses, pelecaniformes, and charadriiformes.

 

Penguins

Penguins (order Sphenisciformes) are flightless marine birds found almost exclusively in the southern hemisphere. Figure 5.37 demonstrates some examples of penguins. Major penguin populations are found in the Southern ocean basin in Antarctica, South America, New Zealand, and South Africa. One species occurs in the cold, nutrient-rich waters of the Galápagos Islands near the equator. Contrary to depictions in popular media, penguins do not occur in the northern hemisphere alongside polar bears. Penguins feed primarily on fish and small invertebrates like krill and squid. There are between 17 and 20 species of extant penguins.

 

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Fig. 5.37. (A) King penguin (Aptenodytes patagonicus) South Georgia Island, south Atlantic ocean basin

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Image courtesy of Samuel Blanc, Wikimedia Commons

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Fig. 5.37. (B) Magellanic penguin (Spheniscus magellanicus), Valdes Peninsula, Argentina

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Image courtesy of David, Flickr

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Fig. 5.37. (C) Adélie penguin (Pygoscelis adeliae), South Shetland Islands. Antarctica

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Image courtesy of ravas51, Flickr

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Tubenoses

Tubenoses (order Procellariiformes) are a diverse group of marine birds characterized by one or two tubes running along their straight hook-tipped bills. Examples of tubenoses include albatrosses, petrels, and shearwaters (Fig. 5.38). There are approximately 125 extant species around the world. Tubenoses mostly nest in colonies on remote islands free from predators. Their diets consist primarily of fish, squid, and small crustaceans.

 

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Fig. 5.38. (A) Light-mantled albatross (Phoebetria palpebrata)

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Image courtesy of Vincent Legendre, Wikimedia Commons

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Fig. 5.38. (B) Christmas shearwaters (Puffinus nativitatis), Tern Island, French Frigate Shoals, Hawai‘i

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Image courtesy of Duncan Wright, U.S. Fish and Wildlife Service (USFWS)

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Fig. 5.38. (C) Blue petrel (Halobaena caerulea), Tasmania, Australia

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Image courtesy of J.J. Harrison, Wikimedia Commons

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Pelecaniformes

Pelecaniformes (order Pelecaniformes) is a group of medium- and large-bodied aquatic birds. Examples include pelicans, frigatebirds, gannets, and cormorants (Fig. 5.39). Although this group encompasses a wide diversity of body forms, most pelecaniform birds have four webbed toes and bare throat patches. There are approximately 60 species within order Pelecaniformes around the world. Most pelecaniform birds eat fish. Pelicans have adapted large throat pouches that allow them to scoop small fish from the water. Cormorants catch fish with their hooked beaks by diving down from the water surface from a floating position.

 

Fig. 5.39. (A) Australian pelican (Pelecanus conspicillatus), Tasmania, Australia

Image courtesy of J.J. Harrison, Wikimedia Commons

Fig. 5.39. (B) Brown pelican (Pelecanus occidentalis) in flight, Bodega Bay, Sonoma County, California

Image courtesy of Frank Schulenburg, Wikimedia Commons

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Fig. 5.39. (C) Double-crested cormorant (Phalacrocorax auritus)

Image courtesy of Mdf, Wikimedia Commons

Fig. 5.39. (D) Magnificent frigatebird (Fregata magnificens), Galápagos Islands

Image courtesy of Benjamint444, Wikimedia Commons

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Charadriiformes

Charadriiformes (order Charadriiformes) is a diverse group of small and medium sized aquatic birds. Examples include plovers, gulls, terns, skimmers, sandpipers, puffins, and auks (Fig. 5.40). There are approximately 350 charadriiform species worldwide, with 305 species considered to be marine birds. Wading shorebirds such as plovers and snipes pick small invertebrates from the sediment on beaches and tidal mudflats. Larger charadriiform birds like gulls and puffins hunt for fish and invertebrates or scavenge on carrion. Gulls­­­, often referred to as “seagulls,” are perhaps the marine bird most familiar to most Americans. However, species in the gull family are rarely found in Hawai‘i and other tropical island communities.

 

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Fig. 5.40. (A) Hooded plover (Thinornis rubricollis), Bruny Island, Tasmania

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Image courtesy of J.J. Harrison, Wikimedia Commons

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Fig. 5.40. (B) Common greenshank (Tringa nebularia), Laem Phak Bia, Ban Laem, Phetchaburi, Thailand

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Image courtesy of J.J. Harrison, Wikimedia Commons

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Fig. 5.40. (C) Western gull (Larus occidentalis), Monterey, California

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Image courtesy Dschwen, Wikimedia Commons

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Fig. 5.40. (D) Sooty tern (Onychoprion fuscatus) on Tern Island, French Frigate Shoals, Northwestern Hawaiian Islands

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Image courtesy of Duncan Wright, U.S. Fish and Wildlife Service (USFWS)

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Fig. 5.40. (E) Black-necked stilt (Himantopus mexicanus), Corte Madera, Marin County, California

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Image courtesy of Frank Schulenberg, Wikimedia Commons

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Fig. 5.40. (F) Atlantic puffin (Fratercula arctica), Iceland

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Image courtesy of Henrik Thorburn, Wikimedia Commons

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Other Marine Birds

Several other bird species use coastal and open ocean resources but are not traditionally classified as marine birds. Examples include herons, sea ducks, and many raptor species (Fig. 5.41). Raptors, or birds-of-prey, are general terms used to describe eagles, hawks, falcons, and vultures. The eagle genus Haliaetus consists of 10 species of sea eagles, including the bald eagle, erne, Stellar’s sea eagle, and African fish eagle. The osprey, or sea hawk, (Pandion haliaetus) is another common marine raptor (Fig. 5.41 B). These raptor species use their excellent vision and sharp claws to locate and capture fish.

 

Fig. 5.41. (A) Black-crowned night heron (Nycticorax nycticorax) with fish prey

Image courtesy of Alain Carpentier, Wikimedia Commons

Fig. 5.41. (B) Osprey (Pandion haliaetus) with fish, Ocean Beach, San Francisco, California

Image courtesy of K. Schneider, Flickr

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Structure and Function

Like other reptiles, birds have skin covered in keratin scales. Keratin is a fibrous protein produced in the outer skin cells of many vertebrate animals including many fishes, amphibians, reptiles, birds, and mammals. Keratin is found in scales, horns, claws, turtle shells, bird feathers, and mammal hair. Bird scales are most readily observed on their feet, ankles, and other featherless skin patches.

 

All birds have feathers covering most of their body surfaces (Fig. 5.42 A). Feathers are lightweight growths of keratin extending from the skin. The two basic types of feathers are vaned feathers and down feathers. Vaned feathers have a stiff supporting shaft running through its center (Fig. 5.42 B and C). Fine branches or barbs emerge from each shaft, held together by microscopic hooks. This system of interlocking hooks allows vaned feathers to support birds’ flight. Vaned feathers also provide birds with color patterns and waterproofing. The term plumage refers to the feather patterns visible on a bird’s exterior surfaces (Fig. 5.42 A). In contrast to vaned feathers, down feathers are usually much shorter with soft central shafts and fluffy branches (Fig. 5.42 D). They grow layered underneath the vaned feathers. These fluffy branches allow down feathers to insulate birds and protect them from dangerous changes in body temperature. Some bird species use their own down feathers to line the interior of their nests (Fig. 5.42 E).

 

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Fig. 5.42. (A) Colorful feather plumage on a scarlet macaw (Ara macao)

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Image courtesy of Steve Evans, Flickr

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Fig. 5.42. (B) Close-up view of the central shaft and branched barbs on a vaned feather from a male Indian peafowl (Pavo cristatus)

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Image courtesy of Michael Maggs, Wikimedia Commons

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Fig. 5.42. (C) Vaned feathers on a parrot

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Image courtesy of psyberartist, Flickr

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Fig. 5.42. (D) Down feather from a goose

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Image courtesy of Fuzzy Thompson, Flickr

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Fig. 5.42. (E) Common eider (Somateria mollissima) sitting on eggs in a nest lined with down feathers

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Image courtesy of Fred Leviez, Wikimedia Commons

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All tetrapods have hard bony internal skeletons (Fig. 5.43 A). These bones are constructed of calcium mineral. In contrast to other tetrapods, bird bones are mostly hollow and lightweight. Ancient Chinese from the Yellow River Valley used the hollow bones of red-crowned cranes (Grus japonensis) to make flutes (Fig. 5.43 B). Having hollow and lightweight bones allows most bird species to fly.

 

Fig. 5.43. (A) Skeleton of a sarus crane (Antigone antigone)

Image courtesy of Eyton, TC (1869), adapted from Wikimedia Commons

Fig. 5.43. (B) Flutes discovered in the Yellow River Valley, China. They are between 7,000 and 9,000 years old, made from wing bones of the red-crowned crane (Grus japonensis).

Image courtesy of the U.S. Department of Energy's Brookhaven National Laboratory

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All birds have wing-shaped front limbs. The combination of feather-covered wings and lightweight skeletons allow most bird species to fly. The fastest and longest ranging animals on Earth are birds. Several bird species are flightless and have evolved smaller wings than their flying relatives. Examples of flightless birds include penguins, kiwis, the emu, and the ostrich.

 

Adaptations

Marine birds have evolved several adaptations that allow them to survive in ocean conditions. Many species that float atop the water surface have evolved webbed feet (Fig. 5.44 A) and dense oil-covered waterproof feathers (Fig. 5.44 B). Examples of surface-swimming marine birds include gulls, albatrosses, pelicans, and puffins. Penguins have evolved streamlined bodies and powerful flipper-like wings (Fig. 5.44 B). These wings allow penguins to swim not only at the water surface, but also submerged below. Many penguin species also exhibit porpoising behavior, leaping in and out of the water often when swimming long distances (Fig. 5.44 C & D).

 

Fig. 5.44. (A) Webbed feet on a blue-footed booby (Sula nebouxii), Galápagos Islands

Image courtesy of Derek Keats, Flickr

Fig. 5.44. (B) Gentoo penguin (Pygoscelis papua), Peterman Island in Antarctic Peninsula

Image courtesy of Priya Venkatesh, Wikimedia Commons

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Fig. 5.44. (C) Gentoo penguins (Pygoscelis papua) exhibiting porpoising swim behavior, Antarctica

Image courtesy of Gilad Rom, Flickr

Fig. 5.44. (D) Adélie penguins (Pygoscelis adeliae) exhibiting porpoising swim behavior, Antarctica

Image courtesy of Jason Auch, Flickr

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Marine birds have evolved several adaptations that allow them to survive in ocean conditions. Many species that float atop the water surface have evolved webbed feet (Fig. 5.44 A) and dense oil-covered waterproof feathers (Fig. 5.44 B). Examples of surface-swimming marine birds include gulls, albatrosses, pelicans, and puffins. Penguins have evolved streamlined bodies and powerful flipper-like wings (Fig. 5.44 B). These wings allow penguins to swim not only at the water surface, but also submerged below. Many penguin species also exhibit porpoising behavior, leaping in and out of the water often when swimming long distances (Fig. 5.44 C & D).

 

 

Fig. 5.45. Diagram of bird beak forms and functions

Image courtesy of L. Shyamal, Wikimedia Commons

All birds have hard external mouthparts called beaks or bills. Birds have evolved a wide diversity of beak shapes (Fig. 5.45). These forms are adaptations suited for a variety of functions. For example, a long thin bill helps avocets, curlews, and many other wading shorebirds (order Charadriiformes) to pick small invertebrate prey from tidal mudflats (Figs. 5.46 A and 5.47 B). Pelicans have adapted a large pouch-like beak and throat that allows them to scoop several small fish from the water in a single gulp (Fig. 5.46 B). Skimmers (genus Rynchops) are tern-like marine birds in the order Charadriiformes. They are unusual because their lower beaks are longer than their upper beaks (Fig. 5.46 C). Skimmers catch small fish by flying very low with their lower beaks slicing into the water (Fig. 5.46 D)

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Fig. 5.46. (A) American avocet (Recurvirostra americana)

Image courtesy of William H. Majoros, Wikimedia Commons

Fig. 5.46. (B) Australian pelican (Pelecanus conspicillatus), Bouddi National Park, New South Wales, Australia

Image courtesy of Greg Schechter, Flickr

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Fig. 5.46. (C) Black skimmer (Rynchops niger), Sunset Beach, North Carolina

Image courtesy of Dick Daniels, Wikimedia Commons

Fig. 5.46. (D) Black skimmer (Rynchops niger) feeding, Pantanal, Brazil

Image courtesy of Charles J. Sharp, Wikimedia Commons

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Energy Acquisition

Like other reptiles, birds acquire energy from a wide variety of sources. Many terrestrial and freshwater bird species feed on plant matter like grasses, aquatic plants, fruits, and seeds.

 

Most marine birds are carnivorous predators. Wading shorebirds (within the order Charadriiformes) like plovers, sandpipers, and snipes mostly feed on small invertebrates plucked with their pointed beaks from coastal beaches and mudflats (Figs. 5.46 A, 5.47 A, and 5.47 B).

 

Fig. 5.47. (A) Black-necked stilt (Himantopus mexicanus) foraging for small invertebrate prey in a shallow salt marsh, Bolsa Chica Ecological Reserve, Huntington Beach, California

Image courtesy of Regular Daddy, Wikimedia Commons

Fig. 5.47. (B) Long-billed curlew (Numenius americanus), eating a sand crab on Morro Strand State Beach, Morro Bay, California

Image courtesy of Mike Baird, Flickr

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Fig. 5.47. (C) American herring gull (Larus smithsonianus) eating a starfish, Plum Island Nature Preserve, Massachusetts

Image courtesy of stevehdc, Flickr

Fig. 5.47. (D) Immature great frigatebird (Fregata minor) with a sooty tern (Onychoprion fuscata) chick snatched from breeding colony, Tern Island, French Frigate Shoals, Northwestern Hawaiian Islands

Image courtesy of Duncan Wright, U.S. Fish and Wildlife Service (USFWS)

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Many marine birds are active predators of swimming prey such as fish, squid, and jellyfish. Gulls, terns, and albatrosses generally feed by scooping prey from the water surface or shallow diving. In contrast, pelicans, penguins, puffins, and cormorants are capable of diving several meters below the water surface by flapping their powerful streamlined wings underwater.

 

Gannets and boobies (family Sulidae within order Pelecaniformes) feed mainly by plunge-diving into the water after their swimming prey (Fig. 5.48 A). This is accomplished by locating schools of fish and squid from heights of up to 45 meters (m) and then diving steeply with their wings folded back (Fig. 5.48 B). Plunge-diving gannets strike the water surface at speeds up to 100 kilometers per hour (62 miles per hour) with their heads and necks outstretched and beaks tightly shut. They can plunge-dive to 5 m deep and swim down further if necessary.

 

Fig. 5.48. (A) Action sequence of a plunge-diving northern gannet (Morus bassanus), Bangor, County Down, Northern Ireland

Image courtesy of Simon Rodgers, Flickr

Fig. 5.48. (B) Gannets fold their wings back behind their tails immediately before striking the water surface.

Image courtesy of Mike Pennington, Geograph.org.uk

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Some marine birds also acquire their necessary energy from other birds. Gulls, frigatebirds, and other species are known to steal food caught by other birds (Fig. 5.49 A). This type of biological interaction is called kleptoparasitism. It can occur between different species (“interspecific”; Figs. 5.49 A and B) as well as between members of the same species (“intraspecific”; Figs. 5.49 C and D). Large marine birds like gulls, frigatebirds, giant petrels, and pelicans have also been observed preying on other birds.

 

Fig. 5.49. (A) Two laughing gulls (Leucophaeus atricilla) harassing a tern with a fish, Stone Harbor, New Jersey

Image courtesy of Alberto_VO5, Flickr

Fig. 5.49. (B) Laughing gull (Leucophaeus atricilla) preparing to steal food from a feeding brown pelican (Pelecanus occidentalis), Virginia

Image courtesy of Claire Powers, Flickr

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Fig. 5.49. (C) Food stealing behavior between two frigatebirds, Santiago Island, Galápagos Islands

Image courtesy of A. Davey, Flickr

Fig. 5.49. (D) Food stealing behavior between two cormorants

Image courtesy of Juan Lacruz, Wikimedia Commons

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Growth, Development & Reproduction

All bird offspring hatch from hard-shelled eggs laid in nests. In many species of marine birds, the parents provide some degree of parental care for their young offspring (Fig. 5.50). Parental care can include incubating eggs and providing food, shelter, and protection from predators.

 

Fig. 5.50. (A) Blue-footed booby (Sula nebouxii) incubating eggs in a nest, Wolf Island, Galápagos Islands

Image courtesy of Diego Delso, Wikimedia Commons

Fig. 5.50. (B) Both male and female king penguins (Aptenodytes patagonicus) take turns insulating their single egg balanced atop their feet, South Georgia Island, south Atlantic ocean basin

Image courtesy of Amanda B, Flickr

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Fig. 5.50. (C) Adult male Ascension frigatebird (Fregata aquila) with chick, Boatswain Bird Island, Ascension Island, south Atlantic ocean basin

Image courtesy of Drew Avery, Flickr

Fig. 5.50. (D) Emperor penguin (Aptenodytes forsteri) feeding its chick with regurgitated fish, crustaceans and squid, Atka Bay, Weddell Sea, Antarctica

Image courtesy of Dr. Hannes Grobe, Alfred Wegener Institute (AWI)

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The plumage or feather patterns on most bird species changes as they grow from juveniles into adults. Newly hatched chicks are often covered in thick, fluffy down feathers (Figs. 5.51 A and 5.51 B). This insulating layer of feathers eventually molts or falls off as the young bird grows into adulthood (Fig. 5.51 B).

 

Fig. 5.51. (A) Black-browed albatross (Thalassarche melanophris) and chick, West Point Island, Falkland Islands

Image courtesy of Liam Quinn, Flickr

Fig. 5.51. (B) King penguin (Aptenodytes patagonicus patagonicus) chick in juvenile plumage, Salisbury Plain, South Georgia Island, south Atlantic ocean basin. Other king penguin chicks in the background are molting their juvenile feathers.

Image courtesy of Liam Quinn, Flickr

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Courtship is the ritual behavior displayed between potential mates of the same species. Examples of courtship behavior can include dance-like movements, vocalizations or calls, and displays of physical beauty, strength, fighting prowess, or nest building skill. Several species of marine birds display complex courtship and mating behaviors. Mating is the pairing of two individuals for sexual reproduction. All birds produce offspring through sexual reproduction.

 

To review sexual reproduction, go to the Growth, Development, and Reproduction topic in Algae and Aquatic Plants.

 

Albatrosses (family Diomedeidae within the “tubenoses”) are well known for their complex courtship behavior. This includes vocalizations and display behavior where courting birds will touch beaks (Fig. 5.52 A), spread their wings, and then point their beaks skyward (Fig. 5.52 B). Ornithologists, or bird biologists, call this courtship behavior “sky calling.”

 

Fig. 5.52. (A) Bill touching courtship behavior in waved albatross (Phoebastria irrorata), Española Island, Galápagos Islands

Image courtesy of mrccos, Flickr

Fig. 5.52. (B) “Sky calling” courtship behavior in wandering albatross (Diomedea exulans), Kerguelen Islands, southern Indian ocean basin

Image courtesy of Dimitri Damasceno, Flickr

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Fig. 5.52. (C) Male great frigatebird (Fregata minor; left) displaying its red throat pouch to a female (right) on Santa Cruz Island, Galápagos Islands.

Image courtesy of BRJ INC., Flickr

Fig. 5.52. (D) Two male blue-footed booby (Sula nebouxii) exhibiting “parading” dance courtship behavior, Santa Cruz Island, Galápagos Islands

Image courtesy of Scott Ableman, Flickr

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In many bird species, the females select male mating partners based on these courtship displays. Frigatebirds (Fregata spp.) are well known for the males’ bright red throat pouches. Male frigatebirds inflate their throat pouches in a courtship display for females (Fig. 5.52 C). Male boobies (Sula spp.) exhibit “parading” behavior for females by walking upright, swaying from side to side, and alternatingly lifting their brightly colored feet (Fig. 5.52 D).

 

Most bird species are socially monogamous. Monogamy is the condition where an organism has only one mating partner, often for their entire lifespan.

 

Behavior

Many bird species are highly social and occur in large groups (Fig. 5.53). Almost 95 percent of all marine birds breed in large colonies. A rookery is a colony of nesting and breeding birds. Colonial nesting birds typically breed and hatch their eggs all at once. This strategy is an adaptation that can overwhelm predators with more newly hatched chicks than they can consume.

 

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Fig. 5.53. Tens of thousands of king penguins (Aptenodytes patagonicus) nest together in a large rookery, Gold Harbour, South Georgia, southern Atlantic ocean basin

Image copyright and source

Image courtesy of David Cook, Flickr

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Unlike most other animals, most birds are capable of efficient travel over long distances. This ability allows these birds to migrate long distances in search for food, habitat, and other seasonally limited resources or conditions. Migration is the regular seasonal movement of species, typically north-south in direction between wintering and breeding grounds. The bar-tailed godwit (Limosa lapponica; order Charadriiformes) is a large wading shorebird (Fig. 5.54 A) that takes the longest non-stop flight of any bird species. Scientists made this discovery by satellite-tracking tagged birds migrating from New Zealand to the Yellow Sea over 9 days without stopping (Fig. 5.54 B).

 

Fig. 5.54. (A) Bar-tailed godwit (Limosa lapponica), Hokkaido, Japan

Image courtesy of Tokumi Ohsaka, Wikimedia Commons

Fig. 5.54. (B) Map of routes taken by tagged bar-tailed godwits migrating from New Zealand to the Yellow Sea, northwestern Pacific ocean basin

Image courtesy of U.S. Geological Survey (USGS) Alaska Science Center

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