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Seabirds (also known as marine birds) are
bird Birds are a group of warm-blooded vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With ...

bird
s that are
adapted In biology, adaptation has three related meanings. Firstly, it is the dynamic evolutionary process that fits organisms to their environment, enhancing their Fitness (biology), evolutionary fitness. Secondly, it is a state reached by the popula ...

adapted
to life within the
marine Marine is an adjective meaning of or pertaining to the sea or ocean The ocean (also the sea or the world ocean) is the body of salt water which covers approximately 71% of the surface of the Earth.
environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking
convergent evolution Convergent evolution is the independent evolution Evolution is change in the heritable Heredity, also called inheritance or biological inheritance, is the passing on of Phenotypic trait, traits from parents to their offspring; eit ...
, as the same environmental problems and feeding
niches
niches
have resulted in similar adaptations. The first seabirds evolved in the
Cretaceous The Cretaceous ( ) is a geological period A geological period is one of the several subdivisions of geologic time enabling cross-referencing of rocks and geologic events from place to place. These periods form elements of a hierarchy of division ...

Cretaceous
period Period may refer to: Common uses * Era, a length or span of time * Full stop (or period), a punctuation mark Arts, entertainment, and media * Period (music), a concept in musical composition * Period, a descriptor for a historical or period drama ...
, and modern seabird families emerged in the
Paleogene The Paleogene ( ; also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period and system that spans 43 million years from the end of the Cretaceous The Cretaceous ( ) is a geological period A geologi ...
. In general, seabirds live longer,
breed A breed is a specific group of domestic animals having homogeneous appearance (phenotype), homogeneous behavior, and/or other characteristics that distinguish it from other organisms of the same species. In literature, there exist several slight ...

breed
later and have fewer young than other birds do, but they invest a great deal of time in their young. Most
species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individu ...

species
nest in
colonies In political science, a colony is a territory subject to a form of foreign rule. Though dominated by the foreign colonizers, colonies remain separate from the administration of the original country of the colonizers, the metropole, metropolitan ...
, which can vary in size from a few dozen birds to millions. Many species are famous for undertaking long annual migrations, crossing the
equator The Equator is a circle of latitude, about in circumference, that divides Earth into the Northern Hemisphere, Northern and Southern Hemisphere, Southern hemispheres. It is an imaginary line located at 0 degrees latitude, halfway between the N ...

equator
or circumnavigating the Earth in some cases. They feed both at the ocean's surface and below it, and even feed on each other. Seabirds can be highly
pelagic The pelagic zone consists of the water column A water column is a concept Concepts are defined as abstract ideas A mental representation (or cognitive representation), in philosophy of mind Philosophy of mind is a branch of philosophy ...
, coastal, or in some cases spend a part of the year away from the sea entirely. Seabirds and humans have a long history together: they have provided food to
hunters Hunting is the practice of seeking, pursuing and capturing or killing wildlife A ground pangolin Wildlife traditionally refers to undomesticated animal Animals (also called Metazoa) are multicellular eukaryotic organisms that ...

hunters
, guided
fishermen A fisher or fisherman is someone who captures fish Fish are Aquatic animal, aquatic, craniate, gill-bearing animals that lack Limb (anatomy), limbs with Digit (anatomy), digits. They form a sister group to the tunicates, together forming t ...

fishermen
to fishing stocks and led
sailor A sailor, seaman, mariner, or seafarer is a person who works aboard a watercraft Watercraft, also known as water vessels or waterborne vessels, are vehicles A vehicle (from la, vehiculum) is a machine A machine is any physical sys ...

sailor
s to land. Many species are currently
threatened Threatened Species are any species (including animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume org ...
by human activities, such as from
oil spill An oil spill is the release of a liquid petroleum Petroleum (), also known as crude oil and oil, is a #Latent heat of vaporization, naturally occurring, yellowish-black liquid found in geological formations beneath the Earth, Earth's surfac ...
s, getting trapped in nets, and by
climate change Contemporary climate change includes both the global warming caused by humans, and its impacts on Earth's weather patterns. There have been previous periods of climate change, but the current changes are more rapid than any known even ...
and severe weather.
Conservation Conservation is the preservation or efficient use of resources, or the conservation of various quantities under physical laws. Conservation may also refer to: Environment and natural resources * Nature conservation, the protection and manageme ...
efforts include the establishment of wildlife refugees and adjustments to fishing techniques.


Classification

There exists no single definition of which groups, families and species are seabirds, and most definitions are in some way arbitrary. Elizabeth Shreiber and Joanne Burger, two seabird scientists, said, "The one common characteristic that all seabirds share is that they feed in
saltwater Saline water (more commonly known as salt water) is water Water is an Inorganic compound, inorganic, Transparency and translucency, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the ...

saltwater
; but, as seems to be true with any statement in biology, some do not."Schreiber, Elizabeth A. and Burger, Joanne (2001) ''Biology of Marine Birds''. Boca Raton: CRC Press, However, by convention all of the
Sphenisciformes (penguins)
Sphenisciformes (penguins)
and
Procellariiformes Procellariiformes is an order Order or ORDER or Orders may refer to: * Orderliness Orderliness is associated with other qualities such as cleanliness Cleanliness is both the abstract state of being clean and free from germs, dirt, trash, or ...
(
albatross Albatrosses are very large Seabird, seabirds in the family (biology), family Diomedeidae. They range widely in the Southern Ocean and the North Pacific Ocean, Pacific. They are absent from the North Atlantic Ocean, Atlantic, although fossil rem ...

albatross
es and
petrel Petrels are tube-nosed seabirds in the bird order Procellariiformes. Description The common name does not indicate relationship beyond that point, as "petrels" occur in three of the four families within that group (all except the albatross fa ...

petrel
s), all of the
Suliformes The order Suliformes (, dubbed "Phalacrocoraciformes" by ''Christidis & Boles 2008'') is an order recognised by the International Ornithologist's Union. In regard to the recent evidence that the traditional Pelecaniformes is polyphyletic File:M ...
(
gannet Gannets are seabirds Seabirds (also known as marine birds) are bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves , characterised by feathers, toothless beaked jaws, the Oviparity, layi ...

gannet
s and
cormorant Phalacrocoracidae is a family In human society, family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of families is to maintain ...

cormorant
s) except the
darter The darters, anhingas, or snakebirds are mainly tropical The tropics are the region of Earth surrounding the Equator. They are delimited in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in ...

darter
s, and some of the
Charadriiformes Charadriiformes (, from '' Charadrius'', the type genus Type may refer to: Science and technology Computing * Typing Typing is the process of writing or inputting text by pressing keys on a typewriter, computer keyboard, cell phone, or calcula ...

Charadriiformes
(the
skua The skuas are a group of predatory seabird Seabirds (also known as marine birds) are bird Birds are a group of warm-blooded vertebrates constituting the class Class or The Class may refer to: Common uses not otherwise categ ...

skua
s,
gull Gulls, or colloquially seagulls, are seabirds of the family Laridae in the suborder Lari. They are most closely related to the terns (family Sternidae) and only distantly related to auks, Skimmer (bird), skimmers and even more distantly to wade ...

gull
s,
tern Terns are seabirds in the family (biology), family Laridae that have a worldwide distribution and are normally found near the sea, rivers, or wetlands. Terns are treated as a subgroup of the family Laridae which includes gulls and Skimmer (bir ...

tern
s,
auk An auk or alcid is a bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves , characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabo ...
s and skimmers) are classified as seabirds. The
phalarope __NOTOC__ A phalarope is any of three living species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as ...
s are usually included as well, since although they are
wader 245px, A flock of Dunlins and Red knots Waders are birds of the order Charadriiformes commonly found along shorelines and mudflats that wikt:wade#Etymology 1, wade in order to foraging, forage for food (such as insects or crustaceans) in the m ...
s ("shorebirds" in North America), two of the three species (
Red Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength Image:dominant wavelength.png, frame, Dominant/complementary wavelength example on the CIE color ...
and
Red-necked
Red-necked
) are oceanic for nine months of the year, crossing the equator to feed pelagically.
Loon Loons (North America) or divers (United Kingdom / Ireland) are a group of aquatic bird Birds are a group of s constituting the Aves , characterised by s, toothless beaked jaws, the of eggs, a high rate, a four-chambered , and a s ...

Loon
s and
grebe Grebes () are aquatic diving birds in the order (biology), order Podicipediformes . Grebes are widely distributed birds of freshwater, with some species also occurring in sea, marine habitats during Bird migration, migration and winter. The order ...

grebe
s, which nest on lakes but winter at sea, are usually categorized as water birds, not seabirds. Although there are a number of sea ducks in the family
Anatidae The Anatidae are the biological family (biology), family of water birds that includes ducks, goose, geese, and swans. The family has a cosmopolitan distribution, occurring on all the world's continents. These birds are adapted for aquatic locomo ...
that are truly marine in the winter, by convention they are usually excluded from the seabird grouping. Many waders (or shorebirds) and
heron The herons are long-legged, long-necked, freshwater and coastal bird Birds are a group of warm-blooded vertebrates constituting the class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a ...

heron
s are also highly marine, living on the sea's edge (coast), but are also not treated as seabirds.
Sea eagle A sea eagle (also called erne or ern, mostly in reference to the white-tailed eagle) is any of the birds of prey in the genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of thin ...
s and other fish-eating birds of prey are also typically excluded, however tied to marine environments they may be. German paleontologist
Gerald Mayr Gerald Mayr is a German paleontology, palaeontologist who is Curator of Ornithology at the Naturmuseum Senckenberg, Senckenberg Research Institute in Frankfurt, Frankfurt am Main, Hesse. He has published extensively on fossil birds, especially the P ...
defined the "core waterbird" clade
Aequornithes Aequornithes (, from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the ...
in 2010. This lineage gives rise to the
Gaviiformes Gaviiformes is an order (biology), order of aquatic birds containing the loons or divers and their closest extinct relatives. Modern gaviiformes are found in many parts of North America and northern Eurasia (Europe, Asia and debatably Africa), tho ...
,
Sphenisciformes Penguins ( order Sphenisciformes , family In human society, family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of families ...
, Procellariiformes,
Ciconiiformes Storks are large, long-legged, long-necked wading bird Waders or shorebirds are bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves , characterised by feathers, toothless beaked jaws, the ...
, Suliformes and
Pelecaniformes The Pelecaniformes are an order Order or ORDER or Orders may refer to: * Orderliness Orderliness is associated with other qualities such as cleanliness Cleanliness is both the abstract state of being clean and free from germs, dirt, trash, or ...
. The tropicbirds are part of a lineage—
Eurypygimorphae Eurypygimorphae or Phaethontimorphae is a clade of birds that contains the orders Phaethontiformes (tropicbirds) and Eurypygiformes (kagu and sunbittern) recovered by genome analysis. The relationship was first identified in 2013 based on their nu ...
—that is a
sister group In phylogenetics, a sister group or sister taxon comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and taxon B are sister groups to eac ...
to the Aequornithes.


Evolution and fossil record

Seabirds, by virtue of living in a
geologically Geology (from the Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following peri ...

geologically
depositional environment (that is, in the sea where
sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently sediment transport, transported by the action of wind, water, or ice or by the force of gravity acting on the particles. ...

sediment
s are readily laid down), are well represented in the
fossil A fossil (from Classical Latin Classical Latin is the form of Latin language Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication used by humans, inc ...

fossil
record. They are first known to occur in the
Cretaceous The Cretaceous ( ) is a geological period A geological period is one of the several subdivisions of geologic time enabling cross-referencing of rocks and geologic events from place to place. These periods form elements of a hierarchy of division ...

Cretaceous
period, the earliest being the
Hesperornithiformes Hesperornithes is an extinct and highly specialized group of aquatic avialans closely related to the ancestors of modern bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves , characterised by f ...
, like ''Hesperornis regalis'', a flightless loon-like seabird that could dive in a fashion similar to grebes and loons (using its feet to move underwater) but had a beak filled with sharp teeth. Flying Cretaceous seabirds do not exceed wingspans of two meters; any sizes were taken by piscivorous
pterosaurs Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") were flying reptile Reptiles are tetrapod Tetrapods (; from Greek 'four' and 'foot') are four-limbed animals constituting the superclass Tetrapoda . It includes ...

pterosaurs
. While ''Hesperornis'' is not thought to have left descendants, the earliest
modern Modern may refer to: History *Modern history Human history, also known as world history, is the description of humanity's past. It is informed by archaeology Archaeology or archeology is the study of human activity through the recov ...

modern
seabirds also occurred in the Cretaceous, with a species called '' Tytthostonyx glauconiticus'', which has features suggestive of Procellariiformes and Fregatidae.Olson, S.; Parris, D.C. (1987).
The Cretaceous Birds of New Jersey.
''Smithsonian Contributions to Paleontology'', 63: 22pp.
As a clade, the Aequornithes either became seabirds in a single transition in the Cretaceous or some lineages such as pelicans and frigatebirds adapted to sea living independently from freshwater-dwelling ancestors. In the
Paleogene The Paleogene ( ; also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period and system that spans 43 million years from the end of the Cretaceous The Cretaceous ( ) is a geological period A geologi ...
both pterosaurs and marine reptiles became extinct, allowing seabirds to expand ecologically. These post-extinction seas were dominated by early
Procellariidae The Procellariidae is a group of s that comprises the s, the s, the s, the , and the s. This family is part of the bird (or tubenoses), which also includes the es and the s. The procellariids are the most numerous family of tubenoses, and th ...
, giant
penguin Penguins (order (biology), order Sphenisciformes , family (biology), family Spheniscidae ) are a group of Water bird, aquatic flightless bird, flightless birds. They live almost exclusively in the southern hemisphere: only one species, the Gal ...

penguin
s and two
extinct Extinction is the termination of a kind of organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biol ...
families In human society, family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of families is to maintain the w ...
, the
Pelagornithidae The Pelagornithidae, commonly called pelagornithids, pseudodontorns, bony-toothed birds, false-toothed birds or pseudotooth birds, are a prehistoric family (biology), family of large seabirds. Their fossil remains have been found all over the worl ...
and the
Plotopteridae Plotopteridae is the name of an extinct family (biology), family of flightless seabirds from the order Suliformes. Related to the gannets and booby, boobies, they exhibited remarkable convergent evolution with the penguins, particularly with the n ...
(a group of large seabirds that looked like the penguins). Modern genera began their wide radiation in the
Miocene The Miocene ( ) is the first geological epoch In geochronology, an epoch is a subdivision of the geologic timescale that is longer than an age (geology), age but shorter than a period (geology), period. The current epoch is the Holocene Epoch of ...
, although the
genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxonomy), circumscribing) and classifying gr ...
''
Puffinus ''Puffinus'' is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to a ...

Puffinus
'' (which includes today's
Manx shearwater The Manx shearwater (''Puffinus puffinus'') is a medium-sized shearwater in the seabird Seabirds (also known as marine birds) are bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves , char ...
and
sooty shearwater The sooty shearwater (''Ardenna grisea'') is a medium-large shearwater Shearwaters are medium-sized long-winged seabird Seabirds (also known as marine birds) are bird Birds are a group of warm-blooded vertebrates constituting the ...
) might date back to the
Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define ...
. Within the Charadriiformes, the gulls and allies (
Lari The suborder Lari is the part of the order Charadriiformes Charadriiformes (, from '' Charadrius'', the type genus Type may refer to: Science and technology Computing * Typing Typing is the process of writing or inputting text by pressing ...

Lari
) became seabirds in the late Eocene, and then waders in the middle Miocene (
Langhian The Langhian is, in the ICS geologic timescale The geologic time scale (GTS) is a system of chronological dating that classifies Geology, geological strata (stratigraphy) in time. It is used by geologists, paleontology, paleontologists, and oth ...
). The highest diversity of seabirds apparently existed during the Late Miocene and the
Pliocene The Pliocene ( ; also Pleiocene) epoch (geology), Epoch is the epoch in the geologic timescale that extends from 5.333 million to 2.58food web A food web is the natural interconnection of food chains and a graphical representation of what-eats-what in an ecological community. Another name for food web is Consumer-resource systems, consumer-resource system. Ecologists can broadly lump a ...

food web
had undergone a period of upheaval due to extinction of considerable numbers of marine species; subsequently, the spread of marine mammals seems to have prevented seabirds from reaching their erstwhile diversity.


Characteristics


Adaptations to life at sea

Seabirds have made numerous adaptations to living on and feeding in the sea.
Wing A wing is a type of fin A fin is a thin component or appendage attached to a larger body or structure. Fins typically function as foils that produce lift or thrust Thrust is a reaction (physics), reaction force (physics), force describ ...

Wing
morphology has been shaped by the
niche Niche may refer to: Science *Developmental niche{{third-party, date=October 2020 The developmental niche is a theoretical framework for understanding and analyzing how culture Culture () is an umbrella term which encompasses the social behav ...

niche
an individual species or family has
evolved Evolution is change in the heritable Heredity, also called inheritance or biological inheritance, is the passing on of Phenotypic trait, traits from parents to their offspring; either through asexual reproduction or sexual reproduction, ...

evolved
, so that looking at a wing's shape and loading can tell a scientist about its life feeding behaviour. Longer wings and low wing loading are typical of more
pelagic The pelagic zone consists of the water column A water column is a concept Concepts are defined as abstract ideas A mental representation (or cognitive representation), in philosophy of mind Philosophy of mind is a branch of philosophy ...
species, while diving species have shorter wings.Gaston, Anthony J. (2004). ''Seabirds: A Natural History'' New Haven:Yale University Press, Species such as the
wandering albatross The wandering albatross, snowy albatross, white-winged albatross or goonie (''Diomedea exulans'') is a large seabird Seabirds (also known as marine birds) are bird Birds are a group of warm-blooded vertebrates constituting the class ( ...
, which forage over huge areas of sea, have a reduced capacity for powered flight and are dependent on a type of
gliding Gliding is a recreational activity and competitive air sport The term "air sports" covers a range of aerial activities, including air racing, aerobatics, aeromodelling, hang gliding, human powered aircraft, parachuting, paragliding and skydiv ...
called
dynamic soaring Dynamic soaring is a flying technique used to gain energy by repeatedly crossing the boundary between air masses of different velocity. Such zones of wind gradient are generally found close to obstacles and close to the surface, so the technique is ...
(where the wind deflected by waves provides lift) as well as slope soaring. Seabirds also almost always have
webbed feet The webbed foot is a specialized limb present in a variety of vertebrates that aids in locomotion. This adaptation is primarily found in semiaquatic species, and has convergently evolved many times across vertebrate taxa. It likely arose fro ...
, to aid movement on the surface as well as assisting diving in some species. The
Procellariiformes Procellariiformes is an order Order or ORDER or Orders may refer to: * Orderliness Orderliness is associated with other qualities such as cleanliness Cleanliness is both the abstract state of being clean and free from germs, dirt, trash, or ...
are unusual among birds in having a strong
sense of smell The sense of smell, or olfaction, is the special sense In medicine Medicine is the Art (skill), art, science, and Praxis (process) , practice of caring for a patient and managing the diagnosis, prognosis, Preventive medicine, prevention, the ...
, which is used to find widely distributed food in a vast ocean, and help distinguish familiar nest odours from unfamiliar ones. Salt glands are used by seabirds to deal with the
salt Salt is a mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure fo ...
they ingest by drinking and feeding (particularly on
crustacean Crustaceans (Crustacea ) form a large, diverse arthropod taxon which includes such animals as crabs, lobsters, crayfish, Caridea, shrimp, krill, Dendrobranchiata, prawns, woodlice, barnacles, copepods, amphipoda, amphipods and mantis shrimp. The ...
s), and to help them osmoregulate.Harrison, C. S. (1990) ''Seabirds of Hawaii, Natural History and Conservation'' Ithaca:Cornell University Press, The
excretion Excretion is a process in which metabolic waste Metabolic wastes or excrements are Chemical substance, substances left over from metabolism, metabolic processes (such as cellular respiration) which cannot be used by the organism (they are surplus ...
s from these glands (which are positioned in the head of the birds, emerging from the
nasal cavity The nasal cavity is a large, air-filled space above and behind the nose A nose is a protuberance in vertebrates that houses the nostrils, or nares, which receive and expel air for Respiration (physiology), respiration alongside the mouth. Beh ...

nasal cavity
) are almost pure
sodium chloride Sodium chloride , commonly known as salt (although sea salt also contains other chemical salt (chemistry), salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With Molar mass, molar ...
. With the exception of the
cormorant Phalacrocoracidae is a family In human society, family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of families is to maintain ...

cormorant
s and some terns, and in common with most other birds, all seabirds have waterproof
plumage Plumage ( "feather") is a layer of feather Feathers are epidermal growths that form a distinctive outer covering, or plumage Plumage ( "feather") is a layer of feather Feathers are epidermal growths that form a distinctive outer ...
. However, compared to land birds, they have far more feathers protecting their bodies. This dense plumage is better able to protect the bird from getting wet, and cold is kept out by a dense layer of
down feather The down of bird Birds are a group of warm-blooded vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological k ...
s. The cormorants possess a layer of unique feathers that retain a smaller layer of air (compared to other diving birds) but otherwise soak up water. This allows them to swim without fighting the
buoyancy Buoyancy (), or upthrust, is an upward exerted by a that opposes the of a partially or fully immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus the pressure at the bo ...

buoyancy
that retaining air in the feathers causes, yet retain enough air to prevent the bird losing excessive heat through contact with water. The plumage of most seabirds is less colourful than that of land birds, restricted in the main to variations of black, white or grey. A few species sport colourful plumes (such as the tropicbirds and some penguins), but most of the colour in seabirds appears in the bills and legs. The plumage of seabirds is thought in many cases to be for
camouflage Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard The leopard (''Pan ...

camouflage
, both defensive (the colour of
US Navy ), (unofficial)."''Non sibi sed patriae''" ( en, "Not for self but for country") (unofficial). , colors = Blue and gold  , colors_label = Colors , march = "Anchors Aweigh "Anchors Aweigh" is the fight song of the United States Naval A ...
battleship A battleship is a large armored warship A warship or combatant ship is a that is built and primarily intended for . Usually they belong to the of a state. As well as being armed, warships are designed to withstand damage and are usually ...

battleship
s is the same as that of Antarctic prions, and in both cases it reduces visibility at sea) and aggressive (the white underside possessed by many seabirds helps hide them from prey below). The usually black wing tips help prevent wear, as they contain melanins to make them black that helps the feathers resist abrasion.


Diet and feeding

Seabirds evolved to exploit different food resources in the world's seas and oceans, and to a great extent, their
physiology Physiology (; ) is the scientific Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity or awareness, of someone or something, such as facts A fact is an occurrence in the real world. ...
and
behaviour Behavior (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United States. Currently, American English ...
have been shaped by their
diet Diet may refer to: Food * Diet (nutrition) In nutrition, diet is the sum of food consumed by a person or other organism. The word diet often implies the use of specific intake of nutrition for #Health, health or #Weight management, weight-mana ...
. These evolutionary forces have often caused species in different families and even orders to evolve similar strategies and adaptations to the same problems, leading to remarkable
convergent evolution Convergent evolution is the independent evolution Evolution is change in the heritable Heredity, also called inheritance or biological inheritance, is the passing on of Phenotypic trait, traits from parents to their offspring; eit ...
, such as that between auks and penguins. There are four basic feeding strategies, or ecological guilds, for feeding at sea: surface feeding, pursuit diving, plunge diving and predation of
higher vertebrates Amniotes (from Greek ἀμνίον ''amnion'', "membrane surrounding the fetus", earlier "bowl in which the blood of sacrificed animals was caught", from ἀμνός ''amnos'', "lamb") are a clade A clade (; from grc, , ''klados'', "bran ...
; within these guilds there are multiple variations on the theme.


Surface feeding

Many seabirds feed on the ocean's surface, as the action of marine
currents Currents or The Current may refer to: Science and technology * Current (fluid), the flow of a liquid or a gas ** Air current, a flow of air ** Ocean current, a current in the ocean *** Rip current, a kind of water current ** Current (stream), c ...
often concentrates food such as
krill Krill are small crustacean Crustaceans (Crustacea ) form a large, diverse arthropod An arthropod (, (gen. ποδός)) is an invertebrate Invertebrates are animals that neither possess nor develop a vertebral column (commonly known as a ...

krill
,
forage fish Forage fish, also called prey fish or bait fish, are small pelagic fish which are preyed on by larger predators for food. Predators include other larger fish, seabirds and marine mammals. Typical ocean forage fish feed near the base of the food ...

forage fish
,
squid Squid are cephalopod A cephalopod is any member of the mollusca Mollusca is the second-largest phylum In biology, a phylum (; plural The plural (sometimes list of glossing abbreviations, abbreviated ), in many languages, is ...

squid
or other prey items within reach of a dipped head. Surface feeding itself can be broken up into two different approaches, surface feeding while flying (for example as practiced by
gadfly petrel The gadfly petrels or ''Pterodroma'' are a genus of about 35 species of petrels, part of the seabird Seabirds (also known as marine birds) are bird Birds are a group of warm-blooded vertebrates constituting the class (biology), clas ...
s,
frigatebird Frigatebirds (also listed as "frigate bird", "frigate-bird", "frigate", "frigate-petrel") are a family In human society, family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (b ...
s and
storm petrel Storm petrel may refer to one of two bird families In human society, family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relatio ...
s), and surface feeding while swimming (examples of which are practiced by
fulmar The fulmars are tubenosed seabirds of the family In human society A society is a Social group, group of individuals involved in persistent Social relation, social interaction, or a large social group sharing the same spatial or socia ...

fulmar
s,
gull Gulls, or colloquially seagulls, are seabirds of the family Laridae in the suborder Lari. They are most closely related to the terns (family Sternidae) and only distantly related to auks, Skimmer (bird), skimmers and even more distantly to wade ...

gull
s, many of the
shearwater Shearwaters are medium-sized long-winged seabird Seabirds (also known as marine birds) are bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves , characterised by feathers, toothless beaked ...
s and gadfly petrels). Surface feeders in flight include some of the most acrobatic of seabirds, which either snatch morsels from the water (as do frigate-birds and some terns), or "walk", pattering and hovering on the water's surface, as some of the storm-petrels do. Many of these do not ever land in the water, and some, such as the frigatebirds, have difficulty getting airborne again should they do so. Another seabird family that does not land while feeding is the skimmer, which has a unique fishing method: flying along the surface with the lower mandible in the water—this shuts automatically when the bill touches something in the water. The skimmer's bill reflects its unusual lifestyle, with the lower mandible uniquely being longer than the upper one. Surface feeders that swim often have unique bills as well, adapted for their specific prey.
Prions Prions are misfolded protein Protein folding is the physical process Physical changes are changes affecting the form of a chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matte ...
have special bills with filters called
lamellae Lamella (plural lamellae) means a small plate or flake in Latin, and in English may refer to: Biology * Lamella (mycology) "False" gills of '' Craterellus tubaeformis'' A lamella, or gill, is a papery hymenophoreA hymenophore refers to the hy ...
to filter out
plankton Plankton are the diverse collection of organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology ...

plankton
from mouthfuls of water,Brooke, M. (2004). ''Albatrosses and Petrels Across the World''. Oxford University Press, Oxford, UK and many albatrosses and petrels have hooked bills to snatch fast-moving prey. On the other hand, most gulls are versatile and opportunistic feeders who will eat a wide variety of prey, both at sea and on land.


Pursuit diving

Pursuit diving exerts greater pressures (both evolutionary and physiological) on seabirds, but the reward is a greater area in which to feed than is available to surface feeders. Underwater
propulsion Propulsion is the action or process of pushing or pulling to drive an object forward. The term is derived from two Latin words: '' pro'', meaning'' before'' or ''forward''; and '' pellere'', meaning ''to drive''. A propulsion system consists of ...
is provided by wings (as used by penguins, auks,
diving petrel The diving petrels (Genus ''Pelecanoides'') are seabird Seabirds (also known as marine birds) are bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves , characterised by feathers, toothless ...
s and some other species of petrel) or
feet The foot (plural: feet) is an anatomical Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemist ...
(as used by cormorants,
grebe Grebes () are aquatic diving birds in the order (biology), order Podicipediformes . Grebes are widely distributed birds of freshwater, with some species also occurring in sea, marine habitats during Bird migration, migration and winter. The order ...

grebe
s,
loon Loons (North America) or divers (United Kingdom / Ireland) are a group of aquatic bird Birds are a group of s constituting the Aves , characterised by s, toothless beaked jaws, the of eggs, a high rate, a four-chambered , and a s ...

loon
s and several types of fish-eating
duck Duck is the common name for numerous species of waterfowl Anseriformes is an order (biology), order of birds that comprise about 180 living species in three families: Anhimidae (the 3 screamers), Anseranatidae (the magpie goose), and Anati ...

duck
s). Wing-propelled divers are generally faster than foot-propelled divers. The use of wings or feet for diving has limited their utility in other situations: loons and grebes walk with extreme difficulty (if at all), penguins cannot fly, and auks have sacrificed flight efficiency in favour of diving. For example, the
razorbill The razorbill, razor-billed auk, or lesser auk (''Alca torda'') is a colonial seabird in the Monotypic taxon, monotypic genus ''Alca'' of the family Alcidae, the auks. It is the closest living relative of the extinct great auk (''Pinguinis impen ...

razorbill
(an Atlantic auk) requires 64% more energy to fly than a petrel of equivalent size.Gaston, Anthony J.; Jones, Ian L. (1998). ''The Auks'', Oxford University Press, Oxford, Many
shearwater Shearwaters are medium-sized long-winged seabird Seabirds (also known as marine birds) are bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves , characterised by feathers, toothless beaked ...
s are intermediate between the two, having longer wings than typical wing-propelled divers but heavier wing loadings than the other surface-feeding procellariids, leaving them capable of diving to considerable depths while still being efficient long-distance travellers. The
short-tailed shearwater The short-tailed shearwater or slender-billed shearwater (''Ardenna tenuirostris''; formerly ''Puffinus tenuirostris''), also called yolla or moonbird, and commonly known as the muttonbird in Australia, is the most abundant seabird species in Aust ...

short-tailed shearwater
is the deepest diver of the shearwaters, having been recorded diving below . Some albatross species are also capable of limited diving, with
light-mantled sooty albatross The light-mantled albatross (''Phoebetria palpebrata'') also known as the grey-mantled albatross or the light-mantled sooty albatross, is a small albatross in the genus ''Phoebetria'', which it shares with the sooty albatross. The light-mantled al ...
es holding the record at . Of all the wing-propelled pursuit divers, the most efficient in the air are the albatrosses, and they are also the poorest divers. This is the dominant guild in polar and subpolar environments, but it is energetically inefficient in warmer waters. With their poor flying ability, many wing-propelled pursuit divers are more limited in their foraging range than other guilds.


Plunge diving

Gannets, booby, boobies, tropicbirds, some terns and brown pelicans all engage in plunge diving, taking fast moving prey by diving into the water from flight. Plunge diving allows birds to use the energy from the momentum of the dive to combat natural buoyancy (caused by air trapped in plumage), and thus uses less energy than the dedicated pursuit divers, allowing them to utilise more widely distributed food resources, for example, in impoverished tropics, tropical seas. In general, this is the most specialised method of hunting employed by seabirds; other non-specialists (such as gulls and skuas) may employ it but do so with less skill and from lower heights. In brown pelicans the skills of plunge diving take several years to fully develop—once mature, they can dive from 20 m (70 ft) above the water's surface, shifting the body before impact to avoid injury. It may be that plunge divers are restricted in their hunting grounds to clear waters that afford a view of their prey from the air. While they are the dominant Guild (ecology), guild in the tropics, the link between plunge diving and water clarity is inconclusive. Some plunge divers (as well as some surface feeders) are dependent on dolphins and tuna to push shoaling fish up towards the surface.


Kleptoparasitism, scavenging and predation

This catch-all category refers to other seabird strategies that involve the next trophic level up. Kleptoparasitism, Kleptoparasites are seabirds that make a part of their living stealing food of other seabirds. Most famously,
frigatebird Frigatebirds (also listed as "frigate bird", "frigate-bird", "frigate", "frigate-petrel") are a family In human society, family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (b ...
s and
skua The skuas are a group of predatory seabird Seabirds (also known as marine birds) are bird Birds are a group of warm-blooded vertebrates constituting the class Class or The Class may refer to: Common uses not otherwise categ ...

skua
s engage in this behaviour, although gulls, terns and other species will steal food opportunistically. The nocturnal animal, nocturnal nesting behaviour of some seabirds has been interpreted as arising due to pressure from this aerial piracy. Kleptoparasitism is not thought to play a significant part of the diet of any species, and is instead a supplement to food obtained by hunting. A study of great frigatebirds stealing from masked booby, masked boobies estimated that the frigatebirds could at most obtain 40% of the food they needed, and on average obtained only 5%. Many species of gull will feed on seabird and sea mammal carrion when the opportunity arises, as will giant petrels. Some species of albatross also engage in scavenging: an analysis of regurgitated
squid Squid are cephalopod A cephalopod is any member of the mollusca Mollusca is the second-largest phylum In biology, a phylum (; plural The plural (sometimes list of glossing abbreviations, abbreviated ), in many languages, is ...

squid
beaks has shown that many of the squid eaten are too large to have been caught alive, and include mid-water species likely to be beyond the reach of albatrosses. Some species will also feed on other seabirds; for example, gulls, skuas and pelicans will often take eggs, chicks and even small adult seabirds from nesting colonies, while the giant petrels can kill prey up to the size of small penguins and seal pups.


Life history

Seabirds' life histories are dramatically different from those of land birds. In general, they are K-selected, live much longer (anywhere between twenty and sixty years), delay breeding for longer (for up to ten years), and invest more effort into fewer young. Most species will only have one clutch (eggs), clutch a year, unless they lose the first (with a few exceptions, like the Cassin's auklet), and many species (like the Procellariiformes, tubenoses and sulidae, sulids) will only lay one egg a year. Care of young is protracted, extending for as long as six months, among the longest for birds. For example, once common guillemot chicks fledge, they remain with the male parent for several months at sea. The frigatebirds have the longest period of parental care of any bird except a few raptors and the southern ground hornbill, with each chick fledging after four to six months and continued assistance after that for up to fourteen months. Due to the extended period of care, breeding occurs every two years rather than annually for some species. This life-history strategy has probably evolved both in response to the challenges of living at sea (collecting widely scattered prey items), the frequency of breeding failures due to unfavourable marine conditions, and the relative lack of predation compared to that of land-living birds. Because of the greater investment in raising the young and because foraging for food may occur far from the nest site, in all seabird species except the phalaropes, both parents participate in caring for the young, and pairs are typically at least seasonally Animal sexuality#Monogamy, monogamous. Many species, such as gulls, auks and penguins, retain the same mate for several seasons, and many
petrel Petrels are tube-nosed seabirds in the bird order Procellariiformes. Description The common name does not indicate relationship beyond that point, as "petrels" occur in three of the four families within that group (all except the albatross fa ...

petrel
species mate for life. Albatrosses and procellariids, which mate for life, take many years to form a pair bond before they breed, and the albatrosses have an elaborate breeding dance that is part of pair-bond formation.


Breeding and colonies

Ninety-five percent of seabirds are colonial, and seabird colonies are among the largest bird colonies in the world, providing one of Earth's great wildlife spectacles. Colonies of over a million birds have been recorded, both in the tropics (such as Kiritimati in the Pacific Ocean, Pacific) and in the polar latitudes (as in Antarctica). Seabird colonies occur exclusively for the purpose of breeding; non-breeding birds will only collect together outside the breeding season in areas where prey species are densely aggregated. Seabird colonies are highly variable. Individual nesting sites can be widely spaced, as in an albatross colony, or densely packed as with a murre colony. In most seabird colonies, several different species will nest on the same colony, often exhibiting some Niche differentiation, niche separation. Seabirds can nest in trees (if any are available), on the ground (with or without bird nest, nests), on cliffs, in burrows under the ground and in rocky crevices. Competition can be strong both within species and between species, with aggressive species such as sooty terns pushing less dominant species out of the most desirable nesting spaces. The tropical Bonin petrel nests during the winter to avoid competition with the more aggressive wedge-tailed shearwater. When the seasons overlap, the wedge-tailed shearwaters will kill young Bonin petrels in order to use their burrows. Many seabirds show remarkable site fidelity, returning to the same burrow, nest or site for many years, and they will defend that site from rivals with great vigour. This increases breeding success, provides a place for returning mates to reunite, and reduces the costs of prospecting for a new site. Young adults breeding for the first time usually return to their natal colony, and often nest close to where they hatched. This tendency, known as philopatry, is so strong that a study of Laysan albatrosses found that the average distance between hatching site and the site where a bird established its own territory was ; another study, this time on Cory's shearwaters nesting near Corsica, found that of nine out of 61 male chicks that returned to breed at their natal colony bred in the burrow they were raised in, and two actually bred with their own mother. Colonies are usually situated on islands, cliffs or headlands, which land mammals have difficulty accessing.Moors, P. J.; Atkinson, I. A. E. (1984). ''Predation on seabirds by introduced animals, and factors affecting its severity''. In ''Status and Conservation of the World's Seabirds''. Cambridge: ICBP. This is thought to provide protection to seabirds, which are often very clumsy on land. Coloniality often arises in types of bird that do not defend feeding territories (such as Swift (bird), swifts, which have a very variable prey source); this may be a reason why it arises more frequently in seabirds. There are other possible advantages: colonies may act as information centres, where seabirds returning to the sea to forage can find out where prey is by studying returning individuals of the same species. There are disadvantages to colonial life, particularly the spread of disease. Colonies also attract the attention of predation, predators, principally other birds, and many species attend their colonies nocturnally to avoid predation. Birds from different colonies often forage in different areas to avoid competition.


Migration

Like many birds, seabirds often bird migration, migrate after the breeding season. Of these, the trip taken by the Arctic tern is the farthest of any bird, crossing the
equator The Equator is a circle of latitude, about in circumference, that divides Earth into the Northern Hemisphere, Northern and Southern Hemisphere, Southern hemispheres. It is an imaginary line located at 0 degrees latitude, halfway between the N ...

equator
in order to spend the Austral summer in Antarctica. Other species also undertake trans-equatorial trips, both from the north to the south, and from south to north. The population of elegant terns, which nest off Baja California, splits after the breeding season with some birds travelling north to the Central Coast of California and some travelling as far south as Peru and Chile to feed in the Humboldt Current. The
sooty shearwater The sooty shearwater (''Ardenna grisea'') is a medium-large shearwater Shearwaters are medium-sized long-winged seabird Seabirds (also known as marine birds) are bird Birds are a group of warm-blooded vertebrates constituting the ...
undertakes an annual migration cycle that rivals that of the Arctic tern; birds that nest in New Zealand and Chile and spend the northern summer feeding in the North Pacific off Japan, Alaska and California, an annual round trip of . Other species also migrate shorter distances away from the breeding sites, their distribution at sea determined by the availability of food. If oceanic conditions are unsuitable, seabirds will emigrate to more productive areas, sometimes permanently if the bird is young. After fledging, juvenile birds often disperse further than adults, and to different areas, so are commonly sighted far from a species' normal range. Some species, such as the auks, do not have a concerted migration effort, but drift southwards as the winter approaches. Other species, such as some of the storm petrels, diving petrels and cormorants, never disperse at all, staying near their breeding colonies year round.


Away from the sea

While the definition of seabirds suggests that the birds in question spend their lives on the ocean, many seabird families have many species that spend some or even most of their lives inland away from the sea. Most strikingly, many species breed tens, hundreds or even thousands of miles inland. Some of these species still return to the ocean to feed; for example, the snow petrel, the nests of which have been found inland on the Antarctic mainland, are unlikely to find anything to eat around their breeding sites. The marbled murrelet nests inland in old growth forest, seeking huge conifers with large branches to nest on. Other species, such as the California gull, nest and feed inland on lakes, and then move to the coasts in the winter. Some cormorant, pelican, gull and tern species have individuals that never visit the sea at all, spending their lives on lakes, rivers, swamps and, in the case of some of the gulls, cities and agriculture, agricultural land. In these cases it is thought that these terrestrial or freshwater birds evolved from marine ancestors. Some seabirds, principally those that nest in tundra, as skuas and phalaropes do, will migrate over land as well. The more marine species, such as petrels, auks and
gannet Gannets are seabirds Seabirds (also known as marine birds) are bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves , characterised by feathers, toothless beaked jaws, the Oviparity, layi ...

gannet
s, are more restricted in their habits, but are occasionally seen inland as vagrants. This most commonly happens to young inexperienced birds, but can happen in great numbers to exhausted adults after large storms, an event known as a ''wreck''.


Relationship with humans


Seabirds and fisheries

Seabirds have had a long association with both fishery, fisheries and
sailor A sailor, seaman, mariner, or seafarer is a person who works aboard a watercraft Watercraft, also known as water vessels or waterborne vessels, are vehicles A vehicle (from la, vehiculum) is a machine A machine is any physical sys ...

sailor
s, and both have drawn benefits and disadvantages from the relationship. Fishermen have traditionally used seabirds as indicators of both Shoaling and schooling, fish shoals, underwater bank (topography), banks that might indicate fish stocks, and of potential landfall. In fact, the known association of seabirds with land was instrumental in allowing the Polynesians to locate tiny landmasses in the Pacific. Seabirds have provided food for fishermen away from home, as well as bait. Famously, tethered cormorants have been used to catch fish directly. Indirectly, fisheries have also benefited from guano from colonies of seabirds acting as fertilizer for the surrounding seas. Negative effects on fisheries are mostly restricted to raiding by birds on aquaculture, although long-line fishing, long-lining fisheries also have to deal with bait (luring substance), bait stealing. There have been claims of prey depletion by seabirds of fishery stocks, and while there is some evidence of this, the effects of seabirds are considered smaller than that of marine mammals and predatory fish (like tuna). Some seabird species have benefited from fisheries, particularly from discarded fish and offal. These discards compose 30% of the food of seabirds in the North Sea, for example, and compose up to 70% of the total food of some seabird populations. This can have other impacts; for example, the spread of the northern fulmar through the United Kingdom is attributed in part to the availability of discards. Discards generally benefit surface feeders, such as gannets and petrels, to the detriment of pursuit divers like penguins and guillemots, which can get entangled in the nets. Fisheries also have negative effects on seabirds, and these effects, particularly on the long-lived and slow-breeding albatrosses, are a source of increasing concern to conservationists. The bycatch of seabirds entangled in nets or hooked on fishing lines has had a big impact on seabird numbers; for example, an estimated 100,000 albatrosses are hooked and drown each year on tuna lines set out by long-line fisheries. Overall, many hundreds of thousands of birds are trapped and killed each year, a source of concern for some of the rarest species (for example, only about 2,000 short-tailed albatrosses are known to still exist). Seabirds are also thought to suffer when overfishing occurs. Changes to the marine ecosystems caused by dredging, which alters the biodiversity of the seafloor, can also have a negative impact.


Exploitation

The hunting of seabirds and the collecting of seabird egg (biology), eggs have contributed to the declines of many species, and the
extinct Extinction is the termination of a kind of organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biol ...
ion of several, including the great auk and the spectacled cormorant. Seabirds have been hunted for food by coastal peoples throughout history—one of the earliest instances known is in southern Chile, where archeology, archaeological excavations in middens has shown hunting of albatrosses, cormorants and shearwaters from 5000 BP. This pressure has led to some species becoming extinct in many places; in particular, at least 20 species of an original 29 no longer breed on Easter Island. In the 19th century, the hunting of seabirds for fat deposits and feathers for the Hat, millinery trade reached industrial levels. wikt:muttonbirding, Muttonbirding (harvesting shearwater chicks) developed as important industries in both New Zealand and Tasmania, and the name of one species, the providence petrel, is derived from its seemingly miraculous arrival on Norfolk Island where it provided a windfall for starving European settlers. In the Falkland Islands, hundreds of thousands of penguins were harvested for their oil each year. Seabird eggs have also long been an important source of food for sailors undertaking long sea voyages, as well as being taken when settlements grow in areas near a colony. Eggers from San Francisco, California, San Francisco took almost half a million eggs a year from the Farallon Islands in the mid-19th century, a period in the islands' history from which the seabird species are still recovering. Both hunting and egging continue today, although not at the levels that occurred in the past, and generally in a more controlled manner. For example, the Māori people, Māori of Stewart Island/Rakiura continue to harvest the chicks of the sooty shearwater as they have done for centuries, using traditional stewardship, ''kaitiakitanga'', to manage the harvest, but now also work with the University of Otago in studying the populations. In Greenland, however, uncontrolled hunting is pushing many species into steep decline.


Other threats

Other human factors have led to declines and even extinctions in seabird populations and species. Of these, perhaps the most serious are introduced species. Seabirds, breeding predominantly on small isolated islands, are vulnerable to predators because they have lost many behaviours associated with defence from predators. Feral cats can take seabirds as large as albatrosses, and many introduced rodents, such as the Polynesian rat, Pacific rat, take eggs hidden in burrows. Introduced goats, cattle, rabbits and other herbivores can create problems, particularly when species need vegetation to protect or shade their young. The disturbance of breeding colonies by humans is often a problem as well—visitors, even well-meaning tourists, can flush brooding adults off a colony, leaving chicks and eggs vulnerable to predators. The build-up of toxins and pollutants in seabirds is also a concern. Seabirds, being apex predators, suffered from the ravages of the insecticide DDT until it was banned; DDT was implicated, for example, in embryo development problems and the skewed sex ratio of western gulls in southern California. Oil spills are also a threat to seabirds: the oil is toxic, and bird feathers become saturated by the oil, causing them to lose their waterproofing. Oil pollution in particular threatens species with restricted ranges or already depressed populations. Climate change mainly affect seabirds via changes to their habitat: various processes in the ocean lead to decreased availability of food and colonies are more often flooded as a consequence of sea level rise and extreme rainfall events. Heat stress from extreme temperatures is an additional threat. Some seabirds have used changing wind patterns to forage further and more efficiently.


Conservation

The threats faced by seabirds have not gone unnoticed by scientists or the conservation movement. As early as 1903, U.S. President Theodore Roosevelt was convinced of the need to declare Pelican Island National Wildlife Refuge, Pelican Island in Florida a National Wildlife Refuge to protect the bird colonies (including the nesting brown pelicans), and in 1909 he protected the Farallon Islands. Today many important seabird colonies are given some measure of protection, from Heron Island, Australia, Heron Island in Australia to Triangle Island in British Columbia. Island restoration techniques, pioneered by New Zealand, enable the removal of exotic invaders from increasingly large islands. Feral cats have been removed from Ascension Island, Arctic foxes from many islands in the Aleutian Islands, and rats from Campbell Island, New Zealand, Campbell Island. The removal of these introduced species has led to increases in numbers of species under pressure and even the return of extirpated ones. After the removal of cats from Ascension Island, seabirds began to nest there again for the first time in over a hundred years. Seabird mortality caused by Longline bycatch in Hawaii, long-line fisheries can be greatly reduced by techniques such as setting long-line bait at night, dying the bait blue, setting the bait underwater, increasing the amount of weight on lines and by using bird scarers, and their deployment is increasingly required by many national fishing fleets. One of the Millennium Projects in the UK was the Scottish Seabird Centre, near the important bird sanctuaries on Bass Rock, Fidra and the surrounding islands. The area is home to huge colonies of gannets, puffins, skuas and other seabirds. The centre allows visitors to watch live video from the islands as well as learn about the threats the birds face and how we can protect them, and has helped to significantly raise the profile of seabird conservation in the UK. Seabird tourism can provide income for coastal communities as well as raise the profile of seabird conservation, although it needs to be managed to ensure it does not harm the colonies and nesting birds. For example, the northern royal albatross colony at Taiaroa Head in New Zealand attracts 40,000 visitors a year. The plight of albatross and large seabirds, as well as other marine creatures, being taken as bycatch by long-line fisheries, has been addressed by a large number of non-governmental organizations (including BirdLife International, the American Bird Conservancy and the Royal Society for the Protection of Birds). This led to the Agreement on the Conservation of Albatrosses and Petrels, a legally binding treaty designed to protect these threatened species, which has been ratified by thirteen countries as of 2021 (Argentina, Australia, Brazil, Chile, Ecuador, France, New Zealand, Norway, Peru, South Africa, Spain, Uruguay, United Kingdom).


Role in culture

Many seabirds are little studied and poorly known because they live far out at sea and breed in isolated colonies. Some seabirds, particularly the albatrosses and gulls, are more well known to humans. The albatross has been described as "the most legendary of birds", and have a variety of myths and legends associated with them. While it is widely considered unlucky to harm them, the notion that sailors believed that is a myth that derives from Samuel Taylor Coleridge's famous poem, "The Rime of the Ancient Mariner", in which a sailor is punished for killing an albatross by having to wear its corpse around his neck. Sailors did, however, consider it unlucky to touch a storm petrel, especially one that landed on the ship. Gulls are one of the most commonly seen seabirds because they frequent human-made habitats (such as cities and landfill, dumps) and often show a fearless nature. Gulls have been used as metaphors, as in ''Jonathan Livingston Seagull'' by Richard Bach, or to denote a closeness to the sea; in ''The Lord of the Rings'', they appear in the insignia of Gondor and therefore Númenor (used in the design of the films), and they call Legolas to (and across) the sea. Pelicans have long been associated with mercy and altruism because of an early Christianity, Christian myth that they split open their breast to feed their starving chicks.


Seabird families

The following are the groups of birds normally classed as seabirds.
Sphenisciformes Penguins ( order Sphenisciformes , family In human society, family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of families ...
(Antarctic and southern waters; 16 species) * Spheniscidae
penguin Penguins (order (biology), order Sphenisciformes , family (biology), family Spheniscidae ) are a group of Water bird, aquatic flightless bird, flightless birds. They live almost exclusively in the southern hemisphere: only one species, the Gal ...

penguin
s
Procellariiformes Procellariiformes is an order Order or ORDER or Orders may refer to: * Orderliness Orderliness is associated with other qualities such as cleanliness Cleanliness is both the abstract state of being clean and free from germs, dirt, trash, or ...
(Tubenoses: pan-oceanic and pelagic; 93 species) * Diomedeidae
albatross Albatrosses are very large Seabird, seabirds in the family (biology), family Diomedeidae. They range widely in the Southern Ocean and the North Pacific Ocean, Pacific. They are absent from the North Atlantic Ocean, Atlantic, although fossil rem ...

albatross
es * Procellariidae
fulmar The fulmars are tubenosed seabirds of the family In human society A society is a Social group, group of individuals involved in persistent Social relation, social interaction, or a large social group sharing the same spatial or socia ...

fulmar
s, prion (bird), prions,
shearwater Shearwaters are medium-sized long-winged seabird Seabirds (also known as marine birds) are bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves , characterised by feathers, toothless beaked ...
s, gadfly petrel, gadfly and other
petrel Petrels are tube-nosed seabirds in the bird order Procellariiformes. Description The common name does not indicate relationship beyond that point, as "petrels" occur in three of the four families within that group (all except the albatross fa ...

petrel
s * Pelacanoididae
diving petrel The diving petrels (Genus ''Pelecanoides'') are seabird Seabirds (also known as marine birds) are bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves , characterised by feathers, toothless ...
s * Hydrobatidae
storm petrel Storm petrel may refer to one of two bird families In human society, family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relatio ...
s
Pelecaniformes The Pelecaniformes are an order Order or ORDER or Orders may refer to: * Orderliness Orderliness is associated with other qualities such as cleanliness Cleanliness is both the abstract state of being clean and free from germs, dirt, trash, or ...
(Worldwide; 8 species) * Pelecanidae pelicans
Suliformes The order Suliformes (, dubbed "Phalacrocoraciformes" by ''Christidis & Boles 2008'') is an order recognised by the International Ornithologist's Union. In regard to the recent evidence that the traditional Pelecaniformes is polyphyletic File:M ...
(Worldwide; about 56 species) * Sulidae
gannet Gannets are seabirds Seabirds (also known as marine birds) are bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves , characterised by feathers, toothless beaked jaws, the Oviparity, layi ...

gannet
s and booby, boobies * Phalacrocoracidae
cormorant Phalacrocoracidae is a family In human society, family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of families is to maintain ...

cormorant
s * Fregatidae
frigatebird Frigatebirds (also listed as "frigate bird", "frigate-bird", "frigate", "frigate-petrel") are a family In human society, family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (b ...
s Phaethontiformes (Worldwide tropical seas; 3 species) * Phaethontidae tropicbirds
Charadriiformes Charadriiformes (, from '' Charadrius'', the type genus Type may refer to: Science and technology Computing * Typing Typing is the process of writing or inputting text by pressing keys on a typewriter, computer keyboard, cell phone, or calcula ...

Charadriiformes
(Worldwide; 305 species, but only the families listed are classed as seabirds.) * Stercorariidae
skua The skuas are a group of predatory seabird Seabirds (also known as marine birds) are bird Birds are a group of warm-blooded vertebrates constituting the class Class or The Class may refer to: Common uses not otherwise categ ...

skua
s * Laridae
gull Gulls, or colloquially seagulls, are seabirds of the family Laridae in the suborder Lari. They are most closely related to the terns (family Sternidae) and only distantly related to auks, Skimmer (bird), skimmers and even more distantly to wade ...

gull
s * Sternidae
tern Terns are seabirds in the family (biology), family Laridae that have a worldwide distribution and are normally found near the sea, rivers, or wetlands. Terns are treated as a subgroup of the family Laridae which includes gulls and Skimmer (bir ...

tern
s * Rhynchopidae skimmers * Alcidae
auk An auk or alcid is a bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves , characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabo ...
s For an alternative taxonomy of these groups, see also Sibley-Ahlquist taxonomy.


References


Further reading

*


External links

*
Seabirds.net
A data portal for global seabird databases and information outlet for the World Seabird Union
Marine Ornithology, the Journal of Seabird Science and Conservation
{{Authority control Seabirds,