Seabirds (also known as marine birds) are
bird
Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...
s that are
adapted to life within the
marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking
convergent evolution
Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...
, as the same environmental problems and feeding
niches have resulted in similar adaptations. The first seabirds evolved in the
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...
period, 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 Period million years ago (Mya) to the beginning of ...
.
In general, seabirds live longer,
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 Taxonomy (biology), 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 individuals of ...
nest in
colonies
In modern parlance, 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 '' metropolitan state' ...
, 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 and Southern hemispheres. It is an imaginary line located at 0 degrees latitude, halfway between the North and South poles. The term can al ...
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, 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, guided
fishermen to fishing stocks and led
sailor
A sailor, seaman, mariner, or seafarer is a person who works aboard a watercraft as part of its crew, and may work in any one of a number of different fields that are related to the operation and maintenance of a ship.
The profession of the ...
s to land. Many species are currently
threatened by human activities, such as from
oil spill
An oil spill is the release of a liquid petroleum hydrocarbon into the environment, especially the marine ecosystem, due to human activity, and is a form of pollution. The term is usually given to marine oil spills, where oil is released into ...
s, getting trapped in nets, and by
climate change
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...
and severe weather.
Conservation 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; 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) and
Procellariiformes (
albatross
Albatrosses, of the biological family Diomedeidae, are large seabirds related to the procellariids, storm petrels, and diving petrels in the order Procellariiformes (the tubenoses). They range widely in the Southern Ocean and the North P ...
es and
petrels), all of the
Suliformes (
gannets and
cormorant
Phalacrocoracidae is a family of approximately 40 species of aquatic birds commonly known as cormorants and shags. Several different classifications of the family have been proposed, but in 2021 the IOC adopted a consensus taxonomy of seven ge ...
s) except the
darter
The darters, anhingas, or snakebirds are mainly tropical waterbirds in the family Anhingidae, which contains a single genus, ''Anhinga''. There are four living species, three of which are very common and widespread while the fourth is rarer and ...
s, and some of the
Charadriiformes
Charadriiformes (, from '' Charadrius'', the type genus of family Charadriidae) is a diverse order of small to medium-large birds. It includes about 390 species and has members in all parts of the world. Most charadriiform birds live near water ...
(the
skua
The skuas are a group of predatory seabirds with seven species forming the genus ''Stercorarius'', the only genus in the family Stercorariidae. The three smaller skuas, the long-tailed skua, the Arctic skua, and the pomarine skua are called j ...
s,
gull
Gulls, or colloquially seagulls, are seabirds of the family Laridae in the suborder Lari. They are most closely related to the terns and skimmers and only distantly related to auks, and even more distantly to waders. Until the 21st century, ...
s,
tern
Terns are seabirds in the 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 skimmers and consists o ...
s,
auks and
skimmer
Skimmer may refer to: Animals
*Skimmer (bird), a common name for birds in the genus ''Rynchops''
*Skimmer (dragonfly), a common name for dragonflies in the family Libellulidae
*Water strider or skimmer, a common name for insects in the family Ge ...
s) are classified as seabirds. The
phalaropes are usually included as well, since although they are
wader
245px, A flock of Red_knot.html" ;"title="Dunlins and Red knot">Dunlins and Red knots
Waders or shorebirds are birds of the order Charadriiformes commonly found wikt:wade#Etymology 1, wading along shorelines and mudflats in order to foraging, ...
s ("shorebirds" in North America), two of the three species (
Red and
Red-necked) are oceanic for nine months of the year, crossing the equator to feed pelagically.
Loons and
grebe
Grebes () are aquatic diving birds in the order Podicipediformes . Grebes are widely distributed freshwater birds, with some species also found in marine habitats during migration and winter. Some flightless species exist as well, most notably ...
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
The sea ducks (''Mergini'') are a tribe of the duck subfamily of birds, the Anatinae. The taxonomy of this group is incomplete. Some authorities separate the group as a subfamily, while others remove some genera. Most species within the group ...
in the family
Anatidae 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 birds in the family Ardeidae, with 72 recognised species, some of which are referred to as egrets or bitterns rather than herons. Members of the genera ''Botaurus'' and ''Ixobrychu ...
s are also highly marine, living on the sea's edge (coast), but are also not treated as seabirds.
Sea eagles and other fish-eating birds of prey are also typically excluded, however tied to marine environments they may be.
German paleontologist
Gerald Mayr defined the "core waterbird" clade
Aequornithes in 2010. This lineage gives rise to the
Gaviiformes,
Sphenisciformes, Procellariiformes,
Ciconiiformes, Suliformes and
Pelecaniformes.
The tropicbirds are part of a lineage—
Eurypygimorphae—that is a
sister group
In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, 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 ...
to the Aequornithes.
Evolution and fossil record
Seabirds, by virtue of living in a
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 transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sa ...
s are readily laid down), are well represented in the
fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
record.
They are first known to occur in the
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...
period, the earliest being the
Hesperornithiformes
Hesperornithes is an extinct and highly specialized group of aquatic avialans closely related to the ancestors of modern birds. They inhabited both marine and freshwater habitats in the Northern Hemisphere, and include genera such as ''Hesperorni ...
, 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.
While ''Hesperornis'' is not thought to have left descendants, the earliest
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 Period million years ago (Mya) to the beginning of ...
both pterosaurs and marine reptiles became extinct, allowing seabirds to expand ecologically. These post-extinction seas were dominated by early
Procellariidae, giant
penguin
Penguins ( order Sphenisciformes , family Spheniscidae ) are a group of aquatic flightless birds. They live almost exclusively in the Southern Hemisphere: only one species, the Galápagos penguin, is found north of the Equator. Highly adapt ...
s and two
extinct families, the
Pelagornithidae and the
Plotopteridae (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 of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recent" ...
, although the
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...
''
Puffinus'' (which includes today's
Manx shearwater and
sooty shearwater
The sooty shearwater (''Ardenna grisea'') is a medium-large shearwater in the seabird family Procellariidae. In New Zealand, it is also known by its Māori name , and as muttonbird, like its relatives the wedge-tailed shearwater (''A. pacif ...
) might date back to the
Oligocene
The Oligocene ( ) is a geologic epoch of the Paleogene 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 the epoch are well identified but ...
.
Within the Charadriiformes, the gulls and allies (
Lari
Lari may refer to:
Currency
* Georgian lari, the currency of Georgia
* Maldivian laari, or lari, a coin denomination of the rufiyaa of the Maldives
Places
*Lari Constituency, an electoral constituency in Kenya
* Lari, Ardabil, or Lahrud, a ...
) became seabirds in the late Eocene, and then waders in the middle Miocene (
Langhian).
The highest diversity of seabirds apparently existed during the Late Miocene and the
Pliocene
The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58[food 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 system. Ecologists can broadly lump all life forms into one ...](_blank)
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 that produces lift while moving through air or some other fluid. Accordingly, wings have streamlined cross-sections that are subject to aerodynamic forces and act as airfoils. A wing's aerodynamic efficiency is exp ...
morphology has been shaped by the
niche an individual species or family has
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 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 from the family Diomedeidae, which has a circumpolar range in the Southern Ocean. It was the last species of albatross to be de ...
, 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 in which pilots fly unpowered aircraft known as gliders or sailplanes using naturally occurring currents of rising air in the atmosphere to remain airborne. The word ''soaring'' is ...
called
dynamic soaring (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 with interdigital membranes (webbings) that aids in aquatic locomotion, present in a variety of tetrapod vertebrates. This adaptation is primarily found in semiaquatic species, and has convergently evolved m ...
, to aid movement on the surface as well as assisting diving in some species. The
Procellariiformes are unusual among birds in having a strong
sense of smell, 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 composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quanti ...
they ingest by drinking and feeding (particularly on
crustacean
Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean gro ...
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
is eliminated from an organism. In vertebrates this is primarily carried out by the lungs, kidneys, and skin. This is in contrast with secretion, where the substance may have specific tasks afte ...
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 in the middle of the face. The nasal septum divides the cavity into two cavities, also known as fossae. Each cavity is the continuation of one of the two nostrils. The nasal ...
) are almost pure
sodium chloride
Sodium chloride , commonly known as salt (although sea salt also contains other chemical salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With molar masses of 22.99 and 35 ...
.
With the exception of the
cormorant
Phalacrocoracidae is a family of approximately 40 species of aquatic birds commonly known as cormorants and shags. Several different classifications of the family have been proposed, but in 2021 the IOC adopted a consensus taxonomy of seven ge ...
s and some terns, and in common with most other birds, all seabirds have waterproof
plumage
Plumage ( "feather") is a layer of feathers that covers a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage differ between species and subspecies and may vary with age classes. Within species, ...
. 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 feathers. 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 force exerted by a fluid that opposes the weight 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 p ...
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's spotted coat, the b ...
, both defensive (the colour of US Navy
The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...
battleships 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 study of functions and mechanisms in a living system. As a sub-discipline of biology, physiology focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out the chemic ...
and behaviour have been shaped by their diet. 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 of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...
, 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; 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 often concentrates food such as 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 ...
, squid
True squid are molluscs with an elongated soft body, large eyes, eight arms, and two tentacles in the superorder Decapodiformes, though many other molluscs within the broader Neocoleoidea are also called squid despite not strictly fitting ...
, 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
Flying may refer to:
* Flight, the process of flying
* Aviation, the creation and operation of aircraft
Music
Albums
* ''Flying'' (Grammatrain album), 1997
* ''Flying'' (Jonathan Fagerlund album), 2008
* ''Flying'' (UFO album), 1971
* ''Fl ...
(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 order Procellariiformes. The gadfly petrels are named for their speedy weaving flight, as if evading gadflies ( horseflies). The flight action is ...
s, frigatebird
Frigatebirds are a family of seabirds called Fregatidae which are found across all tropical and subtropical oceans. The five extant species are classified in a single genus, ''Fregata''. All have predominantly black plumage, long, deeply forke ...
s, and storm petrels), and surface feeding while swimming (examples of which are practiced by fulmars, gull
Gulls, or colloquially seagulls, are seabirds of the family Laridae in the suborder Lari. They are most closely related to the terns and skimmers and only distantly related to auks, and even more distantly to waders. Until the 21st century, ...
s, many of the shearwaters 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
Skimmer may refer to: Animals
*Skimmer (bird), a common name for birds in the genus ''Rynchops''
*Skimmer (dragonfly), a common name for dragonflies in the family Libellulidae
*Water strider or skimmer, a common name for insects in the family Ge ...
, 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 proteins that have the ability to transmit their misfolded shape onto normal variants of the same protein. They characterize several fatal and transmissible neurodegenerative diseases in humans and many other animals. It ...
have special bills with filters called lamellae to filter out plankton
Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a cr ...
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 generation of force by any combination of pushing or pulling to modify the translational motion of an object, which is typically a rigid body (or an articulated rigid body) but may also concern a fluid. The term is derived from ...
is provided by wings (as used by penguins, auks, diving petrels and some other species of petrel) or feet (as used by cormorants, grebe
Grebes () are aquatic diving birds in the order Podicipediformes . Grebes are widely distributed freshwater birds, with some species also found in marine habitats during migration and winter. Some flightless species exist as well, most notably ...
s, loons and several types of fish-eating duck
Duck is the common name for numerous species of waterfowl in the family Anatidae. Ducks are generally smaller and shorter-necked than swans and geese, which are members of the same family. Divided among several subfamilies, they are a fo ...
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 and the only extant member of the genus '' Alca'' of the family Alcidae, the auks. It is the closest living relative of the extinct great auk (''Pinguinis i ...
(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 shearwaters 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 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 albatrosses 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, boobies, tropicbirds, some terns, and brown pelican
The brown pelican (''Pelecanus occidentalis'') is a bird of the pelican family, Pelecanidae, one of three species found in the Americas and one of two that feed by diving into water. It is found on the Atlantic Coast from New Jersey to the mo ...
s all engage in plunge diving, taking fast-moving prey by diving into the water from the 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 tropical
The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in
the Southern Hemisphere at S. The tropics are also referred to ...
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
A guild ( ) is an association of artisans and merchants who oversee the practice of their craft/trade in a particular area. The earliest types of guild formed as organizations of tradesmen belonging to a professional association. They sometimes ...
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 dolphin
A dolphin is an aquatic mammal within the infraorder Cetacea. Dolphin species belong to the families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontoporiidae (t ...
s and tuna
A tuna is a saltwater fish that belongs to the tribe Thunnini, a subgrouping of the Scombridae ( mackerel) family. The Thunnini comprise 15 species across five genera, the sizes of which vary greatly, ranging from the bullet tuna (max le ...
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. Kleptoparasites are seabirds that make a part of their living stealing food of other seabirds. Most famously, frigatebird
Frigatebirds are a family of seabirds called Fregatidae which are found across all tropical and subtropical oceans. The five extant species are classified in a single genus, ''Fregata''. All have predominantly black plumage, long, deeply forke ...
s and skua
The skuas are a group of predatory seabirds with seven species forming the genus ''Stercorarius'', the only genus in the family Stercorariidae. The three smaller skuas, the long-tailed skua, the Arctic skua, and the pomarine skua are called j ...
s engage in this behaviour, although gulls, terns and other species will steal food opportunistically. The nocturnal
Nocturnality is an ethology, animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnality, diurnal meaning the opposite.
Nocturnal creatures generally have ...
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 frigatebird
The great frigatebird (''Fregata minor'') is a large seabird in the frigatebird family. There are major nesting populations in the tropical Pacific (including the Galapagos Islands) and Indian Oceans, as well as a tiny population in the South ...
s stealing from 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
Carrion () is the decaying flesh of dead animals, including human flesh.
Overview
Carrion is an important food source for large carnivores and omnivores in most ecosystems. Examples of carrion-eaters (or scavengers) include crows, vultures ...
when the opportunity arises, as will giant petrels. Some species of albatross also engage in scavenging: an analysis of regurgitated squid
True squid are molluscs with an elongated soft body, large eyes, eight arms, and two tentacles in the superorder Decapodiformes, though many other molluscs within the broader Neocoleoidea are also called squid despite not strictly fitting ...
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 a year, unless they lose the first (with a few exceptions, like the Cassin's auklet), and many species (like the tubenoses and 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
Fledging is the stage in a flying animal's life between hatching or birth and becoming capable of flight.
This term is most frequently applied to birds, but is also used for bats. For altricial birds, those that spend more time in vulnera ...
, 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 monogamous. Many species, such as gulls, auks and penguins, retain the same mate for several seasons, and many 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
The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...
) and in the polar latitudes (as in Antarctica
Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest co ...
). 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 separation. Seabirds can nest in trees (if any are available), on the ground (with or without nests), on cliffs, in burrow
An Eastern chipmunk at the entrance of its burrow
A burrow is a hole or tunnel excavated into the ground by an animal to construct a space suitable for habitation or temporary refuge, or as a byproduct of locomotion. Burrows provide a form of s ...
s 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
Fidelity is the quality of faithfulness or loyalty. Its original meaning regarded duty in a broader sense than the related concept of ''fealty''. Both derive from the Latin word ''fidēlis'', meaning "faithful or loyal". In the City of London ...
, 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
Philopatry is the tendency of an organism to stay in or habitually return to a particular area. The causes of philopatry are numerous, but natal philopatry, where animals return to their birthplace to breed, may be the most common. The term derive ...
, 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 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 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 migrate
Migration, migratory, or migrate may refer to: Human migration
* Human migration, physical movement by humans from one region to another
** International migration, when peoples cross state boundaries and stay in the host state for some minimum le ...
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 and Southern hemispheres. It is an imaginary line located at 0 degrees latitude, halfway between the North and South poles. The term can al ...
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
Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...
, 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 in the seabird family Procellariidae. In New Zealand, it is also known by its Māori name , and as muttonbird, like its relatives the wedge-tailed shearwater (''A. pacif ...
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
An old-growth forestalso termed primary forest, virgin forest, late seral forest, primeval forest, or first-growth forestis a forest that has attained great age without significant disturbance, and thereby exhibits unique ecological feature ...
, seeking huge conifer
Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single extant class, Pinopsida. All ex ...
s 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
Pelicans (genus ''Pelecanus'') are a genus of large water birds that make up the family Pelecanidae. They are characterized by a long beak and a large throat pouch used for catching prey and draining water from the scooped-up contents before ...
, 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 agricultural
Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled peopl ...
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
In physical geography, tundra () is a type of biome where tree growth is hindered by frigid temperatures and short growing seasons. The term ''tundra'' comes through Russian (') from the Kildin Sámi word (') meaning "uplands", "treeless mo ...
, as skuas and phalaropes do, will migrate over land as well.
The more marine species, such as petrels, auks and gannets, 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 storm
A storm is any disturbed state of the natural environment or the atmosphere of an astronomical body. It may be marked by significant disruptions to normal conditions such as strong wind, tornadoes, hail, thunder and lightning (a thunderstorm), ...
s, an event known as a ''wreck''.
Relationship with humans
Seabirds and fisheries
Seabirds have had a long association with both fisheries and sailor
A sailor, seaman, mariner, or seafarer is a person who works aboard a watercraft as part of its crew, and may work in any one of a number of different fields that are related to the operation and maintenance of a ship.
The profession of the ...
s, and both have drawn benefits and disadvantages from the relationship.
Fishermen have traditionally used seabirds as indicators of both fish shoals, underwater banks that might indicate fish stocks, and of potential landfall. In fact, the known association of seabirds with land was instrumental in allowing the Polynesia
Polynesia () "many" and νῆσος () "island"), to, Polinisia; mi, Porinihia; haw, Polenekia; fj, Polinisia; sm, Polenisia; rar, Porinetia; ty, Pōrīnetia; tvl, Polenisia; tkl, Polenihia (, ) is a subregion of Oceania, made up of ...
ns 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
Guano (Spanish from qu, wanu) is the accumulated excrement of Seabird, seabirds or bats. As a manure, guano is a highly effective fertilizer due to the high content of nitrogen, phosphate, and potassium, all key nutrients essential for plant ...
from colonies of seabirds acting as fertilizer
A fertilizer (American English) or fertiliser (British English; see spelling differences) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from ...
for the surrounding seas.
Negative effects on fisheries are mostly restricted to raiding by birds on aquaculture
Aquaculture (less commonly spelled aquiculture), also known as aquafarming, is the controlled cultivation ("farming") of aquatic organisms such as fish, crustaceans, mollusks, algae and other organisms of value such as aquatic plants (e.g. lotus ...
, although long-lining fisheries also have to deal with bait
Bait may refer to:
General
* Bait (luring substance), bait as a luring substance
** Fishing bait, bait used for fishing
Film
* ''Bait'' (1950 film), a British crime film by Frank Richardson
* ''Bait'' (1954 film), an American noir film by Hu ...
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 mammal
Marine mammals are aquatic mammals that rely on the ocean and other marine ecosystems for their existence. They include animals such as Pinniped, seals, Cetacea, whales, Sirenia, manatees, sea otters and polar bears. They are an informal group, ...
s and predatory fish (like tuna
A tuna is a saltwater fish that belongs to the tribe Thunnini, a subgrouping of the Scombridae ( mackerel) family. The Thunnini comprise 15 species across five genera, the sizes of which vary greatly, ranging from the bullet tuna (max le ...
).
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
The North Sea lies between Great Britain, Norway, Denmark, Germany, the Netherlands and Belgium. An epeiric sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian S ...
, 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
The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the European mainland, continental mainland. It comprises England, Scotlan ...
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
Hunting is the human practice of seeking, pursuing, capturing, or killing wildlife or feral animals. The most common reasons for humans to hunt are to harvest food (i.e. meat) and useful animal products ( fur/ hide, bone/ tusks, horn/ a ...
of seabirds and the collecting of seabird eggs have contributed to the declines of many species, and the extinction of several, including the great auk
The great auk (''Pinguinus impennis'') is a species of flightless alcid that became extinct in the mid-19th century. It was the only modern species in the genus ''Pinguinus''. It is not closely related to the birds now known as penguins, w ...
and the spectacled cormorant
The spectacled cormorant or Pallas's cormorant (''Urile perspicillatus'') is an extinct marine bird of the cormorant family of seabirds that inhabited Bering Island and possibly other places in the Komandorski Islands and the nearby coast of Ka ...
. Seabirds have been hunted for food by coastal peoples throughout history—one of the earliest instances known is in southern Chile, where archaeological
Archaeology or archeology is the scientific study of human activity through the recovery and analysis of material culture. The archaeological record consists of artifacts, architecture, biofacts or ecofacts, sites, and cultural landscape ...
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
Easter Island ( rap, Rapa Nui; es, Isla de Pascua) is an island and special territory of Chile in the southeastern Pacific Ocean, at the southeasternmost point of the Polynesian Triangle in Oceania. The island is most famous for its nearl ...
. In the 19th century, the hunting of seabirds for fat deposits and feathers for the millinery trade reached industrial levels. 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
Norfolk Island (, ; Norfuk: ''Norf'k Ailen'') is an external territory of Australia located in the Pacific Ocean between New Zealand and New Caledonia, directly east of Australia's Evans Head and about from Lord Howe Island. Together w ...
where it provided a windfall for starving European settlers. In the Falkland Islands
The Falkland Islands (; es, Islas Malvinas, link=no ) is an archipelago in the South Atlantic Ocean on the Patagonian Shelf. The principal islands are about east of South America's southern Patagonian coast and about from Cape Dubou ...
, 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
San Francisco (; Spanish language, Spanish for "Francis of Assisi, Saint Francis"), officially the City and County of San Francisco, is the commercial, financial, and cultural center of Northern California. The city proper is the List of Ca ...
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 of Stewart Island/Rakiura
Stewart Island ( mi, Rakiura, ' glowing skies', officially Stewart Island / Rakiura) is New Zealand's third-largest island, located south of the South Island, across the Foveaux Strait. It is a roughly triangular island with a total land a ...
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
, image_name = University of Otago Registry Building2.jpg
, image_size =
, caption = University clock tower
, motto = la, Sapere aude
, mottoeng = Dare to be wise
, established = 1869; 152 years ago
, type = Public research collegiate u ...
in studying the populations. In Greenland
Greenland ( kl, Kalaallit Nunaat, ; da, Grønland, ) is an island country in North America that is part of the Kingdom of Denmark. It is located between the Arctic and Atlantic oceans, east of the Canadian Arctic Archipelago. Greenland is ...
, 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
An introduced species, alien species, exotic species, adventive species, immigrant species, foreign species, non-indigenous species, or non-native species is a species living outside its native distributional range, but which has arrived the ...
. Seabirds, breeding predominantly on small isolated islands, are vulnerable to predators because they have lost many behaviours associated with defence from predators. Feral cat
A feral cat or a stray cat is an unowned domestic cat (''Felis catus'') that lives outdoors and avoids human contact: it does not allow itself to be handled or touched, and usually remains hidden from humans. Feral cats may breed over dozens ...
s can take seabirds as large as albatrosses, and many introduced rodents, such as the Pacific rat, take eggs hidden in burrows. Introduced goats, cattle, rabbits and other herbivore
A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthp ...
s 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 spill
An oil spill is the release of a liquid petroleum hydrocarbon into the environment, especially the marine ecosystem, due to human activity, and is a form of pollution. The term is usually given to marine oil spills, where oil is released into ...
s 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
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...
mainly affect seabirds via changes to their habitat
In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...
: various processes in the ocean lead to decreased availability of food and colonies are more often flooded as a consequence of sea level rise
Globally, sea levels are rising due to human-caused climate change. Between 1901 and 2018, the globally averaged sea level rose by , or 1–2 mm per year on average.IPCC, 2019Summary for Policymakers InIPCC Special Report on the Ocean and Cry ...
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
The conservation movement, also known as nature conservation, is a political, environmental, and social movement that seeks to manage and protect natural resources, including animal, fungus, and plant species as well as their habitat for the f ...
. As early as 1903, U.S. President Theodore Roosevelt
Theodore Roosevelt Jr. ( ; October 27, 1858 – January 6, 1919), often referred to as Teddy or by his initials, T. R., was an American politician, statesman, soldier, conservationist, naturalist, historian, and writer who served as the 26t ...
was convinced of the need to declare Pelican Island in Florida a National Wildlife Refuge
National Wildlife Refuge System is a designation for certain protected areas of the United States managed by the United States Fish and Wildlife Service. The National Wildlife Refuge System is the system of public lands and waters set aside to ...
to protect the bird colonies (including the nesting brown pelican
The brown pelican (''Pelecanus occidentalis'') is a bird of the pelican family, Pelecanidae, one of three species found in the Americas and one of two that feed by diving into water. It is found on the Atlantic Coast from New Jersey to the mo ...
s), and in 1909 he protected the Farallon Islands. Today many important seabird colonies are given some measure of protection, from Heron Island Heron Island may refer to:
*Heron Island (Queensland), in Australia
*Heron Island (New Brunswick), in Baie des Chaleurs, Canada
* Heron Island (Quebec), in the Saint Lawrence River, Canada
* Heron Island, Berkshire, on the River Thames, England
* H ...
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
Ascension Island is an isolated volcanic island, 7°56′ south of the Equator in the South Atlantic Ocean. It is about from the coast of Africa and from the coast of South America. It is governed as part of the British Overseas Territory o ...
, Arctic foxes from many islands in the Aleutian Islands
The Aleutian Islands ( ; ; ale, Unangam Tanangin, "land of the Aleuts"; possibly from the Chukchi ''aliat'', or "island")—also called the Aleut Islands, Aleutic Islands, or, before 1867, the Catherine Archipelago—are a chain of 14 main, ...
, and rats from 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 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, puffin
Puffins are any of three species of small alcids ( auks) in the bird genus ''Fratercula''. These are pelagic seabirds that feed primarily by diving in the water. They breed in large colonies on coastal cliffs or offshore islands, nesting in c ...
s, 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
The northern royal albatross or toroa, (''Diomedea sanfordi''), is a large seabird in the albatross family. It was split from the closely related southern royal albatross as recently as 1998, though not all scientists support that conclusion and ...
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 organization
A non-governmental organization (NGO) or non-governmental organisation (see American and British English spelling differences#-ise, -ize (-isation, -ization), spelling differences) is an organization that generally is formed independent from g ...
s (including BirdLife International
BirdLife International is a global partnership of non-governmental organizations that strives to conserve birds and their habitats. BirdLife International's priorities include preventing extinction of bird species, identifying and safeguarding ...
, the American Bird Conservancy and the Royal Society for the Protection of Birds
The Royal Society for the Protection of Birds (RSPB) is a charitable organisation registered in England and Wales and in Scotland. It was founded in 1889. It works to promote conservation and protection of birds and the wider environment throu ...
). This led to the Agreement on the Conservation of Albatrosses and Petrels
The Agreement on the Conservation of Albatrosses and Petrels (ACAP) is a legally binding international agreement signed in 2001 and entered into force on 1 February 2004 when South Africa ratified as the fifth Party to the Agreement.
It was crea ...
, 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
Samuel Taylor Coleridge (; 21 October 177225 July 1834) was an English poet, literary critic, philosopher, and theologian who, with his friend William Wordsworth, was a founder of the Romantic Movement in England and a member of the Lak ...
'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 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
''The Lord of the Rings'' is an Epic (genre), epic high-fantasy novel by English author and scholar J. R. R. Tolkien. Set in Middle-earth, intended to be Earth at some time in the distant past, the story began as a sequel to Tolkien's 1937 c ...
'', they appear in the insignia of Gondor
Gondor is a fictional kingdom in J. R. R. Tolkien's writings, described as the greatest realm of Men in the west of Middle-earth at the end of the Third Age. The third volume of ''The Lord of the Rings'', '' The Return of the King'', is large ...
and therefore Númenor (used in the design of the films), and they call Legolas
Legolas (pronounced ) is a fictional character in J. R. R. Tolkien's ''The Lord of the Rings''. He is a Sindar Elf of the Woodland Realm and one of the nine members of the Fellowship who set out to destroy the One Ring. He and the Dwarf Gimli ...
to (and across) the sea. Pelicans have long been associated with mercy and altruism
Altruism is the moral principle, principle and moral courage, moral practice of concern for the welfare and/or happiness of other human kind, human beings or animals, resulting in a quality of life both material and spirituality, spiritual. It ...
because of an early Christian
Christians () are people who follow or adhere to Christianity, a monotheistic Abrahamic religion based on the life and teachings of Jesus Christ. The words '' Christ'' and ''Christian'' derive from the Koine Greek title ''Christós'' (Χρ ...
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 (Antarctic and southern waters; 16 species)
* Spheniscidae penguin
Penguins ( order Sphenisciformes , family Spheniscidae ) are a group of aquatic flightless birds. They live almost exclusively in the Southern Hemisphere: only one species, the Galápagos penguin, is found north of the Equator. Highly adapt ...
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Procellariiformes (Tubenoses: pan-oceanic and pelagic; 93 species)
* Diomedeidae albatross
Albatrosses, of the biological family Diomedeidae, are large seabirds related to the procellariids, storm petrels, and diving petrels in the order Procellariiformes (the tubenoses). They range widely in the Southern Ocean and the North P ...
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* Procellariidae fulmars, prions
Prions are misfolded proteins that have the ability to transmit their misfolded shape onto normal variants of the same protein. They characterize several fatal and transmissible neurodegenerative diseases in humans and many other animals. It ...
, shearwaters, gadfly
Gadfly most commonly refers to:
* Horse-fly or Botfly
* Gadfly (philosophy and social science), a person who upsets the status quo
Gadfly may also refer to:
Entertainment
* ''The Gadfly'', an 1897 novel by Ethel Lilian Voynich
** ''The Gadfly'' ...
and other petrels
* Pelacanoididae diving petrels
* Hydrobatidae storm petrels
Pelecaniformes (Worldwide; 8 species)
* Pelecanidae pelican
Pelicans (genus ''Pelecanus'') are a genus of large water birds that make up the family Pelecanidae. They are characterized by a long beak and a large throat pouch used for catching prey and draining water from the scooped-up contents before ...
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Suliformes (Worldwide; about 56 species)
* Sulidae gannets and boobies
* Phalacrocoracidae cormorant
Phalacrocoracidae is a family of approximately 40 species of aquatic birds commonly known as cormorants and shags. Several different classifications of the family have been proposed, but in 2021 the IOC adopted a consensus taxonomy of seven ge ...
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* Fregatidae frigatebird
Frigatebirds are a family of seabirds called Fregatidae which are found across all tropical and subtropical oceans. The five extant species are classified in a single genus, ''Fregata''. All have predominantly black plumage, long, deeply forke ...
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Phaethontiformes (Worldwide tropical seas; 3 species)
* Phaethontidae tropicbirds
Charadriiformes
Charadriiformes (, from '' Charadrius'', the type genus of family Charadriidae) is a diverse order of small to medium-large birds. It includes about 390 species and has members in all parts of the world. Most charadriiform birds live near water ...
(Worldwide; 305 species, but only the families listed are classed as seabirds.)
* Stercorariidae skua
The skuas are a group of predatory seabirds with seven species forming the genus ''Stercorarius'', the only genus in the family Stercorariidae. The three smaller skuas, the long-tailed skua, the Arctic skua, and the pomarine skua are called j ...
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* Laridae gull
Gulls, or colloquially seagulls, are seabirds of the family Laridae in the suborder Lari. They are most closely related to the terns and skimmers and only distantly related to auks, and even more distantly to waders. Until the 21st century, ...
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* Sternidae tern
Terns are seabirds in the 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 skimmers and consists o ...
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* Rhynchopidae skimmer
Skimmer may refer to: Animals
*Skimmer (bird), a common name for birds in the genus ''Rynchops''
*Skimmer (dragonfly), a common name for dragonflies in the family Libellulidae
*Water strider or skimmer, a common name for insects in the family Ge ...
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* Alcidae auks
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
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