Bird of sea

The term bird of sea returns to a unit in extreme cases rather badly definite: actually, the definition of the group results more than one kind of consensus - not to say a tradition - on the species to be included and those to exclude, only on rules taxonomic, biological or ecological strict. One usually classifies in this group approximately 275 species belonging to 8 families, maintaining with the seamen circle the extremely variable relations.

Beyond the extraordinary variety of the sizes, structures or modes of food, the marine birds share a certain number of characteristics common imposed by the life in aquatic environments to the climatic conditions sometimes very aggressive, without it being often possible to be withdrawn from it: particular structure of the plumage, aptitude for displacement on and in water, longevity, behaviors reproductive, etc They have in particular almost all tendency to nest in dense colonies on the littoral.

Species concerned

Uncertainty on the full number of birds of sea has two origins.

Of the divergences on the specific statute of such or such form. For example, according to whether one regards some albatross species with whole share or as Sous-espèce S of other albatross ( Diomedea exulans , D. epomorpha , D. melanophrys , D. cauta and D. chlororhynchos ), the number of species in this only family varies from 13 to 21.
the integration or not of certain kinds or families (Phalarope marine S, ducks, dive S, etc) in the category of the birds of sea.

The only possible definition of a bird of sea is the following one: a bird which draws whole or part from its food of the sea. Such a definition is not however universally valid since certain species classified in the group feed at sea only in a marginal way or at all (certain Laridae in particular), whereas birds passing of long periods of their annual cycle in seamen circle do not appear in it (dives, marine ducks).

On this basis, one notes that all the marine birds belong today to the order of the Ciconiiformes (classification of Sibley and Monroe). The degree of dependence of the various families with respect to the oceanic habitats is however very variable.

the families of the Phaethontidae , of the Sulidae , the Fregatidae of the Spheniscidae and the Procellariidae comprise only marine species. In the family of the laridé S, the Labbe S ( Stercorariini ), the Nozzle-in-scissors ( Rynchopini ) and the Alcidés are them also exclusively marine.
Three families comprise at the same time marine and continental species. Although attending fresh water especially (2 species only are strictly marine), the Pélican S are integrated into the birds of sea. The cormorants, them, are very mainly sailors (28 species on forty). In fact the laridé S present the most complex situation. In the group of the Seagull S and Gull S ( Larini ), the majority are maritime or sailors, at least partially or except period of reproduction; some species are however strictly continental. In the tribe of the Sternini , the Noddi S are strictly sailors whereas the Guifette S are almost exclusively continental; the Sterne S in a strict sense count more marine species than of species confined with fresh water.

Characteristics of the birds of sea

Whatever their degree of dependence with respect to the seamen circle, the birds of sea cannot strictly speaking be regarded as watery organizations. They indeed form part of some groups of Vertébrés Tétrapodes which evolved/moved to take preferentially or exclusively their water supply full. None of these animals of terrestrial origin, marine tortoises, snakes Hydrophiidae, water birds and marine mammals, has in fact acquired the possibility of breathing in water; they preserved all their lungs, and thus depend on surface for their breathing. In addition, only the Cetacea and the Siréniens became completely independent of the terrestrial environment, never not leaving water, even for the Parturition. Like the seals and the animals Oviparous animals (tortoises, snakes), the birds of sea must necessarily regain the dry land for the laying. Lastly, of all these animals, they are those which are most dependant on the terrestrial environment since, contrary to the snakes and the tortoises, they must ensure themselves the incubation eggs and the breeding of chicks until their independence. For this reason, they are constrained to remain with ground for periods often very long.

Description

The range of the sizes of the marine birds is extremely wide. Whereas smallest, the océanite minute ( Oceanodroma microsoma ) measurement less than 15 cm for a weight slightly lower than 20 G, the albatross hurlor ( Diomedea exulans ) can reach 1,30 m for a weight exceeding 11 kg in certain males; this bird also holds the record of Envergure for the current birds, with more than 3,50 Mr.

The plumage

Coloring

The most obvious characteristic of the plumage of the birds of sea is the general absence of bright colors. Some species are certainly coloured, but the bright colors are generally carried by the nozzle (Macareux or Goéland S for example), the legs (insane S, gull S) or of the particular structures as the pocket gulaire - deprived of feathers - frigate S. the plumage itself is almost systematically a combination of colors white, black, gray or brown. The rare exceptions to this rule relate to small cheecks of feathers gilded on the head of certain penguins (gorfou S) or Alcidé S of the Pacific (crested Macareux).

One wondered a long time about the significance of this general characteristic. Interpretation most traditional advance the idea that it would be cryptic colorings allowing a kind of camouflage opposite at the same time of their predatory and their preys. One for example pointed out that the coloring of the prion of desolation was the same one as that of the buildings of the Royal Navy . In addition, the coloring almost systematically white of the belly of these birds Piscivore S would make them less visible for the fish of which they are nourished.

Sealing

Like all the water birds, but more than the continental species because of their presence on all the seas of the sphere, including in the marine polar regions, birds, organizations Homéotherme S, are subjected at the height to be able of cooling of water. Their capacity to colonize oceanic spaces, it to survive and to feed under water closely depends on their aptitude to resist the strong thermal stresses which the life in these mediums supposes. The sealing of the plumage their is thus essential. It prohibits the liquid element from coming directly into contact with the skin. Better, it spares between the surface of the feathers and the body a layer of air which, with the sleeping bag, ensures the thermo isolation of the animal as well as possible at the same time as it contributes in a way essential with its Flottabilité.

One realized very early exceptional impermeability of the feathers of the birds of sea. At the beginning of the century, it was even used as model for the settling of the first impermeable clothing. The mechanism of the sealing makes however debate. In spite of the report that, in accordance with the textile model, the only fitting of the feathers (intersection of the barbs and barbules) could be enough to explain the sealing, one believed a long time that this one was due to the presence of the secretion uropygienne daily applied to the whole of the plumage by the birds during their long meetings of Toilettage. This idea, from now on largely given up, perdure today in many publications to the use of the public. At the time of the first large oil slicks, this design was at the origin of radical errors in the techniques of cleaning of the mazoutés birds; that led to the total failure of certain attempts at rehabilitation, in particular at the time of the incident of the Torrey Canyon in 1967.

The question of the impermeability of the plumage of the Cormorant S.A. a long time be in the middle of this debate. At the conclusion of their meetings of fishing, these water birds spend long moments indeed on resting places, the spread out wings; their plumage is obviously wet and this behavior was consequently legitimately interpreted like a phase of drying. Many assumptions were put forth to try to explain this apparent paradox which a water bird constitutes with the nontight plumage. Errors now contradicted were even hawked on this subject - and remain widespread - as the alleged absence of gland uropygienne at these birds or its Atrophie. It is only into 2005 that the enigma was solved. The plumage of the cormorants is quite impermeable, which is altogether logical for a plunger species. On the other hand, the feathers consist of an external layer mouillable, and an internal layer which is not it. The plumage is thus wet only in surface : not more than in the other water birds, water does not cross the barrier of the plumage nor thus does not invade the insulating layer of air.

The stroke and the diving

Swim on the surface

With one moment or another of their evolutionary history, all the birds of sea developed adaptations to the stroke on the surface. The exceptional sealing of the plumage in is one, which conditions their buoyancy. But testifies some also the universal existence to palmations, including at most marine of the Limicole S which are the Phalarope S.

Some however have recourse little there, or at all, because of a primarily air lifestyle, in particular for the food. It is especially the case for the frigate S which, in spite of very deep-sea practices and especially developed palmations, are never posed on the sea. It is also true, though with a less degree, for the Labbe S which hardly drive out but with the flight, or the ground in period of reproduction. All the other groups are posed readily on water and move there easily.

In fact, the majority of the species attend only surface or a section of water exceeding only little the length of their body. They are very light birds, of which buoyancy is very high: seagulls, terns, nozzles out of scissors, océanites, fulmars, etc the penetration in the water mass indeed poses with the birds very particular problems because of their intrinsic lightness. This one is dependant at the same time on their adaptation to the flight and the air space located under the feathers which ensures their thermo isolation and their buoyancy. To plunge so much is little deeply thus represents for them a true difficulty and an important energy expenditure to overcome the forces tending to bring back them on the surface.

Dive

Some species reach moderate depths (less 10 m) while plunging in flight of a certain altitude. The speed acquired during piqué is generally enough, but a complement of propulsion can sometimes be obtained by means of the legs and of the wings. The most remarkable example of this technique is that of the insane S. the Gannet generally plunges height of ten meters, striking sea surface with close to 100 km/h; it regularly reaches depths lower than 5 m, but could occasionally go down until about fifteen meters while swimming. The tern S, the Pelican S and the Phaethon S use also this technique, but reach less depths. In all the cases, it acts more dives than of true divings.

Diving

The true diving, that which allows the regular exploitation of zones located beyond 20 m of depth, actually relates to only one small number of species belonging essentially to three groups: the Penguin S, the Alcidé S and the Cormoran S. One can associate some Procellariiforme S there: the Puffin S and the petrel-plungers or Puffinure S. the performances of these plunger birds are however remarkable.

Performances

The knowledge depths of diving remained dependant on anecdotic and not very precise techniques a long time:

observation direct, occasional, by plungers or starting from submarines;
accidental captures in fishing machines which one knew the depths of immersion.

The second method is that which was most often employed, but it was difficult to make sure that the birds had not been taken at the time of the descent or the increase of the machines, more close to surface that the depth to immersion.

The prospects changed in a radical way in the years 1980 because of use of recorders fixed at the birds themselves. The improvement and the miniaturization of the apparatuses since then caused a multiplication of the studies dedicated on this subject. In spite of made progress, there remains however a certain number of problems of precision of measurements, and certain authors underlined the ethical need to take into account the capacity of the birds handled to support without damage the equipment with which one equips them.

Adaptations

Flight

modes & modes of food

all zoophages
diversity of behaviors

dependence of the seamen circle

The marine birds have glands with salt as one meets some in certain reptiles, iguanas or marine tortoises and which their make it possible to excrete the surpluses of salt.

coastal species
deep-sea species

migrations

reproduction

required return to ground (oviparous animals)
colonial reproduction
occupied mediums

demographic profiles

survival
fruitfulness
exchanges

Threats and conservation

Natural regulation

Birds of sea and the man

See too

References and notes

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