When some weigh less than 20 grams, others are breaking records ofspan. They live in the waters polar like in the tropics. The diversity of seabirds does not prevent them from sharing many physical characteristics and behavioral. Common points and differences: an overview.
Sea bird: definition
The term seabird (or seabird) designates any bird which draws all or part of its food of the sea. We generally classify in this group more than 350 species belonging to eight families and maintaining relations with the maritime sector addiction more or less variable:
- The laridae (scissors, gulls, seagulls, skuas, skuas, terns, terns, penguins, common murres, puffins…);
- The phaethontidae (phaeton or straw-in-tail);
- The sulids (crazy);
- The phalacrocoracidae (cormorants);
- The pelecanids (pelicans);
- The frigatidae (frigates);
- The spheniscidae (penguins);
- The procellariidae (petrels, shearwaters, albatrosses).
Some commonalities and differences
The palette of sizes seabirds is extremely extensive. most small, the minute oceanite, measures less than 15 cm and weighs less than 20 g while the wandering albatross can reach 1.30 m and weigh up to 12 kg (it holds the record current wingspan with 3.50 m). A common feature of seabirds is the general lack of color lively and sexual dichromatism. The rare exceptions are small tufts of golden feathers on the heads of certain penguins or Pacific alcids.
The specific wings of seabirds
The form general of the wings of seabirds presents four major models with aerodynamic specific:
- Long, tapered wings suitable for flight plane (albatrosses, petrels, frigates, boobies, phaethons, gulls, terns, skuas);
- Bulky wings to facilitate gliding by ascending thermal (pelicans);
- Short and wide wings suitable for flapping but powerful flight at flush with the water (cormorants);
- Short and thin wings favoring the dive (penguins, puffins, shearwaters).
The waterproof plumage of seabirds
Due to their presence on all the seas of the globe, including the polar regions, seabirds are subject to temperatures sometimes extreme some water. The sealing of the plumage therefore plays a major role in preventing the liquid element from coming into direct contact with the skin. On the other hand, a air layer placed between the feathers and the body favors – with the down – the thermal insulation of the animal while contributing to its buoyancy. For the anecdote, the incomparable impermeability seabird feathers served as a model for the development of the first waterproof clothing in the early 20th centurye century.
Range of seabirds
Sea birds are more numerous in the waters polar than tropical and more diverse in the southern hemisphere than in the northern hemisphere. Among the breeding species of the hemisphere South include Wilson’s Oceanites, Sooty Shearwaters, Slender-billed Shearwaters and Dove Prions. In the hemisphere North, we meet the Cul-Blanc Oceanites, Common Murres, Thick-billed Murres, Atlantic Puffins, Tufted Puffins as well as Little Mergules. Many species of seabirds frequent European coasts and french including the black-headed gull, the herring gull, the common tern, the northern gannet, the great cormorant or the crested cormorant.
Feeding sea birds
Most seabirds eat small fish or zooplankton. Their diet offers a wide range of preys of different sizes and types depending on the size of the seabird. Note that they are more demanding when raising their fish. chicks. Murres and puffins, for example, feed their young exclusively on fish. Food is often distributed in such a way irregular depending on weather conditions and the presence of prey, which explains why seabirds are used to alternating periods of abundance and famine. Many species of seabirds take full advantage of the waste resulting from fishing activities. We can thus observe impressive formations of gulls in the wake of the trawlers who raise their nets making this retrieval a way of life for many species.
Reproduction of sea birds
In most seabirds, the mode of reproduction exhibits common characteristics such as:
- The monogamy. Loyalty in many seabirds is often linked to the long distances to travel to find mates;
- A return to Earth to lay eggs due to species oviparity (development and hatching outside the body);
- The alternate brooding between the female and the male (a few exceptions to be noted such as the emperor penguin whose male alone takes care of the incubation of the egg on the ice floe);
- Reproduction in colony. The vast majority of species come together to reproduce with the particular aim of reducing the risk of predation on eggs and newborns.
Threats to seabirds
The seabird population declined by almost 70% between 1950 and 2010 mainly due to the degradation of marine ecosystems generated by human activities. Most species today are protected but remain strongly impacted by the destruction of their habitat, by the peach (birds accidentally caught with longlines), by overfishing (parents not finding enough to feed their offspring), pollution of water contaminating the plankton they consume or even spills ofhydrocarbons at sea. According to BirdLife International, a partner organization of the Red List of Threatened Species of the International Union for the Conservation of Nature (IUCN), 28% of species are threatened and 10% are considered near threatened. Albatrosses are particularly affected with 17 of the 22 species currently threatened withextinction.