Birds are a class of vertebrates and warm-blooded animals, whose body is covered with feathers of different colors and whose light bones allow them, in most cases, to fly, jump or at least stay in the air.
The birds have a horny beak without teeth, through which they feed and communicate, and which has adapted to the multiple biomes inhabited by these animals, the most diverse and numerous in the world. Their forms are equally varied, ranging from the tiny hummingbird (6 centimeters and a half) to the gigantic Andean condor (130 centimeters in span) or the ostrich (280 centimeters in height).
Not all birds are able to fly, but many swim, glide, jump or even run fast. Many of them are popular as pets, especially those with a melodious song.
Characteristics Of Birds
Although there are several theories regarding the origin of birds, the most widely accepted is that they come directly from the dinosaurs, being the animal group that is closest to the deinonicosaurs, which together with the dromaeosaurs and troodontids constitute the group of paraaves.
In the formulation of these evolutionary theories was the finding of the fossil of Archeopteryx of Berlin, a dinosaur of the upper Jurassic whose body wrapped in feathers was twisted in a manner very similar to those observed in the corpses of modern birds. Even so, it is argued that the most plausible avian ancestor discovered is the Avimimus of the late Cretaceous period.
While not all bird species can fly (penguins swim, for example, and ostriches run), it is one of the distinguishing features of this class of animals, since the ability to move from one ecosystem to another and even from proliferate in isolated territories without greater animal competition, allowed the enormous diversification of avian species.
On the other hand, the faculty of flight boosted most of the evolutionary changes present in the aerodynamic body of birds, from powerful pectoral muscles that accompany the transformation of the forelimbs into wings, to the development of hollow, light, connecting bones. with the powerful respiratory system, the most complex of the animal kingdom.
The air of bird breathing is distributed between the lungs and the various bone cavities, in order to maintain the hyper-oxygenated metabolism and to be able to overcome the flight for extended periods.
Similarly, the lower extremities, the only ones free during the flight, were adapted for a strong solid grip from a strong metatarsal, indispensable in the rapine and for the subjection to the branches of the trees, although also guarantor of stability in the soil.
The diet of birds can be extremely varied, ranging from nectar, fruits and vegetables, leaves and seeds, insects, fungi, carrion and small animals: fish, rodents, reptiles and even other birds or their eggs.
The enormous avian diversity has allowed them, in addition, to adapt their peaks to their nutritional source, an extremely evident feature in species such as the carpenter, the pelican or the hummingbird. Their nutritional needs, facing the flight, are high, so they have developed a fast digestive model.
Having no teeth, the birds can not chew their food, so they have a digestive system adapted for the digestion of whole pieces, often using small stones that they swallow and store in the gizzard, to crush the food and facilitate the digestion.
Many birds prefer a solitary existence or small family nuclei, especially those dedicated to predation. While most small birds are organized in flocks that can reach significant proportions.
Given their high capacity for intelligent thinking, birds are capable of efficient modes of socialization, in terms of food and safety, and can even embark on symbiotic or commensal relationships with members of other species, as do the herons They feed on parasites in the fur of large mammals.
The birds are oviparous, so that once fertilized during intercourse, the female lays eggs with a calcareous shell, which are then hatched until the moment of hatching.
The interesting thing about the coitus of the birds are their complex mating rituals, in which the male usually attracts the female by displaying the colors of their plumage, their song and even building the best possible nest with branches and material that collects from the birds. surroundings.
95% of bird species are monogamous, which allows extensive two-parent care until the clutch is advanced. In this way, in addition, you can defend the territory around the nest, guaranteeing the food of the chicks.
Many of the bird species migrate, taking advantage of the climatic difference between both hemispheres to optimize their food sources or to carry out the breeding season. Some of these migrations are annual, for which animals are prepared by maximizing their reserves of fat and water.
Considering that land birds have a maximum autonomous flight radius of about 2500 km and waders of about 4000 km, it is understood that a total route that often exceeds 10,000 km is an important energy investment in the life of the bird.
There are about 9,000 species of birds, which makes them the most numerous vertebrates in the world, well above amphibians and mammals. They have colonized all possible habitats: desert, insular, jungle, mountainous, maritime, Mediterranean, polar.
8. Zoological classification
The taxonomic group of birds is considered as a class in the traditional zoological systematics, but not in the modern classifications, for which it is located within the superclass of the tetrapods.
Many of these discrepancies with respect to their classification have reason to be in the various existing theories about their evolutionary origin, and the blurred boundaries between avian and non-avian animals product of successive archaeological discoveries of primitive birds and intermediate links prior to their existence.
9. Relationship with man
Birds have fascinated man from the earliest ages. His ability to fly has been a source of inspiration for legends, such as the Greek story of Icarus, and inventions such as paragliding and the airplane. To conquer that inaccessible border of the sky and to rub shoulders with the birds has been a human obsession that hardly the last century could be realized.
Some are regarded as heavenly messengers or emissaries of good news, while others, such as the vulture or the raven, are considered evil or ill omen. The eagle and the falcon have inspired numerous imperial standards and have been part of the western imagination since early: the taps (half eagle-half lion), the rocs (giant birds) or the mythical phoenix, able to revive from its ashes.
Other more domestic birds are still part of the human habitat, such as parrots and cockatoos whose imitative capacity of human language has opened a place for pets; or chickens, turkeys, ducks and other breeding birds that play an important role in the human food industry and in the manufacture of numerous products, such as pillows made from feathers.
More than 120 species of birds became extinct since the 17th century and there are more than 1200 species currently threatened, which points to the violent intrusion of man into his natural habitats, hunting and capture, due to the decorative nature of his plumage and many times to the harmony of their song.
Avian species are among the most affected by oil spills and other high impact ecological accidents, so the main ecological efforts of the world are focused on the conservation of these animals. It is estimated that 16 species have been saved from extinction between 1994 and 2004, but many others have no alternative to extinction.