Birds are a group of endothermic vertebrates, characterized by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a lightweight but strong skeleton. They range in size from the 5 cm (2 in) bee hummingbird to the 2.75 m (9 ft) ostrich, with approximately ten thousand species being spread all around the world.
Fossil records indicate that birds are the last surviving group of dinosaurs, their first appearance taking place around 100 million years ago. Thus, they have had enough time to evolve and diversify at their will. They have learnt to migrate in times of need and establish themselves in locations which provide the food they need, such as southern regions.
Their wings are more or less developed, depending on the specie, however, there are birds with wings but without the ability to fly. Some are among the most intelligent animals, making use tools, and many social species pass on knowledge across generations, which is considered a form of culture. Many species annually migrate great distances. As they are social animals, they communicate with visual signals, calls, and bird songs, and participate in such social behaviours such as cooperative breeding and hunting, flocking, and mobbing of predators.
Birds produce offspring by laying eggs which are fertilised through sexual reproduction. They are usually laid in a nest and incubated by the parents. Most birds have an extended period of parental care after hatching.
Many species of birds are economically important. Domesticated and undomesticated birds are important sources of eggs, meat, and feathers. Songbirds, parrots, and other species are popular as pets, and the excrement of the Guano bird is harvested for use as a fertiliser.
However, there are also species of birds that can be considered pests, such as pigeons or sparrows.
Diversity and anatomy of birds
They can be found on all seven continents, with the most diversity occurring in the tropical regions. Some have developed by themselves in certain regions and some have been introduced by humans, mostly as game. There are also species that have naturally spread from their origin place, as the agricultural practices around them have created a suitable new habitat.
Depending on the specie and their adaptation for the region they live in, the anatomy of birds can differ. As previously mentioned, some use their wings for flight and some do not. However, generally, their skeleton is formed of very lightweight bones, that facilitate flight. Birds have one of the most complex respiratory systems of all animal groups, as upon inhalation, 75% of the fresh air bypasses the lungs and flows directly into a posterior air sac which extends from the lungs and connects with air spaces in the bones and fills them with air. The other 25% of the air goes directly into the lungs. When the bird exhales, the used air flows out of the lung and the stored fresh air from the posterior air sac is simultaneously forced into the lungs. Thus, a bird’s lungs receive a constant supply of fresh air during both inhalation and exhalation.
The most developed part of a birds’ brain is the one that controls the flight-related functions, while the cerebellum coordinates movement and the cerebrum controls behaviour patterns, navigation, mating and nest building. Birds with eyes on the sides of their heads have a wide visual field, while birds with eyes on the front of their heads, such as owls, have binocular vision and can estimate the depth of field.
Feathers are a feature characteristic of birds, as they facilitate flight, provide insulation are also used in display, camouflage, and signaling. Molting of the plumage occurs generally once a year
All these anatomy differences have appeared because of the different adaptation needs a specie has in the location it has settled in.
Diet and migration of birds
Birds’ diets are varied and often include nectar, fruit, plants, seeds, carrion, and various small animals, including other birds. Because birds have no teeth, their digestive system is adapted to process unmasticated food items that are swallowed whole. Birds’ feeding strategies vary by species. Many birds glean for insects, invertebrates, fruit, or seeds. Some hunt insects by suddenly attacking from a branch. Many bird species migrate to take advantage of global differences of seasonal temperatures, therefore optimising availability of food sources and breeding habitat. These migrations vary among the different groups. The ability of birds to return to precise locations across vast distances has been known for some time. Birds navigate during migration using a variety of methods. For diurnal migrants, the sun is used to navigate by day, and a stellar compass is used at night. Birds that use the sun compensate for the changing position of the sun during the day by the use of an internal clock.
Birds also communicate using primarily visual and auditory signals. Calls are used for a variety of purposes, including mate attraction, evaluation of potential mates, bond formation, the claiming and maintenance of territories, the identification of other individuals (such as when parents look for chicks in colonies or when mates reunite at the start of breeding season), and the warning of other birds of potential predators, sometimes with specific information about the nature of the threat.
Breeding and nesting of birds
Bird eggs are usually laid in a nest. Most species create somewhat elaborate nests, which can be cups, domes, plates, beds scrape, mounds, or burrows. Some bird nests, however, are extremely primitive. Incubation, which optimises temperature for chick development, usually begins after the last egg has been laid. Incubation periods range from 10 days (in woodpeckers, cuckoos) to over 80 days (in albatrosses and kiwis).
Information about their relationship with humans
Several bird species have become commercially significant agricultural pests and some pose an aviation hazard. Human activities can also be detrimental, and have threatened numerous bird species with extinction (hunting, avian lead poisoning, pesticides, road kill, and predation by pet cats and dogs are common sources of death for birds).
They can also spread disease easily transmitted to humans, so some type of birds can be considered dangerous.
Domesticated birds raised for meat and eggs, called poultry, are the largest source of animal protein eaten by humans. Many species of birds are also hunted for meat, such as pheasants, wild turkeys, quail, doves, partridge. Birds have been domesticated by humans both as pets and for practical purposes. Colourful birds, such as parrots are bred in captivity or kept as pets.
However, should you end up dealing with pest birds, proper identification is very important as certain products are species-specific. Never underestimate the commitment of pest birds to return to their home. Also, depending on the type of bird, the damage around your house or garden may vary. Some bird species can become a serious nuisance in the wrong locations, such as birds roosting or nesting in a business premises. Not only can they cause a lot of damage, but they can also spread diseases.
Agricultural crops are damaged worldwide by pest birds. Globally speaking, the most common agricultural pest birds include pigeons, crows, gulls, starlings, blackbirds, sparrows, grackles, geese, and woodpeckers. Every country faces individual bird challenges when it comes to agriculture, as birds are naturally drawn to food supplies and can quickly devastate crops.