, Like the reptiles, birds are primarily uricotelic, that is, their kidneys extract nitrogenous waste from their bloodstream and excrete it as uric acid, instead of urea or ammonia, through the ureters into the intestine.
 The affinities of an earlier fossil, the possible galliform Austinornis lentus, dated to about 85 million years ago, are still too controversial to provide a fossil evidence of modern bird diversification. The first type of birds is from the order Accipitriformes.  The cloaca is a multi-purpose opening: waste is expelled through it, most birds mate by joining cloaca, and females lay eggs from it.
Amateur bird enthusiasts (called birdwatchers, twitchers or, more commonly, birders) number in the millions.
Cuculiformes is one of the most famous bird orders, as it contains parasitic bird species – cuckoos. This bird order includes species such as Narina trogon, Red-naped trogon, Cuban trogon, Mountain Trogon, Pavonine Quetzal, and Resplendent Quetzal.
, Water is needed by many birds although their mode of excretion and lack of sweat glands reduces the physiological demands.  The skull bones in adults are fused and do not show cranial sutures.
Flamingos, three species of prion, and some ducks are filter feeders. In some species, other members of the same species—usually close relatives of the breeding pair, such as offspring from previous broods—will help with the raising of the young. Avialae, initially proposed to replace the traditional fossil content of Aves, is often used synonymously with the vernacular term "bird" by these researchers.
Sturkie's Avian Physiology/ edited by G. Causey Whittow. The authors proposed to reserve the term Aves only for the crown group consisting of the last common ancestor of all living birds and all of its descendants, which corresponds to meaning number 4 below. Jones DN, Dekker, René WRJ, Roselaar, Cees S (1995). , The ability of birds to return to precise locations across vast distances has been known for some time; in an experiment conducted in the 1950s, a Manx shearwater released in Boston in the United States returned to its colony in Skomer, in Wales within 13 days, a distance of 5,150 km (3,200 mi). Birds of prey specialise in hunting mammals or other birds, while vultures are specialised scavengers.  Birds are categorised as the biological class Aves in Linnaean taxonomy.
, Domesticated birds raised for meat and eggs, called poultry, are the largest source of animal protein eaten by humans; in 2003, 76 million tons of poultry and 61 million tons of eggs were produced worldwide.
Cladogram following the results of a phylogenetic study by Cau. These cookies will be stored in your browser only with your consent.
Both present-day and extinct species of birds belong to this bird order – Cariamiformes such as Seriemas.  Once the blood reaches the heart, it moves first into the right atrium, then the right ventricle to be pumped through the lungs for further gas exchange of carbon dioxide waste for oxygen. , In some species, both parents care for nestlings and fledglings; in others, such care is the responsibility of only one sex.
 Many bird populations are declining worldwide, with 1,227 species listed as threatened by BirdLife International and the IUCN in 2009.. To find out more about cookies, including how to see what cookies have been set and how to manage and delete them, set your preferences, OPPassessment - easy online administration, Psychologist access to the EJI and CPI 260 tools, Team Development using the MBTI Instrument, Type dynamics in Coaching: a deep dive using the MBTI, Conflict Management Training with TKI - virtual programme, Strong Interest Inventory Certification Programme, Developing Emotional Intelligence Using the EJI, read more on our blog about how aspects of Type dynamics are captured in each.  Costs of flocking include bullying of socially subordinate birds by more dominant birds and the reduction of feeding efficiency in certain cases. , Avialans diversified into a wide variety of forms during the Cretaceous Period. Species in this order diverse and here are some examples: Adams Booby, Red-footed booby, Masked booby, and Australasian Gannet.  These two subdivisions are often given the rank of superorder, although Livezey and Zusi assigned them "cohort" rank. They are gray in color, and have a shade of chestnut, just under their tail. The Peafowl includes two species of birds.  The avian ear lacks external pinnae but is covered by feathers, although in some birds, such as the Asio, Bubo and Otus owls, these feathers form tufts which resemble ears. In several civilisations of ancient Italy, particularly Etruscan and Roman religion, priests were involved in augury, or interpreting the words of birds while the "auspex" (from which the word "auspicious" is derived) watched their activities to foretell events. In religion, birds may serve as either messengers or priests and leaders for a deity, such as in the Cult of Makemake, in which the Tangata manu of Easter Island served as chiefs or as attendants, as in the case of Hugin and Munin, the two common ravens who whispered news into the ears of the Norse god Odin. All Trogoniformes are brightly colored and have long-tails.  The most developed part of the 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.
Finches and Buntings. They prey on fish, ducks, rabbits, raccoons, beavers, geese, gulls, reptiles, etc. Nicholls, (Eds). Suliformes order unites sea birds that nest in colonies such as boobies and gannets.
, Although human activities have allowed the expansion of a few species, such as the barn swallow and European starling, they have caused population decreases or extinction in many other species.
Vultures are easily distinguished because of their bald head and brown bodies. Mesites are nearly flightless and spend most of the time on land. About 60 extant bird species are flightless, as were many extinct birds.