bird

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The three predominant mating systems are polyandry, polygyny, and monogamy. Monogamy is seen in approximately 91% of all bird species. Polygyny constitutes 2% of all birds and polyandry is seen in less than 1%. Monogamous species of males and females pair for the breeding season. In some cases, the individuals may pair for life. Sexual selection theory and the relatively low typical parental investment that males make in offspring would suggest that polygynous mating systems should predominate in the animal kingdom. The real puzzle then is why do males become monogamous at all, especially so often in bird species.In most groups of animals, male parental care is rare, but in birds it is quite common; it is more extensive in birds than in any other vertebrate class. One reason for this large percentage of monogamy with birds is due to the fact that male birds are just as adept at parental care as females. In fact, male care can be seen as important or essential to female fitness. "In one form of monogamy such as with obligate monogamy a female cannot rear a litter without the aid of a male" (Gowaty, 1983). It is assumed that when such male care is necessary, monogamy will evolve directly with this. It seems strange then that a male’s ability to defend mates and resources relies on his ability to separate himself from parental care. hatchlings are completely dependent on parental care.]]The parental behavior most associated with monogamy was male incubation. This is very interesting, because male incubation is the most confining male parental behavior. It not only consumes time, but also may require physiological changes that interfere with usual mating. With the extreme loss of mating opportunities, there is a reduction in the reproductive success among males. "This information then suggests that sexual selection may be less intense in taxa where males incubate, hypothetically because males allocate more effort to parental care and less to mating" (Ketterson and Nolan, 1994). It is understood then that the females associated with these males base their choice of mate on parental behaviors rather than physical appearance. It is surprising that with the amount of time and energy needed, that paternal care is selected for at all. Evolution suggests that a female should choose mates that confer maximum fitness. Therefore, if males contribute to the care of the offspring both male and female fitness may be maximized. "High paternal care has been seen among many species of monogamous mammals and several authors suggest that male investment is one of the primary advantages of monogamous mating (Zeveloff and Boyce, 1980). This suggests then that this mating system whether costly or not must be advantageous in some way or these females would not be selecting males with this behavior. It seems likely that fitness is increased in some way by this behavior of male parental care, but not so extreme that it is adopted by most other species. Surprisingly, there appears to be a lot of research to show that monogamy and paternal behavior are actually maladaptive due to its cost to fitness. However, is this due to the use of male care in this mating system? While the answer may be yes, it also seems to prevail in bird populations for some reason. What this reason is though may never be pin pointed to an exact answer. Some observations are thrown out by a couple of researchers but with no conclusive data or results. The only thing concluded seems to be that it is unnecessary. For now, until more research is done, we must instead be content to just know it persists.

Respiration - Birds respire by means of crosscurrent flow: the air flows at a 90 degree angle to the flow of blood in the lungs capillaries. In addition to the lungs themselves, birds have posterior and anterior air sacs (typically nine) which control air flow through the lungs, but do not play a direct role in gas exchange. There are three parts involved in Respiration (physiology)respiration:

the Anatomical terms of locationanterior air sacs (clavicleinterclavicular, Neckcervicals, and anterior thoracics),

the lungs, and

the Anatomical terms of locationposterior air sacs (posterior thoracics & abdominals).It takes a bird two full breaths (inhaling and exhaling), to completely cycle the air from each inhalation through the lungs and out again. The air flows through air sacs and lungs as follows.

First inhalation: air flows through the trachea and Bronchusbronchi into the posterior air sacs.

First exhalation: air flows from the posterior air sacs to the lungs.

Second inhalation: air flows from the lungs to the anterior air sacs.

Second exhalation: air flows from the anterior sacs back through the trachea and out of the body.In birds, at each inhalation and each exhalation fresh air flows through the lungs in only one direction. Birds are therefore able to Diffusiondiffuse more oxygen into their blood. Unlike humans and other mammals, there is no mixing of oxygen rich air and carbon dioxide rich air. Thus, the partial pressure of oxygen in a bird's lungs is the same as the environment. This is also why you would more likely see a bird on Mount Everest than, say, a mouse.Avian lungs do not have alveoli, as mammalian lungs do, but instead contain millions of tiny passages known as parabronchi, connected at either ends by the dorsobronchi and ventrobronchi. Air flows through the honeycombed walls of the parabronchi and into air capillaries, where oxygen and carbon-dioxide are traded with cross-flowing blood capillaries by diffusion.

Other anatomy - Birds possess a ''ventriculus'', or gizzard, that is composed of four muscular bands that act to rotate and crush food by shifting the food from one area to the next within the gizzard. Depending on the species, the gizzard may contain small pieces of grit or stone that the bird has swallowed to aid in the grinding process of digestion. For birds in captivity, only certain species of birds require grit in their diet for digestion. The use of gizzard stones is a similarity between birds and dinosaurs, which left gizzard stones called gastroliths as trace fossils. Birds also have skeletons possessing unique characteristics. ''See bird skeleton.''

Birds and humans - is an artificial platform for birds to make a nest]]Birds are an important food source for humans. The most commonly eaten species is the domestic chicken and its Egg (biology)eggs, although goosegeese, pheasants, turkey (bird)turkeys, and ducks are also widely eaten. Other birds that have been utilized for food include emus, ostriches, pigeons, grouse, quails, doves, woodcocks, songbirds, and others, including small passerines such as finches.At one time swans and flamingos were delicacies of the rich and powerful, although these are generally protected now.Many species have become extinct through over-hunting, such as the Passenger Pigeon, and many others have become endangered or extinct through habitat destruction, deforestation and intensive agriculture being common causes for declines.Numerous species have come to depend on human activities for food and are widespread to the point of being pests. For example the common pigeon or Rock Dove (''Columba livia'') thrives in urban areas around the world. In North America, introduced House Sparrows, Common Starlings, and House Finches are similarly widespread.Other birds have been used by humans: for example Rock DoveHoming pigeons to carry messages (many are still kept for sport), falcons for hunting, cormorants for fishing. Chickens and pigeons are popular subjects in experimental research in biology and comparative psychology. As birds are extra-sensitive to toxins, the Canary was often used in coal mines to indicate the presence of poisonous gases, so that the miners could escape.Colorful, particularly tropical, birds (e.g., Parrot (family)parrots, and mynahs) are often kept as pets although this has led to smuggling of some endangered species; CITES does considerable work to deter this.Bird diseases that can be contracted by humans include these: psittacosis, salmonellosis, campylobacteriosis, Newcastle's disease, mycobacteriosis (avian tuberculosis), influenza, giardiasis, and cryptosporiadiosis.

Trivia -

To preen or groom their feathers, birds use their bills to brush away foreign particles.

The birds of a region are called the avifauna.

Few birds use chemical defences against predators. Tubenoses can eject an unpleasant slime against an aggressor, and some species of pitohui, found in New Guinea secrete a powerful neurotoxin in their feathers.

Birds are among the most extensively studied animal groups, with hundreds of academic journals devoted to their study.

See also -

Anting (bird activity)Anting

''Archaeopteryx''

Avian pallium

Bird flight

Bird migration

Bird ringing (banding)

Bird skeleton

Birdfeeding

Birding

Carinatae

Conservation status

The biology of eggsEgg biology

Extinct birds

List of birds

List of regional bird listsregional and country bird lists

Oology

Ornithology

Prehistoric birdsBird families and taxonomytaxonomic discussion are given in list of birds and Sibley-Ahlquist taxonomy.

References and external links - sisterlinksBird WikispeciesAves dichotomouskeyAvesAves

bsc-eoc.org - Avibase - The World Bird Database

i-o-c.org - International Ornithological Committee

birdlife.org - Birdlife International - Dedicated to bird conservation worldwide; has a database with about 250,000 records on endangered bird species

birdingonthe.net - Birdingonthe.net

surfbirds.com - Surfbirds Birdwatching and World Birding

worldtwitch.com - Worldtwitch - rare bird news around the world

birdforum.net - BirdForum

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