The chicken (Gallus gallus) is a type of domesticated
fowl, believed to be descended from the wild Indian and
south-east Asian Red Junglefowl.
With a population of more than 24 billion in 2003, there are more chickens in the world than any other bird. They are used to produce two sources of food: their meat, and their eggs.
Chickens generally live five to eleven years depending on the breed. Male chickens are known as roosters (in the U.S., Canada and Australia), cocks, or cockerels. Castrated roosters are called capons. Female chickens are known as hens. Young females are known as pullets. Roosters can usually be differentiated from hens by their striking plumage, marked by long flowing tails and bright pointed feathers on their necks.
However, in some breeds, such as the Sebright, the cock only has slightly pointed neck feathers, and the identification must be made by looking at the comb. Chickens have a fleshy crest on their heads called a comb or cockscomb, and a fleshy piece of hanging skin under their beak called a wattle. These organs help to cool the bird by redirecting blood flow to the skin. Both the male and female have distinctive wattles and combs. In males, the combs are often more prominent, though this is not the case in all varieties.
Domestic chickens are typically fed commercially prepared
feed that includes a protein source as well as grains. Chickens
often scratch at the soil to search for insects and seeds.
Incidents of cannibalism can occur when a curious bird pecks at
a preexisting wound or during fighting (even among female
birds). This is exacerbated in close quarters. In commercial egg
and meat production this is controlled by trimming the beak
(removal of two thirds of the top half and occasionally one
third of the lower half of the beak).
Domestic chickens are not capable of long distance flight, although they are generally capable of flying for short distances such as over fences. Chickens will sometimes fly to explore their surroundings, but usually do so only to flee perceived danger. Because of the risk of escape, chickens raised in open-air pens generally have one of their wings clipped by the breeder — the tips of the longest feathers on one of the wings are cut, resulting in unbalanced flight which the bird cannot sustain for more than a few meters.
Chickens are gregarious birds and live together as a flock. They have a communal approach to the incubation of eggs and raising of young. Individual chickens in a flock will dominate others, establishing a "pecking order," with dominant individuals having priority for access to food and nesting locations. Removing hens or roosters from a flock causes a temporary disruption to this social order until a new pecking order is established.
Chickens will try to lay in nests that already contain eggs, and have been known to move eggs from neighboring nests into their own. Some farmers use fake eggs made from plastic or stone to encourage hens to lay in a particular location. The result of this behavior is that a flock will use only a few preferred locations, rather than having a different nest for every bird.
Hens can also be extremely stubborn about always laying in the same location. It is not unknown for two (or more) hens to try to share the same nest at the same time. If the nest is small, or one of the hens is particularly determined, this may result in chickens trying to lay on top of each other.
Contrary to popular belief, roosters do not crow only at dawn, but may crow at any time of the day or night. Their crowing - a loud and sometimes shrill call - is a territorial signal to other roosters. However, crowing may also result from sudden disturbances within their surroundings.
Recent studies have shown that chickens (and possibly other bird species) still retain vestigial genes to produce teeth in the jaws, although these are dormant in living animals. These are a holdover from primitive birds such as Archaeopteryx, which were descended from theropod dinosaurs. (It has been suggested that chickens are related to Tyrannosaurus rex.)
When a rooster finds food he may call the other chickens to eat it first. He does this by clucking in a high pitch as well as picking up and dropping the food. This behavior can also be observed in mother hens, calling their chicks. In some cases the rooster will drag the wing opposite the hen on the ground, while circling her. This is part of chicken courting ritual. When a hen is used to coming to his "call" the rooster may mount the hen and proceed with the fertilization.
Chicken eggs vary in color depending on the hen, typically ranging from bright white to shades of brown and even blue, green, and recently reported purple (found in South Asia) (Araucana varieties). Sometimes a hen will stop laying and instead will focus on the incubation of eggs, a state that is commonly known as going broody. A broody chicken will sit fast on the nest, and protest or peck in defense if disturbed or removed, and will rarely leave the nest to eat, drink, or dust bathe. While brooding, the hen maintains constant temperature and humidity, as well as turning the eggs regularly.
At the end of the incubation period, which is an average of 21 days, the eggs (if fertilized) will hatch, and the broody hen will take care of her young. Since individual eggs do not all hatch at exactly the same time (the chicken can only lay one egg approximately every 25 hours), the hen will usually stay on the nest for about two days after the first egg hatches. During this time, the newly-hatched chicks live off the egg yolk they absorb just before hatching. The hen can sense the chicks peeping inside the eggs, and will gently cluck to stimulate them to break out of their shells. If the eggs are not fertilized by a rooster and do not hatch, the hen will eventually lose interest and leave the nest.
Modern egg-laying breeds rarely go broody, and those that do often stop part-way through the incubation cycle. Some breeds, such as the Cochin, Cornish and Silkie, regularly go broody and make excellent maternal figures. Chickens used in this capacity are known as utility chickens.
Chicken egg incubation can successfully occur artificially as well. Nearly all chicken eggs will hatch after 21 days of good conditions - 99.5 °F (37.5°C) and around 55% relative humidity (increase to 70% in the last three days of incubation to help soften egg shell). Many commercial incubators are industrial-sized with shelves holding tens of thousands of eggs at a time, with rotation of the eggs a fully automated process.
Home incubators are usually large boxes (lead incubators are popular) and hold a few to 75 eggs. Eggs must be turned three to eight times each week, rotating at least 180 degrees. If eggs aren't turned, the embryo inside will stick to the shell and likely will be hatched with physical defects. This process is natural; hens will stand up three to five times a day and shift the eggs around with their beak.
The meat of the chicken, also called "chicken," is a type of poultry. Because of its relatively low cost among meats, chicken is one of the most used meats in the world. Nearly all parts of the bird can be used for food, and the meat is cooked in many different ways around the world. Popular chicken dishes include fried chicken, chicken soup, Buffalo wings, tandoori chicken, butter chicken, and chicken rice. Chicken is also a staple of fast food restaurants such as KFC, McDonald's, and Burger King. Chicken has a fairly neutral flavor and texture, and is used as a reference point for describing other foods; many are said to 'taste like chicken' if they are indistinctive.
Chickens can make good companion animals and can be tamed by hand feeding, but can sometimes become aggressive. Some have advised against keeping certain breeds around young children, as the chickens can become territorial and violent. In Asia, chickens with striking plumage have long been kept for ornamental purposes, including feather-footed varieties such as the Cochin from Vietnam, the Silkie from China, and the extremely long-tailed Phoenix from Japan. Asian ornamental varieties were imported into the United States and Great Britain in the late 1800s. Distinctive American varieties of chickens have been developed from these Asian breeds. Poultry fanciers began keeping these ornamental birds for exhibition, a practice that continues today.
Individuals in rural communities commonly keep chickens for both ornamental and practical value. Some communities ban only roosters, allowing the quieter hens. Zoos sometimes use chickens instead of insecticides to control insect populations.
Chickens are generally low maintenance. The major challenge is protecting the birds from predators such as dogs, raccoons and foxes. Chickens are usually kept in a roost at night and a pen in the day (unless they are free-range). The floor is covered with bedding such as straw or wood shavings. A bird left out at night is likely to be killed by a predator.
Eggs from household chickens can be quite different from the commercial eggs. Fresh yolks are "perky" and float above the white. The yolk color is frequently a deeper color than the pale yellow of commercially raised eggs and can at times be almost orange.
In the United States, chickens were raised primarily on family
farms until roughly 1960. Originally, the primary value in
poultry keeping was eggs, and meat was considered a byproduct of
egg production. Its supply was less than the demand, and poultry
was expensive. Except in hot weather, eggs can be shipped and
stored without refrigeration for some time before going bad;
this was important in the days before widespread refrigeration.
Farm flocks tended to be small because the hens largely fed themselves through foraging, with some supplementation of grain, scraps, and waste products from other farm ventures. Such feedstuffs were in limited supply, especially in the winter, and this tended to regulate the size of the farm flocks. Soon after poultry keeping gained the attention of agricultural researchers (around 1896), improvements in nutrition and management made poultry keeping more profitable and businesslike.
Prior to about 1910, chicken was served primarily on special occasions or Sunday dinner. Poultry was shipped live or killed, plucked, and packed on ice (but not eviscerated). The "whole, ready-to-cook broiler" wasn't popular until the Fifties, when end-to-end refrigeration and sanitary practices gave consumers more confidence. Before this, poultry were often cleaned by the neighborhood butcher, though cleaning poultry at home was a commonplace kitchen skill.
Two kinds of poultry were generally used: broilers or "spring chickens;" young male chickens, a byproduct of the egg industry, which were sold when still young and tender (generally under 3 pounds live weight), and "stewing hens," also a byproduct of the egg industry, which were old hens past their prime for laying. This is no longer practiced; modern meat chickens are a different breed. Egg-type chicken carcasses no longer appear in stores.
The major milestone in 20th century poultry production was the discovery of vitamin D, which made it possible to keep chickens in confinement year-round. Before this, chickens did not thrive during the winter (due to lack of sunlight), and egg production, incubation, and meat production in the off-season were all very difficult, making poultry a seasonal and expensive proposition. Year-round production lowered costs, especially for broilers.
At the same time, egg production was increased by scientific breeding. After a few false starts (such as the Maine Experiment Station's failure at improving egg production, success was shown by Professor Dryden at the Oregon Experiment Station.
Improvements in production and quality were accompanied by lower labor requirements. In the Thirties through the early Fifties, 1,500 hens was considered to be a full-time job for a farm family. In the late Fifties, egg prices had fallen so dramatically that farmers typically tripled the number of hens they kept, putting three hens into what had been a single-bird cage or converting their floor-confinement houses from a single deck of roosts to triple-decker roosts. Not long after this, prices fell still further and large numbers of egg farmers left the business. This marked the beginning of the transition from family farms to larger, vertically integrated operations.
Robert Plamondon reports that the last family chicken farm in his part of Oregon, Rex Farms, had 30,000 layers and survived into the Nineties. But the standard laying house of the surviving operations is around 125,000 hens.
This fall in profitability was accompanied by a general fall in prices to the consumer, allowing poultry and eggs to lose their status as luxury foods.
The vertical integration of the egg and poultry industries was a late development, occurring after all the major technological changes had been in place for years (including the development of modern broiler rearing techniques, the adoption of the Cornish Cross broiler, the use of laying cages, etc.).
By the late Fifties, poultry production had changed dramatically. Large farms and packing plants could grow birds by the tens of thousands. Chickens could be sent to slaughterhouses for butchering and processing into prepackaged commercial products to be frozen or shipped fresh to markets or wholesalers. Meat-type chickens currently grow to market weight in six to seven weeks whereas only fifty years ago it took three times as long. This is due to genetic selection and nutritional modifications (and not the use of growth hormones, which are illegal for use in poultry in the US and many other countries). Once a meat consumed only occasionally, the common availability and lower cost has made chicken a common meat product within developed nations. Growing concerns over the cholesterol content of red meat in the 1980s and 1990s further resulted in increased consumption of chicken.
Today, eggs are produced on large egg ranches on which environmental parameters are well controlled. Chickens are exposed to artificial light cycles to stimulate egg production year-round. In addition, it is a common practice to induce molting through careful manipulation of light and the amount of food they receive in order to further increase egg size and production.
On average, a chicken lays one egg a day for a number of days (a "clutch"), then does not lay for one or more days, then lays another clutch. Originally, the hen presumably laid one clutch, became broody, and incubated the eggs. Selective breeding over the centuries has produced hens that lay more eggs than they can hatch. Some of this progress was ancient, but most occurred after 1900. In 1900, average egg production was 83 eggs per hen per year. In 2000, it was well over 300.
In the United States, laying hens are butchered after their second egg laying season. In Europe, they are generally butchered after a single season. The laying period begins when the hen is about 18-20 weeks old (depending on breed and season). Males of the egg-type breeds have little commercial value at any age, and all those not used for breeding (roughly fifty percent of all egg-type chickens) are killed soon after hatching. The old hens also have little commercial value. Thus, the main sources of poultry meat 100 years ago (spring chickens and stewing hens) have both been entirely supplanted by meat-type broiler chickens.
Traditionally, chicken production was distributed across the entire agricultural sector. In the Twentieth Century, it gradually moved closer to major cities to take advantage of lower shipping costs. This had the undesirable side effect of turning the chicken manure from a valuable fertilizer that could be used profitably on local farms to an unwanted byproduct. This trend may be reversing itself due to higher disposal costs on the one hand and higher fertilizer prices on the other, making farm regions attractive once more.
From the farmer's point of view, eggs used to be practically the same as currency, with general stores buying eggs for a stated price per dozen. Egg production peaks in the early spring, when farm expenses are high and income is low. On many farms, the flock was the most important source of income, though this was often not appreciated by the farmers, since the money arrived in many small payments. Eggs were a farm operation where even small children could make a valuable contribution.
This Chicken Page is Copyright The Animal Web Guide © 2004 - 2009 Chuck Ayoub