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What the sources say

ChickenGallus gallus domesticus

Every figure, record and mechanism on the Chicken profile was written from a source, and this is the working table behind it: 53 claims checked word for word against these sources. The left column is what the page says. The right column is the source's own words, copied, not paraphrased; a ... marks a cut and[brackets] an insertion. Open any source and check it yourself.

Profile updated

Source
01

Ohio State University Extension

Ohio 4-H Poultry Resource. Ohio State University Extension.

The page sayswhose gizzard does the chewing
The source saysthe gizzard is made up of two sets of strong muscles that act as the bird's teethNote: tagline
The page sayswhose hen usually lays an egg every 26 hours
The source saysA hen usually lays one egg every 26 hoursNote: tagline
The page saysFarms and backyard flocks
The source saysAfter you have decided the goal for your backyard flock (eggs, meat or show)Note: stats.habitat: backyard flocks
The page saysPoultry feed with grains such as corn, wheat and barley
The source saysImportant sources of carbohydrates in poultry diets include corn, wheat, barley, and other grains.Note: stats.diet; the passage says poultry, and the whole document is about chickens
The page saysfree-ranging chickens typically eat small stones
The source saysWhen allowed to free-range, chickens typically eat small stones.Note: stats.diet
The page saysA muscular gizzard that acts as its teeth and grinds the small stones free-ranging chickens typically eat
The source saysthe gizzard is made up of two sets of strong muscles that act as the bird's teeth ... When allowed to free-range, chickens typically eat small stones. ... the strong muscles of the gizzard grind them into tiny piecesNote: stats.superpower
The page sayshas no teeth
The source saysbecause birds do not have teethNote: body
The page saysIts gizzard, a stomach chamber made of two sets of strong muscles, acts as the bird's teeth.
The source saysthe gizzard is made up of two sets of strong muscles that act as the bird's teeth
The page saysFree-ranging chickens typically eat small stones, and the gizzard grinds them into tiny pieces.
The source saysWhen allowed to free-range, chickens typically eat small stones. The acidic environment in the proventriculus softens the stones, and then the strong muscles of the gizzard grind them into tiny pieces.
The page saysGrains such as corn, wheat and barley are important sources of the carbohydrates in poultry diets.
The source saysImportant sources of carbohydrates in poultry diets include corn, wheat, barley, and other grains.
The page saysRaised with good care, the fastest-growing meat birds, the Cornish Cross (a Cornish chicken crossed with a White Rock), weigh 4 to 6 pounds at about seven weeks and 6 to 10 pounds at eight to 12 weeks.
The source saysThe fastest growing birds are a Cornish chicken crossed with a White Rock, which is referred to as a Cornish Cross. Using good livestock care practices, producers will have fryers at approximately seven weeks weighing 4 to 6 pounds, reaching roasting stage of 6 to 10 pounds in eight to 12 weeks.Note: scope: Cornish Cross meat birds at those ages only, not chickens generally; 'raised with good care' carries 'Using good livestock care practices'; 'meat birds' from the Meat Production section heading
The page saysThe average lifespan of a chicken is seven to eight years.
The source sayspotentially seven to eight years, which is the average lifespan of a chicken
The page saysA hen usually lays one egg every 26 hours.
The source saysA hen usually lays one egg every 26 hours
The page saysOvulation, the ovary's release of an egg cell, almost never happens after 3:00 p.m.
The source saysthe ovary releases the next ovum. However, the female chicken reproductive system is sensitive to light exposure, especially the number of hours of light in a day. In chicken hens, ovulation usually occurs under normal daylight conditions and almost never after 3:00 p.m.
The page saysA hen that lays too late in the day skips a day.
The source sayswhen a hen lays an egg too late in the day, the next ovulation occurs the following day, and the hen has a day when it does not lay an egg
The page saysChicks typically show no competitive behavior until after three days of age, and fighting to set the pecking order, the flock's social ladder, begins by 16 days.
The source saysRecently hatched chicks do not typically show any competitive behavior until after three days of age. By 16 days of age, fighting to determine the pecking order begins.Note: 'the flock's social ladder' glosses the source's 'a social hierarchy within chicken flocks'
The page saysHens lay eggs without a rooster, but those eggs are not fertile. A rooster is needed only if you want fertile eggs to hatch into chicks.
The source saysA rooster is not needed for egg production. Hens will lay nonfertile eggs without a rooster, a rooster is only needed if you want fertile eggs in order to hatch chicks.
The page saysA hen has sperm host glands that can store sperm, typically for 10 days to 2 weeks.
The source saysdeep glands known as sperm host glands that can store sperm for long periods of time, typically 10 days to 2 weeks
The page saysHearing seems to be an important one. When another hen was put in the mother's place in the dark, the chicks still found their mother.
The source sayshearing seems to be an important one. When a sitting hen was removed in the dark from her chicks and another broody hen put in her place, the chicks still found their mother hen.
The page sayschicks from three breeds of hens, placed in a pen with hens of those breeds, mostly found the correct breed.
The source saysWhen chicks from three different breeds of hens were removed and placed in a pen with hens of the same breed, most of the chicks were able to find to the correct breed of the mother hen.
The page saysAfter three weeks of age, chicks were less effective at picking out their own hen in a mixed group.
The source saysWhen chicks from different hens were combined and allowed to mingle, they were able to locate the appropriate hen when the hens were placed with the group. After three weeks of age, the chicks were less effective in doing so.
The page saysThe 26-hour egg clock
The source saysA hen usually lays one egg every 26 hoursNote: blockquote lead-in; the sentence beneath keeps 'usually'
The page saysFarms and backyard flocks
The source saysThere are a variety of cleaning and disinfecting materials available for use on organic poultry farmsNote: stats.habitat: farms
The page saysChickens now live in backyard flocks and on farms
The source saysAfter you have decided the goal for your backyard flock (eggs, meat or show)
The page saysChickens now live in backyard flocks and on farms
The source saysThere are a variety of cleaning and disinfecting materials available for use on organic poultry farms
The page saysA hen usually lays one egg every 26 hours
The source saysA hen usually lays one egg every 26 hoursNote: vibe.reason; same quote as the body claim
The page saysa hen that lays too late in the day skips a day
The source sayswhen a hen lays an egg too late in the day, the next ovulation occurs the following day, and the hen has a day when it does not lay an eggNote: vibe.reason; same quote as the body claim
The page saystags: omnivore
The source saysIn addition, when given a worm, even if alone, these chicks ran around as though there might be others in pursuit of the worm. Research has shown that chicks instinctively show fear of stinging insects but try to catch flies.Note: #981: kept. Chicken-specific (a chick behaviour study), animal food on top of the grain diet the profile states
The page saystags: omnivore
The source saysAlthough most poultry will eat insects when allowed open access, geese will graze the grass.Note: #981: poultry scope, which includes chickens; second support
The page saystags: domestic-pet
The source saysIf you are planning to have a small backyard flock of only three to five birds that are enjoyed as pets as well as producers in the local food chain for the family, you may consider a more docile breed.Note: #981: kept as pets too

Source
02

Smithsonian's National Zoo and Conservation Biology Institute

Chicken. Smithsonian's National Zoo and Conservation Biology Institute.

The page saysoutnumbers every other bird species
The source saysThere are more chickens on Earth than any other bird species.Note: tagline; 'every other' paraphrases 'any other'
The page saysa domestic subspecies of the red junglefowl, a species native to southern Asia
The source saysDomestic chickens are a subspecies of red junglefowl (Gallus gallus) , a species native to southern Asia.
The page saysNot Evaluated
The source saysthey are domesticated animals and are not threatened or in danger of being threatenedNote: stats.conservationStatus. The Smithsonian page says only that Kids' Farm animals are domesticated and not threatened; it does not say Not Evaluated. GBIF's Red List category for Gallus gallus domesticus (accepted usage keys 217145895 and 323329087) returns nothing, checked 2026-09-29, so the domestic form has no Red List category; the red junglefowl assessment (LC 2024) is the wild ancestor's and is not cited. Precedent domestic-cat, domestic-dog.
The page saysChickens have four claws on each foot, used to scratch into the earth to find food.
The source saysChickens have four claws on each foot, which are used to scratch into the earth to find food.
The page saysExact size varies greatly among breeds.
The source saysExact size varies greatly among breeds
The page saysChickens are diurnal, meaning active by day, and social.
The source saysChickens are diurnal, social animalsNote: 'meaning active by day' is the writer's gloss of diurnal
The page saysA flock is one rooster with several hens.
The source sayswith one rooster and several hens making up a flock
The page saysA rooster's crow is a shrill call used to communicate territory to other males.
The source saysRoosters are known for their characteristic crow. This shrill call is used to assertively communicate territory to other males.
The page saysHens will not crow, but may cluck to talk to chicks or after laying an egg.
The source saysHens will not crow, but may cluck to communicate with chicks or after laying an egg.
The page saysDomestic chickens are a subspecies of the red junglefowl, a species native to southern Asia.
The source saysDomestic chickens are a subspecies of red junglefowl (Gallus gallus) , a species native to southern Asia.
The page saysThere are more chickens on Earth than any other bird species.
The source saysThere are more chickens on Earth than any other bird species.

Source
03

Rubin et al. 2010

Rubin et al. (2010). Whole-genome resequencing reveals loci under selection during chicken domestication. Nature.

The page saysOne of the most striking selective sweeps, where a favourable gene variant spreads through a population, was found in all domestic chickens.
The source saysidentify selective sweeps of favourable alleles ... One of the most striking selective sweeps found in all domestic chickens occurred at the locus for thyroid stimulating hormone receptor (TSHR)Note: 'where a favourable gene variant spreads' glosses 'selective sweeps of favourable alleles'
The page saysIt sits at the locus for the thyroid stimulating hormone receptor, which is involved in metabolic regulation and photoperiod (day-length) control of reproduction.
The source saysthe locus for thyroid stimulating hormone receptor (TSHR), which has a pivotal role in metabolic regulation and photoperiod control of reproduction in vertebratesNote: 'day-length' glosses photoperiod
The page saystags: domestic-pet
The source saysDuring the twentieth century, specialized layer and broiler breeds were established to circumvent the inherent conflict in selecting for both growth traits (meat production) and reproductive traits (egg production)Note: #981: the tag's definition is 'selectively bred alongside humans'

Source
04

Eriksson et al. 2008

Eriksson et al. (2008). Identification of the Yellow Skin Gene Reveals a Hybrid Origin of the Domestic Chicken. PLoS Genetics.

The page saysThe red junglefowl was presumed to be the sole wild ancestor, but a 2008 study traced the yellow-skin gene to a different species, most likely the grey junglefowl.
The source saysyellow skin does not originate from the red junglefowl ( Gallus gallus ), the presumed sole wild ancestor of the domestic chicken, but most likely from the closely related grey junglefowl ( Gallus sonneratii )Note: 2008 is the reference's publication year
The page saysIts authors called this the first conclusive evidence that the domestic chicken has a hybrid origin.
The source saysThis is the first conclusive evidence for a hybrid origin of the domestic chicken

Source
05

Shimmura, Ohashi & Yoshimura 2015

Shimmura, Ohashi & Yoshimura (2015). The highest-ranking rooster has priority to announce the break of dawn. Scientific Reports.

The page saysIn a 2015 study of small groups, the top-ranking rooster almost always started to crow first each morning, followed by lower-ranking roosters in descending order of rank.
The source saysThe top-ranking rooster almost always started to crow first every morning (97.6 ± 2.9%; Fig. 1c ), followed by lower-ranking roosters in descending order of social rankNote: 2015 is the reference's publication year
The page saysThe ladder even decides who crows first.
The source sayswhen chickens were housed in small groups, the top-ranking rooster determined the timing of predawn crowing

Source
06

Storey et al. 2012

Storey et al. (2012). Investigating the Global Dispersal of Chickens in Prehistory Using Ancient Mitochondrial DNA Signatures. PLoS ONE.

The page saysAncient DNA from directly dated chicken bones, about 1000 years old in Europe and about 3000 years old in the Pacific, indicates multiple prehistoric dispersals from a single Asian centre.
The source saysHaplogroup E mtDNA signatures have been amplified from directly dated samples originating in Europe at 1000 B.P. and in the Pacific at 3000 B.P. indicating multiple prehistoric dispersals from a single Asian centre.
The page saysA Polynesian origin for pre-Columbian chickens found in Chile has been proposed, and questioned by some.
The source saysA Polynesian origin for pre-Columbian chickens recovered from the archaeological site of El Arenal in Chile has recently been proposed ... While this has been questioned by some
The page saysPeople spread the birds themselves.
The source sayssupport for archaeological hypotheses about the prehistoric human transport of chickensNote: linking sentence to the dispersal claim below it

Source
07

Lawal et al. 2020

Lawal et al. (2020). The wild species genome ancestry of domestic chickens. BMC Biology.

The page saysFarms and backyard flocks
The source saysMore than 65 billion chickens are raised annually to produce meat and 80 million metric tons of egg for global human consumption by the commercial sectorNote: stats.habitat: farm-scale keeping
The page saysChickens now live in backyard flocks and on farms, and a 2020 study put the commercial sector at more than 65 billion raised each year for meat.
The source saysMore than 65 billion chickens are raised annually to produce meat and 80 million metric tons of egg for global human consumption by the commercial sectorNote: 2020 is the reference's publication year; backyard flocks and farms carried by the ohio-4h-poultry claims below

How the table was made: a writer drafted the profile from these sources and logged each claim with its quote, a reviewer with nothing but this table checked every sentence said no more than its quote, and a script confirmed each quote appears word for word in the source. The method is in the site'sAbout page.