4 Things About Chickens

4 Things About Chickens

Vision

Behaviour in chickens is often visually mediated since sight is their most vital sense, alluded by the structural size of the eyes relative to the head and brain. They're fixed in place within bony sockets as with most birds, consequently resorting to rapid head movements for situational adjustment.

However, retinal photoreceptors require ~20 milliseconds of consecutive stimulation before the head moves again for the registered image not to be blurry. When walking, their head bob counteracts this flaw by keeping the head and eyes relatively still for consistency.

Otherwise, they have ~300-degree vision with ~30 degrees of overlapping binocular vision at the front for beak precision, nictating membranes (third eyelid) for extra protection, ~40x the retinal nerves of humans and the fourth cone cell pigment type for ultraviolet light perception.

Moreover, chickens have a lateralised brain function for the visual system. The right hemisphere (translating to controlling the left side of the body) is dominant in this context. It's speculated to be linked with how they develop in the egg - orientated where the right eye is exposed to outside light through the shell, while the left is not.

The right eye is short-sighted, whereas the left is long-sighted. When foraging, they can tilt their head sideways to the right, utilising short-sightedness for food on the ground and long-sightedness to scan for aerial predators. The left eye is also more proficient regarding cognitive processes such as human face identification and pecking inhibition when viewing a conspecific taste something undesirable first.

Sociality and Communication

Chickens harbour quite elaborate communication, with 20-30 distinguishable vocalisations. For instance, mating, threat, submission/dominance, battle cry, contentment, excitement, territorial, fear/distress, privacy, alongside danger warnings for ground and aerial predator types with subsequent alarm calls for attacks.

Furthermore, males exhibit 'food call' communications, typically in the presence of one familiar hen or more. Frequencies vary based on individual preference and perception of food quality. Hens are more likely to approach when there are calls suggestive of higher preference.

When there are no others, there's significantly less calling, plus even less with another male. It's indicative that the call receivers get considered in social context - determining if calling is worth the eventual outcome - such as group survival with familiar females or competition with another male.

In groups, there exists the infamous pecking order, a group's social hierarchy relationship dictated by factors like gender, size, maturity/development and personality (e.g. assertiveness). The rankings get established via interactions involving an assessment of their success rate in a confrontation.

Discrimination learning is used to discern the opponent's potential for dominance - outstanding features include feathers providing a flared appearance, long and sharp talons and an intimidating size. If neither side submits after the initial dispute, head pecking and kicking/scratching can ensue. Assessment accuracy can be increased over repeated encounters if the victor is unaccepted after the first.

Intelligence

Chickens are cleverer than everybody thinks; they are as cognitively, emotionally and socially intelligent as most other mammals and birds. Even as chicks, they know an object that gets hidden still exists (object permanence) and can differentiate between the first face they see in life (which likely leaves a considerable impression) and unfamiliar ones - being sensitive to age and picture orientation.

Chicks can learn what foods to eat and avoid from the mother, and the presence alone comforts the chicks by easing distress and fear from uncertainty and vulnerability; therefore, imprinting and maternal relationships are crucial for the development of food preferences, social buffering and mitigation of atypical behavioural patterns.

They have the capacity for empathy, presumably evolved to enhance parental care for offspring survival. It's implicated through the mother's physiology as heart rate, breathing, and vocalisation can rise when the chicks are distressed; the body prepares for the possible defence of the young against a predator. There is less of a basis for empathy between adults, even ones that are familiar with each other.

Chickens have even demonstrated some complex behaviours consisting of observational learning, behavioural inhibition/self-control regarding anticipatory waiting (resisting a small food offering first for a bigger reward later), plus social learning concerning cognitive bias judgement - e.g. pessimistic if their life experience has been distressing in commercial factory farms.

Miscellaneous

Chickens have oil glands on their backs, secreting fatty acids that keep them waterproof, protecting against cold temperatures. The oil loses effectiveness eventually, so they often have dust baths in mini dirt ditches to wash the oil off, then preening the new oil over their feathers.

They have pneumatic (hollow) bones, making them lighter for prompt and agile movements, where the wrist and ankle are fused with the hand and foot bones correspondingly - which grant stability and strength/endurance for landing impacts at the cost of flexibility.

Half an eggshell is the average person's calcium requirement daily for nervous system and bone function, for example, osteoporosis in older people. It can be powdered and mixed with bread for palatability, which is also sustainable, pertaining to food waste reduction.

Lastly, chickens are capable of paradoxical/rapid eye movement (REM) sleep, meaning they can dream. In addition, they're unihemispheric during slow-wave sleep - so half of the brain is asleep at a time. The active half processes stimuli from the one open eye to still watch for predators.