Abnormal behaviour of birds in captivity

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A pet grey parrot displaying signs of extensive feather-plucking. Psittacus erithacus -feather plucking -pet-6.jpg
A pet grey parrot displaying signs of extensive feather-plucking.

Abnormal behavior of birds in captivity has been found to occur among both domesticated and wild birds. [1] Abnormal behavior can be defined in several ways. Statistically, 'abnormal' is when the occurrence, frequency or intensity of a behaviour varies statistically significantly, either more or less, from the normal value. [2] This means that theoretically, almost any behaviour could become 'abnormal' in an individual. Less formally, 'abnormal' includes any activity judged to be outside the normal behaviour pattern for captive birds of that particular class or age. [3] For example, running rather than flying may be a normal behaviour and regularly observed in one species, however, in another species it might be normal but becomes 'abnormal' if it reaches a high frequency, or in another species it is rarely observed and any incidence is considered 'abnormal'. This article does not include 'one-off' behaviours performed by individual birds that might be considered abnormal for that individual, unless these are performed repeatedly by other individuals in the species and are recognised as part of the ethogram of that species.

Contents

Most abnormal behaviours can be categorised collectively (e.g., eliminative, ingestive, stereotypies), however, many abnormal behaviours fall debatably into several of these categories and categorisation is therefore not attempted in this article. Abnormal behaviours here are considered to be related to captive housing but may also be due to medical conditions. The article does not include behaviours in birds that are genetically modified to express abnormal behaviour.

Behaviors

When housed under captive or commercial conditions, birds often show a range of abnormal behaviours. These are often self-injurious or harmful to other individuals, and can include feather and toe pecking, cannibalism, stereotypy, vent pecking, as well as abnormal sexual behaviours such as chronic egg laying.

Feather and toe pecking

Feather pecking is an abnormal behaviour observed in birds in captivity (primarily in laying hens) [4] whereby one bird repeatedly pecks the feathers of another. Toe pecking is a similar occurrence in commercialized hens which includes repeatedly pecking the toes of another. Each of these behaviours have been tied to physiological stress (i.e., extremely enlarged adrenal glands) likely caused by housing conditions in captivity. [5] [6] [7]

Cannibalism

Cannibalism in birds of captivity is a behaviour often linked to feather pecking. With increasing frequency and intensity of feather pecking, the risk and prevalence of cannibalism increases. [4] Since feather pecking leads to increased food consumption due to heat loss through the skin of the bird, and feather pecking is an already aggressive behaviour that consists of cannibalistic qualities, cannibalism is a common consequential effect. Cannibalism is defined as the act of consuming all or part of another individual of the same species as food. [4] [8] [9] [10]

Stereotypy

Stereotypies are invariant, repetitive behaviour patterns with no blatant function or objective, and seem to be restricted to captive and/or mentally-impaired animals. [11] Stereotypies are the result of inability of an animal to perform a normal behaviour due to external environmental conditions or circumstance. A common stereotypy in laying hens is pacing which involves the animal constantly walking back and forth in a seemingly ritualistic manner due to no access to a suitable nest site. [11] The pacing stereotypy is also hypothesized to arise from intentional movements of escape, specifically in captive animals such as birds. The overabundance as well as lack of stimulation associated with the sub-optimal environment of captivity are the common factors amongst development of stereotypy behaviours in birds. [11]

Vent pecking

Vent pecking is an abnormal behaviour observed in birds in captivity that involves pecking and causing damage to the cloaca, its surrounding skin, and underlying tissue of another bird. Occurrence of vent pecking is primarily immediately after a bird has oviposited when the cloaca is red and enlarged. [12] Vent pecking, like feather pecking, is a gateway behaviour to cannibalism due to its cannibalistic features of hostility towards another individual that involves the aggressive tearing and damaging of the skin and tissue. Vent cannibalism was found to be the most common type of cannibalism causing death in autopsy results of laying hens. [13] [14] [15]

Additional behaviors

Causes

When analyzing the behaviour of birds in captivity, what is considered normal or abnormal behaviour is dependent on the form and frequency that the particular behaviour is expressed in the natural environment. [33] Birds raised in pet stores tend to be raised with other birds, however, after being sold and taken to the owner's home, birds in captivity are often housed in isolation and in environments lacking abundant resources or complex stimuli. In the United States, it is estimated that forty million birds are kept caged and improperly cared for. [34] Because of these inappropriate housing conditions, abnormal behaviour patterns may appear in caged birds kept as pets. Once established, these abnormal behaviours in birds are often not alterable. [35]

When social interactions amongst birds are absent or inadequate, abnormal social behaviour may develop. For example, a study regarding parrots that had been isolated in cages demonstrated that most birds showing this social deprivation had significant behavioural disturbances, such as aggressive behaviour, feather picking, self-mutilation, restlessness, screaming, apathetic behavior, and stereotypies. [36] Several parrots living in captivity monitored during a study have displayed behaviors  consisting of screaming excessively and biting. This specific noise made by these birds is encouraged in captivity. Biting however is not a typical defense mechanism used by wild parrots. [32] Cannibalism often occurs in large animal husbandry systems, which are usually impoverished environments with a lack of opportunities. [37] In addition, studies of caged canaries have revealed two common stereotypies. [21] These include spot picking, where birds repeatedly touch a particular spot in the environment with the tip of their beak, and route tracing, a pacing behaviour associated with physical restrictions in movement imposed by the cage. The absence of song learning in zebra finches has also been implicated as a behavioural abnormality. [38] In these birds, the social interaction of a young male with his song tutor is important for normal song development. Without the stimulus, the song, which is necessary for mating behavior, will not be learned.

Researchers have analyzed ways to alleviate some abnormal behaviours in caged birds. Presenting these birds with novel stimuli e.g. a mirror or plastic birds, and social stimuli, such as a brief view of a bird in another cage, significantly reduced stereotypies. [39] In addition, it has been suggested that keeping caged birds in pairs or small groups may reduce the development of abnormal behaviours, however, little quantitative evidence has thus far been collected to support this claim. [36]

Statistically, 1/10 of endangered birds tend to have egg infertility, but this number increases for breeders of endangered species working with captive birds. [31]

In addition to the abnormal behaviours exhibited as a result of commercialized captivity such as for poultry, there also exist problematic behaviours that occur as a function of the social deprivation associated with domestication. Social deprivation is the prevention or reduction of normal interaction between an individual and others in their species. [40] Currently the dominant method for rearing domesticated birds is "hand-rearing" which requires chicks be separated from their parents for periods of time up to several months. [41] The social deprivation associated with this technique of upbringing is one of the most detrimental forms of social deprivation since even short-term disruptions in parental care can cause extreme abnormal behaviour in the affected young. [41] For example, normal sexual and habitat imprinting is altered in both male and female birds as a result of maternal separation, as well as individual ability to adapt to stressors within the environment. [41] Neophobia is the avoidance of novel objects in the environment and is diminished with social deprivation and maternal separation. [41] A lack of neophobia can decrease probability of survival due to the affected animal's lack of hesitation to approach potentially dangerous stimuli. Moreover, many juveniles require a song tutor to accomplish the song learning necessary for successful mating practices. [42] Therefore, socially deprived juveniles may exhibit abnormal vocal and consequent mating behaviours which may be detrimental to their survival.

It is important to note that once established, these abnormal behaviours are often not transformable. [42] There is presently little research regarding a solution to the abnormality caused by captivity in birds; however, it has been suggested that keeping domesticated caged birds in small groups or pairs may reduce the likelihood of developing abnormal behaviours. [43]

See also

Related Research Articles

<span class="mw-page-title-main">Debeaking</span> Trimming of a birds beak, usually performed on domesticated birds

Debeaking, beak trimming, or beak conditioning is the partial removal of the beak of poultry, especially layer hens and turkeys although it may also be performed on quail and ducks. Most commonly, the beak is shortened permanently, although regrowth can occur. The trimmed lower beak is somewhat longer than the upper beak. A similar but separate practice, usually performed by an avian veterinarian or an experienced birdkeeper, involves clipping, filing or sanding the beaks of captive birds for health purposes – in order to correct or temporarily to alleviate overgrowths or deformities and better allow the bird to go about its normal feeding and preening activities. Amongst raptor-keepers, this practice is commonly known as "coping".

<span class="mw-page-title-main">Feather-plucking</span> Maladaptive, behavioural disorder commonly seen in captive birds

Feather-plucking, sometimes termed feather-picking, feather damaging behaviour or pterotillomania, is a maladaptive, behavioural disorder commonly seen in captive birds that chew, bite or pluck their own feathers with their beak, resulting in damage to the feathers and occasionally the skin. It is especially common among parrots, with an estimated 10% of captive parrots exhibiting the disorder. The areas of the body that are mainly pecked or plucked are the more accessible regions such as the neck, chest, flank, inner thigh and ventral wing area. Contour and down feathers are generally identified as the main target, although in some cases, tail and flight feathers are affected. Although feather-plucking shares characteristics with feather pecking commonly seen in commercial poultry, the two behaviours are currently considered to be distinct as in the latter, the birds peck at and pull out the feathers of other individuals.

An ethogram is a catalogue or inventory of behaviours or actions exhibited by an animal used in ethology.

<span class="mw-page-title-main">Behavioral enrichment</span>

Behavioral enrichment is an animal husbandry principle that seeks to enhance the quality of captive animal care by identifying and providing the environmental stimuli necessary for optimal psychological and physiological well-being. Enrichment can either be active or passive, depending on whether it requires direct contact between the animal and the enrichment. A variety of enrichment techniques are used to create desired outcomes similar to an animal's individual and species' history. Each of the techniques used is intended to stimulate the animal's senses similarly to how they would be activated in the wild. Provided enrichment may be seen in the form of auditory, olfactory, habitat factors, food, research projects, training, and objects.

<span class="mw-page-title-main">Battery cage</span> Agricultural technology

Battery cages are a housing system used for various animal production methods, but primarily for egg-laying hens. The name arises from the arrangement of rows and columns of identical cages connected, in a unit, as in an artillery battery. Although the term is usually applied to poultry farming, similar cage systems are used for other animals. Battery cages have generated controversy between advocates for animal welfare and industrial producers.

<span class="mw-page-title-main">Poultry farming</span> Part of animal husbandry

Poultry farming is the form of animal husbandry which raises domesticated birds such as chickens, ducks, turkeys and geese to produce meat or eggs for food. Poultry – mostly chickens – are farmed in great numbers. More than 60 billion chickens are killed for consumption annually. Chickens raised for eggs are known as layers, while chickens raised for meat are called broilers.

Vacuum activities are innate, fixed action patterns (FAPs) of animal behaviour that are performed in the absence of a sign stimulus (releaser) that normally elicit them. This type of abnormal behaviour shows that a key stimulus is not always needed to produce an activity. Vacuum activities often take place when an animal is placed in captivity and is subjected to a lack of stimuli that would normally cause a FAP.

<span class="mw-page-title-main">Dust bathing</span> Animal behavior

Dust bathing is an animal behavior characterized by rolling or moving around in dust, dry earth or sand, with the likely purpose of removing parasites from fur, feathers or skin. Dust bathing is a maintenance behavior performed by a wide range of mammalian and avian species. For some animals, dust baths are necessary to maintain healthy feathers, skin, or fur, similar to bathing in water or wallowing in mud. In some mammals, dust bathing may be a way of transmitting chemical signals to the ground which marks an individual's territory.

<span class="mw-page-title-main">Stereotypy (non-human)</span> Non-pathological pattern of animal behavior which displays very low variability

In animal behaviour, stereotypy, stereotypical or stereotyped behaviour has several meanings, leading to ambiguity in the scientific literature. A stereotypy is a term for a group of phenotypic behaviours that are repetitive, morphologically identical and which possess no obvious goal or function. These behaviours have been defined as 'abnormal', as they exhibit themselves solely in animals subjected to barren environments, scheduled or restricted feedings, social deprivation and other cases of frustration, but do not arise in 'normal' animals in their natural environments. These behaviours may be maladaptive, involving self-injury or reduced reproductive success, and in laboratory animals can confound behavioural research. Stereotypical behaviours are thought to be caused ultimately by artificial environments that do not allow animals to satisfy their normal behavioural needs. Rather than refer to the behaviour as abnormal, it has been suggested that it be described as "behaviour indicative of an abnormal environment".

<span class="mw-page-title-main">Feather pecking</span> When one bird repeatedly pecks at the feathers of another

Feather pecking is a behavioural problem that occurs most frequently amongst domestic hens reared for egg production, although it does occur in other poultry such as pheasants, turkeys, ducks, broiler chickens and is sometimes seen in farmed ostriches. Feather pecking occurs when one bird repeatedly pecks at the feathers of another. The levels of severity may be recognized as mild and severe. Gentle feather pecking is considered to be a normal investigatory behaviour where the feathers of the recipient are hardly disturbed and therefore does not represent a problem. In severe feather pecking, however, the feathers of the recipient are grasped, pulled at and sometimes removed. This is painful for the receiving bird and can lead to trauma of the skin or bleeding, which in turn can lead to cannibalism and death.

Polydipsia is an excessively large water intake. Its occurrence in captive birds has been recorded, although it is a relatively rare abnormal behaviour.

Sham dustbathing is a behaviour performed by some birds when kept in cages with little or no access to litter, during which the birds perform all the elements of normal dustbathing, but in the complete absence of any substrate. This behaviour often has all the activities and temporal patterns of normal dustbathing, i.e. the bird initially scratches and bill-rakes at the ground, then erects its feathers and squats. Once lying down, the behaviour contains four main elements: vertical wing-shaking, head rubbing, bill-raking and scratching with one leg. Normal dustbathing is a maintenance behaviour whose performance results in dust collecting between the feathers. The dust is then subsequently shaken off which reduces the amount of feather lipids and so helps the plumage maintain good insulating capacity and may help control of ectoparasites.

Vent pecking is an abnormal behaviour of birds performed primarily by commercial egg-laying hens. It is characterised by pecking damage to the cloaca, the surrounding skin and underlying tissue. Vent pecking frequently occurs immediately after an egg has been laid when the cloaca often remains partly everted exposing the mucosa, red from the physical trauma of oviposition or bleeding if the tissue is torn by her laying an egg. Vent pecking clearly causes pain and distress to the bird being pecked. Tearing of the skin increases susceptibility to disease and may lead to cannibalism, with possible evisceration of the pecked bird and ultimately, death.

Toe pecking, an abnormal behaviour of birds in captivity, occurs when one bird pecks the toes of another using its beak. This behaviour has been reported in hens and ostriches. Studies have shown that hens exposed to toe pecking have significantly enlarged adrenal glands, indicating increased physiological stress. Hens exposed to toe pecking will step off a raised platform more quickly than control hens, possibly suggesting a heightened fear of elevation. They have also been reported to show depressive behaviour when afflicted by toe-pecking. The act of toe pecking leads to open wounds which are viable for infection and disease to develop. In severe forms, toe pecking can be classified as a cannibalistic behaviour and has been reported as a cause of mortality.

Animal welfare science is the scientific study of the welfare of animals as pets, in zoos, laboratories, on farms and in the wild. Although animal welfare has been of great concern for many thousands of years in religion and culture, the investigation of animal welfare using rigorous scientific methods is a relatively recent development. The world's first Professor of Animal Welfare Science, Donald Broom, was appointed by Cambridge University (UK) in 1986.

<span class="mw-page-title-main">Cannibalism in poultry</span>

Cannibalism in poultry is the act of one individual of a poultry species consuming all or part of another individual of the same species as food. It commonly occurs in flocks of domestic hens reared for egg production, although it can also occur in domestic turkeys, pheasants and other poultry species. Poultry create a social order of dominance known as pecking order. When pressure occurs within the flock, pecking can increase in aggression and escalate to cannibalism. Cannibalism can occur as a consequence of feather pecking which has caused denuded areas and bleeding on a bird's skin. Cannibalism can cause large mortality rates within the flock and large decreases in production due to the stress it causes. Vent pecking, sometimes called 'cloacal cannibalism', is considered to be a separate form of cannibalistic pecking as this occurs in well-feathered birds and only the cloaca is targeted. There are several causes that can lead to cannibalism such as: light and overheating, crowd size, nutrition, injury/death, genetics and learned behaviour. Research has been conducted to attempt to understand why poultry engage in this behaviour, as it is not totally understood. There are known methods of control to reduce cannibalism such as crowd size control, beak trimming, light manipulation, perches, selective genetics and eyewear.

<span class="mw-page-title-main">Furnished cage</span>

A furnished cage, sometimes called enriched cage, colony cage or modified cage, is a type of cage used in poultry farming for egg laying hens. Furnished cages have been designed to overcome some of the welfare concerns of battery cages whilst retaining their economic and husbandry advantages, and also provide some of the welfare advantages over non-cage systems. Many design features of furnished cages have been incorporated because research in animal welfare science has shown them to be of benefit to the hens.

<span class="mw-page-title-main">Chicken eyeglasses</span> Small eyeglasses made for chickens

Chicken eyeglasses, also known as chickens specs, chicken goggles, generically as pick guards and under other names, were small eyeglasses made for chickens intended to prevent feather pecking and cannibalism. They differ from blinders as they allowed the bird to see forward whereas blinders do not. One variety used rose-colored lenses as the coloring was thought to prevent a chicken wearing them from recognizing blood on other chickens which may increase the tendency for abnormal injurious behavior. They were mass-produced and sold throughout the United States as early as the beginning of the 20th century.

<span class="mw-page-title-main">Blinders (poultry)</span>

Blinders, also known as peepers, are devices fitted to, or through, the beaks of poultry to block their forward vision and assist in the control of feather pecking, cannibalism and sometimes egg-eating. A patent for the devices was filed as early as 1935. They are used primarily for game birds, pheasant and quail, but also for turkeys and laying hens. Blinders are opaque and prevent forward vision, unlike similar devices called spectacles which have transparent lenses. Blinders work by reducing the accuracy of pecking at the feathers or body of another bird, rather than spectacles which have coloured lenses and allow the bird to see forwards but alter the perceived colour, particularly of blood. Blinders are held in position with a circlip arrangement or lugs into the nares of the bird, or a pin which pierces through the nasal septum. They can be made of metal (aluminium), neoprene or plastic, and are often brightly coloured making it easy to identify birds which have lost the device. Some versions have a hole in the centre of each of the blinders, thereby allowing restricted forward vision.

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