Bulgarian Journal of Veterinary Medicine, 2020 ONLINE FIRST ISSN 1311-1477; DOI: 10.15547/bjvm.2020-0027 Review TYPES AND CLINICAL PRESENTATION OF DAMAGING BEHAVIOUR FEATHER PECKING AND CANNIBALISM IN BIRDS S. NIKOLOV & D. KANAKOV Department of Internal Non-Infectious Diseases, Faculty of Veterinary Medicine Summary Nikolov, S. & D. Kanakov, 2020. Types and clinical presentation of damaging behaviour feather pecking and cannibalism in birds. Bulg. J. Vet. Med. (online first). Behavioural disorders, including feather pecking and cannibalism, are a common problem in both domestic and wild birds. The consequences of this behaviour on welfare of birds incur serious eco- nomic losses. Pecking behaviour in birds is either normal or injurious. The type of normal pecking behaviour includes non-aggressive feather pecking – allopreening and autopreening. Aggressive feather pecking aimed at maintenance and establishment of hierarchy in the flock is not associated to feathering damage. Injurious pecking causes damage of individual feathers and of feathering as a whole. Two clinical presentations of feather pecking are known in birds. The gentle feather pecking causes minimum damage; it is further divided into normal and stereotyped with bouts; it could how- ever evolve into severe feather pecking manifested with severe pecking, pulling and removal, even consumption of feathers of the victim, which experiences pain. Severe feather pecking results in bleeding from feather follicle, deterioration of plumage and appearance of denuded areas on victim’s body. Prolonged feather pecking leads to tissue damage and consequently, cannibalism. The nume- rous clinical presentations of the latter include pecking of the back, abdomen, neck and wings. Vent pecking and abdominal pecking incur important losses especially during egg-laying. In young birds, pulling and pecking of toes of legs is encountered. All forms of cannibalistic pecking increase morta- lity rates in birds. Transition of various pecking types from one into another could be seen, while the difference between gentle, severe feather pecking and cannibalism is not always distinct. Key words: cannibalism, damaging behaviour, feather pecking, injurious pecking, vent pecking INTRODUCTION The onset of damaging behaviour, such as serious economic losses in many Euro- feather pecking and cannibalism while pean game farms raising wild birds in rearing many birds at a place is an impor- captivity for release and shooting tant problem compromising their welfare (Draycott et al., 2002; 2005). The re- (Rodenburg et al., 2008). This results in levance of the problem is also associated Types and clinical presentation of damaging behaviour feather pecking and cannibalism in birds with increased population of wild birds (Sedlackova et al., 2004; Rodenburg et reared commercially for game meat pro- al., 2013). In general, one bird from a duction (Kuzniacka & Adamski, 2010; flock dominates over another one (Glatz Kokoszynski et al., 2011; Hrabcakova et & Bourke, 2006). This behavioural cate- al., 2012). Despite the extensive research gory is associated to a different morpho- in the field, this bird welfare problem is logy and motivation, linked to hierarchy still actual (Rodenburg et al., 2013). establishment (Van Krimpen et al., 2005; The aim of this review is to provide Bozakova et al., 2017) and serves for set- detailed classification of normal and inju- tlement of competitive interactions (Bo- rious pecking behaviour in birds. It de- zakova et al., 2015; Daigle, 2017). scribes the different types of feather peck- Clinical signs. Aggressive pecking is ing with their definitions, clinical signs, directed at the head and the neck (Sedlac- and resulting damage (localisation) on kova et al., 2004; Rodenburg et al., plumage or tissues. 2013), but should not be confused with Feather pecking in birds is divided feather pecking behaviour (Rodenburg et into normal (physiological) pecking and al., 2008; Bozakova et al., 2012; Daigle, injurious (abnormal, non-physiological) 2017). Pecking at the head by dominating pecking. birds is directed to other flock members with lower hierarchical ranks. In severe cases, bruises of the areas above the eyes, NORMAL (PHYSIOLOGICAL) swollen wattles and ear lobes are observed PECKING (Glatz & Bourke, 2006). Aggressive at- It could be either non-aggressive or ag- tacks are fast energic hits with becks fol- gressive. lowed by escape of the victim or fight with the aggressor (Rodenburg et al., Non-aggressive feather pecking 2013). Facial areas (Kjaer & Hocking, Non-aggressive feather pecking is an ele- 2004), the head, comb, neck are most ment of cognitive and social behaviour. commonly affected. Hierarchical order Allopreening is a specific behaviour of could be changed when new birds are in- birds, representing cleaning of the skin troduced, or if the dominating bird is or feathers of another bird from the wounded or defeated in a fight (Glatz & flock (Sedlackova et al., 2004). Allo- Bourke, 2006; Bozakova et al., 2013). preening is harmless and often Feathers could be damaged, but aggres- performed in a non-aggressive social sive pecking is not the main cause for context (Kjaer & Hocking, 2004). feather loss (Kjaer & Hocking, 2004) and Аutopreening is a specific behaviour does not result in plumage damage of birds, involving cleaning/pecking (Sedlackova et al., 2004; Rodenburg et own feathers or skin (Kjaer & al., 2013). Hocking, 2004). Aggressive pecking INJURIOUS /ABNORMAL (NON-PHYSIOLOGICAL) PECKING Aggressive pecking is a separate form of allopecking, accompanied with menacing Injurious pecking is a general term de- behaviour, which is used to establish and noting forms of gentle and severe feather maintain hierarchical bonds among birds pecking, cannibalistic pecking and vent 2 BJVM, ××, No × S. Nikolov & D. Kanakov pecking (Lambton et al., 2013; Birkl et A typical feather pecking act is de- al., 2017). Injurious pecking could be scribed and illustrated by Wennrich damaging pecking, causing feather da- (1975). The bird performing a feather mage and plumage damage (Bright, 2009; pecking act approaches slowly the victim Drake et al., 2010; Nicol et al., 2013). from the back or from the side, aiming at its feathers. The victim initially ignores Plumage damage the act (Sedlackova et al., 2004; Kjaer & Injurious pecking is associated with plu- Hocking, 2004), but persistent pecking mage damage which may range from could induce an injury (Glatz & Bourke, breakdown of feather tips to removal of 2006) and depending on pecking severity, feathers and appearance of large defeath- the victim vocalises and moves away ered areas on the body (Lambton et al., (Sedlackova et al., 2004). Feather pecking 2013). Although plumage damage is not is directed at the body, mainly the poste- the most reliable sign pointing at injurious rior part, abdomen or tail feathers and pecking, it is usually easier to be detected shows a clear repetitive pattern of feather that the behaviour itself. Plumage damage pecking and plucking, e.g. is of compul- could occur due to feather wearing-off or sive rather than aggressive nature (Van aggression (Nicol et al., 2013). There is a Hierden et al., 2004a; Daigle, 2017). direct association between severe feather Behavioural categories pecking and the degree of plumage da- mage (Lambton et al., 2013). Feather In the bird flock, two main types of birds pecking of high intensity could lead to could be defined in terms of feather peck- rapid defeathering in most birds and that ing: attacking bird and feather pecking is why, additional feather pecking could victim. On the basis of individual experi- not be evaluated on the basis of plumage ence, birds are divided in four behavioural status (Nicol et al., 2013). categories (Daigle et al., 2015). Severe feather pecking is used as a model, as it is Feather pecking easier to be visualised. Birds may behave This is a form of abnormal behaviour as follows: (non-aggressive behavioural disorder), in feather peckers, performing severe which one bird uses its beck to peck the feather pecking, but never receiving it; feathers of another one (Sedlackova et al., victims, which only receive pecks but 2004; Daigle, 2017). Feathers could be never give them; pulled and often, eaten (Nicol et al., 2013; neutral birds, which never receive and Rodenburg et al., 2013; Lambton et al., never give pecks; and 2015). Plucking of feathers causes pain feather pecker-victim, that are peckers (Cloutier et al., 2000;), higher risk from and victims at the same time (Daigle, injuries and outbreak of cannibalism 2017). (Nicol et al., 2013). The extensive loss of feathers covering the body is accompanied GENTLE FEATHER PECKING with impaired flying ability and thermo- regulation, resulting in increased feed Gentle feather pecking is defined as light intake by 1030% from birds (Gilani et pecks on feather tips of another bird, al., 2013). without pulling or plucking of feathers (Parmentier et al., 2009; Lambton et al., BJVM, ××, No × 3 Types and clinical presentation of damaging behaviour feather pecking and cannibalism in birds 2013). It could be observed in young birds characterised with high repetition fre- under the a form of investigatory social quency of pecking at the same site from behaviour (Riedstra & Groothuis, 2002; one bird to another (Van Krimpen et al., Nicol, 2018) or could become a stereo- 2005; Newberry et al., 2007) and could typy. In both cases, feather damage is in- result in minimum feather damage (Glatz significant. Yet, the association between & Bourke, 2006; Nicol, 2018). Gentle gentle feather pecking in young birds and pecking is often ignored by the recipient severe feather pecking in adults is a prob- (Riedstra & Groothuis, 2002; Rodenburg lem (Newberry et al., 2007; Rodenburg et et al., 2008). al., 2008). Feather pinching. It represents Clinical signs. Gentle feather pecking approaching a bird from behind or could be characterised as gentle repeated from one side and gentle pinching of pecks on the feathers of the tail, wings, its feathers. This act usually causes back and neck of the bird (Daigle, 2017). minimum damage (Sedlackova et al., It is usually manifested as bouts, and tar- 2004).