Allopreening as Agonistic Behaviour

Data has been assembled on the incidence of ( = preening) in various species, and from this, and from personal observations, views on its causation and function have been derived. The term allopreening with its converse autopreening, was chosen in preference to mutual to avoid ambiguity; and the terms non-reciprocal, reciprocal, and simultaneous, have been used to describe the type of allopreening. Information was obtained, or observations made, on in 41 different avian families. In most species it resembles the attention given to plumage during autopreening. Since the presence of plumage does not invariably elicit preening behaviour, the behaviour associated with was examined for evidence of its causation. It was found to be closely linked with aggressive behaviour, and in many species attack appeared to give way to allopreening, which appeared to be a replacement, or outlet, for it. If replaces aggression to differing degrees some evidence of the change can be expected. The usual form of attack is pecking at the head. From observations of captive birds it has been found that submissive postures appear to reduce attacks to light pecking, and that when species respond to attacks of individuals of other species as though this were the attack is frustrated, and through habituation may decrease until it resembles allopreening. In the cowbirds preening invitation postures have induced in some species which do not normally show this behaviour. In such circumstances is considered to be the direct result of the frustration of the aggressive drive and to be displacement behaviour having a similar initial movement. In addition to this there appears to be little evidence that occurs as a normal form of preening behaviour. When its functional value as preening is examined it is found that although such preening usually occurs on areas of plumage which a bird cannot reach for itself, yet it occurs only in a minority of species; there is no evidence that species which lack it are at any disadvantage, and in many species where it does occur it occupies only a brief part of the breeding period. It does not therefore appear to be of value as plumage maintenance. Preening invitation postures are considered to be postures resulting from thwarted fleeing, appeasing, or withdrawing behaviour, combined with head positions which initially result from attempts to protect the eyes from, or evade, the bill of the preener without moving away. These head positions could function as postures in which the aggressor ceases to be visible and the tendency to flee is reduced. Allopreening can be regarded as a form of agonistic behaviour in which the normal tendencies of attacking or fleeing, when two individuals are in close proximity, are in conflict with sexual and opposing attacking and fleeing tendencies. In the attacked bird thwarted fleeing will tend to result in a fluffed posture, while the head positions will cut-off the aggressor and reduce still further the fleeing tendencies. In the attacking bird the thwarting of the aggressive tendencies by the refusal of the other bird to flee, together with possible sexual and fleeing conflict, will create a situation where displacement behaviour might be expected, and where the confrontation of the aggressor with the raised feathers of the recipient will increase the likelihood of preening behaviour. This behaviour appears to have become fixed and ritualised in some species. An examination of the known incidence of allopreening, which has been summarised for the Families concerned, shows that certain characters reoccur in association with it and may be factors determining its appearance. These are: Restricted site, where two individuals are forced into close proximity either because of the nature of the nest-site or because they cannot move easily on land; Long absence, which might increase aggressive tendencies; Sociability,such as colony breeding or clumping together, involving close proximity; Long pair-bond, where individuals are in each other's company for a long period; Sexual monomorphism, the sexes closely resembling each other with possibilities of non-recognition on first encounter. There factors make it possible to define the type of bird likely to show allopreening. The one outstanding factor is the enforced proximity of the two individuals. In some species there is apparent evidence of soliciting by males, which might either be a submissive display by a dominant bird reducing the likelihood of aggressive behaviour, or might indicate a change of dominance during a particular period. There are, in some genera where most species allopreen, odd species which do not show it, but which do show special greeting ceremonies on occasions when might be expected. These ceremonies might be alternative ceremonies replacing allopreening.