The Nature of the Predator-Reactions of Waders Towards Humans; With Special Reference To the Role of the Aggressive-, Escape- and Brooding-Drives 1)

Abstract

1) The predator-reactions of waders towards humans are outlined and discussed with special reference to causation. Generally speaking, pure escape is most characteristic of non-breeding birds. While reproductively motivated birds on the nesting ground show a tendency to attack, most often their reactions are due to the conflict between escape and aggression. The nature of the aggression involved is parental, i.e. it is super motivated by the parental side of the major reproductive-drive. The brooding part of the parental-drive plays no important causal role in most predator-reactions (such as displacement-activities, distraction-display) but expresses itself autochthonously on occasions, usually in attempts to return and brood the eggs or young. It is very probably an important element in the nest-protecting displays, however, in which the birds remain on or near the nest at the approach of the predator with the wings spread out. 2) Besides obvious escape and, attack patterns the following main reactions, in the probable order of increasing aggressive content, are evoked by human predators:- a) D i s p I a c e m e n t - a c t i v tie e s - usually feeding, comfort, sleeping and brooding movements; due to thwarted escape and low-intensity conflict between escape and attack. b) D e m o n s t r a t i o n - a mainly aerial and vocal form of reaction shown most commonly by larger species nesting in grassland habitats; in its most complete form due to a stronger conflict and an increased aggressive content. c) Distraction- Display- forms of conspicuous ritualized behaviour releasing and directing hunting behaviour in the predator; also due in full form to an intense conflict with a marked aggressive content. d) T h r e a t B e h a v i o u r - reactions in which attack is more or less imminent but just blocked by escape; includes patterns from intraspecific behaviour. Both demonstration and distraction-display have a marked threat content on occasions, so no clearcut distinction is possible causally between the three categories. While the majority of escape patterns and displacement-activities are also shown by non-breeding birds, demonstration, distraction-display, threat behaviour and attack appear only in reproductively motivated ones. 3) The origin and ritualization of predator-reactions are briefly considered. Distraction-displays, often thought to have evolved from threat and courtship displays through displacement, are now so ritualized that their derivation is obscure. The locomotory intention-movement is tentatively suggested as their primary source of origin. 4) Best progress in the study of predator-reactions can be furthered by the strict following of objective methods of investigation and interpretation. The present review has aimed to indicate such an approach to the general problem of predator-reactions in waders; more precise work on individual species is now desirable.