The Nature of the Predator-Reactions of Breeding Birds 1)

This paper reviews the nature of the reactions of breeding birds to potential predators. The term predator-reaction in such a context is extended to include all reactions from the beginning of the breeding-cycle, and includes attack, threat-display, distraction display (activities selected, apparently, for their deflection function in relation to eggs and young), direct displacements, fleeing, etc. It is maintained that the various reactions, except attack and fleeing themselves, are the outcome of the simultaneous activation of the antagonistic aggressive and escape drives at different levels of integration and threshold due to, among other factors, the stage of the breeding-cycle and the nature of the predator. Evidence is advanced to support the identity of the contributory drives, including examples of aggressive behaviour and difference of reaction in relation to difference in predator. The role of displacement activities is considered. Threat components, which are also due to the activation of aggression and escape, occur as predator-reaction, not simply as displacements (they are that already), but when the drive-complex reaches a certain level of integration in which the aggressive drive is more dominant than in distraction display. Sexual displays, many of which in their functional context are due to inhibition of the major drive, are less easy to fit into the picture in such a way, and their exact relationship is at present obscure. Direct (unritualized) displacements are common predator-reactions. In those species with elaborate distraction display they are a sign of low motivation, but in those species with rare or non-existent distraction display, the displacements tend to grow more complete in performance on increased motivation. Finally, the predator-reactions of the Little Ringed Plover, Charadrius dubius, are outlined briefly in the light of the present analysis.