Modelling antipredator vigilance and flight response in group foragers when warning signals are ambiguous.

The trade-off between feeding and vigilance in flocks of birds has been extensively studied and modelled. An assumption of many models is that if one bird spots the predator, it gives a signal and the rest of the flock takes flight. However, it has been observed that birds do not always respond to signals and in fact many signals turn out to be false alarms. Since taking flight is both costly in time and energy, it may be advantageous for birds not to respond to all alarm calls. A model is developed to show under what circumstances birds should respond to a signal. The model predicts that under most, but not all, circumstances, birds should respond to multiple detections but not to single detections. The model also predicts that if birds respond to all flights, they will have to compensate for the time lost to feeding and the greater energy requirement of spending more time in flight, by being less vigilant, and they have a lower probability of survival than birds which only respond to multiple detections.

[1]  G. Ruxton,et al.  Intraflock variation in the speed of escape-flight response on attack by an avian predator , 1999 .

[2]  A. Houston,et al.  Evolutionarily stable levels of vigilance as a function of group size , 1992, Animal Behaviour.

[3]  R. Trivers.  The Evolution of Reciprocal Altruism , 1971, The Quarterly Review of Biology.

[4]  H. Pulliam,et al.  On the advantages of flocking. , 1973, Journal of theoretical biology.

[5]  R. J. F. Smith,et al.  Evolution of Alarm Signals: Role of Benefits of Retaining Group Members or Territorial Neighbors , 1986, The American Naturalist.

[6]  Modelling responses in vigilance rates to arrivals to and departures from a group of foragers , 1998 .

[7]  S. L. Lima,et al.  Iterated Prisoner's Dilemma: An Approach to Evolutionarily Stable Cooperation , 1989, The American Naturalist.

[8]  G. Ruxton,et al.  Choice of Foraging Area with Respect to Predation Risk in Redshanks: The Effects of Weather and Predator Activity , 1999 .

[9]  S. L. Lima,et al.  Back to the basics of anti-predatory vigilance: the group-size effect , 1995, Animal Behaviour.

[10]  Thomas Caraco,et al.  The scanning behavior of juncos: A game-theoretical approach , 1982 .

[11]  J. M. Davis,et al.  Socially induced flight reactions in pigeons , 1975, Animal Behaviour.

[12]  G. Ruxton.  Group size and anti-predator vigilance: a simple model requiring limited monitoring of other group members , 1996, Animal Behaviour.

[13]  S. L. Lima,et al.  Vigilance while feeding and its relation to the risk of predation , 1987 .

[14]  J. M. Smith,et al.  The Evolution of Alarm Calls , 1965, The American Naturalist.

[15]  A Comparative Study of Some Social Communication Patterns in the Pelecaniformes , 1965 .

[16]  G. Ruxton,et al.  Evidence for a rule governing the avoidance of superfluous escape flights , 2000, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[17]  Lawrence M. Dill,et al.  The Economics of Fleeing from Predators , 1986 .

[18]  G. Roberts.  How many birds does it take to put a flock to flight? , 1997, Animal Behaviour.

[19]  Prof. Dr. Eberhard Curio.  The Ethology of Predation , 1976, Zoophysiology and Ecology.

[20]  Gustaf Rudebeck,et al.  The Choice of Prey and Modes of Hunting of Predatory Birds with Special Reference to Their Selective Effect , 1950 .

[21]  S. L. Lima.  Collective detection of predatory attack by birds in the absence of alarm signals , 1994 .