What is it about?
Laughing Doves were fed maize in an area of 1 square metre. Every few days a model hawk was released along a wire suspected over the feeding area. An old-fashioned movie camera recorded the reaction of the feeding doves to the hawk. As the flock got bigger it was expected that the reaction time would be shorter. It didn't quite work like this. When there were only a handful of birds they were jittery and reacted fast. When the flock size was large, and about 20 doves were packed into the small feeding area, and they spent time jostling each other for positions rather than keeping a lookout for predators. Reaction times were slow. But for a range of flock size in the middle, the hypothesis was demonstrated pretty neatly.
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Why is it important?
This was one of the first papers to show that there is safety in numbers. Response times to detect predators are fast if there are more eyes to watch.
Perspectives
The data analysis was a big challenge. Overall, the correlation between flock size and reaction time was not significant, although it was clearly in the data when you cut off the ends (small flock sizes, and large flock sizes). The paper effectively re-invented, in 1974, a form of "piecewise regression", a statistical method which had been devised only a few years earlier: Victor E. McGee and Willard T. Carleton 1970. Piecewise regression. Journal of the American Statistical Association 65: 1109-1124. It is a pity I had not found this paper when I had to analyse this dataset; it would have made life easier!
Prof Les G Underhill
University of Cape Town
Read the Original
This page is a summary of: Flocking as an anti-predator strategy in doves, Animal Behaviour, August 1975, Elsevier,
DOI: 10.1016/0003-3472(75)90126-8.
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