Occam's Razor

The idea that a sparrow gives a feeding call "for the good of the species" assumes that it knows that is part of a species. And what happens if some sparrows keep the food for themselves?

William of Occam (or Ockham) was a fourteenth century philosopher who suggested that in explaining something, entities should not be needlessly multiplied. Also called the Principle of Parsimony, it suggests the most satisfactory explanation will be the one with the least number of assumptions and logical steps. Thus, you may sometimes read of something being the "most parsimonious" explanation.

Given the fundamental idea that an individual behaves for its own benefit, what explanation can be given for feeding call of a sparrow?

A more immediate reason could be that, with a group of others around it, there is less risk of being the picked off by a predator. Putting it the other way round, there would be more pairs of eyes keeping a lookout, hence more opportunity to concentrate on feeding. On the other hand it has to share the food

Mark Elgar(1) found that, if the food was in crumbs, the first sparrow at the feeding site would chirp at a higher rate than if it were a crust. While there would be a benefit in protection against predators, if the food was a whole piece there was a danger that a bigger sparrow would take it all.

Such a behaviour would have an immediate effect in allowing the sparrow to live longer to have more young, thus any genetic basis would be represented in a larger part of future generations. Nevertheless the group does experience an overall benefit

This allows us to introduce a concept we will use frequently in analysing the literature - the idea of distinguishing proximal causes from ultimate effects.


Elgar, M. A., (1986) House sparrows establish foraging flocks by giving chirrup calls if the food is divisible, Animal Behaviour, 34, pp 169-174 in Hall, M., Halliday, T., (1992) Biology Brain and Behaviour, Part 1, Behaviour and Evolution, Milton Keynes: The Open University Press.

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Bland, J., (2002) About Gender: Occam's Razor
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Last amended 30.11.02