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["Rosemary Royle" <>]

Actually it appears that the unfaithfulness is driven primarily by the females 
who apparently like to increase the odds of breeding successfully by mating 
occasionally outside the "normal" pair bond. (Not putting all her eggs in one 
genetic basket?) It is not always clear what benefit this might accrue (except 
where it means that more than one male might help rear the young) but tests on 
clutches of eggs for a wide range of species show that more often than not 
there is more than one male bird involved.

Rosemary Royle
Wales, UK