Passerine polygyny: a role for parasites?

Demonstrates for European and North American passerine birds that the proportion of individuals infected with blood parasites is significantly lower in polygynous than it is in monogamous species. One possibility is that polygynous species are, on average, more resistant to hematozoa infection. This could arise if there is heritable variation in resistance and if polygyny results in resistant males obtaining more mates. Females in polygynous species might settle with already-mated resistant males rather than unmated, less resistant males if they choose males resistant to parasites currently invading the population or if their decision to settle is influenced by the outcome of male-male competition, which might in part be affected by the health of the combatants. -from Author