THE POLYGYNANDROUS MATING SYSTEM OF THE ALPINE ACCENTOR, PRUNELLA-COLLARIS .2. MULTIPLE PATERNITY AND PARENTAL EFFORT

Parentage was determined by DNA fingerprinting for 110 young from 38 b roods. There was no intraspecific brood parasitism and no young were f athered by males from outside the polygynandrous group. Nineteen (50%) broods were fathered by one male (15 by alpha, four by beta), 17 by t wo males (14 alpha and beta, two alpha and gamma, one beta and gamma) and two by three males (alpha, beta and gamma). A male's paternity sha re of a brood increased with his share of the matings, measured as the proportion of time he gained exclusive access to the female. This rel ationship was the same for alpha and beta males, which suggests that t heir copulations were of equal potency. Alpha males gained a larger sh are of the paternity by guarding fertile females and their overall pat ernity within the group tended to increase with female nesting asynchr ony, although not significantly so, and to decrease with more competin g subordinate males. Males were more likely to help feed nestlings if they gained a greater share of the matings with the mother. There was no difference between alpha and beta males in the relationship between the probability of helping and mating share. Given a choice between t wo synchronous broods, males preferred to help where their mating shar e was greatest. When alpha and beta males helped at the same nest thei r share of the feeds reflected their share of matings, not their domin ance rank. When only one male helped at a nest, alpha males decreased their amount of help with decreased mating share, whereas beta males d id not. This difference may arise because alpha males have greater cha nces of mating with other females in the group, so opportunity costs o f helping are greater for them. How these different helping responses influence female preference for alpha versus beta males is discussed.