Paternity and parental effort in dunnocks Prunella modularis: how good are male chick-feeding rules?

Abstract

In polyandrous dunnocks, natural variation in alpha versus beta male share of matings was correlated with their paternity share (assessed by DNA fingerpringting) and with their share of work in chick feeding. A polyandrous male's share of mating access was a better predictor of his parental effort than was his total amount of mating access, suggesting that a male might monitor his paternity share by comparing his mating success with that of his rival. Males were removed temporarily at various stages of the mating cycle to create experimental variation in mating success. The effects of this on paternity and male parental effort were compared, to test how well a male's chick-feeding behaviour promoted his own reproductive success. Fingerprinting revealed that replacement males sired most of the eggs fertilized during the removal period. Removed males fed chicks only if they had gained matings during egg laying. This behaviour was adaptive because of the greater loss of paternity to replacement males earlier on in the mating cycle, but it led males (1) to undervalue matings achieved before laying, which could fertilize the first eggs in the clutch, and (2) to overvalue later matings, achieved at a time when most or even all of the clutch was fertilized. The removals confirmed that the alpha: beta share of parental effort in polyandry was determined by their share of matings, not by their dominance rank per se. By contrast, experimental manipulation of a monogamous male's mating access did not influence his parental effort, despite paternity loss. Why responses differ in monogamy and polyandry, and why dunnocks do not pass on a paternity marker as a better guide to parental effort than these crude, indirect, cues based on mating access, are discussed.