Multiple ornamentation, female breeding synchrony, and extra-pair mating success of golden whistlers (Pachycephala pectoralis)

Abstract

Considerable variation exists in rates of extra-pair paternity between species, and across and within populations of the same species. Explanations for this variation include ecological (e.g. breeding synchrony), morphological (e.g. ornamentation), and genetic (e.g. relatedness) factors, but it is rare for studies to simultaneously explore these factors within a single population. This is especially true for highly ornamented species, where mate choice based on ornamentation may be more complex than in less-adorned species. We conducted such a study in a migratory population of the highly ornamented golden whistler (Pachycephala pectoralis). We quantified male genetic reproductive success and related it to a range of factors putatively involved in determining extra-pair mating success. We found no effects of genetic factors (male heterozygosity and relatedness) on extra-pair success, nor of territory size, male age, or incubation effort. Instead, males possessing yellower breast plumage and large song repertoires enjoyed higher reproductive success. Additionally, we found a negative relationship between local breeding synchrony and male extra-pair mating success. This may be a consequence of mate guarding during the female fertile period and an inability of males to simultaneously mate-guard and pursue extra-pair fertilisations. In this species, the opportunity for extra-pair matings appears to vary temporally with an ecological variable (local breeding synchrony), while fine-scale, inter-male differences in mating success may be influenced by individual attributes (male ornamentation). The migratory nature of the study population and its lack of natal philopatry may mean that relatedness and inbreeding avoidance are less important considerations in mate choice.