Résumé
We studied the influence of marine resources during a year of abundance and another of extreme scarcity, on sexually selected ornaments of the king penguin ( Aptenodytes patagonicus), a seabird with striking coloured ornaments in both sexes. Displaying birds started their breeding cycle with similar mean body mass each year, but both sexes had significantly larger yellow/orange auricular patches in the year of abundant resources. Colours of the auricular patches and breast were more pure in the good year, and both UV and yellow/orange colours of beak spots were brighter. Comparison of the mating process suggested lower levels of choosiness in both sexes during the unfavourable year, perhaps in order to pair more quickly and partly compensate for a marked delay in breeding initiation. Our results suggest that the expression of sexual traits may substantially vary under different environmental conditions, a predication of some models of mate choice and sexual selection.