SEXUAL IMPRINTING SUPPORTS THE EVOLUTION OF NOVEL MALE TRAITS BY TRANSFERENCE OF A PREFERENCE FOR THE COLOUR RED

Abstract

We investigated if sexual imprinting on birds with a red artificial trait can influence female preference for mates bearing other novel, i.e. not-imprinted traits in male Javanese mannikins (Lonchura leucogastroides). We tested two groups of females in mate choice tests. One group of females was sexually imprinted on parent birds adorned with a red feather on the forehead. The other group was raised by normal unadorned birds and was assumed to be sexually imprinted on the normal unadorned phenotype. Females could choose between unadorned and adorned males in simultaneous double choice tests. The adorned males were ornamented with three different kinds of artificial ornament, which differed from the learned red feather on the forehead in a specific manner. The novel traits were a blue feather which differed from the familiar red feather in colour only, red stripes at the tail which had the same colour as the red feather but differed in shape and position at the body, and blue stripes at the tail (same colour as the blue forehead feather), which were different from the red feather in all three qualities. Females which were sexually imprinted on the red feather showed a similar strong preference for the red stripes at the tail as for the learned red feather. These same females showed no preference for males bearing a blue feather on the forehead or for males bearing blue stripes at the tail. This shows that sexual imprinting on a red trait leads to a preference only for another novel red trait due to transference of a preference for the colour red. The control females which were raised by unadorned birds responded on average indifferently to males bearing any of the artificial traits, i.e. some females rejected adorned males, some females preferred adorned males. To latter females it seems that a novel male ornament is somewhat attractive independent of any previous learning. Sexual imprinting on the red feather can influence female mate preferences for mates bearing other novel artificial traits due to transference of a preference for the colour red. Transference of colour preference makes it possible to react to a stimulus that differs from the imprinting stimulus in size, shape or position and therefore might play an important role in the evolution of conspicuous male traits.