RT21: Female ornaments: Sexually selected or genetically correlated?

Trond Amundsen¹ & Rebecca Irwin²

As recognised by Darwin, extravagant plumes, gaudy colours and other sexual ornaments occur more frequently among male than female birds. Nevertheless, females of a variety of species are quite ornamented, although often to a lesser extent than the males of the same species. Traditionally, female ornaments in birds and other animals have been considered non-adaptive, being merely a genetically correlated response to sexual selection acting on the males. Alternatively, female ornaments maybe subject to sexual selection acting directly on the females, either through male choice or female-female competition. Recent studies of Crested Auklets Aethia cristata and European Bluethroats Luscinia svecica seem to support the idea of sexual selection through male choice, while studies of Barn Swallows Hirundo rustica and Red-winged Blackbirds Agelaius phoeniceus, on the other hand, rather lend support to the genetic correlation hypothesis. The aim of the RTD is twofold: (1) to discuss recent theoretical and empirical results related to female ornaments and mutual mate choice, and (2) to discuss how the two hypotheses regarding female ornamentation can be critically tested and separated through experimental work.