A current model species in our studies of the behavioural ecology of sexual signals is the purple-crowned fairy-wren,

Malurus coronatus. In this species, visual as well as vocal signals are apparent: males, and to a much lesser extent females, display striking seasonal ornamental plumage, and pair members engage in conspicuous duets. Interestingly, although it belongs to the genus Malurus that is characterised by the highest known levels of extra-pair paternity, M. coronatus does not engage in the conspicuous extra-pair sexual displays typical for the genus and males have exceptionally small testes. Such a combination of traits indicative of strong sexual selection (seasonal sexual dichromatism, phylogeny)  as well as  indications of reduction in sexual conflict (small testes, cooperative acoustic signalling) is highly unusual. This provides an opportunity to study these evolutionarily novel adaptations free from phylogenetic inertia.
Therefore, a first aim of my study is to establish the genetic mating system, and relate within-pair and extra-pair reproductive success to relative investment in visual and acoustic signals, and to establish whether there are apparent trade-offs between these signals. In addition, I would also like to examine the role sex hormones play in mediating sexual signalling.

Honesty of bright birds: a role for testosterone?
Plenarvortrag DZG-Tagung Münster 2006

Anne Peters, MPI Seewiesen, Vogelwarte Radolfszell

© 18.12.2006 Deutsche Zoologische Gesellschaft e.V., DZG