DISSERTATION RESEARCH: Forging a Context for Female Mate Choice for Carotenoid Ornaments

Auburn University, Auburn AL

Investigators

Abstract

The overarching goal of this research project is to advance understanding of the evolution of animal ornamentation. Birds feature some of the most elaborate songs, dances, and colors of the animal kingdom, and such displays are generally accepted to have evolved in response to female preferences during mate choice. However, the specific processes that have shaped the ornamental traits remain contentious. In particular, current theory proposes that the yellow-to-red coloration in the ornaments of many bird species is an honest signal of quality, but the mechanisms linking ornament expression to quality, and hence the information content that ornaments present to choosing females, remain unclear. This research project will provide critical tests of how colorful pigments relate to the quality of both colored ornaments and physiological condition in a songbird species, the domestic canary (Serinus canaria). An additional set of experiments will then investigate how the two conspicuous signals of the male canary--brilliant coloration and complex song--interact to shape female mate choice. Using a species that is well-adjusted to captivity enables particularly fine control over experimental variables without subjecting the birds to cage stress, and further allows for a suite of outreach activities using live canaries as "science ambassadors" both to hobbyist canary breeders nationwide and young students across the state of Alabama. While many behavioral studies have examined sexual selection for carotenoid-based coloration, there is no consensus for how carotenoid pigments link to signal honesty and how condition-dependent signals shape female preferences. This research project comprises two complementary sets of experiments assessing both the mechanistic basis of signal honesty and the ultimate function of color signals. The research will address these questions with tight experimental control using the highly amenable captive system of the domestic canary (Serinus canaria). Initial experiments will examine the mechanistic basis for condition-dependence in carotenoid-based ornaments by testing fundamental assumptions about the role of allocation tradeoffs in maintaining signal honesty. Specifically, the researchers will use canaries with knockout mutations that eliminate carotenoid absorption or allocation to examine the benefit of circulating carotenoids and the potential cost of their allocation to plumage in a controlled manner that is not possible in other systems. While these experiments will yield information about the proximate mechanisms that maintain signal honesty, bridging the gap between mechanism and function will greatly advance the importance of this core research to understanding animal behavior. Therefore, the second set of experiments will use a novel mate-choice experimental design with tight control over male display phenotype to examine whether the condition-dependent expression of carotenoid coloration is the target of female preference. These tests will establish the ultimate behavioral context for the mechanism studied in the first experiments by assessing how carotenoid-based plumage coloration impacts mate choice as a component of the overall multimodal songbird display.