Investigating patterns of avian ornamental colouration : intraspecific and interspecific approaches : a thesis presented in partial fulfilment of the requirements for the degree of Masters of Science in Zoology at Massey University, Albany, New Zealand

Research into the evolutionary function of elaborated colouration in birds is continually ongoing. Novel approaches to addressing various aspects of this broad research area may help us consider this topic in a new light. This thesis aimed to consider two different aspects of avian colouration research using novel methods and testing relatively new hypotheses. Firstly, I consider the cost of carotenoid pigmented ornamental colouration - an area of research that is currently under intense debate. Classically carotenoid-based pigmentation has considered carotenoids to function as indicators of sexual quality, with costs being due to carotenoids being diet dependent in birds. Recent research however has argued that carotenoid pigmented colour traits function in agonistic social contexts, and that the cost of using carotenoid pigmentation as an honest indicator of quality is a social one. In this study I test this hypothesis using blackbirds (Turdus merula) and their natural variation in carotenoid-based bill colouration. I replicate a study using model presentations to simulate territory intrusions. Additionally, I examine the feasibility of using three-dimensionally printed models in avian behavioural studies. This study was unsuccessful due to a lack of response rates from territorial males, however it was successful in questioning several differing aspects between my study and the study I replicated. Secondly, I explore the spatial organisation of colouration on the bodies of birds as a way of potentially inferring different functions of elaborate colour traits. In the third chapter I develop a novel method that allows objective analysis of the spatial organisation of colour on the bodies of birds, by removing morphological variation between species. Using this method I present a case study on the spatial organisation of colour elaboration in 2,471 species of passerines. This case study uses a difference in sexual dichromatism as a proxy for colour elaboration and determined where signaling hotspots occur on the bodies of birds. These results demonstrate that conspicuous colouration is most common in the supercilium, chin, and upper breast of passerine birds. In chapter four, I used this method to determine correlations between different life-history traits and different regions of the body. This study aimed to infer the function of different regions of the head in signaling. My results show that the irises in species with tropical life-histories and cooperative breeding strategies are more likely to be elaborately coloured; bills of larger bodied species are more likely to be elaborately coloured than are smaller species; and the spatial organisation of colour effects females more than it does males