HAMILTON and Zuk1 proposed that elaborate secondary sexual characters may have evolved because they act as cues in mate choice by revealing the health of a potential mate. From this theory, they derived the prediction that species which are more liable to parasitic infection should possess well-developed secondary sexual characters. They went on to demonstrate a positive association between prevalence of haematozoa and plumage brightness across species of North American passerine birds. Subsequent analyses by one of us2 on the same colour data confirmed that the relationship with male brightness existed even when the effects of phylogenetic associations were taken into account. The relationship was also found across European passerines when behavioural and ecological correlates of colour and phytogeny were accounted for2. Here, using independently derived plumage brightness scores, we question these conclusions.
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