A lot of variation and asymmetry in the white patches of male capercaillie tails, but no association with mate choice

ABSTRACT

Male western capercaillies ( Tetrao urogallus ) exhibit conspicuous white patches on their elongated black tails. Since males display their tails during courtship to females, and since there are significant individual differences in the size and pattern of these patches among males, these traits could be subject to sexual selection and influence mate choice. The aim of this study was to investigate the significance of the amount and symmetry of these white patches in female choice. The study was based on game camera images collected from 13 display grounds in Southern Finland over a period of 9 years (17 lek‐years and 85 males). The results showed no evidence that the extent of white patches on the tails or their asymmetry affected the likelihood of males to mate. There was no difference whether asymmetry was measured as the absolute difference in the amount of white in individual tail feathers or as relative differences. Nor did the intra‐lek rank order of these traits among males better explain the distribution of matings. It appears that, despite their visibility and considerable individual variation, the tail patterning in males is not a target of female choice, and mate selection is based on other traits. Actually, the significance of the white patches may be to facilitate individual recognition. Capercaillie display is most intense at dawn, when the white markings stand out particularly clearly and can enable females and other males to identify individuals even from a distance.