Veterinary/zoology session

Mate choice signals in animals may convey information on individual quality, but this information can be very diverse. Multiple signals are often present in a single species, but the relationship of these signals to one another is usually unclear. The extent to which information provided by different signals is parallel is particularly rarely examined. In birds, for example, color patches of different origin, such as carotenoid and melanin colors, have been regarded as independent of each other, and their correlations and parallel changes have not yet been examined. In our present work on male and female great tits (Parus major), we assessed the phenotypic integration of carotenoid based yellow breast color and structurally based black crown color, using samples taken in autumn (after the summer molt) and in the spring breeding season. We calculated common principal component axes from spectral data of the two plumage areas, and investigated the amount of variance explained by these axes, the similarity of the axes between seasons and sexes, their condition-dependence, and their possible role in the breeding season. We found a stronger relationship in color between the two plumage areas in spring than immediately after molt. Due to a change in the relative role of different color axes, the principal axes were statistically different in spring than in autumn, probably due to feather abrasion. The two sexes showed similar color axes in both autumn and spring. The color variable linking the saturation of the yellow breast to the ultraviolet reflectance of the crown was correlated with condition during molt in autumn, and with breeding success variables in spring: breeding time in males and clutch size in females. Our results show that it is worth and important to investigate the parallelism of plumage colors of different origin. During this work, we also tested a new statistical method for the assessment of color integration.