V originále
According to the viability indicator hypothesis, ornaments of many bird species honestly signal individual quality and health status. In this study, we investigated the health- and stress-indicating capacity of both feather- and skin-based ornamental traits in the grey partridge (Perdix perdix), a vulnerable avian species of the European agricultural landscape. In 50 free-living males, we assessed individual health status by examining the differential and absolute leukocyte counts, absolute erythrocyte count, complement activity, and pro-inflammatory immune responsiveness to phytohaemagglutinin (PHA). We found that males expressing extensive melanin-pigmented breast ornaments developed stronger skin inflammation after PHA stimulation than males with limited ornaments, suggesting that these are high-quality individuals that are able to mount a robust immune response. Furthermore, we found that the UV signal of the carotenoid-pigmented eye patch ornament is negatively related to the absolute immature erythrocyte count and the peripheral blood heterophil/lymphocyte (H/L) ratio, indicating that males with a slow pace of life and healthier males express skin ornaments with higher UV reflectance. Ornamental colouration in grey partridge males may, therefore, serve as a reliable signal of condition (in terms of resource balance) and health (in terms of stress resistance) to females.