Sexual Plumage Dichromatism In Two Laughingthrush Species

The plain laughingthrush Garrulax davidi concolor (PL) and Elliot,s laughingthrush Trochalopteron elliotii (EL), are two members of family Leiothrichidae, who are both assumed sexually monomorphic. We employed reflectance spectrometry to determine the plumage coloration in these two species in the hand. PL with dull plumage, the males had brighter head plumage than females, there was no significant difference in coloration of wing and breast plumage between two sexes. EL appeared relatively bright and polychrome plumages, and the males had extremely significantly higher carotenoid chroma than female in grayish-white tail end, however, there was no difference in orange wing patch and yellowish-brown hip plumage between sexes. Both male PL and EL had higher reflectance than female in wavelength ranges 300-700 nm. We argued that the patterns of sexual plumage dimorphism in these two babblers might be selective advantage in reducing nest depredation risk and brood parasitism, and it could be viewed as an indicator to assess the pressure of sexual selection between two sexes.