Abstract:Color discriminability in birds is enhanced both by tetrachromacy and colored oil droplets. Most sexually monochromatic passerine birds, from a human visual perspective, were actually sexually dichromatic from an avian visual perspective, based on comparisons of plumage reflectance data using a visual model. In this study, we compared the plumage reflectance, body measurements and patch sizes between male and female Tree Sparrow (Passer montanus saturatus). Totally, 45 individuals (18 males and 27 females) captured in 2014 and fed in the campus of Beijing Normal University were used in this study. In the non-breeding season (15 Jan. 2017) and breeding season (17 Apr. 2017), body size, area of black throat and ear patch, and reflectance spectrums of crown, throat, ear covert and rump were measured from 29 birds each time. Based on multivariate analysis of variance of body measurements (Table 1) and independent t-test of patch sizes (Fig. 1), we found there is no obvious difference between males and females, in both breeding season and non-breeding season. From an avian visual perspective, Tree Sparrow is a sexually monochromatic bird through analysis of bird vision model that based on the plumage reflectance data (Table 2 & 3, Fig. 2). Summarily, there is no sexual dichromatic in Tree Sparrow in our analysis. We wish the above results can provide basic information for the evolution of sexual dichromatism in Old World Sparrows.