sexual dimorphism in eastern rock nuthatch sitta tephronotain in iran

there is little chance for species with competitor to develop intraspecific variability such as sexual dimorphism. sitta tephronota is a well-known rock-dwelling bird species in iran, which occurs in zagros mountains in strong ecological competition with sitta neumayer. thus, no sexual dimorphism is expected for sitta tephronota in this area. despite the role of this species in the rise of the concept of character displacement and the importance of sex identification in field studies, sexual dimorphism in this species is little known. we used analysis of covariance for finding significant sex differences in 14 primary variables and applied a bonferroni correction for multiple p-value thresholds of statistical significance. morphological matrices were analyzed by principal component analysis (pca) in sympatric and allopatric zone separately to determine the distribution of males and females along the first two axes of pca (size and shape) were strongly overlapped both in sympatric and allopatric zones. our results suggest that other factors are involved in explaining the lack of sexual dimorphism in this species.