Application of Two Complementary Molecular Sexing Methods for East Asian Bird Species

Numerous avian species are sexually monomorphic, especially nestlings, posing difficulties in determining their sex by morphological traits alone. Despite the difficulties, sex identification of birds is an essential part of ex situ conservation breeding programs for endangered species, and the sex of individuals is an integral component of information required for research concerning ecology, behavior, genetics, and conservation biology. Therefore, molecular sexing methods are gaining increasing attention as an aid in study and conservation of many bird species. An amplification refractory mutation system (ARMS) method using the sequence differences between CHD1Z and CHD1W was applied for sex identification of 29 East Asian bird species to test the applicability of the method for a wide range of wild bird species. The sex of 25 bird species was successfully identified by the ARMS method using the P2/NP/MP primer set, and the sex of four additional species was identified by another primer set P2/P8. The methods were applied to sex 124 individual samples that were preliminarily sexed by only morphological characteristics of the birds. Of the specimens tested, 16 (12.9%) individuals showed different gender from the preliminary data. This showed that sex identification of monomorphic avian species by external morphology alone has a high risk of misidentification. Therefore, alternative molecular sexing methods are recommended in the sexing process where monomorphic individuals, damaged carcasses or parts of carcasses are involved.