Molecular sexing and stable isotope analyses reveal incomplete sexual dimorphism and potential breeding range of Siberian Rubythroats Luscinia calliope captured in Taiwan

The Siberian Rubythroat Luscinia calliope breeds widely across Siberia and several other north Asian countries, migrating to overwinter to the south, including Taiwan. Its presence in Taiwan presented a unique opportunity to investigate questions which could not be reliably answered before the development of modern molecular techniques. We used molecular sexing techniques to determine whether there is overlap between the sexes in the measurements of colour and morphometric traits. We also used stable hydrogen isotope analysis to determine the potential breeding areas of these individuals. We found consistent morphometric and colour differences between males and females, but with so much variation that no single measurement could be used to sex individuals and, as already suspected, neither size nor colour of the red throat-patch or the bordering sub-malar stripes are reliable field marks for sexing Siberian Rubythroats. However, a combination of wing length and red throat-patch area when entered into a logistic regression correctly identified all males and females. This result could not be repeated when we used a discriminant function with cross-validation, which is currently the standard procedure for sex discrimination. The stable hydrogen isotope analysis showed that individuals captured in Taiwan potentially originate from large parts of its known breeding range, but mostly from southern areas. This suggests a 'leap-frog' migration by this species. Furthermore, larger individuals originated from higher latitudes, in accordance with Bergmann's rule. Modern molecular techniques thus shed interesting new insights into the morphology and ecology of Siberian Rubythroats.

(PDF) Molecular sexing and stable isotope analyses reveal incomplete sexual dimorphism and potential breeding range of Siberian Rubythroats Luscinia calliope captured in Taiwan. Available from: https://www.researchgate.net/publication/279045977_Molecular_sexing_and_stable_isotope_analyses_reveal_incomplete_sexual_dimorphism_and_potential_breeding_range_of_Siberian_Rubythroats_Luscinia_calliope_captured_in_Taiwan [accessed Oct 15 2018].