Determining Sex in Golden Eagle (Aquila Chrysaetos) Chicks

Abstract Incorporating sex ratios of chicks into population viability studies increases knowledge of overall health of endangered populations. Currently a reliable non-invasive method to identify the sex of golden eagle chicks is not available, despite this, claims are commonly made based on morphology. Ten biometric measurements from 43 Scottish golden eagles aged 2-7½ weeks were assessed to see if sex could actually be determined using this non-invasive methodology. Sex was confirmed via molecular analysis of blood samples. Discrete and principal component analyses of the different biometrics could not correctly determine individual chick sex. Therefore, despite being more invasive, molecular sexing remains the recommended tool of choice for accurate sex identification of Scottish golden eagle chicks younger than 7½ weeks of age. This has important implications for golden eagle field studies where empirical morphological measurements are frequently and typically taken, but we have shown are not reliable in determining the sex of such young chicks.