Morphometric sex determination of young Ospreys Pandion haliaetus using discriminant analysis

Capsule Discriminant functions based on morphometric variables provide a reliable method for sex identification of free-living and hacked young Ospreys. Aims To describe an easy, accurate and low-cost method for sex determination of fully grown nestling and fledgling Ospreys Pandion haliaetus based on morphometric measurements. Methods Four different measurements were taken in 114 birds (40–73 days old) and a DNA analysis, using PCR amplification, was carried out for sex identification. A forward stepwise discriminant analysis was performed to build the best explanatory discriminant models, which were subsequently validated using statistics and external samples. Results Our best discriminant function retained forearm and tarsus as the best predictor variables and classified 95.1% of the sample correctly, supported also by external cross-validations with both hacked and free-living birds. Moreover, a discriminant function with only forearm as predictor showed a similar high correct classification power (93.4%). Conclusions These discriminant functions can be used as a reliable and immediate method for sex determination of young Ospreys since they showed high discriminant accuracy, close to that of molecular procedures, and were supported by external cross-validations, both for free-living and hacked birds. Thus, these morphometric measurements should be considered as standard tools for future scientific studies and management of Osprey populations