Identification of the Greater Spotted Eagle Clanga clanga, Lesser Spotted Eagle Clanga pomarina and interspecific hybrids using the morphology of shed flight feathers

ABSTRACT Capsule Shed feathers can be used for the field identification of the Greater Spotted Eagle Clanga clanga and Lesser Spotted Eagle Clanga pomarina, but identification of hybrids is problematic. Aims To provide an easy method for distinguishing the shed flight feathers of the Greater Spotted Eagle, Lesser Spotted Eagle, and their hybrids. Methods We examined seven morphological characteristics and developed multinomial logistic regression models to aid in identification of feathers. Results The most informative feature was the relative feather length. Barring improved the identification of tail feathers, secondaries, and proximal primaries. Feathers of Lesser Spotted Eagles were significantly shorter and more barred than those of Greater Spotted Eagles. Feathers of hybrids were also highly barred but had an intermediate length. The length from the tip to notch, width of the notch, and specific colouration patterns were also included in the best models for specific feather types. The combination of these characteristics resulted in identification accuracies of 89–97% for Lesser Spotted Eagle feathers and 80–100% for Greater Spotted Eagle feathers. However, all F1-hybrids were incorrectly identified as Greater Spotted or Lesser Spotted Eagles. Conclusion Shed feathers could have potential for the non-invasive field identification of spotted eagle species at nest sites. However, the identification of hybrids based on feathers is difficult due to substantial morphological variation and overlap with parent species.