Gender-related morphometric differences in mature and nestling Crowned Eagles, with comments on ringing of eagle nestlings in KwaZulu-Natal, South Africa

Abstract

Although most raptor species are sexually dimorphic, many species are non-discrete in some metrics. A limited amount of existing data for southern Africa suggests that Crowned Eagles Stephanoaetus coronatus exhibit non-discrete sexual dimorphism. Consequently, we investigated gender-related morphometric data of Crowned Eagles with corresponding genetic avian sex tests. Immature (n = 13) and adult (n = 5) Crowned Eagles were trapped, measured and released in KwaZulu-Natal, South Africa from 2012 to 2015. Our results show that tarsus width, body mass, and DI claw (hallux) measurements are suitable for discriminating between sexes of mature Crowned Eagles. We comment on the use of South African Ringing Scheme (SAFRING) and colour read-rings as a marking technique in Crowned Eagles. Furthermore, we suggest suitable parameters for accessing nests and marking nestlings. To aid in the age estimates of nestling eagles, a reference of growth of known-age nestlings is provided.

Keywords: African Crowned Eagle, banding, Crowned Hawk-eagle, growth, morphology, raptor, ringing, Stephanoaetus coronatus