is larger than the average bill of the large members of the genus Aquila but is notably smaller than those of the large species of sea eagle and the Philippine eagle. The gape size of martial eagles is relatively large, however, being proportionally larger than in other booted eagle species behind (albeit considerably behind) the Indian spotted eagle (Clanga hastata) and the steppe eagle (Aquila nipalensis) in relative gape size, indicating a relative specialization towards swallowing large prey whole. Voice The martial eagle is a weak and infrequent vocaliser. Little vocal activity has been reported even during the breeding season. The recorded contact call between pair-members consists of the birds, usually when perched, letting out a low mellow whistle, . More or less the same vocalisation is known to have been uttered by females when male brings food and repeated mildly by large begging young. During territorial aerial display and sometimes when perched, adults may utter a loud, trilling . The territorial call may be heard from some distance. Recent fledglings also at times make this call. A soft may be heard, made by pairs around their nest, perhaps being a mutual contact call. In comparison, the crowned eagle is highly vocal especially in the context of breeding. Habitat The martial eagle is to some degree adaptable to varied habitats but shows an overall preference for open woods and woodland edges, wooded savannah and thornbush habitats. The martial eagle has been recorded at elevations of up to but is not a true mountain dwelling species and resident eagles do not usually exceed an elevation of . These eagles also avoid closed-canopy forests and hyper-arid desert. As such it is mostly absent from Guinean and Congolian forests, despite the species’ requirement for large trees for nesting purposes. It is shown that martial eagles can inhabit forests locally in areas where openings occur. For example, in a bird atlas for the country of Kenya, perhaps surprisingly, 88% of martial eagles were found to reside in well-wooded areas and they occurred in areas where annual rainfall exceeded . In southern Africa, they have adapted to seemingly more open habitats than elsewhere in their range, such as semi-desert and open savanna with scattered trees, wooded hillocks and, as a recent adaptation, around pylons. In the desert areas of Namibia, they utilize ephemeral rivers that flow occasionally and allow large trees to grow. They usually