restricted to the Neotropical hawk eagles but recent molecular studies using mitochondrial DNA have shown that both of those genera are paraphyletic and that Cassin's hawk-eagle forms a clade with the larger booted eagles of the genus Aquila. Its closest relatives are Aquila fasciata and Aquila spilogaster (both formerly of Hieraaetus) which together form a distinct sub-clade of Aquila. The visual similarities with other hawk-eagles can be explained by convergent evolution but there is still some work being done on booted eagle phylogeny in general, so this may change in the future. In 2017, a group of researchers proposed that the official English name be changed from "Cassin's hawk-eagle" to "Cassin's eagle", so that the term hawk-eagle could be restricted to current members of Spizaetus and Niseatus in line with the global effort to make bird names more consistent. This has yet to be implemented by most listing authorities. Distribution and habitat West, central and marginally east Africa; from Sierra Leone east to western Uganda and south through the Congo Basin to northern Angola. Restricted to primary rainforest, A. africana is thought to have been more widespread in the past but its distribution has since contracted with the continued destruction of the Guinea-Congolian Forests. Repeated sightings of individuals in primary rainforest fragments in Kenya's Imenti Forest and the Ndundulu Forest in Tanzania have been interpreted as biogeographical evidence for past links between isolated forests in East Africa and those much further West. Cassin's hawk-eagle's preference for primary forest is so strong that its presence is reduced even in slightly disturbed forest and it is completely absent from secondary forest and open biomes which explains its absence between the forests. Ecology The details of the ecology and behaviour of Cassin's hawk-eagle, like most hawk-eagles, are barely known as it is a secretive and rarely observed species, usually seen when soaring over the forest canopy. Its habitat of choice, primary rainforest, is also notoriously difficult to navigate, making surveys and studies extremely difficult. Before 1970, almost nothing was known about its breeding habits but since then multiple studies have uncovered some details. Both sexes help construct the nest with sticks more than above the forest floor in the canopy of a tree where it is lined with fresh foliage. The clutch size is 1-2 eggs which are laid from October–December in Ghana and Gabon, and in December in Uganda, therefore making it