Cliffs, trees, and ground-nesting raptors

Ill Their recent paper, Martinez-Abrain and Jimenez (2019) presented an appealing hypothesis about the potential evolutionary consequences of being able to build nests on trees for diurnal raptor species. According to the authors, the fact that only some species of cliff-nesting raptors provide sticks, making a "real nest" on the cliff is due to evolutionary load of formerly tree nesters. They provide an analysis showing that probably those species that do not provide nest material when nesting in cliff are the only truly rupicolous species. This suggestion is a very interesting and original one. and allows the authors to make phylogenetically testable predictions. Additionally, some discussion about the previous origin of these species would be inferred from current nesting habits. For example, large eagles like Golden eagle (Aquila chrysaetos), Spanish imperial eagle (A. adalberti). European Imperial Eagles {A. heliaca), Bonelli·s Eagle (A. fasciata) and others that supply nest on cliffs or even they don't breed on cliffs at allâ may have evolved in forests.