As work proposed under [the Global Owl Project] is directed at currently living owl taxa, only an overview of owls in the fossil record is offered here to briefly characterize the knowledge base and timeline of fossil owls.
Fossil owls are known from the Eocene, and some living genera have been identified in Miocene, Oligocene (Brodkorb 1971; Walker, in Burton 1973), and Paleocene deposits (Rich and Bohaska 1976; 1981). Brodkorb (1971) listed some 41 extinct species of owls, 11 of which were Tytonidae, 5 were Protostrigidae, and 25 to Strigidae.
The history of the Tytonidae is an old one, and it is not known whether it originated in the eastern or western hemisphere. The representatives of six genera of the Tytonidae have been described from the Paleocene-Oligocene phosphorites of Quercy, France, which illustrates the differentiation and radiation of tytonid owls before the present era of mainly strigid owls (Mourer-Chauvire 1987).
Sub-recent and Pleistocene Barn Owl (Tyto alba) bones have been found in North America, Nuevo Leon and Yucatan in Mexico, Brazil, Galapagos Islands, New Zealand, southern Europe, and Israel (Brodkorb 1971; Mourer-Chauvire 1975). Other species of extinct sub-recent and Pleistocene Barn Owls have been described from cave deposits in Malta (Tyto melitensis), Mauritius in the western Indian Ocean (Tyto sauzieri), and from the West Indies.
Owls from the West Indies were described by Alexander Wetmore as Tyto cavatica (Puerto Rico), Tyto ostologo (Haiti), and Tyto pollens (Bahama Islands) and by Oscar Arrendondo as Tyto noeli and Tyto riveroi (Cuba) (Arredondo 1976; Olson 1978).
During Upper Miocene times lived Tyto robusta, in the Gargano Peninsula (then an island), Italy (Ballmann 1973, 1976), along with the largest owl Tyto gigantea (larger than the present day European Eagle Owl (Bubo bubo)).
An owl from the Strix group, and of very large size (about 1 m tall), Ornimegalonyx oteroi has been described from Upper Pleistocene cave deposits on Cuba (Arredondo 1975).
As no fossil bones belonging to the European Scops-owl (Otus scops) have been found in deposits in Hungary and France older than Upper and Middle Pleistocene (Mourer-Chauvire 1975) and the majority of related species occur in southeast Asia, the European and African Scops Owls probably have the same Asian source. Fossil fragments of a kind of screech owl of the Otus kennicottii/asio type from the Upper Pliocene of Kansas (Ford 1966) support the hypothesis that these screech owls are derived from a tropical North American (vs. Asian) origin.
The Northern Hawk-owl (Surnia ulula) is monotypic in its genus and no fossil relatives are known. Fossil records exist for this species from the Late Pleistocene in Tennessee, United States (Parmalee and Klippel 1982), France (Mourer-Chauvire 1975), Switzerland, Austria, and Hungary (Janossy 1963).
Fossil records of pygmy owls (Glaucidium) in the Americas are from Pleistocene deposits only (California; Mexico; Brazil; Brodkorb 1971).
Fossils of Burrowing Owls (Speotyto megalopera), somewhat larger and more robust than the present species (Athene cunicularia), have been found in Upper Pliocene deposits in Idaho and Kansas (Ford 1966; Ford and Murray 1967).
The Strix intermedia was described from Middle Pleistocene fossils found in Czechoslovakia and Hungary (Janossy 1972). Leg and wing bones of this owl are intermediate in size and structure between those of current day Strix uralensis and Strix aluco. Pre-Pleistocene fossils of Strix brevis (Ballmann, cited by Janossy 1978) are somewhat larger and have slightly different proportions from those of present day Strix aluco, and lend support to the theory that the species differentiation between Strix uralensis and Strix aluco is yet more complicated.
A representative of the genus Aegolius was already present in the Upper Pliocene of Hungary and remains of Boreal Owls (Aegolius funerus) itself have been reported from there too, from the Upper Pleistocene onward (Janossy 1981). Aegolius funerus and the Northern Saw-whet owl (Aegolius acadicus) have also been reported from the Late Pleistocene in Tennessee (Parmalee and Klippel 1982).
Many species of owl are recorded from the late Pleistocene of Britain (e.g., snowy owls Nyctea scandiaca and European eagle owls Bubo bubo, Harrison 1987), France (snowy owls Nyctea scandiaca gallica, Mourer-Chauvire 1975).
In addition to the owls themselves, fossil assemblages of the bones of small mammals are commonly found in caves throughout the world. Since few such mammals live in caves, it is recognized that these animals were accumulated primarily by cave-roosting owl species, but by other means as well (Andrews 1990). These small mammal remains yield information about environmental and climatic changes, particularly those during the Pleistocene and Holocene.