American Kestrel (Falco sparverius) Science Article 17
Reverse mounting during mating has been reported in a number of avian orders (see James 1983 for review). Several authors imply that the behavior is aberrant (Ficken 1963, Nolan 1978, Thompson and Lanyon 1979), while others suggest that reverse mounting is a normal behavioral trait during courtship (Glick 1954, Kilham 1961, Nuechterlein and Storer 1982).
REED BOWMAN AND ELIZABETH M. CURLEY, Wilson Bull., 98(3), 1986, pp. 412-473