Gyr-Saker Hybrid Falcon
Viewed from a falconer's aspect, each of the falcons has its good qualities & its bad qualities. In order to get the best performance out of the falcons used in falconry, cross-breeding techniques are used to produce hybrids, which hopefully have the better qualities of each species, while avoiding the less good qualities. There is a phenomenon in genetics known as "hybrid vigour" (technically speaking, "heterosis"), wherby particularly strong traits, especially those related to survival, are actually emphasised in cross-bred animals. "Hybrid vigour" is especially noticeable in the young of parents that have a high degree of inbreeding, which is often the case with pure-bred captive birds.
Amongst others, Gyr (Falco rusticolus), Peregrine, Saker (Falco cherrug), Lanner (Falco biamicus) & Lugger (Falco jugger) falcons are regularly crossed, creating such hybrids as Lanner-Lugger falcons.
Occasionally, the hybrids are further crossed, creating hybrids such as Saker-Lanner-Lugger falcons (1/2 Saker, 1/4 Lanner, 1/4 Lugger).
Aside from the ethical implications, it is illegal to release hybrids into the wild, mainly due to the possibility of breeding with native species.
Two Peregrine-Saker tiercels + closeup of one.
Some of the first ever hybrids from 1971.
Photos courtesy of John Morris.
The first hybrid falcons were produced in the early 1970s in Ireland when Ronald Stevens & John Morris housed a Peregrine & a Saker in the same moulting mews, it was not expected that the two would mate & produce young.
Now hybrids are, for the most part, produced by artificial insemination. (In answer to JPJ, AI is that excellent invention by men that allows women to do everything for themselves, freeing men to get on with the important things)
[I have a vague memory, that another reason for hybridisation, especially in the USA, is that there are less stringent regulations regarding import/export of hybrids compared to pure bred birds]
The qualities being looked for in the hybrids of each species are :
Hybridisation is not limited to falcons, in May 2001, after 4 years of trying biologists & falconers in Scotland successfully crossed a male Golden Eagle with a female Steppe Eagle (Aquila nipalensis). This was also the first raptor to be successfully reared from frozen sperm. Other breeders have successful crossed Red-tailed hawks with Harris Hawks.