HB Response to DEFRA/APHA regarding Invasive Alien Species
Dear Mr Henderson,
In response to your request for information to assist with your work for the Non-Native Species Secretariat, I have prepared the following:
In the UK there is no compulsory registration or licensing of falconers and bird of prey keepers. Whilst the Wildlife and Countryside Act 1981 demands that Schedule 4 birds (indigenous species of conservation concern) are registered through DEFRA, there is no facility to do so for any other species. For all captive birds of prey A10’s, proof of captive breeding or legitimate ownership has to be evidenced.
Keepers of birds of prey range from aviculturalists, breeders, pest controllers, bird abatement specialists, educationists, display givers, bird of prey centre and zoo proprietors and staff, and falconers.
Most losses of captive birds of prey are directly from aviaries. Birds lost in the course of falconry are comparatively rare and those more frequently recovered.
Of the species that you ask about Harris Hawks are the most commonly kept and most frequently reported as lost (either by the keeper or members of the public). Harris’s raised in captivity are and remain very tame, they are comfortable with and around people – hence when lost they are seen and reported with some frequency. There are anecdotal reports of individuals surviving for considerable periods of time if not recovered, however they are a desert/arid-country raptor and unsuited to the British climate so the vast majority will not. In addition, there were reports of a Harris Hawk paired with a wild Common Buzzard, successful breeding was suspected but the Harris and potential progeny have long disappeared. No evidence, genetic or otherwise, corroborates this rumour.
Red-tailed Hawks have been flown in the UK since the late 1960’s but are not nearly as frequently used by UK falconers as they were. There was concern about the potential cross breeding with Common Buzzards when the wild population of Buzzards was still restricted and their recent recovery in numbers at a very early stage. A number of UK falconers, concerned at the possibility, stopped flying Red-Tailed Hawks as a result.
Lanner Falcons have been flown in falconry on the British Isles for a millennia, albeit in small numbers. There is no evidence of which I am aware, that indicates that lost Lanner falcons have been able to survive in the wild in the UK. Hybridisation with indigenous Peregrine falcons is biologically possible but has not been seen in the wild here.
Saker Falcons, as the Lanner described above, have been flown in falconry for many years. Again, there is no verified evidence of breeding in the wild on these islands. Biologically they can hybridise with the Peregrine falcon, but this has not been seen outside the captive situation.
Both of the above are arid-country species for which survival in the wild in Britain is challenging.
The Eagle Owl is quite widely kept in aviculture in the UK, but is not really a species used in falconry so not often flow free. It can be debated if the species is actually indigenous to Britain, it certainly was historically. There is evidence of occasional breeding in the wild but it is suspected that those individuals are wanderers from continental Europe. Subspecies of Bubo bubo are kept in smaller numbers and no evidence exists that they are established in the wild.
Hybrid falcons, predominantly Gyr/Saker crosses but including Gyr/Peregrines and Peregrine/Sakers, are widely used in UK falconry. Whilst many of these will be infertile or imprinted on humans, those that can reproduce are biologically capable of breeding with the Peregrine falcon. There are limited reports of them forming pairs with Peregrines, however these remain very rare and evidence of successful breeding is scant.
Large hybrids are sometimes ‘hacked’ by commercial falcon breeding operations – this is a controlled period of liberty during which food is provided for the young falcon whilst it develops physiologically. These falcons, mostly destined for the Middle-East, are caught up after a week or two and exported.
Hybridisation between compatible species does occur in nature. However, it is widely accepted that it is far less likely in numerically healthy populations, and if it does occasionally occur, the genetic introgression is rapidly diluted to extinction. Fortunately wild British birds of prey are showing buoyant populations and the risk of any problem deriving from lost captive exotic or hybrid individuals is very slight. Raptors are slow to reproduce and are highly visible allowing effective mitigation to be carried out should any non-native or hybrid establish itself in the wild in the UK.
Globally there is no recorded incidence where a raptor has become established as a self-sustaining invasive species. At the crux of this matter whether an alien species is invasive or not. There are many alien species in the UK that cause no issues to the native species. So, whilst exotic or hybrid lost hawks are certainly alien, their invasiveness is negligible. Therefore, I assert that there is no evidence that losses from falconry or collections of birds of prey, constitute a risk in the context of your work.
I include below the most recent report from the IBR showing reported losses of exotics or hybrids (i), a report published by the International Association of Falconry and Conservation of Bird of Prey (ii), and evidence submitted to Scottish Heritage by the British Falconers’ Club (iii).
Please feel at liberty to contact The Hawk Board in any bird of prey context.
Best wishes,
Dr Gordon Mellor
The Chairman
The Hawk Board
Falconry – Inscribed by UNESCO as Intangible Cultural Heritage of Mankind
(i): Lost exotics or hybrid birds of prey – UK information derived from the Independent Bird Register (1st December 2019 – 29th February 2020)
Reported lost
AMERICAN KESTREL 5
BALD EAGLE 1
EUROPEAN EAGLE OWL 2
FERRUGINOUS HAWK 1
GYR/SAKER HYBRID 3
HARRIS HAWK 6
PEREGRINE/SAKER HYBRID 2
Total 20
Recovered
AMERICAN KESTREL 1
HARRIS HAWK 3
EUROPEAN EAGLE OWL 1
RED TAIL 1
Total 8
Found dead
GYR/SAKER HYBRID 3
HARRIS HAWK 2
LANNER 1
Total 6
(ii): International Association of Falconry and Conservation of Birds of Prey
IAF is an accredited NGO providing advisory services to UNESCO Intangible Cultural Heritage Committee (NGO-90006) and an accredited member of IUCN International Union for Conservation of Nature.
The exotic and hybrid issue
Even though many of our modern wild landscapes have been changed hugely by humans, mostly for agriculture, concerns about exotics (= species flown outside their natural ranges) and hybrids (inter-species crosses) in falconry have been occasionally raised by conservation or political organisations. It is theorised that lost falconry birds could survive, and then establish themselves as Alien Invasive Species, or reproduce with wild raptors and thereby ‘pollute’ natural gene pools. The IAF is a falconry and conservation organisation, and therefore holds a responsibility to wild raptors, and the habitats and ecosystems in which we fly our birds. We have therefore reviewed the conservation risk and assessed the impact of exotics and hybrids from falconry, and have agreed a Position Statement and Code of Conduct downloadable here; this Position Statement is subject to ongoing review by IAF scientists, officers and delegates. This position statement does not make judgements about the use of exotics or hybrids within falconry, which is a subjective debate for individual falconers to discuss; the statement is based upon an assessment of the evidence for, and risks of, damage to natural ecosystems from alien invasive raptors that could be occasionally lost from falconry.
Risks of alien introgression from falconry?
For aliens to invade, a number of challenging steps must be continually achieved: exotic falconry birds need to be lost to the wild, then survive and compete in an environment they are not adapted to, then reach breeding age, then find a suitable and compatible mate, then be reproductively viable, then successfully raise a brood, and then that brood must go on to complete the same cycle.
What is the risk and evidence that this could happen from falconry birds?
At the heart of falconry is the ancient hunting partnership between human and bird, based upon a fundamental principle that the bird is trained to depend upon, and return to, its falconer. To this end, falconers show particular responsibility to the risks of alien invasion: they train their birds extremely carefully using techniques that have evolved over thousands of years, they invest heavily in the development and deployment of modern and reliable radio telemetry to further minimise the risk of loss. Thus, the risk of alien invasion from Falconry starts from the premise that Falconers do not deliberately release their birds to the wild, and take every step to prevent loss.
Evidence of alien introgression from falconry?
This principle for minimising loss is supported by empirical evidence. In a published study analysing the loss of registered falcons and hybrids in the UK (where hybrids and exotics are widely flown, and had to be reported to a government registration scheme) shows that the latest data (in 2007) for rates of loss of falcon species or their hybrids are ~1% of birds flown per year. Moreover, there is clear evidence for declines from 1990, concording with improvements in radio telemetry. Falconers therefore primarily aim to prevent loss using careful training and modern radio telemetry and, on the basis of UK Falconers, lose a tiny proportion of the birds they fly (only a proportion of which will be exotics or hybrids). What happens to those exotic or hybrid birds that are lost? Do they survive or go on to breed? Because these birds are generally not prepared for life in the wild, and instead are trained to depend upon the falconer, evidence shows that survival and/or breeding attempts by exotics or hybrids is very low. Reports from birdwatchers across many regions in the UK collated in the paper by Fleming et al (2011) paint a picture for extremely infrequent occurrence. On average, about one reported ex-falconry bird per regional bird report per year (only some of which will be exotic or hybrid). Some of the regional reports cover areas as large as Scotland. There is thus limited evidence from this analysis that lost falcons from falconry survive in the wild, and we urge similar analyses and investigations across wider geographical areas. These analyses indicate that there is a low risk of loss on top of a low risk of wild survival, even in a country where (a) falconry has a long history and is quite widely practiced today, and (b) birdwatching and reporting intensity is relatively high. However, there remain anecdotal reports of occasional exotic survival and even breeding attempts in the wild in the UK, with two isolated examples of Harris’ hawks attempting to breed in the UK and recorded in the British Trust for Ornithology’s Bird Atlas 2007-2011. It is important that any further breeding attempts by Harris’ hawks in the UK (or anywhere else) are monitored carefully, the background to their loss investigated, the context for their survival assessed, and the risk of their introgression or persistence managed. Because of isolated incidents like this, which result from irresponsible ownership and flying without appropriate training or telemetry, IAF has instigated and unanimously voted in a Code of Conduct for its member clubs when flying exotics. We also now run a reporting and recording scheme to make any issue more transparent and evidence based.
Falco hybrids
Even though exotics and hybrids are invariably non-adapted, often sterile or subfertile, and any progeny produced will have to fight against sequential dilution by indigenous wild genotypes, concerns have been raised. In 2008, Birdlife International issued concerns about the use of Falco hybrids, and the risk of alien introgression in particular to wild saker falcons. A handful of incidents of hybrid falcons surviving and showing breeding attempts in the wild had been reported, and these events gained traction because of arguments that they could be the start of alien introgression. IAF has been collecting all evidence from bird reports and fellow Falconers of ex-falconry hybrids attempting to breed in the wild since 1995. We have 12 supported records over the last 18 years, most of them unsuccessful, from records across the European Union and North America. Half of the records were in Germany, associated with large-scale hacking of eyass hybrids by big breeders who did not recover all their males; this practice has now ceased. On the basis of this evidence (and even ignoring the obvious sequential genetic dilution that will ensue should any breeding attempt be successful), IAF concludes that this level of ex-falconry hybrid breeding attempt, across 19 years and across such a wide geographical area, does not present any convincing risk of hybrid invasion. Most importantly, no hybrid breeding attempt or success has been reported in the last 7 years. As a further assurance, Nittinger et al (2007) conducted a molecular genetics study of hierofalcons, part of which aimed to compare pre-hybrid (before 1970) wild saker genomes versus those after hybrid use (post 1970). 22 historic saker specimens were compared with 60 contemporary specimens. There was no evidence of an increase in the very low rates of hybridization known from nature, and therefore no evidence for an increase in genetic signature from exfalconry hybrid introgression.
Summary
In summary, despite historical and widespread hybrid and exotic use in falconry, there is ample theoretical and empirical evidence that harmful genetic introgression to indigenous wild populations has NOT occurred.
(iii): Lost Hybrid analysis – aide memoir for Scottish Heritage meeting
If a male hybrid was lost to the wild and survived long enough to enable it to breed with a wild falcon, first of all the wild falcon has to select the male hybrid in favour of a wild tiercel. I suspect that very few wild peregrine falcons would select a hybrid due to subtle differences in wing shape, body shape and colour if there are plenty of wild peregrine tiercels to pair up with.
Using the presumption that 75% of juvenile hacked hybrids that hypothetically escape would die in the first 12 months and using BTO data that finds that the average clutch size for UK nesting peregrines is 3.3 (511 nests surveyed) and assuming that the ratio of chicks (males/females) produced from a hybrid/wild falcon pairing is 50%, I have calculated the figures below;
Let us assume that four hybrid males are lost to the wild. 3 die in the first year (75% rule). Presuming the remaining single male survives to breeding age despite the daily dangers it faces, then pairs up with a wild falcon, there would be a clutch of 3.3 produced. Of the 3.3 in the clutch, 2.475 would die in the first 12 months (75% rule). This leaves 0.825 of a bird. We then assume that 50% are non-viable females which leaves us with 0.4125 of a male hybrid. Obviously, this does not work and so there would have to be considerably more male hybrids lost to the wild to have any effect on our native peregrine population.
Let us now assume that 12 hybrid males hypothetically escape to the wild. 9 die in the first year (75% rule). Presuming the remaining 3 males survive to breeding age despite the daily dangers they face, which is highly unlikely, then they all pair up with wild falcons which again is highly unlikely, the total clutch size would be 9.9. Of the 9.9 in the clutch, 7.425 would die in the first 12 months (75% rule). This leaves 2.475 birds. We then assume that 50% are non-viable females which leaves us with 1.2375 male hybrids that if they survive to breeding age could potentially breed with a wild falcon.
So, it seems that in ideal circumstances, the absolute best-case number of escaped juvenile male hybrids it would take to produce 1 male hybrid that could potentially breed is in fact 12 (notwithstanding the fact that all 3 of the escaped males that survived the first 12 months would then have to survive to breeding age which is unlikely and would have to pair up with wild falcons which again is unlikely).
A better educated estimate is that over 60 male hybrids would have to escape to have any measurable impact on our native peregrine population which currently numbers over 10,000 birds.
Martyn Standley
Director
British Falconer’s Club
February 2020