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Tethered Flight:  A Methodology of Hacking and Imprinting Techniques 

A lot of people are curious as to the methodology of introducing the Peregrine Falcon back into the wild.  After the management plan became reality.  Trusted methods of falconry were heavily relied upon.  It even went as far as purchasing birds for release from local falconists that were about 30 -60 days old and hacking them from platforms in nesting sites that were historically recorded to have Peregrine Falcons.  In falconry Hacking is a tried and true method of training a bird to hunt and grow to become a strong adult with or without parents.  There are risks however.  I have listed here also some Imprinting methods and things that had to be avoided thought the time the reintroduction was taking place.  Please note that while I am familiar with the terminology, every experienced falconist has a proven methodology that works for them and the environment in which the birds must be trained and raised.

Hacking in Falconry:

    Restricted to areas and breeders who fly their own progeny and are prepared to run the risk of losing an eyass or two.  Hacking involves placing an immature eyass in a mock eyrie before she can fly and allowing her a period of liberty in the wild whilst her feathers are completing their growth and hardening off.  She can thereby learn to fly, gain a little muscle, learn about coping with the elements and even make early sorties on game before they are recaptured to take up for training.  In this way, a hacked eyass is the next best thing to a passage hawk, by merit of her wider experience. 

        A shed with one side that opens should be positioned in a secluded spot, where the eyass will be safe.  A group of three or four eyasses is placed onto a nesting platform within the shed when their feathers are half-grown.  The shed must be predator-proof and food should be given at regular times, though a hatch to prevent any risk of imprinting and tied onto a hack board so that the eyasses do not develop the habit of carrying.  A hack bell is fitted, nowadays together with a transmitter with long-life batteries.  Clip rings of different colours can also be fitted on the legs to facilitate identification.

        Over the ensuing weeks, the eyasses are permitted to branch out onto suitable perches inside and outside the hack house.  Food is always made available.  Soon they venture further a field and must be recaptured before they become independent.  If one is seen making a kill, it is time to recapture them.  They will have to be trapped, under license, with a manually operated bowtrap.  One of the few drawbacks to hacked eyasses is that they will be familiar with pitching in trees, which may prove to be their detriment.  They also develop tastes in terms of quarry and switching their preferences can prove difficult.

 Recovery Hacking 

    The release of captive bred Peregrines to supplement dwindling or regionally extinct populations began just over a decade ago.  In areas where Peregrines still nest, these young have sometimes been fostered to wild pairs to supplement natural production.  In areas where no Peregrines were nesting, young have been cross-fostered to together species (Prairie Falcons or Gyrfalcons in North America), or more commonly, “hacked” from artificial nest sites.  Hacking, the controlled release of young falcons form an artificial eyrie, was developed centuries ago by falconers as a means of building flight skills and strength prior to actual training.  It has proved to be a viable reintroduction method as evidence of the success of the Peregrine restoration program in eastern United States. 

    Hack site attendants fulfill the rolls of surrogate parents, by providing food prior to the release and for several weeks after the Peregrines fledge.  The ability of human to protect and teach newly fledged falcons is severely limited, however, in comparison to an adult pair of falcons.  Mortality of hacked Peregrines both during the hack period and during their first year of independence is normally as high if not higher than that of naturally fledged young.  The majority of losses during hacking can be attributed to young not orienting to the hack site and drifting way prior to developing hunting skills, and also to direct losses from predation, primarily by Great Horned Owls.

    The mortality for Peregrines during their first year of life is thought to be between 50-70%.  The mortality of birds after their first year is substantially reduced: 2—30% or possibly even lower owing to the bias in banding recovery estimates.  A total of 775 Peregrines were released in eastern US by The Peregrine Fund between 1975-85.  In 1985, 38-40 pairs of returning Peregrines were located; 25 of these pairs were known to have attempted nesting.  The number of Peregrines that attempted to breed represents slightly less than 10% of the total number of birds previously released that would have been 2 years older by 1985.  Although there are considerable numbers of returning Peregrines that have not been seen, it is likely that 70-80% of hacked Peregrines do not live long enough to attempt breeding.  Most of this mortality, as in many other species, occurs during the first year of life. 

    There are two types of hacking, tame and non (wild or holdover).  Tame-hacking appears to be of rather limited use except with special problem hacks, such as those that experience heavy predation.  Retrapping wild-hacked Peregrines, on the other hand, appears to offer several advantages as a reintroduction technique.  Mortality losses during the first year are substantially reduced, with about twice as many birds surviving to one year of age.  Peregrines released in this way are almost certain to remain at the hack site, potentially increasing site recognition and affinity and also allowing a controlled transition back to the wild state.  These falcons are essentially getting a second hack and are returned to the wild with a full year of hunting experience at a time of good weather and high prey density. 

    There are other advantages to the holdover technique.  Birds are always readily available for release to pair with single birds that have returned to a breeding site.  We have also found these birds to be very useful in straightening out problem hacks where the released young failed to orient to the hack site.  A tethered bird will bring them in, often within minutes.

    The successful establishment of breeding pairs is what hacking ultimately comes down to and the methods that have failed only prove how to go about reintroduction in the future, however disappointing it may be.  The results or rewards come when a couple makes their way back to the hack site to nest, and sometimes it is successful.  Otherwise they may just move on into a similar area with a better nesting location.  The Porcupine Mountains Peregrine population is thought to be a matter of this last case.  All around the state of MI Peregrine Falcons were being released but not many had returned to mate (3 years after hatching is when they mature and can become full adults ready for brooding), but they had spread back out into some more of the historical or natural areas.  Since not many records of the Peregrine population were taken before the affects of DDT took place, much of the historical data of nesting sites were lost and it is unknown whether or not the Porcupine Mountains was such a place.  But I understand how it could be with the high rocky cliffs and the lake it over looks, could be.  It has had a successful nesting pair for over 5 years now.  Originally, the male and female may have been from the Grand Island release or somewhere further down state.


Crèche-reared imprint

By far the most common is the crèche-reared imprint, which is the result of a group of eyasses hand-reared together.  These hawks are normally hand reared from the egg having been hatched in an incubator and never replaced with the parents or foster parents.  Such hawks are likely to scream for food, although some may not.  They may also mantle over food, both on the perch when the austringer is within sight and on the fist.  They may show a degree of aggression towards the austringer.

Food Imprint

The worst sort of imprint is a food imprint.  The term is used to describe a hawk that has been reared by hand in isolation.  Such hawks will scream to be fed and for attention when the austringer is in sight and, responding to the sound of human voices, often when he is not.  During training, her familiarity with people and her consequent lack of fear can easily turn aggression.  When given food on the fist or the lure, she is likely to mantle and scream in threat.  She may also be ‘sticky footed’ on the fist.  When on quarry or the lure, she may attempt to carry.

Dual Imprint

Dual imprinting results when a hawk is reared by a foster parent, which will allow the austringer into the aviary to socialize with the eyass (es).  Provided that the austringer never enters the aviary when the hawk is feeding, but only at times suitable to socialize with her, the hawk should lack the undesirable imprinted traits – and, it is to be hope, will be confidant when taken up for training, lacking all fear of the austringer.  The real merit of this type of imprint has yet to be proved, for whilst it may work well, the advantage gained appears in most cases to be of questionable value; when jessed by this familiar friendly face, the hawk’s confidence is often dented, leaving the austringer with the task of reestablishing it, in much the same way that he would have had to establish confidence with a hawk which parent-reared.

Sociable Imprint

Such imprints are reared in isolation by hand but, in contrast to food imprints, spend nearly all their time in the company of the austringer, relying on him not just for food, but also for socializing - companionship and playtime.  Ideally such an imprint will never scream because she is never allowed to want for anything in the way of warmth, food or companionship.  Sociable imprints will never breed with their own kind, but are usually destined for artificial insemination.  In falconry terms, it is possible to fly an Accipiter reared in this way with a great deal of confidence as she is likely to return to the austringer as much out of friendliness as out of a desire for food.  However, it is extremely difficult to make a good job of imprinting a hawk in this manner and not worth doing with a broadwing.  It is very time consuming and, if it goes wrong, the austringer will be left with a food imprint of the worst order.

Imprints on Training

Many novices make the mistake of thinking that an imprint is going to be easier to train, because it will be       friendlier.  Taking into account the above catalogue of vices, it can be seen that in fact the reverse is true.  Imprints are touchier and extremely difficult to make good.  Even very experienced austringers will be hard     pressed to correct the vices inherent in imprints thought their conditioning and most would prefer not to try.    To work an imprint successfully, the austringer has to have a keen understanding of hawk psychology to        pre-empt the establishment of the vices.