Committee for Eagle Rehabilitation Excellence (CERE)
This committee has been established to address the specific needs of the Golden Eagle entering raptor rehabilitation centers. Representatives from select falconry organizations, eagle rehabilitation centers, veterinary community, eagle biologists and the Native American Community form the working group of this committee. The goal of this committee is to make recommendations for the medical evaluation, husbandry, conditioning requirements and release techniques for each defined age group to enhance their chance of survival once released back to the wild. The following document presents a comprehensive approach for Golden Eagle Rehabilitation.
Vickie Joseph DVM Bird of Prey Health Group
Lynn Tompkins Blue Mountain Wildlife (Oregon)
Bob Fox Wild At Heart (Arizona)
David Mikesic Navajo Nation Zoo
Joe Atkinson Oregon Falconers Association
Carter Wilford Utah Falconers Association
Charlie Kaiser Arizona Falconers Association
Marten Benatar California Hawking Club
Steve Bergh North American Falconry Association
Grainger Hunt Eagle Biologist
RECOMMENDATIONS FOR REHABILITATION
The Committee for Eagle Rehabilitation Excellence (CERE) has been established to address the specific needs of golden eagles (Aquila chrysaetos) entering raptor rehabilitation centers. Representatives from select falconry organizations, eagle rehabilitation centers, the veterinary community, biologists, and the Native American community form the working group of this committee, all with the shared interest in golden eagle welfare and conservation. The varied and often severe injuries that golden eagles experience in the wild and the frequency of such events warrant a more carefully developed approach to their medical care, flight conditioning, and release strategies. Thus far, the fates of individual eagles released to the wild have been poorly documented, and there is justifiable concern about the efficacy of current methodology. The goal of this committee, therefore, is to develop recommendations for medical evaluation, treatment, husbandry, conditioning requirements, release techniques, and other ways of enhancing and verifying post-release survival.
Methods must necessarily vary among age-groups and types of conditions leading to the acquisition of injured or otherwise impaired golden eagles. Our recommendations will be based, where appropriate, on knowledge of golden eagle ecology and behavior, aspects of which differ from those of the bald eagle (Haliaeetus leucocephalus), a species more familiar to rehabilitators. A scientific database for treatment and conditioning will be developed to monitor the eagles’ progress, and the data collected will serve as guidelines to determine if and when the eagle is suitable for release. An additional program for long term tracking of eagles once released is also being developed to evaluate the effectiveness of overall methodology, aspects of which will be appropriately experimental. In that way, procedures can evolve toward better outcomes through adaptive management. In summary, our efforts will provide guidance for veterinarians, raptor rehabilitators, and state and federal agencies administering eagle regulations and permitting.
Golden eagles forage primarily on medium-sized mammals in shrub-steppe and open grasslands, and nest on cliffs and in trees (Kochert et al. 2002). After a long period of intense human persecution owing to a general misunderstanding and dislike of predators, the species received legal protections in the 1960s. Thanks to science, documentary films, and celebratory articles, our society now values golden eagles, and they have become a focus of conservation. There remain, however, a variety of human-related mortality factors that annually take their toll on populations, such as electrocution on distribution lines, lead poisoning, wire-strikes, collisions with vehicles, and wind-turbine blade-strikes (Pagel et al. 2013, Russell & Franson, 2014, Stauber et al. 2010).
Habitat loss and drought effects on food availability are also important factors affecting golden eagles. Every year, veterinarians and wildlife rehabilitation facilities receive injured golden eagles of various ages, as well as eagles too young to fly (nestlings and fledglings). A subset of the latter, still being protected and fed by their parents, would better have been left alone than “rescued.” Some, however, are emaciated, suggesting that they have somehow lost contact with their parents or are suffering from lead poisoning, a symptom of which is emaciation. It is desirable to return these eagle “patients” to the wild, the alternative being to commit them to captivity, an unfortunate fate for such remarkable beings whose life expectancy may exceed thirty years.
Not much has been published to evaluate the current rehabilitation practices to substantiate golden eagle survival after release. For eagles that were competent foragers prior to injury, and whose health can be fully restored, the task of returning them to the wild may simply require proper conditioning. Juveniles, on the other hand, depending on when they were obtained, must also learn to travel and forage prior to their ultimate release.
Developing standards for medical care, rehabilitation strategies, and post-release monitoring will strengthen the effort by all those involved with golden eagles. As for conservation, reducing human-caused injury is vastly more important to golden eagle populations than rehabilitation. Developing better methods for the latter, however, may well help conserve raptor populations elsewhere whose numbers have dwindled to the point at which every individual is of concern. In any case, restoring incapacitated eagles to the wild is part of what it means to live in a civilized society.
Golden eagle and bald eagle behavior: How they differ
Most of the information available to raptor rehabilitators focuses on the bald eagle, a particularly experienced group of experts being the University of Minnesota Raptor Center (https://www.raptor.umn.edu/). Comparatively little guidance exists on golden eagle rehabilitation, however, and rehabilitators are often advised to follow the same approach as developed for the bald eagle (Arent & Goggin 2001, Arent & Martell 1996, Chaplin et al. 1989, Servheen & English 1976). Golden eagles, however, differ from bald eagles in behavior, ecology, life history, response to rehabilitation techniques, and release strategies. These differences should be identified and addressed to increase the post-release survival of golden eagles. For clarification, we suggest reading through the two species accounts in the Birds of North America Series (Bueller et al. 2000, Kochert et al. 2002), particularly the sections on dieting and foraging.
Unlike golden eagles, bald eagles are social and can often be found in congregations along seacoasts, rivers, lakes, estuaries and wetlands, or wherever food is plentiful. This includes both live prey and carrion in the form of fish, diseased waterfowl, and mammals dying from various causes. Lakes and reservoirs, for example, often contain large standing populations of fish, some of which experience seasonal die-offs, and there may be considerable statistical accrual of fatalities floating on the surface throughout the year (Hunt et al. 2002). Even during nesting, carrion may, for the most part, sustain bald eagle pairs and their young. Fledgling and post-fledgling bald eagles can thus be successfully rehabilitated so long as they are able to travel and recognize such opportunities. Consider that juvenile bald eagles in California and Arizona depart their natal territories within a month or so of leaving the nest, and soar northward until they encounter carrion fish concentrations (Hunt et al. 1992, 2009). Not surprisingly, therefore, bald eagles lend themselves more favorably to traditional conditioning and rehabilitation techniques leading to their release, most notably to a water body where they can join company of other bald eagles subsisting on carrion.
The golden eagle, on the other hand, is primarily a solitary raptor, and its food is generally scattered in the landscape and not commonly associated with water bodies or other sites of aggregation. Like bald eagles, golden eagles can subsist on carrion and are proficient in robbing food from other raptors, corvids, and even coyotes and foxes. Diets during the nesting season, however, are largely dependent on catching live prey. Golden eagles spend much of their time soaring high, utilizing ridge-lifts and thermals to cover great distances and enable prey pursuits at high speeds.
Found as breeding pairs in the wild, they aggressively defend breeding territories and may remain in their territory year round. This behavior is particularly intense during the courtship phase in mid-to-late winter through the nesting cycle. Breeding populations of golden eagles in the temperate west are usually found in shrub-steppe and grassland ecosystems and are strongly tied to hare, rabbit, and ground squirrel populations, as well as those of marmots, and prairie dogs (Bredrosian et al. 2017, Steenhof et al. 1997). They are generally more sensitive to human disturbance than bald eagles (Richardson & Miller 1997). Fledgling golden eagles normally take their first flights in late spring or early summer at about ten weeks of age, yet typically remain near their territories for most or all of the summer and often beyond, presumably supported by their parents while learning to forage. The ability of post-fledglings to develop aerial skills to locate carrion and capture prey is essential to their survival, although during their first year, fledgling golden eagles are more dependent on carrion than the older age categories (Watson et al. 2019). In spring, they take advantage of vulnerable young-of-the-year mammals as they first emerge.
The importance of soaring to golden eagles
The very large aerial distances at which golden eagles are able to search the western landscape in a typical day doubtless helps them find both carrion and live prey. Whereas bald eagles can live in flat, often forested landscapes, golden eagles generally require terrain features offering upslope winds and strong thermals. We therefore emphasize that golden eagles obtained as fledglings or recently fledged juveniles (F/PF) and rehabilitated by means of traditional techniques such as creance-flights or flight-pen conditioning without soaring and hunting experience may have little chance of survival.
Slope-soaring versus thermal-soaring:
- Slope-soaring is riding a wave of air deflected by terrain features, much the same way a surfer rides a wave. All raptors use this for traveling and hunting, but they are limited by the characteristics of the terrain they are flying over and the development of upslope winds. Slope-soaring can lead to thermal- soaring, but the process requires time. A detailed description of soaring is found on page 20.
- A thermal is a column of rising air created by temperatures decreasing with altitude. Travel by thermal-soaring involves locating a thermal, flying to it, and working it to gain height, then exiting that thermal to find another, and so on. In this way, raptors can cover vast expanses of relatively flat terrain with little energy output. It is not clear exactly how eagles locate thermals. Possibly they see dust or other particles being pulled upwards, or perhaps they see the heat signature of warm, rising air.
There are thus two distinct methods raptors use to ride the wind. Slope-soaring, in particular, is a very effective way to prospect, hunt, and migrate. Eagles can course back and forth over the length of a hill, for example, looking for food, or they can use ridge-lift to cover large distances (Katzner 2012). If there is nothing to find along a ridge, or a ridge-lift ends during a migratory movement, the eagle will need to find another current of rising air. Relocating to a different hunting area or continuing migration means, in many instances, flying great distances. Powered flying in search of new hunting ground is energetically expensive, and this is when thermal-soaring is used to such advantage as the eagle glides from one elevating current to another. Used in combination, thermal-soaring and slope-soaring are an efficient means for eagles to cross large tracts of land without relying on powered flight.
Like older golden eagles, those in their first-year must cover vast amounts of land to find food and to exploit it. They therefore need to be strong and fit, and have mastered the art of using updrafts to rise thousands of feet into the air and to glide from updraft to updraft. Rehabilitation must provide such skill and conditioning if released eagles are to survive.
Classification of age-groups and their behavior
Golden eagles are considered nestlings from hatch-date to approximately ten weeks of age, when they attempt their first flights. These very young eaglets arriving at raptor rehabilitation facilities are prone to imprinting (see below) if not raised in the appropriate manner. Immediately returning a healthy eaglet to its original nest or fostering to a different nest containing eaglets of similar age is the best rehabilitation technique available. If replacement or fostering are not feasible, then the eaglet must be raised either by foster golden eagles in captivity (a rare prospect), or otherwise prevented from associating humans with food. As the eaglet reaches the fledgling stage, however, it is less likely to imprint, and the rehabilitator may follow the techniques for the fledgling golden eagles (see below).
Fledglings and post-fledging juveniles (F/PF)
Fledglings are 10-12 week-old eagles in the process of exiting the nest and learning to fly. First flights occur in late spring or early summer, after which the young eagles remain within their territories for the rest of the summer and often beyond, looked after by their parents. Eagles at this stage learn to soar by riding thermals and ridge-lifts. Again, soaring is considered one of the most important skills the F/PF must master to survive in the wild. As they learn to use altitude for locating food and pursuing prey (and each other) in a stoop, they master this element of speed and grace under the watch of their parents. Such skills and muscle-strength cannot be developed within flight chambers or by creance-flying. We re-emphasize that a high-soaring eagle, with its prodigious visual acuity, can see ravens, vultures, and raptors on carcasses at great distances over vast areas of landscape and appropriate their food. Recall that post-fledging bald eagles remain with their parents for much shorter periods; they leave their natal territories soon after they begin soaring and gravitate to carrion concentrations.
These eagles have been in the wild for over one year and remain as subadults for three years, gradually changing their plumage. They are considered capable of knowing how to ride thermals and navigating the mountain ridges for traveling and hunting. Meanwhile, they are still developing hunting skills and those involved in obtaining and holding a territory. In areas where eagle populations are depressed (or expanding), second- and third-year subadults may occupy vacant territories and even breed, although less successfully, on average. Their rehabilitation follows those recommended for adults. Satellite telemetry has shown that these non-territorial eagles may occupy large ranges and perform exploratory flights that cover great distances and time. Some evidence has shown that near the end of this period, they may return near their natal site to begin searching for a permanent territory (Murphy et. al 2017).
Golden eagles 5 years old and older are considered adults. Most of these eagles have gained the experience to migrate, hold breeding territories, catch prey, and contribute to the gene pool. Healthy populations, however, contain more adults than places for them to breed. Adults without breeding territories are called floaters.
Imprinting and habituation
Nestling and fledgling eagles are vulnerable to imprinting upon their human handlers/rehabilitators. In the wild, a newly hatched eagle will identify with its parents and siblings, form attachments, and develop proper eagle behavior. When this early period of development is interrupted and the eagle is in a captive environment, imprinting on humans will tend to take place, particularly if the eaglet associates humans with food. This is a dangerous situation as the eagle may become aggressive toward the human handler and other eagles. Imprinted eagles are a concern to public safety, and they must be trained with specialized techniques to mitigate the potential long-term effects of imprinting. Thankfully, most young eagles coming into rehabilitation settings are of the F/PF stage where the greatest vulnerability to imprinting has passed. However, it is advised that even these eagles be raised with other eagles where possible.
Habituation refers to the diminishing physiological or emotional response to a frequently repeated stimulus. In most cases habituation may be temporary. However, when combined with positive reinforcement on a continuous basis, habituation can become permanent and a form of imprinting, especially with nestlings and fledglings. Habituation of adult eagles is rare due to the negative reinforcement of handling, invasive medical procedures, etc. Of particular importance in the handling of very young eagles is to avoid their associating humans with food.
Golden eagles entering rehabilitation facilities
Eagles brought to raptor rehabilitation facilities often have multiple and complex issues (Redig 1993, Joseph 1998, Joseph 2006). The presenting injury may be accompanied by secondary parasitic, bacterial, viral, and fungal infections. Certainly, toxins and their immunosuppressive effects play a major role in many of the eagles coming to the rehabilitator. Identifying all of the medical issues facing these birds and developing the proper treatment and preventative program is essential to the success of rehabilitation.
Raptor rehabilitation facilities who receive eagles must be licensed by federal and state agencies. Often specialized permits may be required to receive and rehabilitate eagles. Additional requirements of the rehabilitation center may include timely reporting and updates required by the state or federal agencies, designating subpermittees who are training the eagle, and import/export requirements for movement of eagles in training. The rehabilitation centers involved with eagle rehabilitation are expected to follow the federal and state requirements.
Note: The rehabilitator, falconer, veterinarian, or any other person coming in contact with eagles follow all state and federal regulations, and when any advice in this document is in conflict with local, state, or federal rehabilitation regulations, the local, state, and federal rehabilitation regulations take precedence.
Upon arrival and intake into rehabilitation/veterinary facilities we recommend the following course of testing, vaccinations, and treatments:
- Complete physical exam to include evaluations for cardiovascular, neurologic, musculoskeletal, ophthalmologic, foot health, wounds etc
- Complete hematology and chemistry profiles.
- Parasite evaluation (external parasites, fecal float, fecal smear).
- Blood lead testing (LeadCare II for in house diagnostics and/or sample sent out to a diagnostic laboratory).
- Whole body radiographs. (Usually performed under anesthesia, and including ventral, dorsal, and lateral views).
- Some eagles will require further testing that might include West Nile Virus testing, and bacterial or fungal culture evaluation.
Recommended supportive care
1. The above procedures are to be performed after the eagle has been stabilized. Depending on its presentation history, hydration status, and nutritional needs, the eagle may require 24-36 hours of supportive care before diagnostics can be run.
2. Supportive care often requires fluid therapy, tube feedings, antibiotics, antifungals, vitamins, and wound care if necessary.
3. Dusting with poultry dust or a similar substance is recommended upon arrival to treat any ectoparasites.
4. Deworming with ivermectin, pyrantel pamoate and praziquantel is recommended for routine anti-parasitic treatment once the hydration status is normal, even if a fecal sample has been deemed negative. Specialty anti-parasitic medications may be necessary following the results of the fecal examination.
5. Treat all cuts, scrapes and open wounds on feet to reduce possibility of developing bumblefoot; placing preventative wraps to the feet if necessary.
6. Identify all underlying medical issues to provide comprehensive supportive care
Prophylactic treatments and vaccinations
West Nile Virus:
All eagles arriving at the center once pronounced medically healthy
should receive three West Nile Virus vaccines, (available now is the
Zoetis Innovator—this is the old Fort Dodge) given three weeks apart, as a preventative program.
Aspergillosis is an infection, usually of the lungs and air sacs caused by the fungus Aspergillus sp. and is especially evident in animals with a weakened immune system. Eagles are very prone to this fungal infection, which is often secondary to the stress of the primary disease (Joseph, V 2000, Redig & Ponder 2010, Beernaert et al. 2010). Treatment for aspergillosis is complicated, time consuming, and expensive. It is very important to start eagles on a preventative program upon arrival at the rehabilitation facility, or after any facility transfer. Three anti-fungal medications used for treatment and prevention are acknowledged below. Only one medication is necessary for preventative treatment, while combination anti-fungal medications may be used to treat an active infection.
Voriconazole (12.5-18 mg/Kg PO SID- BID) for 14-30 days, Itraconazole (10 mg/Kg PO SID-BID) for 14- 30 days, Turbinafine* (10-15 mg/Kg PO SID-BID for 14 -30 days). Anecdotal evidence from veterinarians and falconers suggests the anti-fungal Turbinafine (Lamisil) is also a safe and effective prophylactic for aspergillus; however further clinical studies are needed.
Recommendations for treating golden eagles with a prophylactic anti-fungal course. Time in the flight-pen may range from two weeks to two months.
||WHEN TO INITIATE TREATMENT
|INITIAL INTAKE & MED. TREATMENT
|TRANSFER TO FLIGHT-PEN
|TRANSFER TO NEW FACILITY
|START OF FLIGHT CONDITIONING (FALCONER OR CREANCE)
Note: the above medical recommendations/veterinary care should be performed under the supervision of an experienced and licensed veterinarian or an experienced rehabilitator working under the supervision of a qualified veterinarian. Any administration of drugs or medical procedures and diagnoses of medical conditions must be performed under the care of a licensed veterinarian, and this document serves as a guideline for potential treatment with the ultimate decision being made by the rehabilitator in consultation with the supervising veterinarian.
Accurate rehabilitation cost estimates is essential to developing rehabilitation as a mitigation tool. The following is an estimate of per-eagle costs associated with medical treatment and post-treatment rehabilitation and release (Table 2). Golden eagles admitted to veterinary and/or rehabilitation facilities exhibit a wide range of injuries and symptoms. The resulting treatment may require short or long-term
hospitalization. While some veterinarians and rehabilitation centers are able to donate services, direct medical and rehabilitation costs may range from a low of approximately $2,500 to a high of approximately $7900 per eagle – from intake to release.
This cost estimate is based on recommended standards for medical evaluation, testing, treatment, and conditioning. We recognize that many facilities currently undertaking eagle rehabilitation may not have the resources to conduct such comprehensive testing and evaluation. By developing eagle rehabilitation as a mitigation tool, mitigation revenue may allow various facilities to apply the standardized regimen recommended here and hopefully to make improvements.
It is also recognized that at the time of this publication, estimated costs can continue to increase due to the overall costs of diagnostics and medical supplies. The following table is a guideline.
Table 2: Estimated cost of the medical workup of an injured eagle.
|Intake and Evaluation
|ANESTHETIC TECH/MONITORING (15MIN)
|DIGITAL RADIOGRAPHS 4 VIEW STUDY
|AVIAN COMPREHENSIVE BLOOD PROFILE
|LEAD (PB) TEST (IN-HOUSE LEADCARE II)
|FECAL EXAM; FECAL FLOATATION
|Hospitalization and Treatment
|VORICONIZOLE 50MG TABLET
| IN-HOSPITAL MEDICATIONS
| FEEDING (COTURNIX QUAIL)
| Flight-pen Conditioning
| FEEDING (COTURNIX QUAIL)
|REHABILITATION STAFF TIME
|Falconry Training & Release
|FEEDING (COTURNIX QUAIL)
Replacement and fostering
This technique allows the placement of a nestling back to the original nest or another active nest with similar-aged nestlings. These eaglets only require short-term feeding and medical evaluations (under a week) before being placed in the wild nest. Increasing the brood of eaglets may require food subsidy, for example, regularly leaving food (e.g., dead rabbits) in a conspicuous location at a discrete distance. It is recommended to minimize the time in which the nestling is under human-care, and reduce their interactions with humans during that time, to decrease possible effects of habituation and/or imprinting.
Whereas creance-conditioning is a common tool widely accepted and used in raptor rehabilitation, it has little value in the case of F/PF golden eagles. This technique can be highly stressful and may have questionable value as a conditioning tool for such an aerial species. We argue that the development of slope-soaring and riding thermals, as well as the stamina required for this flight pattern, cannot be accomplished with creance flying, nor does it relate to foraging.
Many raptor facilities have the standard small chambers to house injured raptors for medical evaluation. These chambers may measure 8×8, 8×10, 8×12 feet, or variations thereof. As raptors recover from medical issues, however, much larger flight-chambers should be available for free flight and conditioning. Flight-pen structure will vary with location and climate. The minimum size for a rectangular golden eagle flight chamber should be 4000 square-feet (25 feet tall and at least 100 feet long and 40 feet wide). The height helps the eagle develop flight muscles to gain perches, and the (minimum) 40-foot width allows the eagle to bank and turn without landing; both are important design considerations. Aviary netting should be used on the top and on parts of the sides. This allows maximum airflow, especially in the hot summer, and provides a cushion upon impact with the sides if the eagle collides with them. When left undisturbed, the eagles can be seen flying laps in the flight chamber without touching the sides. A swinging perch is placed at one or both ends to encourage muscle development as they land, and to reduce impact and related foot bruising that could lead to bumblefoot (Remple 2005). Round flight chambers might be preferable to rectangular ones as they optimize usable flight-space and promote continuous flight.
Given the golden eagle’s susceptibility to stress-induced disease, large flight-pens or round barns may provide equivalent or superior conditioning outcomes with less stress and invasive handling (Greene et al. 2004). While eagles may spend considerable time perched in flight-pens, they typically fly laps in early morning and late afternoon, or when staff enter or approach the pen. We urge rehabilitation facilities without a large flight-pen to transfer post-treatment eagles to facilities with these improvements whenever possible. The time spent in the flight-pen will vary for each eagle, depending on the medical problem or injury, and range from two weeks to several months. Food should be provided continuously and introduced surreptitiously to prevent eagles from associating it with humans.
This program utilizes master falconers for the evaluation of eagles requiring special handling and conditioning which a flight chamber cannot provide. The falconer’s role is to work with the eagle and evaluate its free-flight and judge its ability to survive in the wild. In the case of the F/PF eagle, the falconer will provide the necessary training to ensure the young eagle can ride the thermals, soar the mountain ridges and successfully pursue and catch prey before being released (see below).
Adults and subadults
Subadult and adult golden eagles that have lived in the wild have learned the aerial skills of soaring and riding thermals to enable their foraging success. This classification of eagles appears to do well in a large flight-pen for pre-release conditioning. As noted, the flight-pen offers a stress-free environment to build body mass and stamina. Eagles in large flight-pens have been observed flying laps throughout the day, a conditioning process we believe sufficient to successful release and subsequent survival, and therefore worthy of testing.
If a nestling golden eagle arrives with minor medical issues, the goal is to stabilize the eaglet and promptly return it to the nest site. If the nest site is not known, it may be possible to foster the eaglet to an active eagle nest with eaglets of comparable age. There is, however, a short window of opportunity to successfully re-nest an eaglet, and minimizing exposure to humans while in captivity will minimize effects of imprinting/habituation. If injuries require prolonged medical management, then this eaglet must go to an approved hack site, if available, or later enter free-flight conditioning as recommended by this document for fledglings.
Golden eagles obtained, as fledglings are the most challenging group for rehabilitation centers to prepare for release. They should be left alone if encountered on the ground near the nest, as their parents will likely continue to take care of them. Otherwise, eagles of this age-group must be allowed to develop the aerial and foraging skills essential to the acquisition of food and other aspects of their survival. These young eagles, once in captivity, can rarely be fostered, and will therefore have missed the critical developmental window afforded by wild adults, who would provision them over the summer months while they learn aerial skills. Golden eagle rehabilitation techniques with creance flying and flight chamber conditioning will not give these eagles the experience they need to survive once released. Whereas adult and subadult eagles (age when admitted to rehabilitation facility) may be conditioned in a flight-pen and released, fledgling and post-fledgling (F/PF) eagles admitted to rehabilitation facilities before learning to soar and hunt will require more advanced techniques in rehabilitation.
This age-group is a candidate for the free flight program. Fledgling golden eagles are first placed in the eagle flight chamber to be with other eagles to help decrease any potential imprinting or habituation. After 2-4 months, they are then placed with a master falconer to be trained for free flight and hunting. Depending on medical issues, this process may take 6-18 months before the eagle is ready for release. This has been a positive program due to the response and participation by the falconry community (see Falconry Techniques, below).
Hacking has been a successful method with falcons and other raptors, including bald eagles (Simmons et al. 1988). One or more bald eagle nestlings (6-8 weeks of age), for example, are placed in a barred-box on a tower where they are supplied with food without human interaction. The box is opened when the young are approximately 11 weeks of age, and they are free to go. These birds return to the site for food as they learn to forage (mostly scavenge) for themselves. They ultimately abandon the hack site as they gain the experience to survive in the wild.
There is contrastingly little information on hacking golden eagles, and the difficulty with this species is that many come into the rehabilitation facilities as post-fledging juveniles that cannot be expected to do well on a hack tower, perhaps bolting prematurely, for example. Moreover, we have been unable to determine if the golden eagle’s temperament allows hacking in groups of mixed ages and sexes. Any attempts at hacking golden eagles, therefore, would be experimental. To this end, the CERE Committee envisions a pilot experiment to test the efficacy of combining falconry conditioning (see below) with hacking as a way to return juvenile golden eagles to the wild. Below are some excerpts from a draft prospectus we have been developing, although we are not necessarily recommending anything at this point in time.
The idea is to release eagles from an area, identifiable by the birds at great distance when soaring, and where food (carrion) can be proffered for an indefinite period while monitoring their whereabouts with radio-telemetry. Staff would remain on site and include two people, at least one of who would be a highly experienced falconer (see Falconry Techniques, below). Appropriate hacking subjects would include any juvenile golden eagle coming into captivity from fledging to, say, nine months post-fledging. Each would be “manned” and lure-trained over fairly long distances (~300m) by the falconer, this implying that the bird can be flown free and recovered, with confidence, when suitably hungry. The eagle must therefore be flown at response-weight (“flying weight”) during the training period and wear a radio-transmitter. From the point of acquisition, staff would take all necessary steps to avoid imprinting and reject from the program any eagle showing such signs. The falconer would fly the eagle near the facility for at least a month and concentrate on the development of soaring and the eagle’s ability to identify the hack station as a source of food from increasing distances. We predict that, for many birds, such training will progress fairly rapidly to the point of release and passive monitoring. No hack-tower would be necessary, as affixing carcasses to the ground on a continual basis, as typical of “vulture restaurants,” would suffice. A telemetry data-logger could record visits by individual eagles, and a low perch with a scale could be designed to monitor the eagle’s weight. Attendants would be housed, perhaps in a nearby travel trailer, for the duration of the hacking process.
There appears to be little justification for requiring that golden eagles be liberated in the regions where they were obtained. Releases of this highly vagile generalist should instead target safe environments with abundant food. First and foremost, rehabilitators would minimize the effects of drought and prey cycles by choosing an area with a mild climate and a variety of perennially available food. Costs’ permitting, however, there is no reason not to deploy additional hack sites in more xeric circumstances with the realization that there may be years of unsuitability. Sites should not be near a wind farm, dangerously constructed electrical distribution lines, or within a golden eagle nesting territory. The terrain should be hilly, in open grassland or savanna, providing widespread and substantial, large-scale updrafts for soaring. Again, it is important that the hack site be associated with a hilltop or mountain that can be seen and recognized by a soaring eagle from all quadrants. The continual presence of food may result in wild eagles dominating the site, especially in succeeding years, so the entire operation should be portable and even somewhat dispersed, if necessary. Locations should not offer elevated positions from which dominant eagles could monitor attendance and launch attacks.
Proposed Care for Golden Eagle Rehabilitation
Falconry Techniques for Conditioning
Golden eagle falconry has been practiced throughout Eurasia for thousands of years, with a notably strong tradition in Germany, Czech Republic, Slovak Republic, Hungary, and Mongolia. In North America, a small, but growing core of eagle falconers are gradually increasing interest within the general falconry community. By and large, this group is strongly interested in conservation and willing to donate time and resources to eagle rehabilitation. As the rehabilitation community offers expertise in medical evaluation and treatment, the falconry community provides expertise in advanced husbandry, preventative care, and most importantly, raptor behavior modification, physical conditioning, and the development of foraging skills. Furthermore, eagle-falconer candidates undergo significant vetting. Initially, they must pass a state test, a facilities inspection, complete a two-year apprenticeship, then practice falconry for an additional eight years to reach Master level. Only then can they apprentice under a permitted eagle falconer for two more years before receiving an eagle falconry permit. All prospective eagle falconers participating in the program proposed here undergo vetting by the CERE Committee. We suggest that an effective golden eagle rehabilitation program should include experienced eagle falconers as part of a golden eagle Response Network formed by rehabilitators and agency biologists (Goodell J, Joseph V, Atkinson C, Atkinson J 2008).
Falconer requirements to conduct eagle rehabilitation
To qualify, prospective falconer-sub-permittee candidates must meet the following criteria:
- Master Falconer level
- Current falconry license in good standing
- Provide four qualified master falconer references
- Reside in an area suitable for free flight, with an abundance of prey for eagles to hunt
- Fly and hunt the eagle consistent with flight-conditioning training program
- Provide timely updates on eagle’s progress
- Submit to facility inspections, if required by state or federal regulatory agencies
- The eagle will not be exposed to the public during the training process.
- The eagle-falconers will be working with a state and federally approved raptor rehabilitation facility and will conduct themselves as a sub-permittee if required by the state.
- All eagles entering the CERE program remain under the permit of the state-assigned rehabilitation facility and not transferred to the falconer’s license.
- In the event that a falconer does not follow the required training protocol or has acted in a way not deemed to be in the best interest of the eagle, the falconer’s sub-permittee designation will be terminated, and the eagle will be removed from the falconer’s care.
- The final decision to place an eagle in the CERE free flight program will be made by the CERE committee and state rehabilitation facility.
- The falconer will sign a memorandum of understanding with CERE and the state rehabilitation facility acknowledging the above-mentioned criteria and stipulations.
Outline of the Falconry Program
“Manning” is a falconry term describing the process of conditioning a wild-taken raptor (post-fledgling age or older) to accept a falconer in close proximity. This behavioral modification is done in combination with weight management and positive reinforcement using food. While imprinting occurs in nestlings and may become a permanent behavioral state, manning of post-fledgling and older eagles is temporary and does not lead to permanent habituation. Moreover, wild-obtained golden eagles in falconry appear to show a heightened recognition of individuals and respond in fear of strangers even when being flown in falconry conditions. The majority of these birds when released do not show evidence of behavioral changes suggesting permanent habituation. This transition may take 2-8 weeks depending on the personality of the eagle and previous issues.
Lure Training & First Free Flight
Once the new eagle is comfortable on the glove and feeding in the presence of the falconer, the trainer introduces the lure, which will be the main callback method. Calling a rehab eagle to the fist is not recommended as it increases the dependency of the eagle toward the falconer and promotes an unnecessary food-association with people—especially their hands. Raptors that have been trained to come to the glove for small pieces of food are not looking for moving prey; they are waiting for the falconer to put food on the glove. If the eagle is looking for the lure, it is ignoring the trainer, and starting to learn to hunt. Further along in the training, the lure is used to recall the eagle after an unsuccessful chase or flight. The eagle is then offered a very small amount of food to entice it to step from the lure to the fist for another flight. After introduction of the lure, training picks up speed, and free-flying is only days away. Each time the eagle is flown to the lure, the trainer increases the distance. In short order, the creance is removed, and the eagle is flying free. Generally, it takes 3-4 weeks to reach this point in the training process, although this can vary with each individual eagle.
Pursuing live prey
It is important for every eagle to understand the dynamics of pursuing wild prey and what it takes to catch it. The most controlled method is off-the-fist hunting where the falconer walks through a suitable area containing jackrabbits that the eagle can chase. Some eagles can take months to catch their first jackrabbit. Many factors play into this, including hunting and weather conditions, the kind of field in which hunting takes place, cover type, and so on. But this stage cannot be rushed or abbreviated. Regardless of how long it takes, the eagle must become proficient at catching prey. Hunting from the arm of a falconer gives the eagle much needed practice at seizing moving prey, and this repetition will pay off when the eagle hunts on its own after release. A reasonable benchmark is that each eagle needs to catch 12 head of wild game, e.g., jackrabbits, a process that can take anywhere from 3 to 5 months. This practice will benefit the eagle when it hunts on its own after release. There may also be value in encouraging the eagle to displace wild ravens from carrion so as to produce a search image for this source of food.
Soaring is the most important skill a young eagle needs to learn, from finding and remaining in a thermal to eventually jumping off to another current of rising air. (Katzner et al. 2012). The eagle is taken to a suitable hill/mountain, launched off the top and allowed to ride upslope winds and explore. At some point, when the eagle is airborne, the lure is offered to reward the eagle for flying. Each time the eagle goes higher, it is rewarded, and ultimately the eagle will go to great heights and stay aloft for extended periods. The goal is to have the eagle repeat this process multiple times so that it learns to recognize updrafts and their benefits. Without such aids to soaring, a released eagle will not be able to cover the distances it will need to successfully find prey.
To maximize this stage of the training, the eagle should be allowed to soar in optimal conditions. Wild eagles soar on cloudy, stormy days, but an eagle in training will not benefit from these conditions. Once the bird is flying, the trainer should continue to lengthen the distance until the eagle is coming a quarter-mile, two-to-four times in a training session. Then the trainer introduces terrain-updrafts by moving into natural habitats to lure-train. The trainer continues to call the eagle from distance, but now over and across valleys, ridges and other landscapes. It is at this point, when the eagle is flying to the lure, that the trainer will hide it as the eagle closes in, causing the bird to flare up and begin to circle. This is the first step to getting the eagle to soar. Just as distance was increased, now the number of times the eagle is allowed to circle before being called to the lure is increased, with the eagle eventually going to significant heights. With the eagle now circling overhead, the trainer can begin the hunting phase of the training. All raptors will react to the sight of prey, and in the case of eagles, they seem to have a natural interest in jackrabbits. However, their ability to maneuver and capture a running jackrabbit may take time. Descending from a soar at 150mph toward a running jackrabbit takes practice. This falconry-based conditioning method allows the eagle time to practice and make mistakes without their survival in the balance, just as their parents would provide for them in the wild. This stage is usually accomplished during the sixth-to-eighth month of training.
Candidate for release
It must be pointed out that any eagle coming into this program has two phases it will need to go through. The first is medical treatment, which takes as long as necessary to ensure the health of the eagle before it moves on to the second phase, flight training. Just as the medical phase cannot and should not be restricted to a given number of days, neither can, or should, the flight-training. Each eagle must be assessed individually, and its circumstances taken into consideration, which will determine the length of flight-training. Simply put, if the period of flight-training phase is restricted, and the eagle is released before it is ready, all the effort put forth on this eagle’s behalf will be for little or naught. The readiness of an eagle for release, usually after 12 to 18 months of training, should ultimately be determined by the falconer and the CERE committee.
Training during the molt
- Heavy molt
It is very common for an eagle that is in a comfortable routine and being flown, to go into a heavy molt, playing catch-up for lost-time.
- Feather damage
Depending on an eagle’s individual circumstances, it may have come into rehab with feather damage, or such impairment may have occurred, inadvertently, during handling and medicating. Time should to be allowed for damaged feathers to be replaced.
As in all birds, raptor molt timing and sequence coincides with their breeding season—the most physiologically demanding period in their life history—when pairs are feeding nestlings and themselves. During this period, birds molt in a sequential and symmetrical pattern to allow new feathers to grow, without undermining flight ability as they defend the territory and provision their young.
Molt timing is also connected to seasonal photoperiod and the physiological changes, including hormone shifts, which stimulate birds to migrate (Zuberogoitia I 2018). Under falconry conditions, flying during the molt often results in incomplete molts, and while normal in the wild, it is less desirable to falconers who strive for a near-complete flight feather molt. As a result, falconers put their birds into mews in spring, raise their body weight, and often include UVB lighting, with the goal of artificially initiating and accelerating the molt during the summer months. In most state falconry regulations, the taking of game species in falconry is prohibited from April through August. Thus, molting during this time avoids losing birds due to hormonal shifts and readies them for the start of legal hunting seasons on September 1st. The goal of rehabilitation, however, is to release birds as soon as possible. Molting has less relevance to flight training, unless flight feathers are noticeably damaged.
Flying in winter
- Rainy conditions—hunting off-the-fist works best if the grass is dry. Wet grass will hamper eagles and cause frustration because their feathers soak up water, making flight more difficult.
- Snowy conditions—although the eagle will not be hampered by wet feathers, getting to the flying fields may be difficult, and tracking an eagle may be impossible. Losing a not-ready-for-release eagle in winter is a death sentence.
Getting an inexperienced eagle to soar in the winter is also sometimes difficult. Whereas upslope winds are available when there is wind, the ground is cold, creating fewer thermals over flat ground. Encouraging an eagle to soar on a consistent basis requires optimum conditions. Wild eagles do soar in the winter months; however, that occurs after they have become accomplished fliers.
With inexperienced eagles, optimal conditions are necessary.
The progress of conditioning each eagle will be recorded in a scientific database. The data collected will help in developing guidelines to determine if and when an eagle in training is suitable for release. A program for long-term tracking of the eagle, once released, is also being developed. CERE-approved falconers will be utilizing Marshall’s telemetry for obtaining data associated with the eagle’s training. Collectable data points include speed, climb-rate, air temperature, angle of ascent and descent, average flight speed, total distance flown, and maximum altitude above ground level. This information will be entered into a database and compared with other flights to help CERE monitor the training progress of each eagle and help access when each is a candidate for release.
Criteria for release
Pre-release medical data
All eagles prior to release shall have the following
Records of complete physical exams with blood counts and chemistries;
Radiographs should be updated to prove healing from any internal injuries or fractures.
Fecals and parasite treatments should be updated prior to release; as well as any specialty testing if previous disease history necessitates.
Evaluation of the GPS training data obtained to help determine candidate for release
Considerations for long-term surveillance management;
CERE will outline and work with each USFWS region and state to provide the required documents for long term:
- Master Banding Permit from the Bird Banding Lab or sub-permittee under the Master Bander
- Scientific Collection permit
- Research proposal (MOU) with scientific rigor
- State approval and banding lab authorization
Releasing less experienced eagles during the seasonal peak abundance of their prey is preferable, especially when a high proportion of the young of the year prey is present. This will allow the eagle time to gain condition and confidence before periods of prey scarcity in the winter months. This release strategy parallels the reproductive schedule of nesting eagles in which fledgling dates coincide with the occurrence of young ground squirrels and jackrabbits. This helps ensure the juvenile eagle will have at least six months of food available before winter conditions limit availability. As fledglings leave the nest area in late summer and early fall, adult territorial behavior eases, and adults may continue to tolerate young within their territories. By early winter, adult pairs re-assert their territoriality and display less tolerance to immature eagles. To avoid territorial disputes and aggressive adult behavior, as well as optimize prey abundance, we currently recommend release of the F/PF eagle between April and October. This may require training extensions from state and federal agencies.
We also suggest the timing of eagle release in northern latitudes should be considered more carefully than southern areas within the golden eagle range. For example, in the southern range of the black-tailed jackrabbit (i.e. Mojave and Sonora Basin and Range, Central California Valley and others), reproduction can occur year-round, and fossorial sciurids may be above ground nearly year-round except for estivation periods in late summer. In contrast, jackrabbit reproduction in northern regions (e.g., Columbia Plateau, Wyoming Basin, Snake River Plain) may span only three months in the late spring and early summer, and fossorial sciurids may appear in March and April, and return underground by mid-July to estivate during the remaining summer heat.
Evaluating post-release survival rates
Golden eagle rehabilitation may be a viable mitigation tool in the context of industry takes; however, managers need a better understanding of post-release survival rates in rehabilitated birds. The effectiveness of the medical treatments, rehabilitation protocols and flight training prior to release must be evaluated. This can be accomplished with long-term satellite transmitter technology. When properly administered, long-term surveillance has enabled researchers to more accurately estimate juvenile eagle mortality (Murphy et al. 2017, McIntyre et al. 2006). As such, CERE suggests a controlled experiment whereby released eagles are fitted with small PTT backpack transmitters for long term surveillance. The study could aim at comparing post-release mortality rates seen in F/PF eagles (age when first admitted for treatment) conditioned using the various techniques described in this document.
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