JWN Arts & Hawking 

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Proper Weight Control
This article kindly contributed by Harry McElroy
copyright Harry McElroy, 2017

The Harry McElroy 22-Hour Weight Control Model

         To the best of my recollection, I (Harry McElroy) developed the 22-hour weight control method in the 70’s. My notion was one could control a hawk’s weight within 1% of its body weight 27 out of 30 days using this system. Additionally, when the weight varied more than 1% the hawk was still near flight weight and could be flown anyway.

When a hawk is below the desired window it can be fed back up to its normal flight weight before the hunt and, conversely, if over, it is likely to be close enough to be safe to fly anyway. Consider that hawks are usually flown within three general weight ranges: relatively hungry, mid-range weight, or within the high range. In mild climates I normally hawk within the upper part of mid-range. We suffer from a number of predators so, for the sake of safety, good response to fist and lure is essential for the smaller bird-catching raptors.

         The tyro often wonders how to judge the flight weight of his hawk but sad to say we never know the exact weight at which our hawks should be flown and constantly seek a better figure. A young parent-reared aplomado will most likely need to begin its first falconry season hungry, but its weight can be increased as the year passes with a complex pattern of greater muscle development, cooler weather and the trust or bond we seek with our raptors. Weight is only one of many factors in the relationship we form with our feathered friends and yet it is an element of some importance.

Some hawkers prefer to check the weight several times per day when flying the smaller hawks and such is common in hawking the kestrel at birds. My practice, excluding the kestrel, is to weigh before and after hawking.

The hawker familiar with my habits will appreciate that I hunt birds exclusively and as a result hawks are maintained on a high quality ration. I normally feed a combination of pigeon and house sparrow.  Falconers who feed a ration of lower quality such as domestic quail will note increased metabolism and greater variance.

The System

        Using this system, my hawks’ weight is controlled not only through the season but also during the molt.  During the molt it reduces withdrawal in raptors that tend toward that, and facilitates the reduction at the end of the molt during warm weather. It also avoids the health risks of excessive weight gain.  Note, some of the big boys in the sport prevent withdrawal of imprinted gyr falcons by maintaining courtship type contact with their falcons through the molt for several years. 

        This weight control technique is relatively mechanical in nature and consists of weighing the hawk twice daily: once before it is flown and a second time after it is hunted. After the hunt it is fed to a given body weight. For example, a small hawk that metabolizes 28 grams daily and hunts within 320-330 grams might be fed to 353 grams after hawking. Assuming it is flown 2 hours daily, its weight would be about 325 after 22 hours. It is worth mentioning here that I make adjustments in weight in a gradual manner of 1% body weight. For example, a 325 gram hawk would be moved either up or down only 3-4 grams in a day. This approach would be well and good if there were only a few variables, but, in the real world, variables abound. A cold front may blow in or the ration may be changed to include a more (or less) highly nutritional ration, or the hawk may be experiencing a phase where it is metabolizing more or less and so on. As a result, and especially with the smaller raptors, it is wise to check flight weight before leaving for the field.

        If one is maintaining his charge within the mid-range of response weight and is confident of his hawk, it can be flown when well above its mid-range weight after over-feeding for one day because this increase is only the weight of food in the gut. It is common for a hawk to take prey some distance from the falconer and by the time it is found may have eaten well past the normal fed weight. The falconer may have trust with imprinted hawks or even passagers that have been flown several seasons but not the more difficult individuals whose weight must be controlled stringently. With less reliable birds, be sure to bring the hawk back down to the safe flight weight range before venturing back into the field. This is likely to only result in one or perhaps two missed hunting days.


       Over the decades research has indicated many animal forms are born with certain personality traits. Put another way, there are genetic patterns that apparently influence behavior. Recently, some research has focused on various behavioral patterns in bugs. I have based some of my training and conditioning habits on just such inherent qualities. For example, I place hawks into behavioral categories with the top 1/3 being most desirable to handle, the second 1/3 being average, and the lower 1/3 as hawks which are slightly difficult to handle and always, it seems, in need of additional training. This is reflected in weight management with the lower 1/3 being flown thin and in need of exacting control.

Climate Factors

       Aplomado with Scaled Quail, talking with Jessie Brown (researcher, graduate student)

In order to maintain a controlled environment in which a predictable rate of weight gain and loss can be established and maintained, falconers living in the cooler climates where the temperature may vary greatly during the evening can employ this system by taking their hawk into a sheltered area during the night. Some use a garage or spare room in the home and some place the raptor in a hawk box. By keeping the hawk within the confines of a stabilized temperature range when not being flown, one can feel more confident that the 22-hour weight control cycle will remain consistent.

During the fall or in warm weather, we all experience problems with weight control due to an decreased rate of metabolism on the part of the hawk which can “hang on to” even a small ration of food far longer than during the colder days where more energy is needed, and meals therefore more swiftly metabolized, to stay warm. One method, when working with two hawks, is to fly them on an alternating basis. The hawk being flown can be fed well while adjusting the weight of the other for the following day.

 Examples of Weight Control

        As previously mentioned our weather is mild and the daily ration is pigeon and house sparrow in this example. Our, in this case fictitious, subject is a male aplomado.


         Before hunt                           Amount fed                  After hunt

Empty weight: 235 gram                  10 grams                  Fed weight: 250

Empty weight: 230 gram                  15 grams                  Fed weight: 245

Empty weight: 226 gram

         (given 4 gram before flying)         21 more grams                  Fed weight: 245

Empty weight: 230 gram                  25 grams                  Fed weight: 255

Empty weight: 230 gram                  25 grams                  Fed weight: 245

Ongoing Weight Control During The Molt

       By maintaining the hawk on a high quality ration it remains relatively tame and the average raptor can be flown through the end of the molt without causing hunger traces. Our quail season opens September 1st and my intermewed hawks are flown at that time each year.

Throughout the molt, daily handling is maintained to prevent withdrawal. The hawk is flown to the fist in a free-lofting situation and, just as during the hawking season, weight taken before each maintenance session and feeding to a given weight occurs at completion of that session.  Weight range for any molting hawk kept this way should be at the highest point one can predictably get satisfactory response to the fist in the chamber during the summer temperatures.  Note that one is most likely to achieve satisfactory results by running the daily maintenance sessions in the cool of the evenings just after sunset.

A Safe and Sane Method For Weight Reduction

         A trained raptor’s flight weight is one of several key factors influencing performance in the field. Other factors include the hawk’s physical condition, the quality of food it is fed, the degree to which it has bonded with the falconer, its experience level for hunting the quarry produced, weather conditions (especially temperature and wind speed), degree it has adjusted to distractions such as the sudden appearance of strangers, other animals and machinery.

         Because weight control is a significant contributor to overall performance, and because it is also a slippery slope that places the falconer in a position of extreme responsibility, it is important to know how one can safely reduce the weight of a trained raptor without compromising its well being.  While this same method can be applied to all species of raptors in training, we will discuss it here in the context of aplomados and leave to the common sense and good judgment of each falconer to transfer this method over to other species of other sizes.

         As mentioned earlier (see “The System” above), by feeding a specified weight that one has determined will maintain a form of stasis within a 22 hour cycle, a hawk’s flight weight can be predictable kept within a reasonably stable range. In this instance the falconer is using the input of food at a specific amount to predict the hawk will return to a weight the next day that is approximately where it was the day before.

         Using that same line of reasoning, one can do something similar to cause the hawk to lose weight, but in a very controlled and measured fashion.  If by feeding my female aplomado falcon 28 grams a day I can keep here within a reasonable range near a body weight of 325 grams, by reducing this amount by half (14 grams) I should see a gradual decline in her weight. I would not want to do this if she were at her flight weight, it would jeopardize her health to bring her below it.  But if she for some reason were significantly over that weight for a period of time (perhaps were I to need to travel out of town and was forced by circumstance to have her fed by a friend more than her usual daily ration to ensure she was healthy upon my return) I may find the need to cut back her daily rations until she was returned to a reasonable light range. 

        It should be mentioned again at this time that when reducing a hawk’s weight the daily ration absolutely must be one that is of the highest quality because a smaller amount of high quality food will maintain higher levels of vigor and health during the weight loss period that a ration of poor quality, such as “washed” meat, rabbit meat or any other that does not include fresh small bird flesh, skin and body organs. Bones and feathers can and should be included in meals, but should not make up a significant part of the ration by weight. If you are feeding 14 grams, that amount should comprise 14 grams of actual food.

What follows is a fictitious and idealized but realistic scenario with a female aplomado.

         Pre-meal                           Amount fed                  After meal

Empty weight: 355 grams                  14 grams                  Fed weight: 369

Empty weight: 351 grams                  14 grams                  Fed weight: 365

Empty weight: 347 grams                  14 grams                  Fed weight: 261

Empty weight: 343 grams                  14 grams                  Fed weight: 357

Empty weight: 340 grams                  14 grams                  Fed weight: 354

Empty weight: 336 grams                  14 grams                  Fed weight: 350

         At this point the hawk is within its normal flight range, and though the falconer may feel a need to tweak the weight down further for optimum hunting response ad control, this bird will be ready to be flown and so will need careful management to find the daily ration that will cause her to continue to lose, but only a gram or two a day until she reaches perhaps 330 to 325 where she performs and responds at her best in the field.  It is likely the new daily ration will shift to an amount somewhere between the 14 grams fed causing a predictable loss of around 4 grams per day and the 28 grams fed causing her weight to stabilize. So the “tweaking” ration amount may be 21 grams daily until her optimum target weight is reached.