Background on Harris's hawks
The 
Harris's hawk (Parabuteo 
  unicinctus) is not a bird of classical falconry. It is native to the Americas, 
  with the northern extremity of its range sneaking into the Chihuahuan and Sonoran 
  deserts of Texas, New Mexico, and Arizona. Because they are found exclusively 
  in the western hemisphere, Harris's hawks were not known to the Asians who developed 
  the sport of hawking 4000 years ago, nor to western Europeans who produced most 
  of the falconry literature from the Middle Ages right though to the middle of 
  the 20th Century. In the past 25 years, however, the Harris's hawk has become 
  recognized as the most adaptable, successful, and popular gamehawk in the world.
Interestingly, it is not the physical attributes -- appearance, size, speed, or strength -- of the Harris's hawk that have won its place in modern falconry. Harris's hawks are closely related to the red-tailed hawk (Buteo jamaicensis) of North America and the common buzzard (Buteo buteo) of Europe, but Harris's hawks have a smaller, more eagle-like head, shorter wings, longer tail, longer legs, and larger feet than most true buteoine hawks. Personally, I find adult Harris's hawks to be strikingly beautiful, with charcoal-black ground color and muted rufous highlights on some feather edges, cinnamon-red shoulder and leg feathers, and brilliant white undertail coverts and tail tip. The brown eyes are surrounded by a bright yellow eye shield. A female Harris's hawk in hunting condition weighs about 900-1100 grams (~2 pounds), very nearly the same as the peregrine falcon (Falco peregrinus) and female goshawk (Accipiter gentilis) of classical and modern falconry, and to the female red-tailed hawk used in modern falconry. The peregrine is not generally used to hunt ground quarry such as rabbits, but the Harris's hawk can be compared directly to the goshawk and the red-tail. The goshawk is an accipitrine hawk, known among falconers as 'shortwings' for their short, rounded wings designed for rapid acceleration and maneuverability. The goshawk is markedly faster than the 'broadwing' red-tailed and Harris's hawks, can climb and turn much more rapidly, and has substantially greater endurance, something that is especially noticeable when flying into a strong headwind. Goshawks are so quick that I have seen one blast off the falconer's glove to fly down and catch a rabbit, jump off the still-live rabbit in order to discipline a too-inquisitive dog with a quick foot to the nose, then spin around and catch the escaping rabbit a second time, all in a matter of a few seconds in the space of fifty feet. A good goshawk is capable of regularly flying down pheasants in the air, a feat unmatchable by either the red-tail or the Harris's hawk. In strength the goshawk and the Harris's hawk are approximately equal, but both are overshadowed in this department by the red-tail, which has a well-deserved reputation for being able to crash through heavy brush to snag a fleeing rabbit with a desperate but crushing one-footed grip.
The Harris's hawk 
  is not as athletically gifted as the goshawk nor as powerful as the red-tail, 
  but it is uniquely suited to the sport of hawking because, unlike nearly all other 
  birds of prey, it is a social animal whose natural history includes cooperative 
  hunting. Harris's hawks normally hunt in family groups consisting of the breeding 
  pair (or trio, since polyandry is common) and their offspring from the previous 
  year. By hunting cooperatively, Harris's hawks are willing and able to tackle 
  much larger prey than a single hawk could, providing a wider prey base with 
  which to provision the nestlings. Perhaps social behavior and pack hunting have 
  arisen in the Harris's hawk as adaptations to their desert environment, where 
  prey may be scarce or experience large year-to-year fluctuations in population. 
  If wild Harris's hawks are thought of as 'wolves of the air,' it is reasonable 
  to conclude that a squadron of trained Harris's hawks is the domesticated aerial 
  counterpart of a pack of terriers. Like terriers, trained Harris's hawks are 
  eager to chase a wide variety of quarry, are relentless in their pursuit of 
  game, and seem to enjoy a good fight. I've noticed the same traits in the falconers 
  who hunt with Harris's hawks, and it is no coincidence that Jack Russell terriers 
  are often the dog breed of choice for rabbit hawking with Harris's hawks. 
Harris's 
  hawks readily accept their human and canine packmates as integral parts of hunting 
  enterprise. Hawks, humans, and dogs communicate with each other in the field 
  using voice and body language. The level of camaraderie and teamwork is very 
  high, and it is this participatory aspect of hunting with Harris's hawks that 
  I find so enjoyable.
Back to Toby Bradshaw's 
Hawking and Falconry Website.
  For more information, contact 
Toby 
  Bradshaw.
  Last revised: 29-Mar-08