Our Harris Hawks at the Centre include Elsa who has been here since 1995 and Bandit a relative youngster who joined the team in 2007. We have had many others over the years, but as some would hunt they have been passed onto new keepers for this purpose. Sadly our original 'Dale' died in 2013 from liver failure in old age, being approximately 25 years old! Elsa is still our oldest Harris Hawk at around 32 years of age!
Harris Hawks can be found in semi-open habitats in the SW USA and NW Mexico, through Central and South America to Chile and Patagonia.
They build their nests in scrub-type trees from sticks, weeds, twigs lined with moss, grasses and roots. They lay 2-4 eggs, and after hatching the fledglings fly after about 40 days.
Harris Hawks are unusual raptors with their complex social structures with two or three birds helping with the incubating and care, the hunting in family groups. The dominant females will tend to stay 'on guard' whilst the young birds and smaller males will flush out the prey from the ground holes or bushes.
The breeding, or alpha, female, is dominant to all other hawks in the group. Occasionally there is a second female who is subordinate to the alpha female but dominant to all other males in the group. The breeding, or alpha, male is dominant to all other males in the group. Commonly the group contains a beta male, who may attempt, often unsuccessfully, to mate with the alpha female. Finally, there may be several gamma birds, which are subordinate to the alpha and beta individuals. These gamma birds may be either male or female, and usually they are sexually immature individuals. Often they are the juvenile offspring of the alpha pair. All members of the group help with obtaining food, defending the breeding territory, and providing nest protection. These groups also hunt cooperatively. They are able to depend on much larger prey when hunting in groups. This aspect of group hunting and food sharing increases survival rates for birds as individuals.
The diet of Harris' hawks is versatile and varies with prey availability. These hawks feed mostly on small mammals such as rats and mice, but also take birds and lizards. They commonly hunt in groups of about five hawks, increasing their success rate and enabling them to take larger prey such as cottontails and jack rabbits. These hunting groups consist of a breeding pair and other helpers, with the female dominating. They are fast flyers and once they have spotted their prey, they land and take turns trying to scare and actually flush the prey animal until it darts from beneath its hiding place. Another member of the hunting group captures the animal and assumes a posture known as mantling, in which the hawk shields the prey with its wings to hide it from other birds. It has been suggested that group hunting is encouraged by the dense brush and thorny nature of their habitat. There is some evidence that these hawks may feed on carrion if food availability is low.
Great horned owls (Bubo virginianus) pose the greatest predation threat to this species, but coyotes (Canis latrans) and common ravens (Corvus corax) also threaten young hawks. Female Harris' hawks utilize helpers to protect their nests. The helpers perch in saguaros and scan the surroundings for predators. They tend to become excited and will use an alarm call when predators come within their nesting area. Groups consisting of 2 to 5 hawks will attack and harass any predator threatening the nest. The alpha male is most likely to strike the predator as the female stays behind to protect the nest. This establishment of helpers greatly increases the detection of predators and nest success. Harris' hawks are important predators in their ecosystem, controlling populations of many small mammal species, and are of great benefit to farmers whose crops are destroyed by rodents. These hawks feed primarily on small rodents such as mice and rats and therefore alleviate a lot of destruction to crops.
The only negative impact of these hawks is their habit of congregating on electrical transformers, where they are often electrocuted. This has become a great cost to electric companies who are being forced to reinsulate and, in some cases, build arms for perching to reduce the mortality rates of hawks. Electrocution is responsible for the loss of half of the population of breeding hawks.