harris’ hawk

Raptor Free-Flight Returns to Desert Museum

With cooler weather, the raptor free-flight program has returned to the Arizona-Sonora Desert Museum. There are two shows each day at 10 am and 2 pm.

The morning flight features three to five birds which may include Chihuahuan Ravens, Barn Owls, Great Horned Owls, Ferruginous Hawks, Gray Hawks, Prairie Falcons, or Greater Roadrunners. The afternoon flight features a family of Harris’ Hawks.

The shows demonstrate the different behaviors of the birds and their hunting strategies. During the flights, some of the birds fly just inches over your head. After the flights, museum staff usually have the birds on their fist which provides another opportunity to get very close to the birds.

Raptors are birds that eat live prey and also have excellent vision, sharp talons or toenails, and hooked or curved beaks. The ravens and roadrunners are not considered raptors, but they do scavenge and hunt. The raven is an omnivore, and feeds on grains, cactus fruit as well as insects, other invertebrates, reptiles, and carrion. The roadrunner, a member of the cuckoo family, hunts snakes, large insects, lizards, rodents, and various small birds.

The free-flights will be presented each day, weather permitting, through April 11, 2011.

Western Screech Owl, a feisty little raptor

The Western Screech Owl (Otus kennicotti) breeds throughout the western U.S., from southern Canada to Baja California, and other parts of Mexico. This little owl is the fourth and smallest of the raptors I handle and interpret at the Arizona-Sonora Desert Museum. I’ve written previously about the Harris’ Hawk, the Barn Owl, and the American Kestrel. (I also handle snakes.)

Western screech owl

The Western Screech Owl has a body length of 8- to 10 inches, and a wingspan of 20- to 24 inches. (The infamous Cactus Ferruginous Pygmy Owl is slightly smaller.) The yellow eyes are very penetrating. When alert or excited, it raises some feathers on its head – “ear” tufts. The owl is usually gray and streaked with black and white (there is a red race). The only other owl in this region it may be confused with is the Elf Owl, which is much smaller (5 inches in length) and lacks the ear tufts. The screech owl’s toes are zygodactylous (two pointed forward, two pointing backwards). There’s a word for Scrabble fans.

Screech owls generally do not migrate. They are cavity nesters, so you might see one peeking out of a hole in a saguaro cactus. (They will also nest in boxes.) The female lays 4- to 6 eggs, each about 2- to 3 days apart. The chicks hatch after about 26 days and open their eyes after about a week. The female broods the chicks for two weeks while the male brings food. The chicks stay in the nest for about five weeks, all the time being fed by their parents. Life expectancy in the wild is 4- to 6 years, but captive birds are known to have reached an age of 18 years.

The Screech owl is a fierce predator and will attack prey much larger, relative to its size, in comparison with other owls. The screech owl will attack large Norway rats, mice, lizards, insects, smaller birds, scorpions, spiders, ground squirrels, and fish. Its normal habitat in the desert is the wooded areas near mountains, or along tree-lined rivers. In wooded areas, the owl’s dull color makes good camouflage.

Despite its name, the owl doesn’t screech. Instead, it has a series of trilling calls. Screech owls have keen hearing which help in capturing prey, but their hearing is not as specialized as that of the Barn Owl.

Harris’ Hawks, Wolves of the Air

The Harris’ Hawk (Parabuteo unicinctus) is now a common urban dweller. Its body is chocolate brown above and below and it has conspicuous rusty shoulder patches, leggings and wing linings. The base and tip of the tail are white. It is slimmer and longer-tailed than most Hawks (buteos). Wingspan is 40-46 inches.

HH21

Males and females exhibit the same plumage, but the females are up to 40% larger. Weights range from two to three pounds for adults. This size difference is common in birds of prey. And it means that the female is the alpha bird of the flock.

The Harris’ Hawk originated in Central and South America and moved north following riparian corridors. It was not common in the desert in the first part of this century. Beginning in the 1930s, however, cattle ranching and associated water holes were developed, and the hawk was able to extend it range into the desert away from riparian areas. Since the 1980s, the Harris’ Hawk has moved into the city of Tucson in a large way because of development. It apparently thrives in suburban environments, but has yet to learn about electric lines. Electrocution is its largest cause of death in the city.

Harris’ Hawks of the Sonoran desert region are apparently a different subspecies from those in other areas. Our hawks are bigger and live in cooperative packs for both hunting and breeding. Harris’ Hawks in other areas nest and hunt in pairs. The pack is led by an alpha female. Several females may lay 2 to 4 eggs in a single nest. The eggs are incubated for 33-36 days by both sexes. The young fledge about 38 days after hatching. In Arizona, the breeding period is typically from February through October. If hunting is good, they may raise more than one brood per year. The hawks favor saguaros and tall trees such as eucalyptus and ornamental pines or cedar for nesting. Immature hawks may stay with the pack for up to two years, but eventually leave to find other packs.

Harris’ Hawks eat lizards, rabbits, rodents and small birds including doves and quail. They do not take snakes nor do they attack cats or dogs. They have been observed taking Koi fish. In the Southwest, the predominant prey is the desert cottontail rabbit. The hawk’s eyesight is so good, it can spot a rabbit up to a mile away.

The Harris’ Hawk is a very adaptive bird. In hunting, the younger birds may flush the prey while the older birds keep watch from a high perch, and then swoop down on the fleeing animal. Another strategy used is tag-team chasing. This is used for large prey such as jackrabbits. The hawks will tire out the jackrabbit until it becomes easy pickings.

To feed nestlings, prey is passed up the hierarchical chain of command to the alpha female, who feeds the young.

The Great Horned Owl is the hawk’s greatest natural enemy. The owl attacks nestlings and young hawks and can take an adult male, but not the larger adult female. Great Horned Owls, frequently appropriate hawk nests as their own. This means that the hawks frequently have to build several nests in an area. Packs of hawks will attempt to drive owls from the area.

Harris’ Hawks are territorial and will defend their territory against others of their species. However, in the winter, local flocks get together and the young females form new alliances to begin new flocks.

 

The Arizona-Sonora Desert Museum maintains a breeding flock of Harris’ Hawks. These birds perform in the afternoon free flight program from late October through mid-April (it’s too hot during the summer). You can see some videos here and more images here. All during the year, Docents at the museum demonstrate Harris’ hawks and other birds of prey.