Red-tailed hawks (Buteo jamaicensis) are the most commonly observed hawks, and the most commonly seen raptors (birds of prey) in Rocky Mountain National Park. They are often seen throughout the year, but resident hawks may move to lower elevation areas such as the eastern plains of Colorado during severe winters. If they leave the park they are often the first raptors to return in the spring. Some red-tailed hawks migrate south while others move only short distances. During the spring and fall it is not uncommon to see hawks that nest farther north migrate through the park following tributary ridges off the Continental Divide. The resident red-tails often defend their territories and will challenge a migrating hawk if it flies nearby by circling overhead and then swooping and hitting the migrating bird with its talons.
Red-tailed hawks are the largest of the hawks. Adults weigh one and a half to four pounds, with females being about 30% larger than males. They get their name from their rich, russet red broadly rounded tails which are clearly visible while they soar, their favorite mode of hunting. Red-tailed hawks have a diet that usually consists of about 90% rodents with occasional birds, rabbits, and snakes. They feed during daylight and their eyesight is eight times as powerful as a human's.
Red-tailed hawks reach maturity at about three years old, and mate in the spring. Scientists believe they mate for life, and return to the same nest site for years. They build large stick nests in trees about 30 to 60 feet above the ground but sometimes build nests on a ledge high on a cliff. The nests may be used for generations and each breeding pair will add sticks or pine boughs. The nests may become too heavy for a tree to support causing a branch to break and the nest to fall. It is not uncommon for one breeding pair to have two to five alternate nests located within a one square mile area and may be found in different nests from year to year. Other birds of prey may use vacant red-tail hawk nests. Sometimes park rangers who monitor the nests will find a pair of great-horned owls or even peregrine falcons incubating eggs. The red-tail hawks meanwhile will be occupying one of their other nests a 1/4 mile away. They lay one to four eggs in April or May. The eggs hatch in 28 to 34 days, and the male feeds the female while she is incubating the eggs on the nest. Both parents feed the young for about six weeks till they fledge from the nest. They can live to be 10 to 20 years old, depending on their environment.
Red-tail hawks prefer to nest and hunt in the montane zone in ponderosa pine savanna forests. Their nests sometimes are near the park boundary and they may often hunt in open meadows outside the park where one of their principle prey, the Wyoming ground squirrel (Spermophilus elegans), is abundant. Fortunately, populations in Rocky Mountain National Park appear to be generally both healthy and stable, so this beautiful and deadly hunter will remain a common sight for park visitors.