This familiar raptor common to the Great Basin opportunistically uses both tree and cliff substrates for their stick nests. Found on remote outcrops in the shrub-steppe desert, shear canyon walls and the high cliffs of up-lifted mountains, as well as among propagated poplars in agricultural communities, small deciduous galleries in moist canyons, scattered juniper and pinyon woodlands of the foot hills, and stands of high aspens. Red-tailed Hawks construct nests using sticks and twigs, lining the bowl with juniper bark and grasses. They begin their breeding activities in late winter to early spring, producing clutches of up to 5 eggs (usually 3 to 4eggs) which they incubate 28 to 35 days. After hatching the nestlings fledge 42 to 46 days later, usually in late spring to early summer.
Occupation and Nest Starts 2001-2005
The number of known territories, occupied territories and active nests (nest starts) represent all Red-tailed Hawk nests monitored in Utah from 2001 through 2005. More than one nest is often present in a territory, an area used by a single pair during a breeding season. In Utah, the number of nests in a known territory averages just over one, but up to four nests have been found in territory. Behaviors of the adults clue surveyors in to whether or not a known territory is occupied and if a nest start has been initiated. Activities associated with occupation include courtship behaviors such as dual perching and soaring, copulation, prey exchange, and nest building. The best indication of a nest start is the presence of an adult on the nest for a sustained period. With the nests often adjacent to open spaces, or over looking a large area, an adult sitting prominently on the eggs and the mate perched nearby can be easily seen. When present in areas of frequent human activity Red-tailed Hawks tend to be less than skittish often affording excellent looks from a moderate distance.
Success and Productivity & Utah Red-tailed Hawk Nest Fledgling Production 2001-2005
Nestling development and behavior cues indicate nestling age and probable fledgling dates. The pre-fledged nestlings often are active at the nest, standing, playing with sticks or exercising their wings (hop-flapping). They are mostly covered with feathers, except for small patches on the back of their head and under the wing pits. Just a few days before fledging nestlings will begin to explore the areas immediately about the nest, walking out on branches or hopping to adjacent ledges. A nest is considered successful once nestlings have reached at least 80% of the species median fledgling age (35 days for Red-tailed Hawks). All nestlings reaching at least 80% of the median species fledge age are considered to have fledged, unless observations indicate otherwise. Most mortalities discovered after the 80% fledge age appear to have occurred outside of the nest, post-fledging. Immediately after fledging the young hawks walk and hop about their surroundings, quickly learning make short flights. Shortly after fledging they can be seen perched atop prominent features or on tree limbs and clumsily flying in the general area of the nest.
Since the beginning of the standardized surveys in 2001, the total number of known Red-tailed Hawk territories, occupied territories and active nests (nest starts) has increased through 2005. In 2004, the number of occupied territories and nest starts dipped only to rebound in 2005. The hatching and fledging success rate of the northwestern Utah Red-tailed Hawks has remained rather steady during the project. Interestingly, the total number of fledglings has increased through the project with a dip in productivity in 2004, rebounding to a record high in 2005. Our record number of fledglings resulted from a slightly increased number of fledglings per nest start, the usual number of fledglings per successful nest; and a record number of nest starts; even though fledgling success dipped to a record low in 2005. For more information on Red-tailed Hawks please see our state specific annual reports Northwest Utah Nest Survey and Northeast Nevada Nest Survey.