Gray Hawks rarely stray away from cottonwoods and willows along rivers. These tall trees provide good habitat for hunting. In the United States Gray Hawks are more habitat restricted than in other portions of their range. They can live in a wide variety of habitats from thorn scrub, to riverside woodlands, to forest edges and open clearings. Pairs use mainly cottonwood trees to breed and nest, but mesquite woodland surrounding these cottonwoods is important in nest site selection. In Arizona, they prefer large mesquite woodlands near cottonwood and willow trees along streams. Gray Hawks also nest in Arizona walnut, Arizona white oak, and velvet ash. In both Arizona and Texas their nests are highly concentrated along major rivers, such as the Rio Grande. Back to top
Gray Hawks eat almost exclusively vertebrates, mainly reptiles. In Arizona, their most common prey is the whiptail lizard. In other areas they regularly eat spiny lizards, earless lizards, horned lizards, and tree lizards. They also eat snakes, such as whipsnakes and garter snakes, and a few species of toads. Gray Hawks eat a variety of birds too, including nestling songbirds. Examples of bird prey include, Gambel's Quail, doves, kingbirds, and Canyon Towhees. Gray Hawks also eat cottontails, woodrats, deer mice, and invertebrates such as beetles and grasshoppers.Back to top
Gray Hawks nest in outer branches in the upper half of trees, or rarely, close to the main trunk. They nest in many kinds of riparian trees, particularly cottonwood, as well as willow, walnut, ash, and oak.
Both adults help build the nest, using mainly small, live, leafy twigs that they break off from live trees. In Arizona, Gray Hawks use mostly cottonwood branches for the main structure, lining the nest bowl with cottonwood and willow leaves and sometimes bark. They add leafy material to the nest throughout the early stages of nesting. The nests are normally about 20 inches by 15 inches and 4 inches deep.
|Clutch Size:||1-4 eggs|
|Egg Length:||1.8-2.2 in (4.5-5.7 cm)|
|Egg Width:||1.4-1.6 in (3.5-4.2 cm)|
|Incubation Period:||32-34 days|
|Egg Description:||White to pale blue, sometimes spotted with brown.|
|Condition at Hatching:||Half-naked with light-gray down, particularly on the lower back, black bill, and yellow feet and legs.|
Gray Hawks hunt from tall cottonwoods and willows along streams. They perch in the mid to upper canopy and wait for lizards or other reptiles on the ground or on tree trunks before launching a quick descending attack. When looking for prey, they wait on a perch for a little while before moving a short distance to a new one. Gray Hawks catch prey less often by soaring low over open areas. They are probably monogamous. Similar to many other raptors, Gray Hawks perform an undulating flight display when courting. This involves a brief closed-winged stoop followed by an upward glide. Males and females both engage in this flight where they may turn sideways, upside-down, and may cross paths at close distances during steep dives. Males sometimes call to females during these courtship flights. Back to top
Though Gray Hawks are very restricted in the U.S., they range southward through Argentina and are fairly numerous. Partners in Flight estimates a global breeding population of 2 million, with just 1% (or fewer) breeding in the U.S. and 8% spending part of the year in Mexico. They rate an 8 out of 20 on the Continental Concern Score and are not on the 2014 State of the Birds Watch List. Gray Hawks were common in Arizona in the late 1800s, but habitat degradation, particularly the clearing of mesquite and cottonwood forests along streams saw a decrease in their numbers. U.S. populations fluctuated throughout the 1900s, including recent increases in Arizona and Texas. In addition to habitat degradation, depletion of groundwater also threatens Gray Hawk habitat by reducing water levels in streams and contributing to the disappearance of woodlands along streams. Recent population increases are likely due to land recovery after decreases in woodcutting and overgrazing.Back to top
Bibles, Brent D., Richard L. Glinski and R. Roy Johnson. (2002). Gray Hawk (Buteo plagiatus), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.
North American Bird Conservation Initiative. (2014). The State of the Birds 2014 Report. US Department of Interior, Washington, DC, USA.
Partners in Flight (2017). Avian Conservation Assessment Database. 2017.
Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, USA.