Quick Answer
The grey hawk and Cooper’s hawk are two different species of hawk found in North America. The main differences between them are:
- Size – Grey hawks are larger than Cooper’s hawks
- Coloration – Grey hawks are light grey with some rusty brown on the shoulders and tail. Cooper’s hawks have blue-grey upperparts and reddish barred underparts.
- Range – Grey hawks are found in the southwestern United States, Mexico and Central America. Cooper’s hawks are found throughout North America.
- Habitat – Grey hawks prefer open arid country. Cooper’s hawks are found in forests and woodlands.
- Prey – Grey hawks mostly eat lizards and small mammals. Cooper’s hawks prey on other birds and small mammals.
In summary, the grey hawk is a larger, mostly light-colored hawk found in the Southwest that specializes in hunting reptiles. The smaller, woodland-dwelling Cooper’s hawk has more distinctive patterning and preys mostly on other birds.
Size Difference
The grey hawk is significantly larger than the Cooper’s hawk. Grey hawks measure 19-25 inches (48-64 cm) long with a wingspan of around 50 inches (127 cm). They weigh 21-46 oz (600-1300 g).
Comparatively, Cooper’s hawks measure 14-20 inches (36-51 cm) long with a wingspan of 24-35 inches (61-89 cm). They weigh just 7-24 oz (200-680 g).
So the grey hawk is nearly 25% longer and has a wingspan over 40% greater than the Cooper’s hawk. The grey hawk is also over twice as heavy on average as the smaller Cooper’s.
The size difference can be attributed to the fact that grey hawks and Cooper’s hawks hunt different prey and in different habitats. The larger grey hawk is an adept hunter of reptiles and small mammals in open country. The more compact Cooper’s hawk evolved for greater maneuverability when hunting other birds in forested areas.
Plumage Differences
In addition to the size difference, grey hawks and Cooper’s hawks show distinct differences in their plumage that makes them relatively easy to distinguish visually.
The grey hawk’s plumage is predominantly light grey above and pale with rufous barring below. The grey feathers give them a overall much paler look compared to the Cooper’s hawk. The grey hawk’s shoulders and shorter tail feathers also have a rufous tint.
The Cooper’s hawk exhibits more contrast in its plumage. Its upperparts are a blue-grey color while its underparts are reddish orange with blackish bars extending horizontally across the breast. The tail of the Cooper’s hawk is also longer and shows distinct dark banding.
When seen flying overhead, the pale grey hawk shows a mostly uniform upper surface compared to the Cooper’s hawk’s darker grey back and lighter banded tail. At closer range, the reddish barred underside of the Cooper’s is very distinctive from the plain pale underside of the grey.
The differing color patterns provide camouflage for each species’ preferred habitats. The grey hawk’s light color blends in against the open desert landscapes where it hunts. The Cooper’s hawk’s markings help it disappear amongst the trees and match the dappled light of the forests.
Range and Distribution
Grey hawks and Cooper’s hawks have broadly overlapping ranges in North America but significant differences regionally in their distributions.
The grey hawk occupies the southern portion of the continent. Its breeding range extends from the southwestern United States through Mexico and Central America. Populations are found in California, Arizona, New Mexico and Texas. It is scarce and local in the southernmost regions of its range.
The Cooper’s hawk has a much wider distribution across the whole of North America. It breeds in forests widely across Canada, the United States and Mexico. Its range extends as far north as southern Alaska and all provinces and states of Canada and the continental United States except for the driest areas of the Southwest.
During winter, Cooper’s hawks migrate and are found throughout the southern half of North America from coast to coast. Grey hawks are non-migratory and stay year-round in the same region.
So while there is some overlap in the southern U.S. and Mexico, the grey hawk occupies a small fraction of the breeding range that the widespread Cooper’s hawk does. Their ranges differ based on habitat preferences and climate needs.
Habitat Differences
One of the main reasons for the differing ranges is a preference for different habitats between the two hawks.
The grey hawk is most often found in open, arid country. It occupies deserts and scrublands with saguaro cacti and other arid plants. Grasslands, agricultural fields and riparian areas may also be used. It is generally not found in forested areas.
In contrast, the Cooper’s hawk lives in wooded habitats. It prefers mixed forests, deciduous and evergreen woodlands and is also found along forest edges and within urban parks and woodlots throughout its range. It uses the cover of trees for nesting and hunting.
So while the Cooper’s hawk ranges widely across the majority of North American habitats, the grey hawk has very specific habitat needs in hot, dry regions with low rainfall. The Cooper’s hawk’s association with forested land also contributes to its much larger latitudinal distribution.
Hunting and Prey Differences
The differing habitats of grey hawks and Cooper’s hawks means they have adapted to prey on different food sources.
The grey hawk’s prey is dominated by reptiles, especially snakes and lizards. Small mammals like rodents, rabbits and bats make up most of the balance of its diet. Birds and insects are only occasionally eaten. Hunting often occurs from a perch with swoops down to the ground to capture prey.
In contrast, the Cooper’s hawk is specialized for hunting other birds. Other birds such as doves, woodpeckers, pigeons and songbirds are its primary prey. It complements its diet with small mammals including squirrels, rats and mice. Compared to the grey hawk, reptiles and amphibians are a very small portion of its diet.
The Cooper’s hawk often hunts from cover in ambush, utilizing forest edges and thickets. Its technique is reminiscent of the related sharp-shinned hawk, but zips through the forest with more speed and agility thanks to its smaller size.
So the grey hawk relies on reptiles found in open country while the Cooper’s hawk is an adept bird hunter in woodland settings. This correlates with their differing habitat preferences and distributions across North America.
Breeding Behavior
Grey hawks and Cooper’s hawks both nest in trees but differ in some aspects of their breeding biology.
Grey hawks build a relatively small stick nest lined with softer material. Nests are located from 16-100 ft high in various trees or shrubs, including mesquites, pines, sycamores and yuccas. The breeding season lasts from March to June with peak activity April and May. The clutch size is 1-3 eggs. Incubation ranges 24-32 days and the nestling period is about 5-6 weeks.
Cooper’s hawks construct a larger nest of sticks lined with bark strips and leaves. Nest heights range from 45-90 ft in either conifers or deciduous trees. Breeding occurs earlier from March to mid-May, with 1-6 eggs laid. Incubation lasts 30-36 days and young fledge after 24-34 days.
So the Cooper’s hawk has a longer breeding season, builds a larger nest at greater heights, and can lay significantly more eggs. This supports its larger population size and distribution compared to the grey hawk. Both species show aggressive territorial defense of nest sites.
Taxonomy and Classification
The grey hawk and Cooper’s hawk are classified in the same genus Accipiter but are separate species. Their scientific names are:
Grey hawk: Asturina nitida
Cooper’s hawk: Accipiter cooperii
This places them in the large Accipitridae family of diurnal raptors. Other close relatives include the northern goshawk, sharp-shinned hawk and red-shouldered hawk.
There are four recognized subspecies of the grey hawk that show some variation in size and coloration across different parts of its range:
- A. n. nitida – Found in California, Arizona and New Mexico
- A. n. maxima – Large pale subspecies of western Mexico
- A. n. plagiata – Fairly small and dark grey resident of southern Texas through Central America
- A. n. suttoni – Paler grey resident subspecies of the Baja Peninsula
No subspecies are recognized for the relatively uniform Cooper’s hawk across its wide range. Phylogenetically, the Cooper’s hawk is actually more closely related to the world’s small hawks in the Micronisus lineage rather than the grey hawk.
Conservation Status
The grey hawk has a more threatened conservation status than the still common and widespread Cooper’s hawk.
Due to ongoing habitat loss and degradation, the grey hawk is listed as Near Threatened by the IUCN. Partners in Flight estimate a global population of just 130,000 breeding adults. Numbers have declined from historic levels.
In contrast, the Cooper’s hawk is listed as Least Concern by the IUCN. Partners in Flight estimate a breeding population of over 3 million across North America. Despite some historical decline due to DDT, the banning of pesticides allowed Cooper’s hawks to recover to stable population levels.
Ongoing threats to the grey hawk include urbanization, conversion of scrub habitat to agriculture, river channelization, fires and droughts. Range-wide monitoring and habitat protection are needed to safeguard the smaller grey hawk populations.
Quick ID Tips
Here are some quick tips for visually distinguishing between a grey hawk and a Cooper’s hawk:
- The grey hawk appears much paler overall with a lighter grey back
- Cooper’s hawks show dark crowns in contrast to a pale nape band
- Cooper’s hawks have reddish barring on the underparts vs plain on the grey hawk
- Grey hawks have rusty shoulders while Cooper’s are grey
- Cooper’s hawks have long banded tails unlike the grey hawk’s tail
Behaviorally, watch for Cooper’s hawks using cover when hunting while grey hawks perch hunt more in open areas. If seen well, the Cooper’s hawk’s smaller rounded head and nape distinguish it from the grey hawk’s flatter head profile.
Conclusion
In summary, the grey hawk and Cooper’s hawk represent two different species within the Accipiter genus that have evolved to occupy different ecological niches.
The larger grey hawk is a reptile specialist restricted to arid habitats in the Southwest and Mexico. The smaller Cooper’s hawk has broader tastes and hunting skills that allow it to thrive across most of the North American continent.
Key field identification points when distinguishing these species include size, plumage color patterns, tail banding, geographic range, and habitat and prey preferences. Despite some overlap, these hawks highlight the amazing diversity and adaptations of raptors.