[16][17] Genetic studies of three Asian Accipiter species showed that they may not be a monophyletic group, with various clades divisions outside traditional subfamily lines, with even the sharp-shinned hawk-like and aptly named tiny hawk (Microspizias supercillocus) appearing to cluster outside of the genus nearer very dissimilar genera like Buteo and Milvus.

[2][31] The adult's underside shows a bit of whitish base color overlaid heavily with coarse, irregular rufous to cinnamon bands, though these narrow into marginal shaft streaks around the throat.

[32] Juveniles of the species are generally dark brown above, though the feathers are not infrequently edged with rufous to cinnamon and have a variable whitish mottling about the back, wing coverts and, mainly, the scapulars.

[5] Cooper's hawks have a strong flight with stiff beats and short glides, tending to do so on quite level wings with wrist thrust forward yet the head consistently projects.

[36] The eyes of this hawk, as in most predatory birds, face forward, enabling good depth perception for hunting and catching prey while flying at top speeds.

[40] However, Cooper's hawks are one of an estimated 25% of studied bird species that do not appear to correspond to Bergmann's rule (i.e. being larger where living farther north) instead varying in size much more so by longitude.

[40][41] However, in the field, especially when hawks must be identified in at a distance or at unfavorable angles (such as when migrating) or at a brief glance (such as when hunting), even experienced birdwatchers may not always be able to certainly distinguish the two species, especially female sharp-shins against the nearly similarly sized male Cooper's.

[63][66] The sharp-shinned hawk usually evidences a slimmer, slighter look, with more dainty features, and has relatively longer wings and a shorter and more squared tail with a much thinner white tip.

[63][64][68] The most reliable way to distinguish a large juvenile Accipiter in the field are the differing proportions of the two species, followed by the heavier streaking below and irregular tail banding of the goshawk.

In southern Canada, they breed (but do not normally winter) in the southerly parts of the provinces of British Columbia, Alberta, Saskatchewan, Manitoba, Ontario, Quebec to extreme southwestern Nova Scotia.

[1][2][74] Cooper's hawks live almost throughout the contiguous United States, excepting some parts of the southern Great Plains, as well as perhaps a bit of northwestern Maine and northernmost Montana.

[2][80][89][90] In fact, some authors felt the species increased locally in wooded parts of the Rocky mountains after human habitat fragmentation of once continuous woodland areas.

[2][39] Although they often live in areas where deciduous trees are predominant, almost throughout the range they are often attracted to stands of conifers, which, due to their density, provide more extensive shelter and perhaps a more sturdy nesting site.

[107] Despite the success of Cooper's hawks in Tucson, attempts to find breeding activity in Phoenix and Casa Grande were unsuccessful, it is thought that the ambient temperature was too high or beyond thermal tolerance levels.

[108] Although more adaptable in habitat than the sharp-shinned hawk, studies from Pennsylvania have indicated that the species still more often than not prefers sizeable tracts of woodland for breeding and migrating to fragmented, developed areas.

[120] Cooper's hawk's threat display appears to consist of them lowering their heads, raising their "crest" (capital tract), stretching out their wings, spreading the tail and engaging in vocalizations.

[1][2] Despite being classed as sedentary, banding studies have revealed that many Cooper's hawks south of the typical migratory populations engage in some variety of seasonal winter movements.

Furthermore, females of all ages tend to migrate sooner and spend longer in winter quarters than like-age males, the latter staying relatively north and traveling back again earlier.

[5][62] Given their dietary habits, these hawks bore a poor reputation well into the 20th century, with one account describing the species as "noxious", an "avian outlaw" and "a relentless tyrant and murderer of small birds".

[47][50][180][189][190][191][192] The closest rival to the robin in being most widely taken as prey for Cooper's hawks may be the common starling (Sturnus vulgaris), a non-native bird in North America with mean weights when taken of 79 to 82 g (2.8 to 2.9 oz).

[7][47][189] Even among water birds, nonetheless, a wide diversity may be taken, from the tiny 22.9 g (0.81 oz) least sandpiper (Calidris minutilla) to an adult mallard (Anas platyrhynchos) estimated to weigh 1,150 g (2.54 lb) when taken.

[180] Thirteen-lined ground squirrels (Ictidomys tridecemlineatus) were the second most common prey species in a study from Wisconsin and also important in the diet in North Dakota (where they were the most significant contributor of biomass, constituting 23.4%).

In the Wisconsin data, the red-shouldered, the broad-winged and rough-legged hawks (Buteo lagopus) as well as the northern harrier, peregrine falcon (Falco peregrinus) and the American kestrel all had lower mean prey masses.

[95] In what was probably a case of defense of their hunting ground, a female Cooper's hawk was recorded to attack and drive off (without physical contact) a larger peregrine falcon from a perch during winter in Ontario.

Among all known predators, only the raccoon (Procyon lotor) can be considered to rival the great horned owl as the most severe threat to nesting attempts, probably consuming mostly nestlings and eggs but also perhaps some older hawks.

After some regional declines, a radiotagging study in Pennsylvania found that of 19 kestrels, 26% were killed by avian predators, with the suspected culprit in a majority of the cases being Cooper's hawks.

[33] The male is rarely present at nest longer than 3–4 seconds after hatching but at least once was recorded staying for 3 minutes when coming with prey after the female stops heavily brooding.

[51][50][329] Although Cooper's hawks are not known to prey on venomous snakes, one was found dead from envenomation next to a burrow holding both a copperhead (Agkistrodon contortrix) and an eastern diamondback rattlesnake (Crotalus adamanteus).

[431] In Minnesota and Wisconsin, several helminths were recorded and there was one instance of a tissue reaction from Serratospiculum as well as a case was reported of related Serratospiculoides in an injured Cooper's hawk in Yellowstone National Park.

[470] Despite the large, productive and genetically diverse population of Cooper's hawks in Tucson, several authors have hypothesized, controversially, that the city is an ecological trap, due to the unsustainably high turnover for nestlings via Trichomoniasis-related mortality and for adults via frequent lethal collisions.