Hunting methods . Cooper's hawks are known as bold and aggressive predators. Early accounts underestimated the opportunistic nature of Cooper's hawks' hunting behavior and provided little insight into the actual effect the hawks have on their prey. In another Michigan study, most Cooper's hawks were found to be flying from their wooded nests to hunt on agricultural ground. Males in New York usually covered more than , sometimes up to , during hunting efforts when flying away from the nest area. Near
Stevens Point in Wisconsin, males prefer to hunt in quiet woods while females preferred to stay within of the nest making males a more common sight. This differed strongly in Tucson where hawks while hunting mostly in manmade environments such as residential areas,
regional parks, and
golf courses more so than they were prevalent in the environment, though usually where there were large (albeit usually non-native) trees. Cooper's hawk does attack birds attracted to
bird feeders with a fair amount of frequency. However, data from Indiana showed that birds using bird feeders were at no greater risk of attack than those in random transects, and the effect Cooper's can have on feeder birds may be at times exaggerated. If it sees birds when flying, a hunting hawk does not fly directly to them but instead circles around to available trees and bushes often perching for a few moments before launching its attack. If birds become aware of it, the hawk will tend to quickly gain height in hopes of intercepting some prey. During hunts, these hawks may suddenly alight when detecting an available mammal. When hunting bats, they can follow all twists and turns, and may succeed in capture in up to 90% of hunts. An unusual
harrier-like flight was seen in be engaged in by a Cooper's hawk before an attack on
aquatic prey in a
marsh. Despite its
gracile appearance, Cooper's hawk is extremely powerful for its size and presumably able to capture larger prey relative to its size than other raptors such as falcons and
Buteos (including
red-tailed hawks (
Buteo jamaicensis)) due to its unusually high-speed foot
velocity and resulting impact during prey captures. At times, after capture, Cooper's hawk have been seen to hold still living prey underwater, presumably trying to
drown it. Subsequent to the preys' demise, they may eat the victim head first, followed by the
viscera, with the meat eaten lastly. 33% of 45 observed hunts in a study in
Missouri were successful. Post-fledgling
parties of hawks in Wisconsin were seen to hunt in sibling groups of 2–4, mainly pursuing
chipmunks, and were observed to succeed in 56% of 18 hunting attempts. During the first six weeks after the young hatch, in New York, it was estimated that a male Cooper's hawk would need to procure about 66 prey items over the period. In these first six weeks in California, it was thought a minimum of would be required per nestling per day.
Prey spectrum as its prey Cooper's hawk may consume well over 300 prey species from across the range. This predator is known to consume
vertebrate prey almost exclusively. Birds in general form about 50–85% of diet. Another estimate was from for typical prey sizes, or about 5–37% the weight of males and 8–22% the weight of females, respectively. In Oregon, the mean prey sizes of Cooper's hawk was , with larger prey was taken than in greater proportion than their occurrence in the ecosystem (indicating that they locally search out relatively large prey). In Missouri, mean prey sizes were , averaging between amongst the main prey classes. Prey delivered by males averaged an estimated , while the average estimated size of prey delivered by females was . Overall, in Missouri, prey body masses were estimated to range from .
Birds Predation rates and passerines , one of the most widely taken prey for this species. Birds are by far the leading prey for Cooper's hawks in most areas. A wide diversity of birds, considerably over 250 species, are known to be taken, constituting more than three-quarters of known prey species for these hawks. Although prior data mostly reflected the taking of adult birds, a study in Wisconsin revealed that Cooper's hawks may largely take young of the year, mostly fledglings but also not infrequently nestlings, during the breeding season. 74% of ageable bird prey in this study were young of the year. Similarly, in Michigan during summer, immature birds were more than 2.5 times more often delivered to Cooper's hawk nests than adult birds. One study determined that birds that nest in the
canopy level tended to nest fairly close to this hawk but those with mid-level, shrub level and ground level nests nested farther away, indicating that non-canopy-nesting birds are generally taken during the breeding season. Key to prey selection for Cooper's hawk is the availability and abundance of birds in a given region. The robin is regularly hunted in all seasons due to its commonality in
exurban regions, with both adults, at estimated averages of when taken, and young being relatively easy for them to access. Beyond the common robin, nearly all
thrushes in North America (excluding one
species whose breeding range is largely north of Cooper's range and one
rare, little-studied species) are opportunistically hunted by Cooper's hawks. 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 . The starling was the main food for these hawks in
Ithaca, New York, at 28.2% of 857 prey items, and
Terre Haute, Indiana, at 56.5% of 57 prey items, and taken in large but somewhat secondary numbers in Missouri,
Michigan, and Victoria, British Columbia.
California scrub jays (
Aphelocoma californica) are regular supplemental prey in
northern California studies as well. It was hypothesized that Steller's jays may be able to effectively confuse a Cooper's hawk by engaging in a chorus of calls at close range. In
Arizona,
Mexican jays (
Aphelocoma ultramarina) are known to play a key role in
flicker ecology by watching out for Cooper's hawks. Numerous other corvids may be hunted, including most overlapping jays, as well as the
Clark's nutcracker (
Nucifraga columbiana),
black-billed magpie (
Pica hudsonia), possibly
yellow-billed magpie (
Pica nuttalli) and a few species of
crow. One black-billed magpie was caught and killed by a Cooper's hawk when attempting to mob the hawk. Incidents of predation have been witnessed on both young and adult
American crows (
Corvus brachyrhynchos). These hawks are also a potential predator of
fish crow (
Corvus ossifragus). However, crows are potentially dangerous prey to Cooper's hawks. Adult American crows are about the same size as a female Cooper's hawk and can potentially cause considerable damage to a lone raptor during group
mobbing, being capable of inflicting damage with both their feet and bill. In at least one case, a murder of American crows was observed to drive a Cooper's hawk to the ground and possibly seriously injure it, although the fate of the hawk was not certain. In the
Black Hills, although prey species were seldom identified, evidence showed that most regularly selected prey were assorted icterids. Even
meadowlarks, such as the
eastern meadowlark (
Sturnella magna) which was the third most often selected prey in Ithaca, New York, and
bobolinks (
Dolichonyx oryzivorus) are taken despite their preference for
grasslands well outside the typical habitats of Cooper's hawks. During harsh late winter weather in Wisconsin, Cooper's hawks were recorded to eke out an existence living largely off of
pine siskins (
Spinus pinus). In modern terms, certainly the most commonly taken small bird would be the non-native,
house sparrow (
Passer domesticus). Although not known to be taken profusely in all studied urban locales, house sparrows were the leading prey in a study from
Michigan, were nearly a third of observed delivered prey at nests in
Victoria, British Columbia (although were outnumbered by robins in prey remains) and reportedly were the leading prey in
Milwaukee and in
Grand Forks, North Dakota. Similar determent to the local nesting attempts of other small passerines such as warblers has also been reported.
Chickadees seem to regard Cooper's hawks as a moderate threat based on their anti-predator response, with smaller raptors (which are presumably more dangerous) such as sharp-shinned hawks and small owls evoking a rather more aggressive response by chickadees. While usually the smallest avian prey selected by Cooper's hawks are various warblers (presumably taken mainly by male hawks), down to the size of the
Wilson's warbler (
Cardellina pusilla), even smaller passerines are known to be hunted. The smallest known avian prey species have included the
verdin (
Auriparus flaviceps), the
ruby-crowned kinglet (
Corthylio calendula) and the
bushtit (
Psaltriparus minimus). Even smaller birds, the
hummingbirds, are essentially immune to Cooper's hawks (due to their own extreme agility) and were seen to incidentally benefit from nesting close to the hawks in California, due to a low risk of predators approaching while the hawks are present.
Columbids and woodpeckers , in New York City Outside of passerines, almost certainly the most important avian prey type is the
pigeon and dove family. Especially for those living in urban areas, Cooper's hawks have seemed to take to living heavily off of
doves, particularly the abundant and widely found
mourning dove (
Zenaida macroura), at . Mourning doves appear to be hunted regularly in almost any part of the two species' mutual range. In the more rural
north Florida, again the mourning dove leads the prey selection, accounting for 16.5% of 1100 prey items. Flickers are common prey elsewhere as well, such as in
Ithaca, New York. All told, about 20 species (almost all in North America but for a couple poorly studied species) of woodpecker are known to be taken, ranging from the smallest, the
downy woodpecker (
Dryobates pubescens), to the largest, the
pileated woodpecker (
Dryocopus pileatus). Despite the regularity of predation of woodpeckers that are in the open, a study in British Columbia shows indicated Cooper's hawks seldom prey upon woodpecker nests, perhaps due to being unable to access their secluded, smallish nest holes, with the study showing that the most regular predators of such nests were various mammals (from
deermice to
bears).
Galliforms Certainly the most controversial aspect of Cooper's hawks are their predations upon
galliforms. By far the most regularly selected types are
New World quails. Coveys of quails that attempt to evade predators by running into thick vegetation (which can allow them to successfully escape many predators) often find that Cooper's hawks are undeterred by this, as the hawks may chase them either on the wing or on foot into thickets. However, one
grouse was seen to successfully evade a hunting Cooper's hawk by diving belly first into about a foot of snow. Cooper's hawks are often regarded as perhaps the most regular natural predator of
northern bobwhites (
Colinus virginianus). Indeed, the rate of predation by Cooper's does appear to exceed that committed by other species of hawk as well as that by large owls. For instance, during winter in Wisconsin, Cooper's hawks were thought to kill 3.4–12.5% of the local bobwhite population. However, the bobwhite appears to be a secondary prey species in all known studies and there is no evidence that Cooper's hawk predation alone can deplete bobwhite populations, unlike causes directly contributable to man such as
overhunting and
habitat destruction. Most regularly found galliforms in North America (including well-established exotics such as
chukars (
Alectoris chukar) and
common pheasants (
Phasianus colchicus)) are known to fall prey occasionally to Cooper's hawks. These include assorted native
grouse, including even the
grassland-dwelling species (but excluding the more northerly distributed
ptarmigans). Juveniles usually are the more vulnerable and more regularly taken of non-quail galliforms by Cooper's hawks, but the hawks can take adults quite regularly despite the prey's relatively large size. Adult male
sharp-tailed grouse (
Tympanuchus phasianellus), which average , are also known have been successfully preyed upon by Cooper's hawks. Even more impressive accounts show adult
common pheasant estimated to weigh up to can be preyed upon by Cooper's hawks.
Other birds Beyond aforementioned families and orders, other types of birds are taken relatively infrequently. Usually moderate to low numbers of
water birds are taken of any variety. About 5 species each of duck and
heron, a dozen species of
shorebird and a smaller assortment of
grebes and
rails are known in the prey spectrum. Adult ducks and herons of roughly equal weight to Cooper's hawks and other largish adult water birds including
ring-billed gulls (
Larus delewarensis) and
American coots (
Fulica americana) are sometimes tackled by these hawks. Particularly frequency was recorded of
western cattle egrets (
Ardea ibis) in north Florida, where the egrets were the fourth most regularly recorded prey species.
Mammals is an ample meal for a juvenile Cooper's hawk A lower diversity of species and lower overall numbers of
mammals are taken relative to bird prey but mammalian prey can be locally important. High balances of the relatively large
eastern chipmunk (
Tamias striatus) were found in studies from New York, Michigan and Wisconsin. In the western United States, fewer chipmunks are identifiable but such prey is fairly commonly detected. Mammals distantly related to chipmunks, such as
ground squirrels (including
antelope squirrels) can be taken in locally high volume. Golden-mantled and thirteen-lined ground squirrels are fairly small for ground squirrels, the earlier averaging , the latter of similar size.
Tree squirrels are widely taken but secondary prey for Cooper's hawks. The smallish, roughly
American red squirrel (
Tamiasciurus hudsonicus) are not infrequent prey in northerly locations. About 36 red squirrels were recorded in the foods of Cooper's hawk in Ithaca, New York and these squirrels appear to have specific alarm calls that are provoked by these hawks, however the rate of predation by Cooper's appears to be low relative to other predators overall. Reported when taking red squirrels, male Cooper's hawks, being relatively small, may tear the prey into pieces that can be transported by them to the nest. Sizes of tree squirrels taken by Cooper's hawks were studied in Missouri.
Eastern gray squirrels (
Sciurus carolinensis) were taken of up to adult size but
fox squirrels (
Sciurus niger) were only taken as juveniles, as the adults, sometimes scaling up to , were apparently too formidable for Cooper's. The estimated weights of both the gray and fox squirrels taken in Missouri was , with the gray contributing 10.9% of the biomass. One broad study found a somewhat unexpected correlation was found positively relating the previous summer's rodent density to the number of Cooper's hawks. This could be coincidental as rodent populations are probably driven by
acorn production in the year prior to the rodent increases, and many of the birds taken regularly by Cooper's are also partially acorn dependent. Occasionally, Cooper's hawks may capture profitable mammalian prey such as
rabbits and hares. Mainly, predation has been reported on the
cottontail rabbits. Strong numbers of
mountain cottontail (
Sylvilagus nuttallii), averaging about when taken, were reported in northwestern Oregon (7.82% and fifth most regular prey species). Mammals of other orders are taken quite infrequently, with a low volume of
shrews and
moles reported. Occasionally, Cooper's hawks are known to hunt bats. They are said to usually capture bats on the wing rather than search them out. Findings were that in
Carlsbad Caverns that Cooper's (and also sharp-shinned) hawks were the most efficient avian predators of bats near the cave entrance (rating as more successful than most
Buteo hawks and particularly more so than larger and less agile raptors like
red-tailed hawks and
large owls). Per observation in Carlsbad, due to their agility, Cooper's can match the evasive flight of a bat and may be successful in about 90% of observed pursuits. Apart from their well-documented predation of
Mexican free-tailed bats (
Tadarida brasiliensis), quite little is known about which bat species Cooper's hawk's may prey upon and at what level do the local hawks depend on such prey. Apart from caves, sometimes Cooper's hawks have been seen to capture bats in urbanized areas.
Other prey In some areas, respectable numbers of reptiles may be hunted. All told, nearly 30 species of reptile may be hunted by Cooper's hawks. Strong detection of reptilian prey is known in more western locations, especially farther south. In California, it was found that 69% of the diet was reptiles, most of which were assorted lizards (led by
whiptail lizards, nearly of which were estimated to be found in one nest). In rural areas outside of Tucson, a fairly strong presence of (unidentified to species)
spiny lizards, at 13% of 77 prey items, although overall in all areas of the Tucson metropolitan, reptiles constituted a lower 8% of the total 228 prey items. Most lizards encountered and hunted by Cooper's hawks are fairly small but, despite being more scarcely selected, snake prey may show greater size variation. Unlike with reptiles, there is little evidence that Cooper's hawk regularly hunts
amphibians in any area, despite a few species being known in the prey spectrum. While some authors have posited that as much as 2.1% of Cooper's hawks' global prey consists of
invertebrates, The data from the
Jemez Mountains of
New Mexico was largely corresponding with the goshawk occurring in areas with a median of 781 trees per ha, Cooper's in areas with a median of 1229 trees per ha and the sharp-shins in a median of 1482 tree per ha. In the New Mexico data, goshawks used the largest trees with the lowest median canopy coverage (77.4% vs 78.4% for Cooper' s and 83.1% for sharp-shins). In a study from northern Utah, Cooper's hawks were intermediate in most habitat characteristics, being at median elevation (), nest height ( against for sharp-shins and for goshawk) and in areas of intermediate branch density. However, Cooper's nests were the closest in Utah to areas disturbed by humans ( against for sharp-shinned and for goshawk), also closest to water ( against in sharp-shins and for goshawk). There is often some level of distinction in habitat between Cooper's and the sharp-shinned hawk. Compared to sharp-shinned hawks in Wisconsin and Oregon, Cooper's hawks use woods with fewer conifers, less dense stands of trees and stands with taller trees. Often, sharp-shinned hawk nests are lower in the trees and placed in much denser vegetation (often even the sharp-shins with their smaller frames themselves accidentally strike against branches while attempting to enter the nest), to hide the nest more sufficiently against predators. The habitat used by the two species in
Missouri was less distinct (i.e. similar tree species used). However, the sharp-shinned hawk nests in Missouri were at much higher elevations, i.e. above sea level, than those of Cooper's (which were at a mean elevation of ; more surprisingly the stand density was higher here for Cooper's, at a mean of 935.7 trees per ha than those used by sharp-shins, at a mean of 599.3 trees per ha. There was some level of temporal differences between the two species in study in Indiana, where Cooper's hawks were generally active in the early morning but sharp-shinned hawks did not become active until later in the morning (hypothetically to avoid more severe interguild predation by large owls due to its smaller size). Cooper's hawk has a mean home range size that was comparable to the roughly half as large-bodied
Eurasian sparrowhawk, at for Cooper's and for the sparrowhawk. However, data shows that in North America, the home range size of
Accipiter and
Astur species corresponded to the birds' body size, i.e. mean for the goshawk and mean for the sharp-shinned hawk. Many studies have contrasted the diet of Cooper's and sharp-shinned hawk in other areas as well, with the sharp-shinned hawk much more regularly selecting birds weighing under about , a fair amount overlap in birds of and weight classes but birds over this weight range are increasingly more often taken almost exclusively by Cooper's. Also, the sharp-shinned hawk appears to hunt more so birds that dwell at the canopy level in the woodlands (as opposed to ground to shrub height-dwelling birds) within the forest and prefers to attack in heavier cover than Cooper's seemingly. In southern Wisconsin, the food niche breadth was rather higher for Cooper's at 6.9 and the mean prey mass, at , was second only to the red-tailed hawk's. 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. Cooper's hawk is usually a top predator in the daytime but is not immune from attack by other predators. The most common predator of this species is almost certainly the
great horned owl (
Bubo virginianus). This rather large owl (averaging more than three times heavier than a Cooper's hawk) is known to regularly track down fledglings and adults as well as raid the nests of other birds of prey. Many records show great horned owls will visit the nests of birds of prey and pick off the young nightly until the prey resource is exhausted (i.e. all young or sometimes adult birds of prey are killed). Furthermore, given the opportunity, great horned owls readily expropriate the nests built by the raptors they kill as their own. Both the young, especially around the time they leave the nest or are recently fledged, and adult Cooper's hawks are vulnerable to these owls. While little data has been collected on the overall effect great horned owls have on Cooper's hawk populations, it is known that for the larger, more formidable goshawk that as many as 40% of radiotagged juveniles within a study appeared to meet their demise via horned owls. Due to their threat level, the calls of great horned owls provoke a strong response from Cooper's hawks and banders and researchers usually use stimuli of great horned owls to attract a mobbing Cooper's hawks. Reportedly, Cooper's hawks will temporarily tolerate and possibly even cooperate with crows when one or the other spots a great horned owl in the daytime, both species appearing to join forces to mob the threatening owl out of the vicinity. Less is known about the range of nest predators. 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. American crows are known to rob nests of Cooper's hawks as well, especially when the parents have been displaced by the crow's severe mobbing. Some resources have gone as far as to blame the kestrels decline directly on Cooper's hawk predation but subsequent data from the
U.S. Breeding Bird Survey and the
National Audubon Society Christmas Bird Count appear to discount this theory, instead linking the overall declines to inadvertent human causes. Cooper's hawk are also counted as a predator of
merlins (
Falco columbarius). The only confirmed accipitrid that Cooper's hawk have been known to prey upon is their smaller cousins, the sharp-shinned hawks. Furthermore, Cooper's hawks that came into the vicinity were considered potential predators and mobbed as such by nesting
gray hawks. Even more so than diurnal raptors, a wide diversity of owls are known to fall prey to Cooper's hawks. Despite the temporal differences of their activity, the intensive hunting methods of Cooper's hawks may allow them to access roosting owls more readily than other types of hawks.
eastern screech-owls (
Megascops asio),
elf owl (
Micrathene whitneyi),
northern pygmy owl (
Glaucidium gnoma),
ferruginous pygmy owl (
Glaucidium brasilianum),
burrowing owl (
Athene cunicularia), and
northern saw-whet owl (
Aegolius acadicus). Most impressively, an instance was observed where a Cooper's hawk appeared to have preyed upon an adult of the rather larger (averaging about )
barred owl (
Strix varia). ==Breeding==