Cooper's Hawk

Accipiter cooperii

Order:
Accipitriformes
Family:
Accipitridae
Sections

Diet and Foraging

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Figure 6. Cooper's Hawk chasing prey.

Doves are favored prey of this raptor. Drawing by J. Schmitt.

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Cooper's Hawk hunting European Starlings.

Starlings are a major prey item. Studies suggest most attacks target flocks; however, attacks on single birds were more successful.

© Dennis Danner , Indiana , United States , 22 January 2019
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Cooper's Hawk with Rock Pigeon.
© Ronnie Hewlette , North Carolina , United States , 4 February 2019
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Cooper's Hawk preying upon unidentified nestling at nest.
© George Ho , Colorado , United States , 19 June 2019
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Cooper's Hawk at carcass.

It is unclear to what extent Cooper's Hawks scavenge.

© S Marbut , Kansas , United States , 16 February 2018
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Cooper's Hawk drinking.
© Larry Sirvio , Arizona , United States , 17 March 2017

Feeding

Main Foods Taken

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Video: Adult Cooper's Hawk with prey.

Accipiters are specialist predators that eat mostly birds. They sometimes hunt at backyard feeders.

© Timothy Barksdale, Missouri, United States, 28 March 1997

Mostly live ground-dwelling and shrub-dwelling species, especially small to medium-sized songbirds and doves; secondarily small mammals. Among individuals breeding in some central and western states, a higher proportion of mammals in diet (8, 2). Prey items for both adults and subadults had masses ranging from about 30–130 g, or about 5–37% and 8–22% of the mass of eastern male and female Cooper's Hawks, respectively (137).

Microhabitat for Foraging

In southwestern Tennessee, 6 individuals were radio-tracked during the nonbreeding season to assess their preferred habitat use and diet. Forest habitats were used most frequently for foraging, followed by edge habitats, and then open fields, even though fields were just as available as forests; study mentioned but did not account for potential effects of sex-bias (1 male, 5 females) and age-bias of telemetered birds that included both immatures and adults (126).

In Tucson, Arizona, researchers reported that within their home ranges, telemetered, breeding adult male Cooper’s Hawks (n = 9) used residential areas, regional parks, and golf courses, or small neighborhood parks (containing large non-native trees and tracts of remnant native vegetation) more often than expected by chance, likely due to abundance of primary prey (doves) throughout these landscapes that surrounded their nests (138); same habitats selected by adult males (n = 25) during the nonbreeding season (139). By contrast, Murphy et al. (106), found a single adult urban male selected undeveloped woodlands and avoided residential areas and residential areas/businesses in city of Stevens Point, Wisconsin. Further research on > 30 individually marked breeding adult males in Stevens Point suggest foraging common in residential areas (involving backyards and bird feeders), including small neighborhood parks (RNR). Adult females take prey opportunistically within 100 m of nest during the pre-incubation stage at both urban and rural Wisconsin nests (140, RNR). Will pursue prey into buildings with open doors (RNR).

In rural Florida, where food was reported as limiting to breeding populations, Millsap et al. (46) reported adult male Cooper’s Hawks restricted year-round hunting to a home range centered on their nesting area (i.e., territory), females moved over much larger area almost nomadically, and exploited concentrations of prey at places such as chicken farms, bird feeders, and Northern Bobwhite (Colinus virginianus) feeders, and cattle feedlots. Once located, females stayed and exploited foraging site until, presumably, non-profitable. They also frequently observed male Cooper’s Hawks searching tree canopies for bird nests, as well as taking nestling birds from nest boxes. Following a severe spring storm that resulted in deep snow cover in Wisconsin, Pine Siskins (Spinus pinus) were apparently an important alternative above-ground prey (141).

Food Capture and Consumption

Typically relies on concealment and uses a series of brief perch-and-scan episodes to find prey, but also flies close to ground, using bushes and human structures (e.g., buildings) to shield its approach; a sudden burst of speed is the usual pursuit when hunting from a perch (39, 101, 117, 1, 142; Figure 6). Also known to hunt from higher flight, stooping on prey in open habitat (143, 102); occasionally pursues prey on foot (24, 84, 144, 1).

During the breeding season in Missouri, 33% of 45 observed capture attempts were successful (145); but these data do not distinguish among seasons, sexes, or ages; more data needed. Post-fledglings, 44–69 days old, either in groups of 2–4 siblings or as single individuals, successful in 56% of 18 hunting attacks in a suburban Wisconsin landscape; caught mainly eastern chipmunks (Tamais striatus; 144).

In the attack and strike of an adult female used for falconry, the hawk typically ceased flapping about 4 m from the prey and, at about 1.5 m from contact, began swinging the legs forward, with the feet attaining velocities of 11.4 m/s, 15% greater than that of the pelvis (146). Almost 100% of the velocity of the feet was in a horizontal plane at the time of impact. At contact the hawk set its wings in a braking position, held its toes extended, and maintained a body axis to a horizontal angle of about 80°. Prey usually seized with both feet.

Responds to movement of captured prey by strongly grasping it, then relaxing grip, and then clamping down again (39). Will drown its prey in water, holding it under until it ceases to move (147, 148, 149). Holds head of prey when eating; most prey eaten in this sequence: head, viscera, muscle (39).

Roth and Lima (150) examined the hunting behavior of 8 individuals (1 male, 7 females) in urban habitats in Indiana and found that small passerines were at a lower risk of predation than were medium-sized species such as doves. The hawks attacked only birds (i.e., no mammals) and had an overall success rate of 20%. An estimated 95% of prey attacked were European Starling (Sturnus vulgaris), Mourning Dove (Zenaida macroura) and Rock Pigeon (Columba livia). Although readily available to the hawks, House Sparrows (Passer domesticus) were never attacked by females and rarely attacked by the single male. ‘Surprise' attacks, in which the birds used physical obstructions to surprise prey, were more successful than those in open areas, even though the latter were more frequent. Also, even though most attacks targeted flocks, attacks on single birds were more successful.

In contrast to studies in Indiana, House Sparrows were reported as common prey of breeding Cooper’s Hawks in Milwaukee, Wisconsin, Grand Forks, North Dakota, Albuquerque, New Mexico, and Victoria, British Columbia (50). One native (American Robin, Turdus migratorius) and two introduced species (European Starling, House Sparrow) provided most (> 85%) prey recorded in samples where birds identified to species in Victoria, British Columbia (50). Dominance of a few prey species has been observed in most Cooper’s Hawk diet studies (1).

Cooper’s Hawks marked with radio-transmitters in Indiana hunted roosting prey (species unreported) at night, using illumination of urban lighting and the moon; hunting more so in urban versus rural birds (151).

Diet

Major Food Items

See Table 2. Relative importance of birds versus mammals varies across regions and among habitat types. Almost all data from breeding season, mostly from southeastern, midwestern and southwestern United States, and southwestern British Columbia. Of 12 studies across North America, 10 (83%) reported bird prey to be dominant, ranging from 56% to 96% of total items tallied (see summary in 1). The most common from smaller to larger: House Sparrow (example: ML81132121) (especially in cities such as Victoria, British Columbia; Milwaukee, Wisconsin; Grand Forks, North Dakota; and Albuquerque, New Mexico; 50, RNR); the Northern Cardinal (Cardinalis cardinalis) and the Northern Mockingbird (Mimus polyglottos); especially in rural Florida; 46); and the American Robin (example: ML40321891), European Starling (example: ML51466291), Blue Jay (Cyanocitta cristata; example: ML79022731), and Mourning Dove (example: ML89762831, ML86930081) in both urban and rural habitats across North America (49, 50, 46). More information needed from nonbreeding seasons, specific habitats, especially urban, and additional geographic areas. Live animals, often sub-adult birds and mammals of medium size (152, 49), especially American Robin, Jays (Cyanocitta, Aphelocoma), Northern Flicker (Colaptes auratus; example: ML164897591), European Starling, Doves (Streptopelia decaocto (example: ML139229481), Zenaida, and Columbina spp. (example: ML90253481; 153) and chipmunks (Tamias, Eutamias; example: ML52422901).

Other avian prey include: various poultry (example: ML91667981), Ring-necked Pheasant (Phasianus colchicus), Ruffed Grouse (Bonasa umbellus), Northern Bobwhite (Colinus virginianus) (154), Cattle Egret (Bubulcus ibis; example: ML141912251), Least Bittern (Ixobrychus exilis), American Crow (Corvus brachyrhynchos), American Kestrel (Falco sparverius; example: ML23766391) (155), Burrowing Owl (Athene cunicularia; ML181710311), (Rock Pigeon (example: ML47256861), various blackbirds (Agelaius, Quiscalus, Molothrus, Sturnella; example ML173716411), Red-bellied Woodpecker (Melanerpes carolinus; example: ML107217651), House Sparrow, Dark-eyed Junco (Junco hyemalis), Greater Roadrunner (Geococcyx californianus; example: ML78974121), Sanderling (Calidris alba; example: ML41764621), Killdeer (Charadrius vociferus; example: ML68001851), various other waterfowl (example: ML53305361, ML40355401), gulls (example: ML129301111), sparrows, and wrens. Other mammalian prey include: hares (Lepus, etc.; example: ML154665921), mice (Peromyscus, Mus, etc.), rats (Rattus, etc.), tree squirrels (both Sciurus and Tamiasciurus; example ML109680621), ground squirrels (Ammospermophilus, Spermophilus, Xerospermophilus; example: ML169274971), and bats (Tadarida). Other prey groups include reptiles (example: ML171826701), amphibians, insects, and fish (84).

Quantitative Analysis

In southwestern Tennessee, diet was dominated by birds (95%, 18 of 19 items), with > 50% being passerines and 21% being Northern Bobwhite (126). In northern Florida, birds comprised 87.5% of prey items by frequency and 74.6% of the biomass delivered to nestlings. Important prey included Mourning Dove (14.5%), Blue Jay (13.5%), Cattle Egret (4.9%), Northern Mockingbird (4.5%), Northern Bobwhite (4.5%), and Northern Cardinal (4.3%) (115). Nestling and fledgling birds made up 64% of the 60 prey items of known age brought to nests (115).

Predation on songbird nests is not uncommon. Cooper's Hawk predation (along with that of other nest predators) negatively affected Willow Flycatcher (Empidonax traillii) nest success in California, where nest predation was the most important (76%) cause of nest failure (156). In Ponderosa Pine (Pinus ponderosa) forest in California, Cooper's Hawks were responsible for 25% of nest predation on Dusky Flycatcher (E. oberholseri) nests; here again, predation was most significant (96%) cause of nest failure (157). There is one record of nest predation by Cooper's Hawk at a Golden-cheeked Warbler (Setophaga chrysoparia) nest (158).

Schmidt and Ostfeld (159) showed that abundance of Cooper's Hawk and Sharp-shinned Hawk were positively related to the previous summer's rodent density, as well as to acorn abundance two autumns previous to that (acorn abundance probably driving rodent abundance). After a 1-year lag, accipiter numbers may increase in response to rodent increases, and after a 2-year lag, to acorn abundance.

Estes and Mannan (153) compared provisioning rates at urban and rural nests in Arizona. Urban hawks provisioned about twice the amount of prey biomass (per hour per nestling) as rural pairs, probably because prey were more abundant and available, with doves making up 57% of prey deliveries to urban nests, but only 4% to rural nests. A high proportion of doves in the diet may explain the high incidence of trichomoniasis-related death in urban nestlings (previously demonstrated for urban nestlings in Arizona by 110, 5, and 6; see also Demography and Populations: Disease and Body Parasites and Causes of Mortality).

Food Selection and Storage

May take prey easiest to catch (160); most breeding season prey items, avian or otherwise, are young-of-the-year, ground-foraging animals (49). The larger female hawk often takes larger prey than the male (39, 161, 162, 163), but not always (164).

During breeding season, both sexes cache uneaten prey on horizontal branches and retrieve it for themselves and their young; caching may be as frequent as 1/d for females with nestlings (RNR, JB; J. Papp, personal communication). No information on caching outside the breeding season.

Nutrition and Energetics

For a nest in New York (160), an average of 66 medium-sized (e.g., American Robin) prey items required to raise a young bird to age 6 wk. In California (165), 62 g of food/d or about 2,740 g during its first 6 wk. A captive male in fall–winter consumed an average of 63 g/d; a female in spring–summer, ate an average of 70 g/d; these values were 19.7% and 16% of body weight, respectively (166). Incubating females are ordinarily fed 3 times/d by mates (39, RNR, JB). Rates of prey delivery to nestlings vary with stage of nesting (see also Breeding: Parental Care) and probably with weather. Little information available on provisioning rates. In mixed-grass prairie habitats in the Northern Great Plains, provisioning rates for 2 nests averaged 0.52 items/h over 9 days of observation (167).

In 136 hours of observation at nesting territories in New Mexico occupied by adult (after-second-year) females, Lien et al. (168) observed 92 prey deliveries, whereas in 120 hours of observation at territories occupied by younger (second-year) females they observed 65 prey deliveries. Prey delivery rates at nests of after-second-year females always averaged higher than at nests with second-year females, particularly in the later stages of the nestling period. Despite a relative unimportance of prey density in influencing prey delivery rates, nesting territories with second-year females had an average of 694 fewer prey individuals per km2 than nesting territories occupied by after-second-year females (168).

Metabolism and Temperature Regulation

Rates of metabolic heat production for fasting captive and migrant individuals averaged 2,516.3 mW for males and 2,655.5 mW for females; rates for North American accipiters appear higher than those of other falconiforms of similar size (142).

Drinking, Pellet-Casting, and Defecation

No data on drinking and pellet-casting. An incubating female defecated at least 3 times in one day, but not at the nest (39).

Recommended Citation

Rosenfield, R. N., K. K. Madden, J. Bielefeldt, and O. E. Curtis (2019). Cooper's Hawk (Accipiter cooperii), version 3.0. In The Birds of North America (P. G. Rodewald, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bna.coohaw.03