Cooper's hawk (Astur cooperii) is a medium-sized hawk native to the North American continent and found from southern Canada to Mexico. This species was formerly placed in the genus Accipiter.
As in many birds of prey, the male is smaller than the female.Snyder, N. F., & Wiley, J. W. (1976). Sexual size dimorphism in hawks and owls of North America (No. 20). American Ornithologists' Union. The birds found east of the Mississippi River tend to be larger on average than the birds found to the west.Pearlstine, E. V., & Thompson, D. B. (2004). Geographic variation in morphology of four species of migratory raptors. Journal of Raptor Research, 38(4), 334–342. It is easily confused with the smaller but similar sharp-shinned hawk (Accipiter striatus).
The species was named in 1828 by Charles Lucien Bonaparte in honor of his friend and fellow ornithologist, William Cooper.Palmer, R. S., ed. (1988). Handbook of North American birds. Volume 5 Diurnal Raptors (part 2). Other common names for Cooper's hawk include: big blue darter, chicken hawk, flying cross, hen hawk, quail hawk, striker, and swift hawk. Many of the names applied to Cooper's hawks refer to their ability to hunt large and evasive prey using extremely well-developed agility.
This species primarily hunts small to medium-sized birds, but also commonly takes small mammals and sometimes reptiles.
Like most related hawks, Cooper's hawks prefer to nest in tall trees with extensive canopy cover and can commonly produce up to two to four fledglings depending on conditions.
Breeding attempts may be compromised by poor weather, predators, and anthropogenic causes, in particular the use of industrial pesticides and other chemical pollution in the 20th century.Snyder, N. F. R. (1974). Can the Cooper's Hawk survive? National Geographic Magazine, 145:432–442. Despite historic declines due to anthropogenic causes, the bird's population is increasing as of 2024.
Taxonomy
Cooper's hawk was formally described by the French naturalist Charles Lucien Bonaparte in 1828 from a specimen collected near Bordentown, New Jersey. He coined the binomial name Falco cooperii. The specific epithet and the common name were chosen to honor naturalist William Cooper, one of the founders of the New York Lyceum of Natural History (later the New York Academy of Sciences) in New York City. Other common names include big blue darter and chicken hawk. Cooper's hawk was formerly placed in the genus Accipiter. In 2024, a comprehensive molecular phylogenetic study of the Accipitridae confirmed earlier work that had shown that the genus was polyphyletic. To resolve the nonmonophyly, Accipiter was divided into six separate genera. The genus Astur had been introduced in 1828 by French naturalist Charles Lucien Bonaparte with the Eurasian goshawk (Astur gentilis) later designated as the type species. The genus was resurrected to accommodate Cooper's hawk together with eight other species that had previously been placed in Accipiter.
Apparently, Cooper's hawk was the earliest Astur known to colonize North America with a well-defined fossil record dating back perhaps 0.5-1 million years (the goshawk came second). Despite the considerably wider range of the sharp-shinned hawk, still considered as Accipiter, unlike the prior species, the ancestors of the sharp-shinned hawk came over the Bering Land Bridge last.Brodkorb, P. (1964). Catalogue of fossil birds: Part 2 (Anseriformes through Galliformes).Emslie, S. D., Speth, J. D., & Wiseman, R. N. (1992). Two prehistoric puebloan avifaunas from the Pecos Valley, southeastern New Mexico. Journal of Ethnobiology, 12(1), 83–115. Genetic testing has indicated that Cooper's hawk is quite closely related to the American goshawk, unlike the similar superficial characteristics of Cooper's to the sharp-shinned hawk, a close relative of the Eurasian sparrowhawk, which were likely obtained through convergent evolution.Newton, I. (2010). The sparrowhawk. A&C Black. A natural hybrid of a Cooper's hawk and an American goshawk with intermediate physical characteristics was verified via genetic testing of a migrant juvenile in Cape May and was thought to indicate a northward expansion of Cooper's range into historic goshawk range.Haughey, C. L., Nelson, A., Napier, P., Rosenfield, R. N., Sonsthagen, S. A., & Talbot, S. L. (2019). Genetic confirmation of a natural hybrid between a Northern Goshawk (Accipiter gentilis) and a Cooper's Hawk (A. cooperii). The Wilson Journal of Ornithology.
No subspecies of Cooper's hawk is recognized. A previously described subspecies, A. c. mexicanus, was discounted due to being weakly differentiated.Hellmayr, C. E., & Conover, B. (1949). Catalogue of birds of the Americas and the adjacent islands. Vol. 13, Part I, No. 4: Cathartidae-Acciptridae-Pandionidae-Falconidae. Chicago: Zool. Series, Field Mus. Nat. Hist.) Genetic markers indicate that westerly birds such those in British Columbia are genetically different from those in the Upper Midwest, indicating that Cooper's hawks were restricted to at least two Pleistocene glacial refugia, with the Rocky Mountains acting as a natural barrier to gene flow between hawks on either side.Sonsthagen, S. A., Rosenfield, R. N., Bielefeldt, J., Murphy, R. K., Stewart, A. C., Stout, W. E., & Talbot, S. L. (2012). Genetic and morphological divergence among Cooper's Hawk (Accipiter cooperii) populations breeding in north-central and western North America. The Auk, 129(3), 427–437.
Several of the other similar, largish Astur species in the Americas appear to be closely related, possibly within a species complex, to Cooper's hawk, namely the bicolored hawk (A. bicolor), widely distributed from southern Mexico to Central and northern South America, and the Chilean hawk (A. chilensis).Lerner, H. R., & Mindell, D. P. (2005). Phylogeny of eagles, Old World vultures, and other Accipitridae based on nuclear and mitochondrial DNA. Molecular phylogenetics and evolution, 37(2), 327–346.Breman, F. C., Jordaens, K., Sonet, G., Nagy, Z. T., Van Houdt, J., & Louette, M. (2013). DNA barcoding and evolutionary relationships in Accipiter Brisson, 1760 (Aves, Falconiformes: Accipitridae) with a focus on African and Eurasian representatives. Journal of Ornithology, 154(1), 265–287.Stresemann, E., & Amadon, D. (1979). Order Falconiformes. In Check-list of the Birds of the World (E. Mayr and G. W. Cottrell, Editors. Museum of Comparative Zoology, Cambridge, MA, USA. pp. 271–425. While some degree of obvious difference from these species is seen in appearance, distribution, and behavior, Cooper's hawk is now often considered sister to Gundlach's hawk (A. gundlachi endemic to Cuba), and together these two are sister to the bicolored hawk.
In general, the relationship between Cooper's and Gundlach's hawks is muddled and genetic testing indicated that Gundlach's possibly may be insufficiently distinct to separate the species.Rodríguez-Santana, F. (2010). Reports of Cooper's Hawks (Accipiter cooperii), Swainson's Hawks (Buteo swainsoni), and Short-tailed Hawks (Buteo brachyurus) in Cuba. Journal of Raptor Research, 44(2), 146–150.Reynard, G. B., Short, L. L., Garrido, O. H., & Alayón, G. G. (1987). Nesting, Voice, Status, and Relationships of the Endemic Cuban Gundlach's Hawk (Accipiter gundlachi). The Wilson Bulletin, 73–77. Almost certainly, Cooper's hawk would at least qualify as the paraspecies for Gundlach's hawk, and datum have indicated fairly recent colonization and hybridization between the two.
Description
Cooper's hawk is a medium-sized hawk, but roughly average to small-sized for an Astur species. Compared to related species, it tends to have moderate-length wings, a long, often graduated or even wedge-shaped tail, and long though moderately thick legs and toes. Its eyes tend to be set well forward in the sides of the relatively large and squarish-looking head (though the head can look somewhat rounded if the feathers on the nape are held flush) and a relatively short but robust bill. It has a hooked bill well-adapted for tearing the flesh of prey, as is typical of raptors.Dewey, T. and V. Perepelyuk. (2000). Accipiter cooperii, Animal Diversity Web. Accessed April 22, 2010.
Generally, Cooper's hawks can be considered secretive, often perching within the canopy, but uses more open perches, especially in the western part of the range or in winter, when they may use leafless or isolated trees, utility poles, or exposed stumps. On perched hawks, the wing tips tend to appear to cover less than one-third of the tail, sometimes seeming to barely cover the covert feathers.
As adults, they may be a solid blue-gray or brown-gray color above. Adults usually have a well-defined crown of blackish-brown feathers above a paler nape and hind neck offset against their streaked, rufous cheeks. Their tails are blue-gray on top and pale underneath, barred with three black bands in a rather even pattern and ending in a rather conspicuous white tip. The adult's underside shows a whitish base color overlaid heavily with coarse, irregular rufous to cinnamon bands, though these narrow into marginal shaft streaks around the throat. Against the rich color on the rest of the underside, the pure white on adults is conspicuous. Adult females typically are slightly more brownish or grayish above, while some adult males can range rarely into almost a powder blue color.
Although little regional variation is seen in the plumage, adult coloring in the Pacific Northwest typically is slightly darker overall. Aberrant pale plumage was recorded in at least four birds, all of which were almost completely white and lacked any underside streaking. These birds had faded back color and lacked strong barring on the tail. An aberrant dark female was also recorded. As a juvenile, she had a blackish-brown (rather than mid-brown) back and dark, inky feathers below with grayish ground color barely showing. Later, she produced an aberrant male with similar characteristics that successfully fledged. The latter two were possible cases of melanism; such dark variations are virtually unprecedented in any Astur or Accipiter species.Morrow, J., & Morrow, L. (2015). Aberrant plumages in Cooper's Hawks. Journal of Raptor Research, 49(4), 501–505.
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. Juveniles tend to have streaking or washing of tawny on the cheeks, ending in a light nuchal strip, giving them a hooded appearance unlike the capped appearance of adults (some juveniles, unlike adults, also may manifest a slim supercilium). The crown is brown on juveniles rather than blackish as in adults. The tail is similar to that of the adult but more brownish and sometimes shows an additional fourth band. The juvenile has more pale white to cream base color showing than older birds, with variable dusky throat striping and mid-brown streaks, which appear as sharply defined from about the lower throat to the lower breast. The juvenile may have brown to black spots or bars on the thighs with thin black streaks mostly ending at the belly and conspicuous white crissum and undertail coverts. Juveniles may tend to appear more "disheveled" and less compact than adults in feather composition.Brown, Leslie and Amadon, Dean (1986) Eagles, Hawks and Falcons of the World. The Wellfleet Press. .