Editing Cooper's hawk (section)

== Description ==
[[File:Accipiter-cooperii-01.jpg|thumb|upright=0.75|Adults may be either brown-grey or blue-grey above, with a distinctive, sizable head]]

Cooper's hawk is a medium-sized hawk and relatively large for an ''Astur''. Compared to related species, they tend to have moderate-length wings, a long, often graduated or even wedge-shaped tail and long though moderately thick legs and toes.<ref name= Ferguson-Lees/> Their 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.<ref name= Ferguson-Lees/> They have hooked [[beak|bills]] that are well-adapted for tearing the flesh of prey, as is typical of raptorial birds.<ref name="umich2000"/> 

Generally, Cooper's hawks can be considered secretive, often perching within the [[Canopy (biology)|canopy]], but can use more open perches, especially in the western part of the range or in winter when they may use leafless or isolated trees, [[utility pole]]s or [[Tree stump|exposed stumps]].<ref name="Ferguson-Lees" /> 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.<ref name="Ferguson-Lees" />

As adults, they may be a solid [[blue-gray]] or brown-gray color above.<ref name="Palmer" /> Adults usually have a well-defined crown of blackish-brown feathers above a paler nape and hindneck offset against their streaked rufous cheeks.<ref name="Ferguson-Lees" /> Their tail is 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.<ref name="Ferguson-Lees" /><ref name="allaboutbirds1">{{cite web| url= http://www.allaboutbirds.org/guide/Coopers_Hawk/lifehistory |title= ''Cooper's Hawk''| publisher= Lab. of Ornithology, [[Cornell University]]| website= allaboutbirds.org}}</ref> 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. Against the rich color on the rest of the underside, the pure white {{birdgloss|crissum}} on adults is conspicuous.<ref name="Ferguson-Lees" /> Adult females may average slightly more brownish or grayish above, while some adult males can range rarely into almost a powder blue color.<ref name="Palmer" /> 

Although little regional variation is known in the plumage, adult coloring in the [[Pacific Northwest]] averages slightly darker overall.<ref name=BOW /> Aberrant pale plumage was recorded in at least four total birds of both sexes, all of which were almost completely white and lacked any underside streaking. These birds had faded back color and lacking 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]] and such dark variations are virtually unprecedented in any ''Accipiter'' species.<ref name="Morrow">Morrow, J., & Morrow, L. (2015). ''Aberrant plumages in Cooper's Hawks''. Journal of Raptor Research, 49(4), 501–505.</ref>

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. Juvenile Cooper's 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, may manifest a slim [[supercilium]] as well). 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.<ref name="Ferguson-Lees" /> Juveniles can tend to appear more "disheveled" and less compact than adults in feather composition.<ref name="Brown">Brown, Leslie and Amadon, Dean (1986) ''Eagles, Hawks and Falcons of the World''. The Wellfleet Press. {{ISBN|978-1555214722}}.</ref> 

In flight, though usually considered medium-sized, Cooper's hawks can appear fairly small.<ref name="Palmer" /> This effect is emphasized by the short wings relative to the elongated tail (unlike unrelated hawks, the wingspan is usually less than twice as broad as the total length).<ref name="Ferguson-Lees" /> The species tends to have rounded wings, a long rounded tail and long legs, much like other ''Accipiters''.<ref name="Palmer" /> 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.<ref name="Ferguson-Lees" /> The 5 outer functional primaries are notched on their inner webs, the outermost is the longest, the next outermost nearly as long.<ref name="Palmer" /> When soaring, these hawks do so on flattish or, more commonly, slightly raised wings, with fairly straight leading edges. Against the barred underbody on adults, the wings are more or less flecked in similar color, with pale greyish flight feathers and a broadly white-tipped tail correspondingly barred with dark gray. Meanwhile, the upperside of adults is essentially all blue-grey. Juvenile are mostly dark above though manifest a hooded effect on the head and a rufous-buff edges and especially whitish mottling, the latter can be fairly apparent. Juveniles are mainly whitish below with neatly dark streaks about the wing linings, breast, flanks and thighs, with bars on the axillaries and flight feathers. The tail of the juvenile has a broadly white tip and bars like adults but the ground color is a paler shade of gray.<ref name="Ferguson-Lees" /><ref name="Palmer" />
[[File:Cooper's hawk in Prospect Park (22513).jpg|thumb|left|A juvenile Cooper's hawk in Brooklyn, New York]]
Adults have eyes ranging from light orange to red, with males averaging darker in eye color, while those of juveniles are yellow.<ref name= Ferguson-Lees/> Among 370 breeding hawks from different parts of the range, 1-year-old males usually had light orange eyes and 1-year-old females usually yellow eyes. Meanwhile, males of 2 or more years old always had consistently darker eyes than the eyes of females of the same relative age, with most males of the age having largely either orange (40.4%) or dark orange (32.3%) eyes, while female eyes at this stage were light orange or lighter. From the second year, the eyes of Cooper's hawks may grow darker still but stop darkening shortly thereafter. 3-year or older males were found to have predominantly dark orange (37.3% vs 21.6% of similar age females), red (34.6% vs 3.3% of similar age females) or mid-orange (26.6% vs 55% of similar age females).<ref name= Rosenfield>Rosenfield R. N. & Bielefeldt, S. A. (1992). ''Reanalysis of Relationships among Eye Color, Age and Sex in the Cooper's hawk''. J. Raptor Res, 31(4), 313–316.</ref> For unclear reasons, far more adults in [[British Columbia]] and [[North Dakota]] (83% of males, 63% of females) had dark orange or red eyes (which also manifested at an earlier age in British Columbia) than mature hawks in [[Wisconsin]] (49% of males, 14% of females). Most females over 2 years old in Wisconsin were found to have light orange eyes.<ref name= Rosenfield2>Rosenfield, R. N., Bielefeldt, J., Rosenfield, L. J., Stewart, A. C., Murphy, R. K., Grosshuesch, D. A., & Bozek, M. A. (2003). ''Comparative relationships among eye color, age, and sex in three North American populations of Cooper's Hawks''. The Wilson Journal of Ornithology, 115(3), 225–230.</ref> The purpose of bright eye color in the hawks may be correlated to feeding stimulation of nestling hawks (i.e. darker orange or red objects may be more perceptible and tend to be pecked at more so than duller colors).<ref>Snyder, N. F., & Snyder, H. A. (1974). ''Function of eye coloration in North American accipiters''. Condor, 219–222.</ref> 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. Adults have greenish yellow ceres and have legs of orangish to yellow while these parts on juveniles are a paler hue, yellow-green to yellow.<ref name= Ferguson-Lees/><ref name= Brown/> 

The prebasic [[Molting|molt]] begins in late April–May and takes about 4 months. The female usually begins to molt about 7–10 days sooner than the male. Molts occur inward towards the body on the wing feathers. Tail molt may generally start with the middle tail feathers, proceeding posteriorly to the upper tail coverts, also starting with the median feathers on the scapulars.<ref name="Palmer" /><ref name="Henny">Henny, C. J., Olson, R. A., & Fleming, T. L. (1985). ''Breeding chronology, molt, and measurements of Accipiter hawks in northeastern Oregon''. Journal of Field Ornithology, 97–112.</ref> Up to 36% of juvenile feathers may be retained in the second pre-basic molt.<ref name="Pyle">Pyle, P. (2005). ''First-cycle molts in North American Falconiformes''. Journal of Raptor Research, 39:378–385.</ref> Arrested molt has been recorded in the late nesting period, often pausing after the third primary is molted. Molts tend to be halted especially when food supplies are down during the brooding stage, and may be resumed after the stress of feeding the brooding diminishes.<ref name="Palmer" /><ref name="Henny" /><ref name="Howell">Howell, S. N. G. (2010). ''Peterson Reference Guide to Molt in North American Birds''. Houghton Mifflin Harcourt Company, Boston, MA, USA.</ref>

===Size===
Cooper's hawks are fairly variable in size. There is usually minimal to no overlap in dimensions between the sexes, with females being considerably larger than males.<ref name= Palmer/> On average, she may be about 20% larger linearly and around 40% heavier (though can be up to 125% more massive).<ref name= Ferguson-Lees/> More westerly Cooper's hawks (roughly west of the [[Rocky mountains]]) show slightly less pronounced [[sexual dimorphism]] than hawks of the species elsewhere.<ref name= Smith>Smith, J. P., Hoffman, S. W., & Gessaman, J. A. (1990). ''Regional Size Differences among Fall-Migrant Accipiters in North America''. Journal of Field Ornithology, 192–200.</ref> 

Sexual dimorphism in Cooper's hawks is most reliably measured by wing size, talon size, then body mass. Although there is some margin of error, within a given region dimensions of the two sexes never overlap in these regards (but may overlap marginally in tarsal and tail lengths).<ref name="Hoffman" /> In general terms, ''Accipiter'' species are among the most sexually dimorphic in size of all raptorial birds.<ref name="Reynolds">{{Cite journal | last=Reynolds | first=Richard T. | date=1972 | title=Sexual dimorphism in ''Accipiter'' hawks: A new hypothesis | journal=The Condor | volume=74 | issue=2 | pages=191-197 | doi=10.2307/1366283 | url=https://sora.unm.edu/node/102162 }}</ref> Sexual dimorphism in ''Accipiters'' may be due to greater male efficiency through smaller size and resulting agility in food gathering for the family group. Meanwhile, the female may be better suited to the rigors of brooding (including perhaps most nest defense) due to her larger size, also allowing the sexes to compete less on the same food sources.<ref name="Snyder" /><ref name="Reynolds" /> 

Geographic variation in body size has also been found, with more easterly hawks tending to be rather larger on average than those found in western North America.<ref name="umich2000">Dewey, T. and V. Perepelyuk. (2000). [http://animaldiversity.ummz.umich.edu/site/accounts/information/Accipiter_cooperii.html ''Accipiter cooperii''], Animal Diversity Web. Accessed April 22, 2010.</ref><ref name="Mueller">Mueller, H. C., & Berger, D. D. (1981). ''Age, sex, and seasonal differences in size of Cooper's Hawks''. Journal of Field Ornithology, 52(2), 112–126.</ref> On the contrary, in the [[Southwestern United States|American southwest]], the species may reportedly reach its largest sizes but there is little evidence that these birds average distinctly larger than the large bodied individuals measured in the more northeasterly parts of the species' range in North America, from eastern [[North Dakota]] to [[New Jersey]].<ref name=BOW /><ref name="Whaley">Whaley, W. H., & White, C. M. (1994). ''Trends in geographic variation of Cooper's hawk and northern goshawk in North America: a multivariate analysis''. Western Foundation of Vertebrate Zoology.</ref> The size variation evidenced in Cooper's hawks is apparently the most pronounced of any of the three North American species of ''Accipiter''.<ref name="Smith" /> 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]].<ref>Meiri, S., & Dayan, T. (2003). ''On the validity of Bergmann's rule''. Journal of biogeography, 30(3), 331–351.</ref> Furthermore, juveniles can differ somewhat in size, tending to be slightly lighter and smaller than older birds, but not infrequently averaging longer in tail and especially wing length.<ref name="Mueller" /><ref name="Rosenfield3">Rosenfield, R. N., Rosenfield, L. J., Bielefeldt, J., Murphy, R. K., Stewart, A. C., Stout, W. E., Driscoll, T.G. & Bozek, M. A. (2010). ''Comparative morphology of northern populations of breeding Cooper's Hawks''. The Condor, 112(2), 347–355.</ref> Total length of full-grown birds can vary from {{convert|35|to|46|cm|in|abbr=on}} in males and {{convert|42|to|50|cm|in|abbr=on}} in females.<ref name="Palmer" /><ref name="umich2000" /><ref name="allaboutbirds1" /> Wingspan may range from {{convert|62|to|99|cm|in|abbr=on}}, with an average of around {{convert|84|cm|in|abbr=on}}.<ref name="Palmer" /><ref name="HBW">White, C.M., Boesman, P. & Marks, J.S. (2020). ''Cooper's Hawk (Accipiter cooperii)''. In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona.</ref><ref name="Cartron">Cartron, J. L. E. (Ed.). (2010). ''Raptors of New Mexico''. UNM Press.</ref>
 
[[File:Hawk (28346062734).jpg|thumb|An adult Cooper's hawk illustrates its mid-sized frame and very long tail]]
Body mass, along with standard measurements, is much more frequently measured than total length or wingspan in different populations.<ref name= Palmer/> Museum specimens from the western United States averaged {{convert|280|g|oz|abbr=on}} in 48 males and {{convert|473|g|lb|abbr=on}} in 20 females, while those sourced from the eastern United States averaged {{convert|338|g|oz|abbr=on}} in 16 males and {{convert|566|g|lb|abbr=on}} in 31 females.<ref name= Friedmann>Friedmann, H. (1950). ''Birds of North and Middle America, Part 2''. U.S. National Museum Bulletin no. 50.</ref> Average weight of 104 male migrating hawks in [[Cedar Grove, Wisconsin]] was {{convert|342|g|oz|abbr=on}} (with adults averaging 4% heavier than juveniles), whilst the average of 115 females migrants was {{convert|518|g|lb|abbr=on}} (with adult averaging about 5.5% heavier than juveniles).<ref name= Mueller/> A different sample of Wisconsin Cooper's hawks reportedly averaged {{convert|327|g|oz|abbr=on}} in males (sample size 60) and {{convert|580.3|g|lb|abbr=on}} in females (sample size 57).<ref name= Rosenfield3/> At [[Cape May Point]], [[New Jersey]], weights were similar as in Wisconsin (although only hatching-year juveniles were apparently weighed), with averages of {{convert|339.2|and|347|g|oz|abbr=on}} in two samples of males and {{convert|518|and|530.3|g|lb|abbr=on}} in the two samples for females.<ref name= Pearlstine/><ref name= Smith/> Migrant hawks in the [[Goshute Mountains]] of [[Nevada]] were significantly lighter than the eastern ones at {{convert|269|g|oz|abbr=on}} in 183 first year males and {{convert|281|g|oz|abbr=on}} in 177 older males and {{convert|399|g|oz|abbr=on}} in 310 first year females and {{convert|439|g|oz|abbr=on}} in 416 older females.<ref name= Smith/> Weights were similar to the Goshutes in the [[Marin Headlands]], California where 50 males (all first-years) averaged {{convert|288|g|oz|abbr=on}} and 117 first-year females averaged {{convert|417|g|oz|abbr=on}}.<ref name= Smith/><ref name= Pitzer>Pitzer, S., Hull, J., Ernest, H. B., & Hull, A. C. (2008). ''Sex determination of three raptor species using morphology and molecular techniques''. Journal of Field Ornithology, 79(1), 71–79.</ref> Averaged between early and late summer, the average mass of males in [[Oregon]] was {{convert|280.7|g|oz|abbr=on}} and that of females was reported at {{convert|488.4|g|lb|abbr=on}}.<ref name= Henny/> The average weights of Cooper's hawks from Oregon was about 19.4% lower in males and 14.5% lower in females than those from Wisconsin but the Oregon hawks evidenced less seasonal variation in weight.<ref name= Henny/> In [[British Columbia]], males averaged {{convert|295.8|g|oz|abbr=on}} and females averaged {{convert|525.5|g|lb|abbr=on}} while in western and eastern North Dakota, males averaged {{convert|301.5|and|318.7|g|oz|abbr=on}} and females averaged {{convert|514.3|and|563.3|g|lb|abbr=on}}.<ref name= BOW/><ref name= Rosenfield3/> In northern Florida, males averaged {{convert|288|g|oz|abbr=on}} and females averaged {{convert|523|g|lb|abbr=on}}.<ref name= Millsap>Millsap, B. A., Breen, T. F., & Phillips, L. M. (2013). ''Ecology of the Cooper's Hawk in north Florida''. North American Fauna, 78(00), 1–58.</ref> In general, males may weigh anywhere from {{convert|215|to|390|g|oz|abbr=on}} and females anywhere from {{convert|305.8|to|701|g|lb|abbr=on}}, the lightest hawks generally being juveniles recorded from the Goshutes of Nevada, the heaviest known being adults from Wisconsin.<ref name= Hoffman>Hoffman, S. W., Smith, J. P., & Gessaman, J. A. (1990). ''Size of Fall-Migrant Accipiters from the Goshute Mountains of Nevada (Tamaño de migrantes otoñales (Accipitrinae) de las Montañas Goshute, Nevada)''. Journal of Field Ornithology, 201–211.</ref><ref name= Rosenfield4>Rosenfield, R. N., Bielefeldt, J., Haynes, T. G., Hardin, M. G., Glassen, F. J., & Booms, T. L. (2016). ''Body mass of female Cooper's Hawks is unrelated to longevity and breeding dispersal: Implications for the study of breeding dispersal''. Journal of Raptor Research, 50(3), 305–312.</ref>

Among standard measurements, the [[Wing chord (biology)|wing chord]] may vary from {{convert|214|to|252|mm|in|abbr=on}} in males and from {{convert|247|to|278|mm|in|abbr=on}} in females.<ref name= Ferguson-Lees/><ref name= Rosenfield5>Rosenfield, L. J. (2006). ''Comparative morphology among three northern populations of breeding Cooper's Hawks'' (Doctoral dissertation, University of Wisconsin—Stevens Point).</ref> Wing chord is generally commensurate with body mass, averaging largest in the heavier hawks of eastern North Dakota, where males averaged {{convert|232.6|mm|in|abbr=on}} and females {{convert|264.3|mm|in|abbr=on}}, and in Wisconsin, where males averaged {{convert|236.9|mm|in|abbr=on}} and females {{convert|267.1|mm|in|abbr=on}} (those from Cape May also being similar to those two samples). However, smaller, more westerly hawks such as those in the Goshute mountains, where males measured at a mean of {{convert|224.1|mm|in|abbr=on}} and females at a mean of {{convert|254.8|mm|in|abbr=on}}, and in British Columbia, with a male mean of {{convert|227|mm|in|abbr=on}} and female mean of {{convert|256.8|mm|in|abbr=on}}, were proportionately longer winged relative to their other body proportions.<ref name= BOW/><ref name= Rosenfield3/><ref name= Hoffman/> The tail of males may vary from {{convert|166|to|211|mm|in|abbr=on}} and that of females at {{convert|203|to|242|mm|in|abbr=on}}, consistently over {{convert|200|mm|in|abbr=on}} in females and averaging under {{convert|190|mm|in|abbr=on}} in males.<ref name= Ferguson-Lees/><ref name= Brown/><ref name= Hoffman/><ref name= Rosenfield5/> In [[Tibiotarsus|tarsus]] length, males may vary from {{convert|55.2|to|73|mm|in|abbr=on}}, with an average of {{convert|64.1|mm|in|abbr=on}} in museum specimens, and females from {{convert|62|to|76|mm|in|abbr=on}}, with an average of {{convert|71.1|mm|in|abbr=on}} in museum specimens.<ref name= Ferguson-Lees/><ref name= Friedmann/><ref name= Hoffman/><ref>{{cite web| url= http://www.royalbcmuseum.bc.ca/Natural_History/Bones/Tarsus/tarsus57.htm |title= ''Avian Osteology: Tarsometatarsus'' |website= RoyalBCMuseum.bc.ca| publisher= Royal British Columbia Museum Corporation | access-date= August 21, 2012}}</ref> The [[Beak|culmen]] may measure from {{convert|11.7|to|17.5|mm|in|abbr=on}} in males, averaging about {{convert|16|mm|in|abbr=on}}, and from {{convert|17.5|to|23|mm|in|abbr=on}} in females, averaging about {{convert|19|mm|in|abbr=on}}.<ref name= Friedmann/><ref name= Hoffman/><ref name= Rosenfield5/><ref>{{cite book| first1= Emmet Reid| last1= Blake |title=''Manual of Neotropical Birds'' |url=https://books.google.com/books?id=YP0AX3LW8jYC&pg=PA301 |access-date=August 21, 2012 |date=July 1, 1977 |publisher= University of Chicago Press |isbn=978-0-226-05641-8 |pages=301–}}</ref> The [[Claw|hallux claw]], the enlarged rear talon featured on nearly all accipitrids, may measure from {{convert|17|to|21.7|mm|in|abbr=on}} in males, averaging about {{convert|19.2|mm|in|abbr=on}}, and from {{convert|19.8|to|26.7|mm|in|abbr=on}} in females, averaging about {{convert|23.3|mm|in|abbr=on}}.<ref name= Hoffman/><ref name= Rosenfield5/> The footpad of Cooper's hawks may measure in males {{convert|61|to|70.2|mm|in|abbr=on}}, averaging {{convert|66|mm|in|abbr=on}} in 42, and in females {{convert|74.1|to|83.5|mm|in|abbr=on}}, averaging {{convert|76.8|mm|in|abbr=on}} in 23.<ref name= Whaley/> For unclear reasons, the smaller-bodied hawks found in British Columbia were found to be proportionately larger footed, median toe length between sexes of {{convert|37.3|mm|in|abbr=on}}, than the larger bodied ones in Wisconsin.<ref name= Feet>Rosenfield, R. N., Stewart, A. C., Stout, W. E., Sonsthagen, S. A., & Frater, P. N. (2020). ''Do British Columbia Cooper's Hawks Have Big Feet?'' British Columbia Birds, 30.</ref>

===Voice===
{{ Listen
| filename = Accipiter cooperii - Cooper's Hawk - XC74741.ogg
| title = Cooper's hawk vocalization
| description = A Cooper's hawk calling from an urban park in Minnesota
}}
Some authors have claimed that during breeding Cooper's hawks may utter well over 40 call variations, which would rank them as having among the most varied collection of calls recorded for any raptor. However, many such variations are probably quite subtle (marginal differences in harshness, clarity, tempo and volume) and other authors have diagnosed only four overall call types.<ref name= Palmer/><ref name= Meng>Meng, H. K. (1951). ''Cooper's Hawk, Accipiter cooperii''. Unpublished thesis, Cornell Univ., Ithaca, New York.</ref><ref name= Rosenfield6>Rosenfield, R. N., & Bielefeldt, J. (1991). ''Vocalizations of Cooper's Hawks during the pre-incubation stage''. The Condor, 93(3), 659–665.</ref> The typical call of a Cooper's hawk is a harsh, cackling yelp. This call may be translated as ''keh-keh-keh''..., males tending to have a higher pitched, less raspy and faster-paced voice than females.<ref name= Ferguson-Lees/><ref name= Brown/> 

However, some variants uttered by males were deeper than the female's version of said calls.<ref name="Fitch">Fitch, H. S. (1958). ''Home ranges, territories, and seasonal movements of vertebrates of the Natural History Reservation''. University of Kansas Publications Museum of Natural History, 11:63–326.</ref> A still more modulated and raucous version is given during the dawn chorus.<ref name="Brown" /> Some studies have indicated that pairs nesting in more deeply wooded areas may vocalize more frequently due to inferior sight lines.<ref name="Rosenfield6" /> However, hawks nesting in urban areas of [[Arizona]] do not seem to vocalize less than their rural nesting counterparts.<ref name="Estes">Estes, W. A., & Mannan, R. W. (2003). ''Feeding behavior of Cooper's Hawks at urban and rural nests in southeastern Arizona''. The Condor, 105(1), 107–116.</ref> There is perhaps some evidence that individual hawk's voices may become lower pitched with age.<ref name="Brown" /> When coming with food to the nest or while displaying during courtship, the male may let out a [[nighthawk]]-like ''kik'', apparently this call is more prevalent in pairs using thicker woods.<ref name=BOW /><ref name="Brown" /><ref name="Rosenfield6" /> Infrequently, females may utter the ''kik'' call as well, apparently when looking for her mate or gathering nesting materials.<ref name="Rosenfield6" /> Many soft calls have been recorded in intimate or "conversational" interactions, exclusively between breeding pairs and between mothers and their broods.<ref name="Ferguson-Lees" /><ref name="Palmer" /> 

The initial call of the young is a ''cheep'' or ''chirrp'', which by the time they are fledgling young alters to a penetrating hunger call, ''eeeeeeee-oo'' or ''tseeeee-ar'' (among different transliterations).<ref name="Ferguson-Lees" /><ref name=BOW /><ref name="Layne">Layne, J. N. (1986). ''Observations on Cooper's Hawk nesting in south central Florida''. Florida Field Naturalist, 14:85–112.</ref> The higher pitched calls of the young may even extend to females nesting within their first year while still in immature plumage.<ref name="Brown" /> Females have what is often thought of as their own hunger cry, ''whaaaa'', heard especially in poorer food areas, when the male appears.<ref name=BOW /><ref name="Estes" /> Nonetheless, the females ''whaaaa'' call has also been uttered in different contexts, such as during nest building and during a "postural bowing" display, and some authors inferred that it may be a means of communicating to the male that it is not dangerous for him to approach her (as female ''Accipiters'' can be dangerous to the much smaller males).<ref name="Meng" /><ref name="Rosenfield6" /><ref name="Rosenfield7">Rosenfield, R. N., & Bielefeldt, J. (1991). ''Undescribed bowing display in the Cooper's Hawk''. The Condor, 93(1), 191–193.</ref> Generally, Cooper's hawks are silent outside the breeding season.<ref name="Ferguson-Lees" /> Rarely, though, some males that appear to be isolated from any other hawks of their species have been known to call during winter.<ref name="Rosenfield8">Rosenfield, R. N. (2018). ''The Cooper's Hawk: Breeding Ecology & Natural History of a Winged Huntsman''. Hancock House Publishers.</ref>

===Confusion species===
[[File:Coopers Hawk From The Crossley ID Guide Eastern Birds.jpg|thumb|left|Composite image of Cooper's hawks for identification]]

''Accipiter'' species in North America are arguably the most vexing raptor to identify in the continent.<ref name= Crossley>Crossley, R., Liguori, J., & Sullivan, B. L. (2013). ''The Crossley ID Guide: Raptors''. Princeton University Press.</ref><ref name= Liguori>Liguori, J. (2005). ''Hawks from every angle: how to identify raptors in flight''. Princeton University Press.</ref><ref name= Clark>Clark. W.S. (1984). ''Field identification of Accipiters in North America''. Birding, 16: 251–263.</ref> The other two species in North America are the smaller [[sharp-shinned hawk]] (''Accipiter striatus'') and the larger [[northern goshawk]] (''Accipiter gentilis''). Compared to the other two ''Accipiters'', Cooper's have an intermediate amount of feathering at top of the tarsus, as well as intermediate relative middle toe length and eye proportions, but have relatively the longest tail and the shortest wings of the three.<ref name= Palmer/> Cooper's and sharp-shinned hawk are very similar (sometimes considered almost identical) in plumage characteristics at all stages of development.<ref name= Ferguson-Lees/><ref name= Liguori/> Most Cooper's hawks are considerably larger than most sharp-shinned hawks.<ref name= Palmer/> Generally, Cooper's species is [[crow]]-sized, with the males about the size of a [[Fish crow|small crow]] and the females the size of a [[American crow|large crow]], while most sharp-shinned hawks are about the size of a large [[Steller's jay|jay]].<ref name= Brown/> Also in the hand, Cooper's hawks and sharp-shinned hawks may be fairly reliably distinguished by their sizes, with the smallest male Cooper's always being heavier and larger clawed than the largest female sharp-shinned hawk (with a 97–98% difference in dimensions of the wing and tail).<ref name= Smith/><ref name= Hoffman/> 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 [[birdwatcher]]s may not always be able to certainly distinguish the two species, especially female sharp-shins against the nearly similarly sized male Cooper's.<ref name= Crossley/><ref>Roberts, T. S. (1932). ''Manual for the identification of the birds of Minnesota and neighboring states''. U of Minnesota Press.</ref> 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. Other slight differences may be noted in plumage via the sharp-shins lacking the capped appearance of adult Cooper's (being more hooded) and being generally slightly darker above. 

Juvenile sharp-shins, upon relatively leisurely study, can be seen to differ from juvenile Cooper's by having clearer supercilia, browner cheeks and less extensive whitish mottling above and also coarser streaking below extending more to belly.<ref name="Ferguson-Lees" /><ref name="Crossley" /> Bare parts, mostly distinguishable as well at close range, differ by the more centered and clearly relatively larger eyes and notably stick-like legs of the sharp-shins.<ref name="Ferguson-Lees" /><ref name="Liguori" /> However, often these features can often be difficult to impossible to discern when the hawks are seen in the wild.<ref name="Ferguson-Lees" /><ref name="Crossley" /><ref>Liguori, J. (2011). ''Hawks at a distance: identification of migrant raptors''. Princeton University Press.</ref> More distinctive in the field is the larger, more protruding head of the flying Cooper's hawks rather than the compact, rounded head of the sharp-shins which barely appear to exceed the leading edge of the wings in flight.<ref name="Crossley" /><ref name="Liguori" /><ref name="Clark" /><ref name="Dunne">Dunne, P., Sibley, D., & Sutton, C. (1988). ''Hawks in flight: the flight identification of North American migrant raptors''. Houghton Mifflin Harcourt (HMH).</ref> Sometimes Cooper's is considered to look like a "flying cross" in comparison to the sharp-shins. ''Accipiter'' hawks of all species are seen mostly flying with quick, consecutive wing beats and a short glide (sometimes abbreviated as "flap-flap-glide"), though the species may also soar as well.<ref>{{cite web |url=http://www.mbr-pwrc.usgs.gov/Infocenter/i3330id.html |title=''Cooper's hawk Accipiter cooperii'' |access-date=November 18, 2008 |author1=Robbins, C.S. |author2=Bruun, B. |author3=Zim, H.S. |date=July 3, 2008 |work=Patuxent Wildlife Research Center |publisher=USGS |archive-date=January 2, 2020 |archive-url=https://web.archive.org/web/20200102124816/https://www.mbr-pwrc.usgs.gov/Infocenter/i3330id.html |url-status=dead }}</ref><ref>{{cite web|title= Cooper's Hawk Identification| publisher= Lab. of Ornithology, Cornell University| url= http://www.allaboutbirds.org/guide/coopers_hawk/id| website= allaboutbirds.org| access-date= August 21, 2012}}</ref> However, the sharp-shinned hawk has a more buoyant flight with faster wing beats than Cooper's and soars with flatter wings (although again variations in the field make these characteristics far from foolproof).<ref name="Crossley" /><ref name="Liguori" /><ref name="Dunne" />

[[File:Accipiter cooperii striatusDO1908P0203A.jpg|right|thumb|Comparison of a male Cooper's hawk (left) with [[Meadowlark|prey]] and a female [[sharp-shinned hawk]] (right) with [[Rose-breasted grosbeak|prey]]. Both prey items are about one third the weight of the respective hawks.]] 
As for the northern goshawk, the smallest male is still usually "clearly" larger than most large female Cooper's hawks.<ref name= Ferguson-Lees/> In the Goshutes mountains, migrant male goshawks overlapped with female Cooper's hawks only in the length of the tail and the tarsus, with the body mass especially being quite distinct.<ref name= Hoffman/> In Oregon, male goshawks averaged no less than 34% more massive than female Cooper's hawks, however the footpad of Cooper's females was almost the same size (7% larger on average in the latter) as the male goshawks (these may be features adapted to procuring birds as prey more so as bird-hunting raptors tend to have more elongated foot morphology).<ref name= Henny/><ref>Fowler, D. W., Freedman, E. A., & Scannella, J. B. (2009). ''Predatory functional morphology in raptors: interdigital variation in talon size is related to prey restraint and immobilisation technique''. PLOS ONE, 4(11).</ref> Proportionately, goshawks have longer, broader wings, shorter tail and a generally more [[Buteo|''Buteo''-like]] form overall.<ref name= Ferguson-Lees/><ref name= Liguori/> Adult goshawks also have broad supercilia, pale gray color on the underside and a much darker [[Slate|coloring]] on the back. Given reasonable views, adult goshawks are very different looking and hard to mistake for any Cooper's hawk.<ref name= Palmer/> 

Meanwhile, the juvenile goshawk is much paler edged above than the smaller Cooper's, including a panel formed along larger wing coverts. Below, juvenile goshawks have heavier streaks of a darker brown color than juvenile Cooper's. Also, the banding on the tail is off-set on goshawks, creating a zigzag effect on the tail, unlike the even barring on the juvenile Cooper's.<ref name="Ferguson-Lees" /><ref name=BOW /> Again, though, female Cooper's and male goshawks can come close to the same size and the not dissimilar juvenile plumage of the two species can lead to regular misidentification, especially to those with less prior experience viewing the more scarce goshawk.<ref name="Crossley" /><ref name="Liguori" /><ref name="Dunne" /> 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.<ref name="Crossley" /><ref name="Clark" /> For Cooper's hawk, there may be a possible and marginal overlap with the [[bicolored hawk]] (''Accipiter bicolor'') in southern Mexico and Central America. The latter species of similar form and size but at all ages is generally unmarked with bars or streaks below, also with a more or less uniform mantle.<ref name="Ferguson-Lees" /><ref name="HBW" /> 

Vagrating migrant Cooper's hawks to [[Cuba]] may very rarely occur alongside another close relative, [[Gundlach's hawk]] (''Accipiter gundlachi''), which is quite similar in most aspects to Cooper's but is slightly larger with a darker hue about the back and the cap, a gray cheek, more dense and rich rufous color on the underside and wing panel in adults and darker and more heavy streaking in juvenile form.<ref name="Ferguson-Lees" /><ref name="HBW" /><ref name="Rodriguez-Santana">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.</ref><ref>Garrido, O. H. (1985). ''Cuban endangered birds''. Ornithological Monographs, 992–999.</ref> 

More unlikely to be mistaken for a Cooper's hawk are some [[Buteoninae|buteonine hawks]] such as [[gray hawk]]s (''Buteo plagiatus''), [[roadside hawk]]s (''Rupornis magnirostris'') (in Mexico and points south) and [[broad-winged hawk]]s (''Buteo platypterus'') which are all similar in size to Cooper's as well as the slightly larger [[red-shouldered hawk]] (''Buteo lineatus''). Even the most similar buteonine hawks have notably different proportions than a Cooper's hawk, possessing relatively much longer wings and a much shorter tail. Given reasonable views, all such species are fairly to extremely different in plumage even in juvenile form.<ref name="Ferguson-Lees" /><ref name="Crossley" />