Cooper's hawk numbers are bouncing back: despite historic declines due to anthropogenic causes, the bird's population is increasing as of 2024. 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. 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.
Female Cooper's hawks dwarf their mates: she may be about 20% larger linearly and around 40% (though can be up to 125% ) heavier. Total length of full-grown birds can vary from 35 to 46 cm (14 to 18 in) in males and 42 to 50 cm (17 to 20 in) in females, while wingspan may range from 62 to 99 cm (24 to 39 in). Among standard measurements, the wing chord may vary from 214 to 252 mm (8.4 to 9.9 in) in males and from 247 to 278 mm (9.7 to 10.9 in) in females, a gap that never overlaps within a region and underpins the pair's complementary hunting roles.
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. Males two or older typically have either orange (40.4%) or dark orange (32.3%) eyes, while females' eyes at this stage were light orange or lighter. Three-year or older males were found to have predominantly dark orange (37.3% vs 21.6% of similar-aged females), red (34.6% vs 3.3%) or mid-orange (26.6% vs 55%), showing how eye hue intensifies with maturity and may aid nestling feeding.
Cooper's hawks boast a vocal arsenal rivaling any raptor: during breeding, Cooper's hawks may utter well over 40 claimed call variations, which would rank them as having among the most varied collection of such for any raptor, but probably quite subtle (marginal differences in harshness, clarity, tempo and volume). The typical call is a harsh, cackling yelp, keh-keh-keh, with males tending to have a higher-pitched, less-raspy, faster-paced voice than females. Generally, Cooper's hawks are silent outside the breeding season.
Cooper's hawk is a deep-time pioneer: 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 with the goshawk came second. 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. 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.
Sources
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Through the forest canopy, the Cooper's Hawk slices with deadly precision, its slate-grey wings beating in a swift, staccato rhythm as it pursues its quarry with relentless intent. With eyes that burn like dark, polished onyx, this agile predator navigates the dense underbrush with ease, its long, rounded tail feathers expertly steering it through the tangled vegetation. As it bursts into a sun-dappled clearing, the Cooper's Hawk's wings flash with a fleeting glimpse of warm, chestnut-brown color, a fleeting hint of beauty in a creature honed for speed and stealth.
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