Cooper's Hawk

Accipiter species in North America are arguably the most vexing raptor to identify in the continent.[63][64][65] 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.[5] The Cooper's and sharp-shinned hawk are very similar (sometimes considered almost identical) in plumage characteristics at all stages of development.[2][64] Most Cooper's hawks are considerably larger than most sharp-shinned hawks.[5] Generally, the Cooper's species is crow-sized, with the males about the size of a small crow and the females the size of a large crow, while most sharp-shinned hawks are about the size of a large jay.[33] 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).[40][41] 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 birdwatchers may not always be able to certainly distinguish the two species, especially female sharp-shins against the nearly similarly sized male Cooper's.[63][66] 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 difference 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.