When building a case for a successful ID of a juvenile Accipiter (Sharp-shinned or Cooper’s in particular), another feature to look for is the presence/absence of a tawny, streaky head, nape and mantle. Though not a primary indicator of species, juvenile Cooper’s Hawks (top) show this quite consistently and Sharp-shinned Hawks (bottom) generally show a reduction (or absence) of this particular feature. I adjusted the size of the Sharp-shinned Hawks below to limit the discrepancy in size between the two species.

Photo: Study skins from the Canadian Museum of Nature collections in Gatineau, Quebec.