Fall is just around the corner and hawks will be migrating south soon...and I can't wait! One of the tips for identifying Cooper’s Hawk from Sharp-shinned Hawk is that Sharp-shinned Hawk may cock its tails up in certain conditions, whereas Cooper’s are not supposed to exhibit this behavior. Yes, it is true that most accipiters you see with its tail in this posture will be Sharp-shined Hawks, but I have mentioned several times in the past “no field mark or behavior is 100% reliable”, and “a combination of traits makes an I.D.” Note in the photo above, both the juvenile Sharp-shinned Hawk (left) and juvenile Cooper’s Hawk (right) have their tails cocked upward. This is uncommon on Cooper’s, but it does happen.
There are several other traits normally associated with telling Cooper’s from Sharp-shinned that are not even close to 100% reliable. Some are not worth mentioning since they are often difficult or impossible to see in the field. However, the extent of the streaking on underbody, and the shape of the tail tip are worth mentioning. It is often said that the streaking to the underbody of juvenile Sharp-shinned is more prominent than that of Cooper’s, but this is not always true. There are many Cooper’s Hawks that are more heavily marked below than typical Sharp-shinneds. Also, the tail tip on Cooper’s is usually rounded compared to the square-tipped tail on Sharp-shinned. But, many Sharp-shinned Hawks (especially juvenile females) show rounded tail tips, and Cooper's Hawks can show squarish tails due to molt, wear or just anomally. These features are shown in 'Hawks From Every Angle' and 'Hawks at a Distance' so I won’t clog this post with multiple photos. Anyway, beware of using a cocked tail alone to ID an accipiter...and if you were wondering, I have yet to see a Goshawk do this but wouldn't be surprised if they do knowing how long their tails are.