Telling the difference between these hawks can be challenging

A group of birders along Four-Mile Creek Greenway were recently treated to leisurely looks at both Copper’s and sharp-shinned hawks.

If you feed birds regularly you are probably familiar with one or both of these species. They are the hawks that will zip in to a feeding area with hopes of procuring an easy meal at the expense of an unwary patron.

Both species are closely related and very similar in plumages; both the adults and immatures. Identifying them as to species offers some challenges and often even expert birders have to let them go as “unidentified.”

It is fairly unusual to get extended looks at both species on the same short outing. They are nervous, high-strung hawks and when hunting don’t sit still very long. So how can casual birders identify these two species?

First, size can matter. But not always. Sharp-shinned hawks are smaller than Cooper’s. Females of both species can be 30 percent larger than males. So, the largest size difference is between male sharp-shins, which can appear tiny; and female Cooper’s which can be quite large. Female sharp-shins and male Cooper’s are the ones that present challenges.

As we walked along the greenway I noticed a swift hawk sailing through the trees and we all watched as it flew over our heads and landed prominently on a limb. It was one of those intermediate individuals. It was also an immature bird.

I suspected a male Cooper’s but wasn’t sure yet. But the bird was unusually cooperative and here is what we saw: A tail tip that was somewhat rounded, not square cut; areas of pale feathering on the back; thin streaking on the upper breast that stopped about half way down the underparts.

All of those characters indicate Cooper’s, and I am confident that is what it was. Sharpies generally have a more square-cut tail, the backs of immatures are more uniform in color, and the breast streaking is heavier and extends down onto the lower belly. These are general identifying features and there can be much variation among individuals however.

Later, one of our group pointed a hawk soaring just above the trees and gaining altitude. We all got extended looks at a tiny hawk with an obvious square-cut tail. This was clearly a sharp-shinned hawk, likely a male.

This story was originally published November 23, 2016 at 5:03 PM with the headline "Telling the difference between these hawks can be challenging."