Good Natured in St. Charles: Twin-like hawks now no longer kissing cousins

I remember exactly where I was when I read the news.

I was sitting in the waiting room at the vet’s office, having just played a game of keep away with my dog Kit. (Keeping her away from the treats in the Science Diet display, that is.) After a vet tech came and got her for her nail trim, I said hi to a couple of other dogs, then pulled out my phone. And that’s when I saw it. A blurb from the Utah-based advocacy group HawkWatch International:

“For those of you not in the know, the Cooper’s Hawk and American Goshawk have left the Accipiter genus and are now Asturs. It turns out the incredibly hard-to-identify Sharp-shinned and Cooper’s Hawk aren’t as closely related as previously thought!”

OK, so maybe this little bulletin is not as earth-shaking as other recent headlines. But to a mediocre birder like me, who has only a rudimentary grasp of taxonomy (the practice of classifying organisms), this announcement might just as well have read, “The sky isn’t blue and grass isn’t green!”

For most of my naturalist career, I’ve struggled to distinguish between Cooper’s and sharpies, species so similar I figured they had to be connected. This perception dates at least as far back as 1999, the year I began volunteering at the nature center at Tekakwitha Woods in St. Charles. A new taxidermy mount had arrived, and no one was quite sure whether it was a female sharp-shinned hawk, Accipiter striatus, or a male Cooper’s, which at the time had the scientific name Accipiter cooperii.

I knew Cooper’s in general were the larger of the two, but also learned there is considerable overlap between the two species. I recall another volunteer dubbing the bird a Coop-shin, which was – again, as a mediocre birder – close enough for me.

So many things about these birds are, to my uneducated eye, nearly identical. They both have lovely reddish-orange bars across the breast and are bluish-gray across the back. Their tails have thick, dark bands, and their eyes are red. And both specialize in feeding on other birds.

But they also have their differences. For one, in our area of Kane County, Cooper’s simply are more common. They’ve adapted well to a suburban lifestyle, and might just as likely be found nesting in a Norway maple on a parkway as in an oak tree in a nature preserve.

Sharpies, meanwhile, require dense forests for breeding, and that’s an ecosystem we don’t really have. When we do see sharpies, it’s usually during migration or in winter.

Then there are the physical traits. Cooper’s, as noted above, are larger, with the size of the female often being compared to that of a crow. Female sharpies are smaller, comparable in size to – I kid you not – a male Cooper’s, according to Cornell’s All About Birds website.

In the field though, size can be difficult to gauge, so other features like head shape, markings and legs come into play. Cooper’s heads are flatter, and have a distinctive “cap” of dark feathers on top; sharpies’ heads are rounder, and have a “hood” of darker feathers that extends to the nape. Coops have thicker legs that appear shorter in relation to the body; sharpies’ legs often are described as pencil like, and appear longer.

But for those of us who aren’t great with binoculars or whose eyes don’t pick up on subtle details, Cooper’s and sharp-shins look practically identical. How is it that these beautiful birds are not kissing cousins?

To answer that question, let’s turn to that old adage – the one that goes something like: “The only constant is change.” It’s true in life and in taxonomy.

The more information that research reveals about the plants and animals around us, particularly their genetic makeup, the more informed decisions taxonomists can make about the organisms’ classification.

In the case of the Coops and sharpies, it’s been known for a while that their genus, Accipiter, is polyphyletic – not an everyday word, for sure! It’s derived from the Greek word polyphylos, which means of many tribes, and is applied when a group of organisms is descended from more than one common ancestor. To taxonomists, that sort of categorizing is, shall we say, no bueno.

Other notable changes in the eBird 2024 Taxonomy Update include splitting the barn owl into three separate species, the herring gull into four, and the house wren into seven; meanwhile, the common, hoary and lesser redpolls have been combined into one species, Acanthis flammea. All told, this year’s eBird Taxonomy Update includes three newly described species, 141 species gained through splits, and 16 species taken away by lumping species together. The new number of bird species worldwide is … drum roll: 11,145!

In one last note about names, another group, the American Ornithological Society, last year announced a separate project wherein birds whose common names include the name of a person will be changed to names that, ah, do not. They’re currently working on a group of between 70 and 80 birds native to North America that includes, you guessed it …

The Cooper’s hawk.

• Pam Otto is a naturalist and the outreach ambassador for the St. Charles Park District. She can be reached at potto@stcparks.org.