Blue Circler

Posted by Greg Gillson

Male Northern Harrier, Hagg Lake, Oregon, 7 July 2007 by Greg Gillson.

I don't remember now exactly what I was doing--or why I've never noticed before--but a few days ago I noted the scientific name of the Northern Harrier was Circus cyaneus.  Circus, yes, that's Latin for circle. I thought perhaps that harriers received the genus name Circus for their rounded facial disks, similar to owls. But I was wrong. According to The Audubon Society Encyclopedia of North American Birds by John K. Terres, it actually refers to circling in the air--soaring--a habit common to many hawks.

But now wait a minute. Doesn't cyaneus mean blue? Yes. But why not griseus, meaning gray? The upper parts of male harriers are gray--not blue, and females are brown.

When Linnaeus first proposed his naming scheme in 1766, he lumped all non-vulture hawks and falcons into the genus Falco, now used only for falcons. Thus, there already was a Falco griseus, the Gray Falcon, so the harrier became Falco cyaneus. Later, in 1799, the genus was renamed to Circus for harriers.

I hope you're still with me, because this circuitous story isn't nearly finished. (In the immortal words of Vizzini, "Wait till I get going! Now, where was I?")

Female Northern Harrier, Eugene, Oregon, 4 October 2008 by Greg Gillson.

The bird Linnaeus named Falco (now Circus) cyaneus is called the Hen Harrier in Europe. The European Hen Harrier and the American Northern Harrier are currently considered just variants of the same species. But that wasn't always the case. In fact, the North American bird was listed by Linnaeus as a distinct species, Circus hudsonius, a reference to Hudson Bay, and known for many years as the Marsh Hawk. But today the Northern Harrier (Circus cyaneus hudsonius) is considered simply a subspecies of the nominate Hen Harrier (Circus cyaneus cyaneus).

Not content to leave well-enough alone, my research took me to the American Ornithology Union (AOU) checklists of the past. I wanted to discover when Marsh Hawk became Northern Harrier.

The AOU's first check-list (yes, they used the word with the hyphen before usage changed to "checklist") in 1886 called this bird Marsh Hawk (Circus hudsonius). The AOU in 1957 "lumped" this bird with that in Europe and gave it the trinomial we have already discussed, changing it to Circus cyaneus hudsonius. In 1983 the AOU, in a move to make American and British common bird names match (remember the change of Duck Hawk to Peregrine and Pigeon Hawk to Merlin?), changed the common name of Marsh Hawk to Northern Harrier.

Now I don't know why the AOU naming committee didn't change the name to Hen Harrier. It makes no sense not to, looking at it now. And they couldn't just simply change from Marsh Hawk to Marsh Harrier, as there are several types of Marsh Harriers in Europe already.

So there you have it. Or not.

You see, there's a movement afoot to give back full species status to the American Northern Harrier, again giving it the binomial Circus hudsonius.

Juvenile Northern Harrier, Forest Grove, Oregon, 27 September 2003 digiscoped by Greg Gillson.

In his 2001 book, Raptors of the World, James Ferguson-Lees, treated the Hen Harrier of Europe, the Northern Harrier of North American, and the Cinereous Harrier (Circus cinereus) of South America all as separate species of one superspecies. He says that the adults of Northern Harrier are intermediate in plumage characters between Hen Harrier and Cinereous Harrier. Juvenile Hen Harriers are considerably different from juveniles of the two American forms.

More recently, Dobson & Clarke (2011. Inconsistency in the taxonomy of Hen and Northern Harriers: causes and consequences. British Birds 104(4): 192-201) again argued that Hen Harriers and Northern Harriers should be considered separate species.

Whether the AOU will adopt this British treatment any time soon or not is unknown. If they do, we (like this interesting raptor) will have come full circle.