Photo credit: Dan Lory

Pity the poor field mouse. Menaced by predators like the coyote, the fox, the snake, it's a wonder any mouse survives long enough to raise a family of its own. Oh sure, every rodent who's ever read a biology book knows that it has oodles of brothers and sisters exactly so that there will be someone to pass the torch to the next generation. But somehow "Don't worry, there's strength in numbers; your species will survive" is not very comforting to an individual mouse staring down a hungry garter snake. Where's a poor mouse to look for help?

Not up. There is plenty of danger from the sky as well, and one more flying menace has just entered stage left. The Northern Harrier is back in town.

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I'm happy when the first cold snap of autumn comes to Chicago, because it usually signals the return of this graceful hunter from its nesting sites further north. True to form, last week brought the first Northern Harrier that I have seen since spring. After a summer watching Kestrels and Cooper's Hawks and Peregrine Falcons in the skies over my favorite lakefront park, there was no mistaking the Northern Harrier--even from about 300 yards away. Narrow body, long tail, and wings that seem too long for its frame, it cruises gently at grass-top level, low over the fields. Then it will abruptly bounce up 10 or 20 feet, hover for a few seconds with shallow wing beats, and pounce. A minute later--after devouring the rodent or small bird it caught--up it pops, to resume the hunt.

The Northern Harrier doesn't quite fit in with other hawks common to the midwest. They nest on the ground, and they prefer the ground or a fence post for a perch. I've never seen one perched in a tree. They usually don't soar, like a Red-tailed or a Broad-winged Hawk. Instead, they calmly weave back and forth across the field, just over the grasses, covering every inch of their territory, like a mellow but efficient crop-duster. And if one flies close enough for you to see its face, you might mistake it for an owl. Its facial feathers flare out, giving it a disc-like face similar to an owl. All the better to hear those field mice scampering for cover when the Harrier's shadow passes overhead. The male is gray above and white below, earning it the nickname Gray Ghost.

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As if to reinforce their owlishness, I read that Northern Harriers often hang out with owls. In the cold months of winter, harriers roost on the ground communally, often together with Short-eared Owls, who are also ground-perchers. My experience bears this out; I have often seen Harriers and Short-eared Owls together in the same field at dusk, as the harriers yield the field to the owls for the night shift.

Northern Harriers are on the decline in North America, as the open prairies shrink and disappear. It's a fate shared by Meadowlarks, Bobolink and other birds of the grasslands. Let's hope the inexorable advance of humanity figures out a way to leave room for the Gray Ghost...and for the field mice, of course!

Dan's Feathursday Feature is a weekly contribution to the COS blog featuring the thoughts, insights and pictures of Chicago birder, Dan Lory on birds of the Chicago region.