Hawks of the marsh
Have you ever wondered why certain birds look the way they do? I certainly have. This article isn’t about owls, but why do they look the way they do? They have such an odd face.
Take the short-eared owl as an example. It has a round face — in fact, that shape of face is referred to as a facial disc. It’s a characteristic of all of the owls. It even seems as if it could be a satellite dish. That would make a good explanation for how they can hunt so well in the dark, except that owls were around a long time before the Global Positioning System or spy satellites were in place.
Studies have shown, however, that this facial disc pattern of feathers is critical to the success of owls that hunt in total darkness or that hunt through a snow cover. These owls, the short-eared owl again being a good example, have an incredible ability to hear and locate prey they will never see.
The disc apparently acts as a parabolic dish of the same type that you attach to your house to receive a satellite TV signal. For the owl, the disc concentrates sound waves and directs them to the owl’s ear openings. If the feathers that form this disc are removed, the owl makes mistakes in locating the prey, mistakes that it did not make before.
So, the facial disc works in the same way as a satellite dish, but it picks up mouse signals rather than television signals — mouse signals being, in my opinion, a whole lot more interesting than most television signals anyway. And mice, I might add, have been around for as long as the owls have.
As I indicated, all owls have this facial characteristic to augment their extremely acute hearing. And they are the only birds that do, except for a single type of hawk. That hawk is the harrier, and the northern harrier is the species we see in North America.
Now, back in the days when I was just starting as a birder — way back when the American kestrel was known as the “sparrow hawk” and the merlin was called the “pigeon hawk” — the harrier had the name “marsh hawk,” a name I still prefer. As you will see, it’s so very descriptive.
The northern harrier occurs across North America and northern Eurasia, thus the bland “northern harrier” name was given when our “marsh hawk” was lumped with their “hen harrier.” I can see why the Eurasian name needed to be changed, but marsh hawk was so good. “Marsh harrier” would have been a better compromise, in my humble opinion. I am, however, very grateful that the two falcons were renamed. Merlin, especially, is such a great name.
Whatever you call it, this member of the hawk family is owllike in many ways. First of all, it too has acute hearing and uses this skill to a high degree in its hunting. It uses sight more than most owls do, but it is certainly wired for sound. Not only does it have the facial disc of an owl to concentrate and direct sound to its ears, but it also has larger ear openings than do the other hawks.
Second, the northern harrier uses a hunting style, a nesting style, a migration style, and a body style quite similar to that of the short-eared owl. In fact, on a winter evening, at a time when both species prefer to hunt, and in areas where the two seem to hunt together, it can be difficult to tell the two apart.
They both fly low to the ground, often following a fence row or ditch. They both drop suddenly when prey is located. They both have long, slender bodies and glide on long wings, flapping only when absolutely necessary. Both sit on low perches and both roost on the ground at night. In fact, the two species often roost together where large numbers are found wintering together.
As owllike as the northern harrier may seem, it is still very much a hawk, albeit a unique hawk, to be sure. It is the only harrier species in North America, although there are many more throughout the world. The northern harriers, as are few others among the hawks, are sexually dimorphic, meaning the sexes look different. In fact, without prior experience with harriers, you might confuse a male and a female, and even a juvenile bird, as separate species. All, however, have the characteristic harrier white rump patch that, along with their wing design and flight pattern, is a sure key to identification.
While females tend to be rather plain in streaks of various shades of brown, juveniles are more showy with a back that is femalelike, but a body of rich orange or cinnamon. Although smaller, the male is the real showoff. Unlike any other raptor in our area, the male northern harrier has back and wings of silvery gray and a body of crisp white. This combination gives it a ghostlike appearance in the fading light of dusk.
In full daylight, though, while skimming along at reed or grass-top level, the combination of mostly gray, with a large white rump patch, and black wing tips and trailing edge, is nothing less than startling as the bird suddenly pops up over a small rise. Many a duck hunter has panicked within a well-hidden blind at the sudden encounter.
As their old name implies, these harriers are hawks of the marsh. They will actually be found in any open area containing a dense cover of grasses or reeds, for it is in these areas that harriers hunt so adeptly with their keen sight and hearing. Their hunting flight is a slow, graceful patrol over suitable terrain. Often covering 100 miles in a day, harriers trace a pattern back and forth over a field or marsh, methodically covering every bit of ground.
As they hunt, their low-to-the-ground flight is distinctive. Their wings are so long and their bodies so narrow that they glide with the wings forming a V-shape above them. This pattern is called a dihedral and is not seen so exaggerated in the larger hawks with their heavier wing loadings. As a silhouette, a gliding harrier is reminiscent of the characteristic dihedral of the turkey vulture as it scouts for food from a much higher vantage.
The harrier’s flight can be so slow that they frequently tip their elevated V from side to side, appearing quite unstable. They are, however, anything but. Those who have carefully studied their gliding flight describe it as distinctive, graceful, buoyant, skimming, and coursing. When a promising spot is located, harriers can also hover in kestrellike fashion while deciding if a pounce is warranted.
Once prey is spotted or heard, the harrier drops feet-first to capture animals seemingly safe under the vegetation cover. In many areas, especially where competition with larger hawks is severe, harriers become a crepuscular species, hunting primarily at dawn and dusk. Their owllike hearing allows them to partition the resource in the same way the owls do, and thus avoid the thievery they suffer from larger hawks during daylight hours.
And what is it that harriers are watching and listening for so patiently as they glide along? Primarily it is small mammals. Voles, the short-eared, short-tailed mice so common in fields and marshes are their dietary staple. Male harriers, especially, will also take small birds, large insects, lizards, snakes and frogs. The bigger females can kill jackrabbits and larger birds to the size of a small duck.
The American coot, the “it’s what’s for dinner” bird for so many predators that hunt over water, is a prime target for harriers as well. I have not seen it myself, but apparently a female harrier kills a coot by landing on it and holding it underwater until it drowns. The harrier uses her own wings as a life board to stay afloat, then uses them as paddles to get to shore. Where would this country be without voles and coots? It would be a pretty hungry place, I’ll tell you that.
As do other hawks, harriers can also soar, but do not do so to hunt. This traveling flight is more typical of that of the other raptors, and migrating harriers are often confused with the smaller hawks, the accipiters, and the falcons. They still retain their distinctive dihedral, though, but add more flapping flight to the pattern.
During the winter, harriers can be found in just about any open-country habitat. For nesting, however, northern harriers are more specific — they want marshy areas, and are very much “marsh harriers.” They are unique among the hawks in being ground nesters, and they are again similar to short-eared owls in this respect.
During the breeding season, male northern harriers show off yet another distinctive type of flight. They have a courtship display that involves a series of U-shaped dives that can be quite breathtaking. The series will usually include 25 or more dives or loops that involve some sort of somersault at the top of each. I guess that the more dizzy the male, the better his reproductive potential.
Actually, when it comes to aerial acrobatics, the females aren’t bad either. While females care for the nest, males do all the hunting for females and young. They do not, however, bring food to the nest. Instead, the female flies up to meet the male who drops the food down to her. She does a roll and a twist, grabbing the food in midair. She then makes several false landings to disguise the position of the nest.
Several winters ago I watched a shrubby field for several hours as the afternoon waned. Before it started getting dark, two northern harriers began cruising the field. As darkness became noticeable, five short-eared owls appeared. At first the owls simply perched and watched, but soon joined the harriers. Both species crisscrossed the field, sometimes coming within yards of each other. This congenial coursing went on unabated until it was too dark to follow.
Although that was my first experience in seeing the owl and the harrier together, over the years northern harriers have been one of the more common species I have seen year-round in the Inland Northwest. With their hunting habit of flying close to the ground, lazily quartering over open country, they do not inspire the same awe one often feels at seeing one of the larger hawk species soaring overhead.
But there is a lot to be said for spending some time admiring these owllike hawks. They are methodical and they are diligent. They are obvious and yet they are spooky. They are birds of the open country, and not of the trees. They are unique, and they are harriers to be sure, but they are harriers of the marsh. They are our hawk of the marsh.