We’ve reached that time of the year when winter is starting to flex her muscles. The leaves are off the trees, snow has already been seen, the morning temperatures are frequently below freezing, and only the most stubborn of the dandelions can still be found blooming in the short grass. The summer birds are now long gone and a decent bird species count has dropped from somewhere in the 60s to somewhere in the 30s.
On weekends, I can routinely observe somewhere between 18-24 species of birds; most of them the familiar old “regulars” that show up every day. The ones that I really have to keep an eye out for are the “X-factor” species that might only show up once per month. If they happen to land on the deck for a moment or two while I’m doing laundry, or cooking breakfast, then I will most likely miss them and be completely unaware that they were ever there. With the X-factor species, it is really all about luck.
Such is the case with the northern harrier (Circus hudsonius), a species of hawk that may not be familiar to everyone. Unlike the ubiquitous red-tailed hawk (Buteo jamaicensis), which is a large “soaring” hawk that spends its time circling above fields and intently staring at the ground for signs of prey, the northern harrier is a low-altitude hunter that is able to almost float above fields and marshes at low speeds. This is a hint that the two species have very different hunting styles.
Red-tails hunt by sight and they require a moving target. Harriers, on the other hand, use both sight and sound for hunting prey. The low, slow flight over the ground allows the harriers to search for any movement that they might be able to spot, but they also spend a lot of time listening for prey. The soft sounds of small mammals scurrying through dry grass is something that red-tails could never pick up on, but the harriers are equipped to deal with.
The secret is found in the feathers on a harrier’s face. If you look at today’s photo you will see a gorgeous adult female. I was lucky to get the blue sky behind her so that there was good contrast between the feathers on her body. I want you to look carefully at the delicate arc of “speckled” feathers that seems to separate her face from her neck. This is an array of feathers that is actually quite similar to the “facial discs” seen on an owl’s face.
Hidden under the feathers of the head are the bird’s ears and a concave circular disc of feathers surrounding the eye can act like a parabolic microphone to collect and focus noises. Think of the round dishes around microphones on the sidelines of NFL games and you’ll have the idea. With the right equipment, a person (or a bird) can hear quiet noises quite clearly and in the case of the harrier it allows targeting information for an attempt to grab a small animal. Sometimes, the harrier will dive at a noise and just hope for the best.
During the breeding season the northern harrier is a denizen of marshes, pastures, large fields and the open tundra found up in Canada. Here in Massachusetts, we are near the southern limit of the breeding range, but we can see quite a few of these birds during the winter. The key is to make sure that you look in the right places. Fallow farm fields are good places to look, as are the open grassy areas at quiet airports. Anywhere that relatively short vegetation full of mice and voles can be found is prime harrier hunting habitat.
So strong is this bond between bird and grassland that the northern harrier actually nests on the ground. Both sexes cooperate in nest construction. A platform of coarse vegetation (like cattail stalks and willow branches) is built to lift the eggs off the actual ground. Then, the nest is lined with finer plant materials that provide soft insulation for eggs and chicks. After the two-week building project is completed, the female will lay four to five eggs in the nest. The female is the only parent to incubate, while the male provides food. It is easy to tell the sexes apart because adult males are a pale, pearl gray.
These are the “ghosts” that I spoke of earlier. Unmistakable in their low gliding flight, the birds hold their wings in a “V” much like a turkey vulture. During the breeding season, the adult males will go through elaborate “sky dancing” displays and they will mate with more than one female if the chance presents itself. This all depends on the abundance of food in any given place. Past observations have seen certain males able to maintain “relationships” with up to five different females at the same time. Such males have to be master hunters in order to keep everyone fed!
The tundra is no place for a harrier to try to spend the winter, so they migrate as far south as Central America, the islands of the Caribbean and even northwestern Colombia. Here in Massachusetts, we are in the northern extreme of the winter range, but the Massachusetts Audubon Society characterizes the harrier as a common species from August to March. Put yourself in the right habitat and you just might catch sight of one of these beautiful birds floating slowly over the ground as it searches for food.
Bill Danielson has been a professional writer and nature photographer for 28 years. He has worked for the National Park Service, the US Forest Service, the Nature Conservancy and the Massachusetts State Parks and he currently teaches high school biology and physics. For more information visit his website at www.speakingofnature.com, or go to Speaking of Nature on Facebook.