by Dr. Sarah Treanor Bois, PhD
Director of Research & Conservation at the Linda Loring Nature Foundation
Years ago, my husband and I eloped at a Nantucket conservation property. When we got to the location, we couldn’t decide exactly which spot to say our “I Do’s.” As we weighed the pros and cons of beach versus grassland, a female Northern Harrier flew low overhead. She landed on a post by one of the beach entrances and projectile pooped into the path. “That looks like the way,” I said to my betrothed. Seventeen years later the harrier blessing is still strong.
The Northern Harrier is a ground-nesting raptor of open marshes and grasslands, easily recognized by its low, gliding flight and white rump patch. They are Accipiter Hawks in the same family as eagles, vultures, and kites. However, their flat faces make them look more like an owl than any of their closest relatives. Their facial disks allow them to hunt by sound as well as by sight much like an owl— a good feature when hunting in the fog of the gray lady.
Female Harriers are light brown above and buffy below. The undersides are heavily streaked with dark brown. Females are also about 20 percent larger than the males. Adult males are smaller and gray with black wingtips. This helps give it the nickname “grey ghost,” a perfect moniker for a foggy day in the moors. The juveniles, which are likely out and about now, are mostly dark brown above and cinnamon colored below. Having just fledged, they may also appear a little clumsy on the wing. All three age classes have the distinctive white rump patch easily distinguishable from other birds of prey in our area.
Harriers hunt almost exclusively on the wing for small mammals like meadow voles, white-footed mice, and even other small birds and sometimes snakes. They’ll also take the occasional rabbit. Unlike other hawks, Harriers have historically been favored by farmers because they eat agricultural pests that can damage crops without going for chickens.
You might see them in flight and hunting—a common sight in the moorlands and grasslands around Nantucket. In flight, Northern Harriers are distinctive; their long slim bodies and slender tail gliding low over a grassland or marsh holding their wings in a V-shape. They seem to barely flap their wings as they hover over the heathlands looking for a snack.
Also known as “marsh hawks,” these birds inhabited Massachusetts in “considerable numbers” in the 1830s, making use of the widespread fields, meadows, and wetlands during the state’s greatest agricultural era. At the beginning of the twentieth century, observers still called the species a “common summer resident.” Their decline was noted by the 1920s, and, as the state continued to revert to forest throughout the twentieth century, the breeding population waned in turn.
Today in Massachusetts, the Islands are clearly the place to find Harriers. Nantucket, Tuckernuck, Martha’s Vineyard, and the Elizabeth Islands accounted for nearly all Northern Harrier breeding activity in the state in the 1970s. In fact, no Harrier breeding was confirmed anywhere else in the state during that time. The species is still in recovery today and protected. There is marked recovery to the populations outside the Cape and Islands, but Nantucket and Martha’s Vineyard remain stronghold breeding sites for the species.
Northern Harriers are listed under the Massachusetts Endangered Species Act as a species of Special Concern. Their declining populations are primarily due to loss of open habitats throughout much of their breeding range. Historically Northern Harriers were known as Marsh Hawks, indicating their other habitat preference, also in decline throughout the eastern US.
What makes Nantucket such a good place for Northern Harriers? First of all, Nantucket has extensive acreages of sandplain grassland, heathland, and open marsh habitats— perfect for nesting Harriers. These habitats have been extirpated or highly fragmented in other areas. Another plus for Nantucket is the lack of mammals. Sure, we have rabbits, shrews, rats, and field mice, but aside from our deer herds, there are no large mammals, particularly mammal predators (we will save feral cats for another day). On Nantucket, we have no raccoons, foxes, chipmunks, or even skunks. This lack of mammalian predators is a bonus for ground-nesting birds like Harriers.
Northern Harrier nests, despite being on the ground, are highly secretive. I was once conducting vegetation surveys along the south coast of the island. Unbeknownst to me, there was a Northern Harrier nest right in my transact path. I screamed bloody murder when the adult female flew directly up at me just as I was about to step on the nest. She had been covering the hatchlings with her camouflage body until necessary to move. Before I could bolt away, I saw three little wrinkly chicks covered in white fuzz. No bigger than avocados. They must have only been a few days old, nestled in a grassy nest surrounded by black huckleberry shrubs. As I hightailed it out of there, my heart still racing, the mother hen was chiding me with chirps. She threatened with her talons, dive-bombing me, but I had already abandoned my plant surveys for the day.
Northern Harriers are year-round residents of Nantucket, a fact that makes me like them even more. We frequently see them cruising for a meal in the dead of winter. Of course, there are some migrants as well which arrived to Nantucket in March. Fortunately for Harriers, they nest early in the season: they start to establish territories in early spring and nest where few (except maybe an intrepid ecologist) dare to tread.
After the young have fledged, they may hunt together with their parents through the remainder of the summer, until they disperse on their own or are driven off. Now is a great time to see Harriers around the island with both adults and “teenager” birds trying to figure out flying.
To view Harriers on Nantucket, check out any open heathland, grassland, or marsh habitat. Head of the Plains (Nantucket Conservation Foundation), the Linda Loring Nature Foundation property on Eel Point Road, or Smooth Hummocks (Nantucket Land Bank) are all great properties for sightings.
