The raptor sat immobile atop the bare branches of a dead pine. Nothing moved except its feathers, which were being blown by the wind sighing down the center of the Penjajawoc Marsh in Bangor. Its quiet demeanor belied its intent, for it was hunting.

Finally it turned its head, and I saw the unique feature that set it apart from other diurnal (daytime) birds of prey: it had facial disks resembling those of an owl.

It was this characteristic that the hawk was bringing to bear as it listened for movement of its prey. The structure of these facial feathers effectively funnels sound into its large ear openings, which are hidden underneath its feathers. Owls, perhaps better known for this feature, are also blessed with exceptional hearing because of it.

The northern harrier, also known as the marsh hawk, can hear movement of its prey up to 12 feet away because of these facial disks. You may think this is no big feat until you consider that its prey consists of meadow voles and other small rodents.

These animals generally don’t make a whole lot of noise. A moose makes a lot of noise as it moves through its surroundings. A mouse doesn’t – at least, not to our ears.

As I watched, the harrier lifted off from the tree and began a leisurely flight above the waving marsh grass. At first it followed the line of vegetation edging the marsh. Every now and then, it paused and hovered in the air like a kestrel, perhaps spotting a fleeting opportunity. When it had no luck using that tactic, it began a systematic quartering of the wetland.

I caught my breath as the hawk suddenly dove into the tall vegetation. It re-emerged a few seconds later, but I could discern no prey caught in its talons.

Marsh hawks also prey upon other small- to medium-sized mammals, as well as small songbirds and waterfowl. The female of the species is larger and heavier than the male, which is typical of birds of prey. Her back is a beautiful chocolate brown; her under parts are light buff with dark streaks. The male has a starkly different plumage: electric, light-blue above and dazzling white below, with inky black edging to the wings.

Both sexes can be identified by a large, white rump patch which is visible when viewed from the top. They have long, slender wings with a span of more than 31/2 feet. Their tails are also long and slim.

The male is known for his courtship and territorial display. He performs a “sky dance” by undulating in flight, up to 74 times in each sequence of flights. Steeply ascending and descending, he barrels through the sky as if on an invisible roller coaster.

The northern harrier is the only member of its species to be found in the United States; several other species of this group are found throughout the rest of the world. In the Northeast, the U.S. Fish and Wildlife Service lists it as a species of management concern because of habitat loss.

The last I saw of the harrier – a female – she was trying her luck on the other side of the marsh. The darkness of her wings and brightness of her rump patch stood out against the marsh vegetation and the gray, rain-laden clouds. She coursed back and forth, and finally disappeared into the distance.

Chris Corio, a volunteer at Fields Pond Nature Center in Holden, can be reached at fieldspond@juno.com