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Northern Harriers
Wednesday August 8, 2018   |
The specialized facial disc is evident in this photo of a first-year Northern Harrier.

Northern Harriers are specialized hawks with some interesting adaptations. Unlike any other hawks, harriers have a specially adapted facial disc, similar to owls, that surrounds the face with specialized feathers that funnel sounds to their ears. The facial disc permits harriers to hunt by sound as much or more than by sight, but they use both senses for best success as they fly or glide slow and low over the top of grasslands, hayfields and wetlands in search of small mammals.

Male Northern Harriers perform spectacular mating displays during spring that include deep undulating flights that sometimes incorporate barrel rolls that make this “sky dance” one of nature’s great spectacles.

It’s always fun when you can distinguish the sex and age of species when you identify them in the field. Northern Harriers are one of the few American birds of prey that you can separate males from females by the color of their plumage: Males are colored silver-gray and females are colored medium-brown. You can also distinguish first-year harriers that resemble adult females, but first-year harriers have a rich rufous-brown coloration.

A male Northern Harrier on the hunt.

The Northern Harrier is the only harrier found in North America, although a dozen other harrier species are found worldwide. Birding Wire editor Paul Konrad shared that when he studied the birds of northeast China, there were three species of harriers nesting in the region, including the dramatic-looking Pied Harriers. And while conducting field work in eastern South Africa Paul observed four harrier species in the open grasslands there, including the rare Black Harriers.

Range: Throughout most of southern Canada and the United States. Winter from the center of North America south through Mexico and Central America.

Habitats: Grasslands and wet meadows, especially near wetlands.

Mating: Most pairs are monogamous, but during an extensive long-term study, about one-quarter of nesting harriers were polygamous, which includes more than one female. Higher incidence of polygamy was observed during periods of high vole populations.

Nest Sites: A flimsy nest of sticks and grass is built by both adults on the ground in thick grass or tall sedges.

Clutch Size: 4 to 6 light blue-white eggs, usually unmarked. Some clutches may number 8 to 10 eggs during seasons of abundant prey.

Incubation Period: Female incubates about 32 days; male feeds female during incubation.

Nestling Period: Male and female provide food and care for nestlings.

Fledging: Almost 7 weeks. During the extended post-fledging period, when fledglings learn to fly and hunt, the adults continue to be feed and protect them.

Food: Primarily small mammals, particularly voles and mice, but some birds become adept at catching small birds, at least during part of the year. Some harriers wintering in the Imperial Valley of California occasionally prey on Cattle Egrets, an exceptionally large prey species for Northern Harriers. 

Conservation Status: Fairly common and widespread, but declining during recent decades, probably due to reduced grassland and wetland habitats.

A female Northern Harrier's brown color is very different from males', but immatures are a bit more difficult to discern in the field. Compare the different shades of brown in the female and immature plumages in the above photos.

Photographs by Paul Konrad

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