Northern Harriers are Unique
Ro Wauer, February 22, 2004, The Victoria Advocate, © 2004
Earlier known as "marsh hawk," due to their use of marshy habitats during the nesting season, their current name fits them much better on their wintering grounds. Then they are more likely to be found over weedy fields and croplands during their residency in South Texas. Their method of hunting is very different from all other hawks. Instead of flying high above the ground or perching on a tree or pole and watching for prey, then diving on the subject, harriers slowly fly low to the ground. They essentially search their feeding areas, flying back-and-forth in a deliberate process. Once they discover a prey species, they suddenly drop onto their subject, often times doubling back. But what is truly unique about this species is its use of both visual and audio clues. Unlike other hunting hawks that hunt only by sight, harriers are also able to zero in on sounds, such as rodent squeaks. This hunting method has been described as a search-pause-pounce strategy.
The audio-location ability of northern harriers is performed by an amazing system of triangulation, similar to that used by owls. A close look at a northern harrier will reveal sound-reflecting disks, special facial characteristics that are missing from other hawks. This feature has prompted some ornithologists to consider placing harriers into a new and special family or subfamily.
In addition to those unique features, studies of nesting harriers have revealed that 25 percent of nesting females, usually subadults, are involved with polygamy, several females mating with one male. And male harrier's courtship can be an amazing display of "sky dancing," tumbling, rolling, and looping to impress their ladies. However, once incubation begins, the male harrier rarely visits the nest. He does, however, provide his fair share of food for the female and nestlings. He transfers prey in flight to the female, who then sneaks back to the next after several false landings to confuse any watching predators.
Northern harriers are long-winged hawks that occur in South Texas only during migration and in winter. Adult males look considerably different from females and young birds. They are sexually dimorphic. Males possess contrasting black-and-white plumage, while females are buff-colored with striped underparts. Both are slender, possess a white rump that usually is obvious even at a distance, and have a long tail. Flight is distinct as they course low over the ground with a few but quick wingbeats, tilting constantly from side to side. At night they roost on the ground, usually in groups of other northern harriers, and sometimes with short-eared owls.
Our northern harrier is North America's only representative of 10 harriers found worldwide. All are of the genus "Circus," a Greek name referring to their circling flight. The species name is "cyaneus," Latin for blue, referring to the adult male's slaty blue color. They all look very much alike and practice the same hunting technique.
Wintering northern harriers leave us in spring to return to their nesting grounds from the Texas Panhandle northward across the northern half of the U.S. Some are already beginning to move northward, and so as they pass through our area, they are worth watching. They are one of our most unique raptors.