Nature Bulletin No. 414-A    April 10, 1971
Forest Preserve District of Cook County
George W. Dunne, President
Roland F. Eisenbeis, Supt. of Conservation

****:THE MARSH HAWK

In the DesPlaines River valley between the river and the Santa Fe RR., 
northeast of Mannheim Road bridge, lies one of the last remnants of the 
original Illinois prairies -- often burned but never plowed and never 
mowed. It is the home of a pair of Marsh Hawks -- apparently they mate 
for life -- and once, by marking where the female flew up from a tangle 
of dead grasses, we found their nest.

This is the only American hawk that always nests on the ground. When 
hunting, it skims low over a big marsh or an upland prairie, tirelessly 
quartering back and forth like a well-trained bird dog. Now and then it 
makes a few deliberate wing strokes but when it spies a moving prey the 
hawk halts -- may even do a back somersault -- hovers an instant with 
rapidly beating wings, and then pounces. His trademark is a 
conspicuous white rump.

The Rough-legged Hawk frequently hunts in much the same way, 
though not nearly so low, and has a white patch at the base of the tail, 
but is a heavier darker broad-winged hawk that nests in the far north 
and is seen here only in winter. The other broad-winged hawks, such as 
the Red-tailed and the Red-shouldered, customarily soar high in the sky, 
with fan-shaped tails. The marsh hawk, the only North American 
species of a group called Harriers, has a slender body, a long square-
tipped tail, and long narrow wings that are rounded at the tip. The wings 
of the Duck Hawk and other Falcons are pointed. The Goshawk, 
Cooper's Hawk and Sharp-shinned Hawk have long tails but their wings 
are short.

When the marsh hawk pounces successfully he flaps upward and flies 
swiftly away. Over the nest, he calls with a plaintive "Pee, pee, pee" to 
his mate who rises to meet him and grasps the victim in midair when he 
drops it. Their courting maneuvers are also unique. Then and only then 
you may see a pair soaring 'way up yonder until the male suddenly 
closes his wings and turns a series of somersaults as he drops almost to 
earth. This performance may be repeated again and again.

Like most hawks and eagles, the females average larger than the males: 
from 19 to 24 inches in length, with a wingspread from 43 to 54 inches; 
while the male's length seldom exceeds 20 inches, with a wingspread 
from 40 to 45 inches. He is pale blue-gray above, except for that white 
rump, with a lighter breast, white abdomen, and wing tips that look as if 
they had been dipped in ink. She is dark brown above, with a white 
rump, and heavily streaked with brown beneath. She raises only one 
brood per year, usually laying 4 to 6 dull white eggs. The nestlings are 
blind, helpless and covered with whitish down when hatched. 

Marsh hawks breed from Siberia to Prince Edward Island in the Gulf of 
St. Lawrence, and south over most of the open grasslands in Canada 
and the United States. A few winter in our northern states but most of 
them migrate southward in flocks of 20 to 50, some as far as Panama 
and Colombia. They prey to some extent on ducklings and songbirds 
but principally on field mice, ground squirrels, snakes, lizards and 
frogs; and a pair may destroy 1000 or more mice during its nesting 
season For this reason they are protected by law in Illinois and most 
states, and are often called "Flying Mouse Traps."