fee AYU BON BULLETIN 
Published Quarterly by the 
Peele OF sieht Ue D:U. BONA) S10; Gibbs Y 
ROOSEVELT ROAD AND LAKE SHORE DRIVE, CHICAGO 5, ILL. 
Number 88& December, 1958 
Hawk Migration over Thatcher Woods 
By ISABEL B. WASSON AND MARGUERITE SHAWVAN 
ON TUESDAY MORNING, September 29, a spectacular flight of hawks passed 
low over Thatcher Woods in the Cook County Forest Preserves. We counted 
more than 300 hawks between 9 a.m. and noon. There were seven species, 
including three bald eagles. 
The day was sunny, with temperatures in the low seventies. The wind 
was from the northeast. We went to the woods at 8:30 a.m. to make a 
routine check on sparrows and warblers, and found our first flock of white- 
throated sparrows. Suddenly a sharp-shinned hawk alighted in a tree over 
us. While looking at him we noticed several hawks circling in the sky. To 
get a better view we returned to the slough behind Trailside Museum. 
Those first hawks had passed on south but more were coming out of the 
north — five six, seven — new ones appeared as fast as we counted. They 
wheeled in circles, always moving southward. The hawks had broad wing's 
and short, wide tails, with two conspicuous white and black bands across 
the tail. No doubt of it, a flight of broad-winged hawks was on. We sat 
down on the curb behind the skating house, took out paper and pencil and 
began to keep the score. For three hours we counted hawks. 
The broad-wings fiew over in loose flocks of six to eight. Once a big 
flight of 45 was in the sky at once. They were a circling mass which moved 
south in two or three minutes. The hawks flew leisurely on the northeast 
wind with scarcely a wing beat. By noon we had counted 176 of them. 
Flying even lower and more swiftly came the sharp-shinned hawks, 
often called blue darters because of their blue-gray backs and direct, swift 
flight. With short, rounded wings and long, slender tails, they beat their 
way across our open space — quick flaps and a sail. Sometimes the sharp- 
shins seemed to be flying toward the sun, only to turn and plunge toward 
the tree tops. They are small hawks, about the size of a brown thrasher, 
and belong to the accipiter group of hawks which in England are considered 
the only true hawks. The broad-wings belong to the buteo group which in 
England are called buzzards. By noon we had counted 142 sharp-shinned 
hawks. 
Seattered among the southward streaming host were four red-tailed 
hawks, one red-shouldered, four Cooper’s, and several falcons or duck 
hawks. And last of all came three mighty birds in black, with wing spread 
twice that of the broad-wing'ss. As they approached we could see the sun 
shining on one white head. . . Bald eagles! At least one was in full adult 
plumage. They flew over well above us. 
pt" 
