Testes UsDeU 1S ON Bi bo: bee N 
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Stomach Contents of Illinois Raptorial Birds 
Edward A. Munyer, Curator of Zoology, and 
Paul W. Parmalee, Assistant Director, 
Illinots State Museum, Springfield 
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Remains of prey from stomachs of some rapforial birds. Left to right: Top, skull and 
jaws of a vole (Barn Owl); skull and jaws of a Norway rat (Great Horned Owl); bird 
(Screech Owl). Middle, part of a cottontail’s hind foot (Great Horned Owl); two house 
mice (Red-tailed Hawk); two least shrews (Red-tailed Hawk). Bottom, camel cricket 
(Screech Owl); grasshoppers (Great Horned Owl); crayfish (Barred Owl); hornworm 
larva (Great Horned Owl). Scale in centimeters. 
The predatory habits of hawks and owls have been studied for many years, 
and our knowledge of their dietary habits is consequently quite extensive. 
A number of different methods are used in gathering information; the late 
Dr. Paul L. Errington (1932) categorized them as follows: (1) Field obser- 
vation — through “sign reading”; (2) Nest studies — involving, for example, 
constant observation, as from a blind; (3) Gullet examinations — where 
“gullet food material” is forced by a gentle squeezing upward and out of 
the mouths of young living birds; (4) Tethering — accomplished by tether- 
ing young birds on the ground where they are located and fed by the adults; 
(5) Pellet examinations; and (6) Stomach examinations. The data presented 
here are based on an examination of 51 stomachs of 13 species collected in 
twenty-four counties. Thirty-seven stomachs (14 hawks and 23 owls) con- 
tained remains of the prey animals listed. 
