id presumably other insects and mice, the shrike often 
vers a few feet above ground, then drops on its prey 
Vandercook 1921). Shrikes also drop on prey from an 
svated perch. 
yecimen Data 
There are many references in the Illinois literature 
the occurrence of “white-rumped”’ shrikes in the state 
varsen 1897, Ridgway 1878, Loucks 1891, Gault 1899, 
ocher 1934). The identification of the Illinois breeding 
pulation was clarified by Ridgway (1889), and more 
lly by Miller (1931) who observed that though some 
inois specimens showed intergradation toward the 
stern race excubitorides, the Illinois population is 
operly allocated to Lanius ludovicianus migrans. An 
excellent series of 75 specimens, including many known 
nesting birds in the Survey collection, helps to verify the 
identification. Males appear more variable in color than 
females and about 20 percent of the males show some 
characters of the western form, but none are truly repre- 
sentative of excubitorides. 
We have examined only 14 winter specimens, all 
migrans. The possibility of a winter influx of western 
shrikes exists, particularly to the western edge of the 
state, but identification of the western population depends 
on the collection of specimens. There are no consistent 
size differences between the sexes (Table 4). Winter 
specimens (in the hand, at least) can be sexed consis- 
tently on the basis of the gray vermiculations on the 
breast of females, males being much more nearly immacu- 
late on the breast (Fig. 10). Wear reduces the difference 
Taste 4.— Weights and measurements of loggerhead shrikes collected in southern Illinois, 1971-1972. 
Number of Gross Weight (grams) Wing Chord (mm) Tail Length (mm) 
e and Sex Months ce 
PCCEMEDS Range Mean Range Mean Range Mean 
ult male Jan. a 54.2-64.7 DShD 96°4—"99°4 97.8 92705965 94.1 
April Ly, ES WE a) 35..0 92. 7=101.8 9877 88 .6-101 .4 95no 
July 4 AS. 2= 561 3029 99 .0-100.8 Ooks (badly worn) 
Sept.-Oct. 8 Ol Gao 8 54.4 (moulting) (moulting) 
ult female Jan. 7 20.63/20 DoD Ooo 122 97.8 SOI = 20022 94.6 
April 16 D0,9=74,3 Olet SF Eh 95.6 O0e2— 080 93:1 
July 7 46.8-95.0 50.9 O17 79720 g4 2 S122 97.0 94.2 
Fig. 10. — Sexual dimorphism in winter specimens of loggerhead shrikes. Females (right side) show more vermiculations on 
ast. 
13 
