1951-1971) when mileage data were also provided, ob- 
ryers saw one loggerhead per 40 party miles traveled 
. southern Illinois, one per 260 miles in central Illinois, 
ad one per 3,000 miles in the northern region (for re- 
ons see Fig. 8). The marked fluctuations in winter 
ypulations of the loggerhead shrike (Fig. 9) remain to 
» explained. Musselman (1939) suggested that more 
wikes remained in Adams County in “mild years,” but 
e know of no objective studies on the relationship of 
ike populations to climate. The sharp decline of the 
orthern and central Illinois breeding population of 
rikes is not observable in the winter population figures, 
id this observation implies that the winter population 
ay be different from the breeding population. We have 
sted that extreme west-central Illinois seems to have 
gher winter populations of loggerheads than other areas 
30 
NO 
Nn 
NO 
oO 
SOUTH 
a 
oO 
4) 
A 
Ih \ 
\ I \\ | 
\ /\\ ‘ 
eae 
1945 1950 
ro) 
LOGGERHEAD SHRIKES COUNTED PER 100 PARTY HOURS 
oO 
n 
0 een] 
1940 
th 
of central Illinois, but better census data are needed to 
confirm this. 
Food Habits 
The impaling of prey items in thorn trees, or on 
barbed wire fences is a well-known habit of shrikes. We 
once observed a shrike impaling dead birds, small mi- 
grants killed in September at a TV tower, on a nearby 
barbed wire fence. The use and function of the food 
cache is not fully known or understood (Ridgway 1889). 
Depending on the source of information, we obtain 
two quite different pictures of the shrike’s food habits in 
Illinois. 
Direct field observations of foraging shrikes and of 
shrike food caches in all regions of the state have indi- 
cated that the loggerhead shrike is primarily predaceous 
CENTRAL 
/ A io 
(\N my 
j NORTH v3! 
f \0 Xe 
1955 1960 1965 1970 
Fig. 9. — Annual variation in winter populations of the loggerhead shrike, based on Audubon Christmas counts in three regions 
€ state. Graph lines show the number of loggerheads seen per 100 party hours. 
11 
