Fig. 7.— Loggerhead shrike nest with eggs in osage orange near Bondville, Illinois, June 17, 1907. Photo by Alfred O. Gross. 
s. The old oological records show a higher percentage 
five-ege clutches in the north than in central and 
thern Illinois, yet they indicated that even in the 
th the most frequent clutch size was six eggs. There 
no recent data for the north. 
The loggerhead shrike has a notably high level of 
ing success for a songbird. A sample of 20 nests in 
Iside hedges (red cedar, rose, sassafras, honeysuckle ) 
outheastern Illinois in 1967 had a success rate (com- 
ed by the exposure day method, Mayfield 1961) of 
ercent (65 percent for eggs). By comparison, brown 
Shers nesting in the same hedges had a success rate 
nly 42 percent of eggs (Graber et al. 1970). In east- 
PABLE 2. — Clutch sizes of loggerhead shrikes in Illinois. 
Number Average Percent of Nests by Clutch Size 
on 
of Nests Clutch 7 Eggs 6 Eggs 5 Eggs 4 Eggs 3 Eggs 
h* 37 5.9 24 41 35 0 O 
ral 72 ayes; 10 54 26 8 1 
h 25 Sei) 4 68 24 4 0 
The data for northern Illinois are mainly old museum records 
nd 1900 or before). The central and southern Illinois data are more 
» Mainly since 1957. 
“hw: 
“/P 
43 | 
lt 
central Illinois between 1958 and 1964, nesting success of 
shrikes in osage hedges was 71 percent (62 percent for 
eggs) in a sample of 25 nests. Thrashers in the same 
hedges had nesting success that varied annually from 34 
to 38 percent of the eggs. Nests of thrashers and other 
species less fierce than shrikes perhaps aid shrike nests 
by absorbing most of the predation. The causes of failure 
of shrike nests are apparently unknown. We have never 
witnessed nest predation, and there is no reference on 
the subject in the Illinois literature. There are no data 
on the care of the young or duration of parental care. 
Young shrikes often remain in or near the nest tree for 
several days after fledging. Successful nests produced an 
average of 4.8 young per nest in central Illinois and 4.6 
per nest in the south. Based on nesting successes of 71 
percent and 80 percent, respectively, productivity at this 
stage is about 3 to 4 young per breeding pair, yet the fall 
populations are not particularly high (Fig. 4). 
Fall Migration 
The loggerhead shrike populations of northern and 
central [linois had virtually disappeared 2 years before 
we started our censuses of the migration, and our seasonal 
!) 
