Taste 12.— Fledging success of brown thrashers (computed by exposure-day method, Mayfield 1961 We 
April-May June-July 
Region Year Number Percent Fledged Number Percent Fledged 
Nests Eggs Nests Eggs Nests Eggs Nests Eggs 
rthwest 1968 34 124 Bee 20 Ly) 48 46 38 
st Central 1958 OS 198 41 34 29 96 35 30 
1959 40 148 48 38 24 67 60 53 
itheast 1967 34 119 44 aye 122 36 2g 29 
Success exceptionally low because of a number of nests lost in a very severe hailstorm. 
in September and October for northern and central 
nois. There are few records for the southern zone. 
r census data (Fig. 20) show the onset of apparent 
ulation changes in mid-August in central and northern 
nois, and in late August in the southern part of the 
ie. The highest migrant populations occur throughout 
tember in all regions, falling fast in early October 
rth and central) or late September (south). There 
ears to be a sparse but fairly regular trickle of migra- 
1 throughout November, but these birds may be the 
ter residents. 
The thrasher is a surprisingly infrequent victim among 
migrants killed at television towers in Illinois in view 
he number of thrashers seen on the censuses and the 
nber of catbirds killed at these towers. In a sample of 
ty thousands of birds picked up at central Illinois 
ers, thrashers comprise only one-tenth of 1 percent 
ne total. 
As in the case of the catbird, we have never heard a 
enizable thrasher call during the hundreds of hours 
e spent listening to the night calls of migrants. 
As in the spring, fall numbers of thrashers were highest 
entral Illinois, and lowest in the southern region. De- 
an expected population increase from spring to fall, 
fall counts of thrashers were never as high as the 
1g counts. For the state, in general, we saw about 
thrashers in the spring to one in the fall, and in 
-central Illinois the discrepancy was especially great 
ing: five; fall: one). 
(here are only a few published recovery records for 
shers banded in Illinois (Lincoln 1927, Bartel 1945). 
ter recoveries are from Mississippi, Louisiana, and 
tern Arkansas, about 600-700 miles south or slightly 
of south of the place of banding (Fig. 26). Two 
‘ially interesting recoveries were from birds banded 
‘stlings from the same nest by Bartel (1945) at Blue 
d in May, 1937. One was found at Baton Rouge, 
siana, November 7, 1937, and the other was shot at 
sett, Arkansas, January 15, 1938. 
er Records 
1 the past several years, thrashers have been recorded 
where in the state every winter (Fig. 27). Prior to 
the Audubon Christmas count coverage was poor 
ise the number of observers was relatively small, 
especially in southern Illinois. Thrashers were recorded 
on only about 2 percent of all Christmas counts in 
northern Illinois, and 4 percent of the counts in the 
central zone (Fig. 28). With increasing coverage after 
1940 the frequency of occurrence has been generally in- 
creasing, even out of proportion to the number of ob- 
Coy ie 
/ SCALE 
/ fe} 100 200 300 400 MILES 
== r A 
\ fo} 200 400 600 KILOMETERS 
a ALBERS PROJECTION 
Fig. 26.— Recovery records of brown thrashers banded in 
Illinois. The only spring recovery was due north in Wisconsin. 
o3 
