BROWN THRASHER 
BREEDING RECORDS 
NESTS OR YOUNG 
@ i950 — 
A i900 — 1950 
® BEFORE 1900 
PAIRS OR 
SINGING MALES 
oO 1950 — 
A 1900 — 1950 
a aes 
ler HAM 
——1 FAYETTE | wy 
Fig. 21.— Breeding records for the brown thrasher in I[]h- 
nois. Singing male records are for June only. 
township in Illinois, yet published nesting records are 
lacking for many counties in the state (Fig. Ze 
Nesting Habitats and Populations 
The favorite habitats of the thrasher, judging from 
population densities, are hedgerows and other roadside 
or field edge plantings, thickets, and shrub-grown areas 
(Ridgway 1889, Gates 1911, Beecher 1942). The species 
also nests in woodlands, both natural forests and those 
modified by man (Beecher 1942). The thrasher is a 
species of the forest edge and not the forest interior 
(Kendeigh 1944 and others). Holmes (1950), comparing 
bird populations of three forest habitats in Piatt County, 
found no thrashers in flcodplain forest or upland forest, 
but a density of three pairs per 100 acres in forest edge. 
In southern Illinois the large block forests, even the forest 
edges, are relatively little used by thrashers. 
The thrasher is as closely tied to edge situations, for 
example, hedgerows, as any Illinois species. ‘The habitats 
it uses most are those that are the least available (Fig. 22) 
and probably most endangered. Furthermore, the data 
on residential habitat indicate that the thrasher is not 
28 
BROWN THRASHER 
Habitat Use 
70 
60 — USE - NORTH and CENTRAL 
50 AVAILABILITY-NORTH and CENTRAL _7 USE SOUTH 
AVAILABILITY - SOUTH 
40 
HABITAT USE AND AVAILABILITY 
3@ 
w” 
ae 2 
2 3 o - o 
a 6 fe ® = 
20 \z a me] ® 
2) a o mo) 
\ e <a x rs 
6 Ve Oe e « 3 
2 ee 8 5 
10 45 4 we: < 
& \G ee 
S Pm \ = 
Soe E) 
Fig. 22.— Availability of habitats for the brown thrash 
(and, in general, for the mimids) in relation to their use. T 
scale shows the percent of Illinois land (availability) in ea 
kind of habitat, and also the percent of the Illinois bro, 
thrasher population (use) in each habitat. 
very adaptive to man. Early in this century, thrash 
populations were high in human residential areas, b 
now they are relatively low (Graber & Graber 1963). 
The most apparent requirement of the nesting habuil 
is shrubby cover, and thorny and/or dense plants 2 
particularly favored (Table 8). There was marked var 
tion in the species of plants used for nesting between t 
southern and northern areas of Illinois. The list 1s v 
doubtedly incomplete, and we have no data on the re 
tive availability of plant species used by thrashers. Lout 
(1891) felt that most nests in the Peoria area were plac 
in “hedges,” i.e., osage orange. In northeastern I]linc 
Benjamin Gault (field notes, 1885-1915) also record 
most thrasher nests in osage orange. Nearly all nests 
forest edge habitat in Piatt County were in hawtho 
(Allison 1947, Weise 1951). The species also nests on | 
ground, and Musselman (1920) recorded thrashers ne 
ing 2 years in a bird house with the top raised. 
Population figures for the thrasher in major habit 
(Table 9) show marked regional variation, and 0 
variation from year to year. There is evidence that | 
thrasher population in Illinois has declined greatly si 
the turn of the century, especially in the south (Gral 
& Graber 1963). 
The only data available on the size of nesting 
tories of brown thrashers is for forest-edge habitat 
Piatt County (Allison 1947, Hensley 1948, and Re 
1949). Territories averaged 1.6 acres in 1946, 2.8 
1947, and 2.7 in 1948. They were larger when the popt 
tion was lower, and smaller when it was higher (Hens 
1948). 
