central Illinois, where the winter sparrow hawk popu- 
lation has always been relatively low. 
The record for the red-tailed hawk is fairly uniform 
except for a high density peak in central Illinois in the 
early 1930’s, figs. 13 and 14. Again the pattern of peaks 
is higher in early years than in later years. 
The record for the marsh hawk shows no consistent 
declining trend in central and southern Illinois, figs. 
16 and 17. However, for later years there is a sugges- 
tion of decline in central Illinois and of increase in the 
southern region. 
Like that for the marsh hawk, the census record for 
the red-shouldered hawk shows no consistent declining 
trend in the state, figs. 19 and 20. In the record for 
central Illinois, high density peaks occured in early 
years (before 1930); in southern Illinois, red-shouldered 
hawks have increased in recent years. 
The rough-legged hawk was seen in central [Illinois 
with increasing frequency from 1900 to about 1920, after 
which the frequency tended to fall until about 1945- 
1950, fig. 22. The density of rough-legged hawk popu- 
lations tended to follow the pattern of frequency; the 
population has decreased decidedly from 1900 to recent 
years, fig. 23. 
Both early and late in the period, numbers of rough- 
legged hawks fell to zero in some years; it is the peaks 
that best show the decline. A 3- to 5-year cycle has 
been suggested by Wallace (1955:218) for both old and 
new world rough-legged hawks. The relatively complete 
record for central Illinois shows a fairly consistent 4- 
year cycle. In the 1930’s rough-legged hawk numbers 
fell so low that annual fluctuations did not show. This 
level continued until the mid-1940’s, when the numbers 
increased somewhat. 
Though the record for the barred owl is very incom- 
plete and has the largest gaps in the early years, the 
population trend shows the familiar pattern, the popu- 
lation being higher in early years and lower in later 
years. Records for other species of owls are even less 
complete, and their population trends were not evaluated. 
Although winter populations of raptors as a group 
have generally decreased, the decrease is not reflected 
in each species of raptor. 
The decrease in hawk populations has been attrib- 
uted by Nice (1945:10) to both shooting of hawks and 
destruction of habitat. The effect of habitat destruction 
is difficult to evaluate because there are not sufficient 
statistical data on the extent of habitat change in IIli- 
nois. Also, the total effect of a change in habitat on 
any one species of raptor is virtually unknown. A given 
change may be detrimental to one species and beneficial 
to another. Before we can evaluate the effect of habi- 
tat change, we need more precise information both on 
the ecology of all species of raptors and on the kind 
and amount of habitat change. 
The effect of shooting would be most apparent among 
the less wary species and those species that are most 
frequently encountered. The rough-legged hawk, a rela- 
tively lethargic species, has suffered the most severe 
decrease in numbers of any of the species here con- 
sidered. The red-tailed hawk and the sparrow hawk also 
have declined in numbers, and they are the species 
which have been reported with greatest frequency. 
Returns from raptors banded in other states help to 
point out man’s role in the population decline. Cooke 
(1941:151) said, “‘It is probably a safe estimate that 
nine-tenths of the recoveries {banded birds of prey | 
represent birds killed.’’ Lincoln (1936) presented evi- 
dence that 75 per cent of the band recoveries for eastern 
species of raptors represented birds killed by man. 
Even for a species as rigidly protected as the bald 
eagle the proportion of banded birds killed by man is 
high—60 per cent as figured from data published by 
Broley (1947:7).These figures are difficult to evaluate. 
They are biased on one hand because the most likely 
source of band returns are birds taken by shooting or 
trapping and on the other because many bands probably 
go unreported. 
Since 1900 the laws concerning protection of hawks 
and owls in Illinois have changed greatly. Until 1919 
there was no explicit protection for any species of hawk. 
In 1919 most raptors gained legal protection, except 
the accipiters, duck hawk, pigeon hawk, and great horn- 
ed owl. These were left unprotected until 1959, when 
the Illinois legislature passed a law protecting all spe- 
cies of hawks and owls. A few other states (Connecti- 
cut, Indiana, and Michigan, for example) give complete 
protection to hawks and owls, but most states continue 
to permit thekilling of certain species of birds of prey— 
usually the accipiters and the great horned owl. Such 
limited protective laws for raptors are only partially 
effective; they ultimately depend upon the shooter’s 
ability to identify the different species of raptors, and 
field identification of birds in this group is difficult 
for the untrained observer. 
Christmas census data from Illinois show that ob- 
servers encountered the protected species seven times 
as often as the species that were unprotected; conse- 
quently, it is the former group that is likely to suffer 
at the hands of the shooter as long as any species goes 
unprotected. During the period 1919-1959, when Illinois 
had protective regulations covering only some species 
of hawks and owls, the protected species declined in 
numbers in spite of legal protection. 
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