ILLINOIS BIRDS: Mimidae 
) T MAY SEEM SURPRISING to many people that 
inci is still very poorly explored ornithologically, 
specially in any quantitative sense. In terms of real 
inderstanding of what bird populations are, or of what 
hey do, the study of Illinois birds is little advanced from 
vhat it was a century ago. 
The accelerating changes in the land, which began 
ven before young Robert Ridgway started his studies of 
llinois birds in the 1860’s, have brought us to a poten- 
ally precarious ecological state. As a species, man is 
rowding other living things out of existence without 
nowing whether or to what extent he is dependent upon 
rem. Now, increasingly, we need knowledge that there 
little time to acquire. We need more than just a list 
f the state’s various natural resources. We need the 
nswers to a great many questions — questions on the 
istribution of populations, their reproductive potential 
nd food habits, their energy and habitat requirements, 
leir migration routes, and ultimately their ecological 
‘lationship to every other part of the environment. The 
aswers will come, if at all, only through the efforts of 
large number of dedicated students, bird students of all 
yes, throughout the state. 
The series of papers on Illinois birds, of which this is 
e first, hopefully will provide a foundation for the work 
those students. The papers will attempt to summarize 
hat has been recorded about Illinois birds. The series, 
hen complete, will include information on all of the 
ecies known to occur in Illinois, past and present. The 
pers are based primarily on (1) a compilation of data 
om published literature, (2) the authors’ field notes and 
ose of Benjamin T. Gault, and (3) specimens in the 
entific collections of the Natural History Survey and the 
uicago Museum of Natural History. 
Unless otherwise stated, our discussions of the various 
ecies of birds refer only to the species in Illinois. To 
ep the work within some reasonable bounds, we have 
entially ignored literature and data other than that for 
inois. Even a complete summary of the Illinois litera- 
‘€ is not entirely practicable. On just the family Mimi- 
e, for example, we have about 1,500 references. To 
nmarize information from so many sources we adopted 
olicy of emphasizing those data which could be readily 
antified, and have put as much of the information as 
could into figures and graphs. The graphs on the an- 
al cycle are based on the literature for the extremes of 
sration and nesting dates, and on our own field work, 
ecially daily counts made mainly by R. R. Graber in 
special study areas (Fig. 1) during 1967, 1968, 1969, 
This paper, in the biological notes series, is published in part with 
ate funds. _Dr. Richard R. Graber is a Wildlife Specialist in the 
Richard R. Graber, Jean W. Graber, and Ethelyn L. Kirk 
and 1970. In each area counts were made along a care- 
fully selected route varying in length from 80 to 105 
miles in different regions. The routes were chosen to 
provide the maximum counts for the greatest number of 
species. Depending primarily on the numbers of birds 
seen, a route usually required 8-12 hours to cover. Each 
day, 4-6 hours were spent on woody habitats, 1-2 hours 
on open fields, 1 on aquatic habitats, and the rest on 
roadside habitats (driving). In making migration cen- 
suses, it was not our goal to obtain the maximum count 
possible for a particular species, but to get a representa- 
tive count for each species in relation to all the rest. 
We were interested in daily and seasonal variation in 
the numbers of all species. 
Obviously our 1-year studies in different regions of 
the state cannot truly represent either the whole state or 
any sizable part of it. These studies were intended only 
as comparative reference points for other workers. It is 
our hope that, over the years, other students will make 
quantitative studies in every county in the state. Par- 
ticularly needed are data on the variations of populations 
from year to year in the same area, following the fine 
example of Dr. S. C. Kendeigh and his students in east- 
central Illinois. 
The figures showing seasonal variation in egg laying 
are based on our repeated searches of the same areas 
throughout the breeding season. 
We have prepared Illinois distribution maps for all of 
the native species, even those which we suspect nest in 
every township of Illinois. We adopted this policy 
especially to encourage students to fill in the gaps. It is 
a mistake to make assumptions about any phase of the 
biology of a population. Distribution patterns are not 
static, especially in this time of accelerating habitat de- 
struction, and as yet we do not truly know the distribution 
of any species in Illinois. Hopefully, students throughout 
the state will be encouraged to undertake county-wide or 
township studies to work out both the geographic and 
ecological distribution of each species in great detail. 
Only from the vantage point which such detailed studies 
provide can we see how populations and distributions 
change. The maps are based on our own field work, and 
on the literature when the published record included 
precise details on date and locality. Our references to 
regions of the state — north, central and south — follow 
Smith & Parmalee (1955). 
In drawing up the North American distribution maps, 
we have tried to be conservative, drawing limits at points 
where the species was of fairly regular occurrence. There 
are altogether too few recent faunistic papers from which 
to work out the broad distribution of each species, and for 
some regions our judgments as to the patterns of distribu- 
tion were based on old literature. The maps are based 
The Library of the 
OCT 2 71970 
University of illinois 
Bt iiphana.Pkameni.. 
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