The Abundance of Birds in the Chicago Region 
By RUDYERD BOULTON 
For many years in this country field studies have been under- 
taken in an attempt to determine the abundance of birds in a given 
region. One of the first of such studies was Judd’s “Birds of a Mary- 
land Farm,” designed primarily to express the relation of birds to 
agriculture in a limited area. For many years Bird Lore’s Christmas 
Bird Census has accumulated abundance figures concerning the status 
of bird life in a nation-wide scale in early winter. The early attempts 
to evaluate shifting populations naturally have been improved on in 
recent years and much progress has been made, particularly with 
game birds. Persons interested in ducks and bob-white, while prob- 
ably no more numerous in the aggregate than those whose primary 
interest is in non-game birds, are certainly better organized and have 
more funds for investigation at their disposal. 
The Chicago Ornithological Society has in the past few years 
concentrated much effort on this problem. Field notes of members 
systematically made and reported have been the means by which com- 
parative figures on the abundance of certain species have been pub- 
lished in the Chicago report of Bird Lore’s Season Department. The 
Purple Martin Census taken two years ago yielded results of value 
and Beecher’s studies on the abundance of birds in the Fox Lake Dis- 
trict are a model of their kind. 
Last year, in order to add further data to our growing knowledge 
of this important field, a questionnaire in the form of a contest was 
prepared. Contributors to this listed (by estimation from their ex- 
perience with birds in the Chicago Region) species in the order of 
their abundance for five distinct ecological habitats. The results were 
treated statistically so that the average of all lists was regarded as 
normal. The deviation of each individual from the normal was his 
individual score. The lower the score, the closer he had come to the 
normal, or average. 
Naturally, such a method gives but one result. That is, what 
species the most experienced and competent bird students in the Chi- 
cago Region collectively regard as most abundant. This may or may 
not be close to the actual truth, depending on the competence with which 
the estimations were made and on the uniformity of the estimator’s 
conception of the different habitats. However, such straws as this 
show how the wind blows and ean serve as useful yardsticks for eval- 
uating results obtained by other methods. 
The results of the questionnaire were as follows, the most com- 
mon bird being regarded as No. 1, the next No. 2, and so on: 
By 
