A Comparative Study of Bird Populations in Illinois, 1906-1909 and 1956-1958

Abstract

On August 29, 1906, Alfred O. Gross and Howard A. Ray, working for the Illinois State Laboratory of Natural History (a parent organization of the Illinois Natural History Survey) under the direction of Stephen A. Forbes, began a series of statewide, cross-country censuses of birds in Illinois. These censuses were continued at intervals until September, 1909, and the data collected were published in a series of papers (Forbes 1907, 1908, 1913; Forbes & Gross 1921, 1922, 1923) that provided a quantitative record of the Illinois bird populations of that period and a potential basis for evaluating the adjustment of bird populations to a changing environment. In 1956—1958, we conducted statewide censuses similar to those of the 1906-1909 survey. In this paper we present an analysis of our field data and compare these data with those from the first survey.