Illinois Natural History Survey - University of Illinois

The Illinois Spring Bird Count was initiated by Vernon Kleen of the Illinois Department of Natural Resources in 1975. This bird count consists of volunteers conducting bird censuses on the Saturday that falls between May 4th and May 10th. The censuses are conducted in all 102 counties in Illinois, however in any given year a few counties are not censused. The participants record all birds seen or heard, along with the number of hours they spend "owling" (pre-dawn hours), the number of hours spent looking for birds during the day, the number of miles driven in a car, and the number of miles walked.

The Illinois Natural History Survey is providing this website to allow both the thousands of volunteers, and other interested parties with the ability to view the 30+ years of data. When searching through the data please let us know of any errors, as there will probably be some. The data generated from the Spring Bird Count can be used to estimate changes in populations of species throughout the state. Below is a graph of the number of crows detected per party hour throughout Illinois and in Cook County (i.e. Chicago). The graph shows a large decline in their population after the arrival of West Nile virus in Illinois. The next series of graphs shows the changes in selected species. Henslow's Sparrows, Double-crested Cormorants, and Wild Turkeys have shown large increases, Loggerheaded Shrikes and Upland Sandpipers show large declines, and Swainson's Thrushes exhibit very large fluctuations from year to year, which are probably correlated with regional weather patterns affecting migration.

It also should be noted that because of the nature of the data, declines or increases in certain species population trends may not accurately reflect true changes in populations and statistical tests should be preformed to determine if observed trends differ from a stable (no change) trend. Please contact Michael Ward ( for questions about the data or errors detected in the data.

Click to view any of the following graphs (each will open in a new window):

Illinois Natural History Survey

1816 South Oak Street, MC 652
Champaign, IL 61820

Terms of use. Email the Web Administrator with questions or comments.

© 2012 University of Illinois Board of Trustees. All rights reserved.
For permissions information, contact the Illinois Natural History Survey.

Staff Intranet