The Illinois Natural History Survey is provides the ability to view, query, graph, and download the data generated by the Spring Bird Count. When searching through the data please let us know of any errors, as there could possibly 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 the West Nile virus in Illinois.
The next series of graphs show 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 is 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 performed to determine if observed trends differ from a stable (no change) trend. Please contact Tara Beveroth (beveroth@illinois.edu) or Michael Ward (mpward@illinois.edu) for questions about the data or errors detected in the data.