Book Review by Gail Goldberger
A CENTURY OF CHANGE
Commissioned by the Illinois Natural History Survey, data compiled from bird counts at three fifty-year intervals, and repeated at the same locations, make up the oldest standardized survey in the nation.
A Century of Counts
From 1906 to 1909, in a first study of its kind, Alfred Gross, a University of Illinois graduate, along with his assistant Howard Ray, crisscrossed Illinois counting birds for the Illinois Natural History Survey (INHS). For three years, in all seasons, they traveled by whatever means possible—foot, train, horseback, steamboat—conducting transects across the southern, central and northern parts of the state, border to border. They compiled a species count of birds using a specific, repeatable method, forming a baseline for research and comparison in years to come.
Red-headed Woodpecker. Photo by Jay Paredes.
Courtesy of allaboutbirds.org
Fifty years later, during the summers and winters of 1956 to 1958, husband and wife ornithologist team Richard and Jean Graber repeated these surveys. From 2006 to 2008, one-hundred years after the initial surveys, six naturalists retained by the INHS again conducted these surveys, adding point counts to their methodology. ILLINOIS BIRDS: A CENTURY OF CHANGE is a compilation of their research and a look back over time at land use changes and changes in bird populations.
This is a benchmark book because of the time period and geography covered. Though the research does not take into account all bird species and all locations, enough major bird groups were encountered to provide conclusions deemed reliable, along with implications and predictions for the future.
Research Methodology and Results
Evaluating changes in bird populations is challenging and complex. INHS chose to look at occupancy rates, measured as increasing, decreasing, or stable. Eighty percent of the 133 species detected were encountered often enough to estimate how their populations changed over time, and 73 sites in the state were used as a basis for comparison.
In these counts, the number of species observed during transect surveys rose from 93 in the 1900s to 128 in the 1950s to 133 in the 2000s. The most recent count included 26 species that weren’t found at all in the first, and only one that had disappeared, the Bachman’s sparrow. However, there were other species not found in the 2000s surveys that were found in the 1906- 09 surveys and are still seen in the state today, like the prairie chicken.
Though land use has changed substantially, and the human population has increased, one-third of the bird species surveyed had stable occupancy rates, and slightly more (40%) had increases rather than decreases. The northern region had the most stability (50%), and the central region had the greatest increases (46%). All three regions had roughly the same proportion of declining species, despite differences in landscape.
Bobolinks. Photo by Greg Massey. Courtesy of allaboutbirds.org.
Population and Land Use Changes
In the last century, Illinois’ population increased from five to 13 million. Urban and developed areas, with 85% of the population, are the fastest growing land use category.
There are 4.5 million fewer acres of pastures, hayfields and grasslands. Prairies, savannas, and shrublands have also declined. Acreage of corn and soybean row crops increased, with greater yields coming from the same acreages. Forests have gained some ground, mostly in southern Illinois, due to population loss and abandoned marginal croplands.
Factors Affecting Changes in Bird Counts
Upland Sandpiper. Photo by Michael J. Andersen.
Courtesy of allaboutbirds.org.
As land use changes, so do bird species. Shrubland and savanna birds like red-headed woodpeckers, brown thrashers, field sparrows and bobwhites have been in decline for a century. In the last fifty years, grasslands with meadowlarks, dickcissels, and bobolinks have given way to row crop fields with horned larks and blackbirds. Grassland ground-nesters like quail and pheasant are also among the “losers.”
Habitat quality and land management also affect birds. Habitat preservation and restoration are very beneficial. Illinois has preserved over 1.5 million acres of bird habitat (USGS 2010). The use of chemicals and pesticides less persistent than DDT, and improved water quality, has also helped sustain some species.
Notably however, are other factors influencing change. Among these are:
- The introduction of species (exotics, invasives) from other areas;
- Range expansions;
- Climate change; and
- Adaptation (the “wildcard ”)
Some species are better at adaptation than others, and these are going to “win ” out. Success favors the generalists, as opposed to the specialists. The implications of this are that the more we can do to preserve or create conditions preferred by the specialists, the more likely we are to avoid their extirpation.