100 Years of Changing Bird Populations in Illinois

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100 Years of Changing Bird Populations in Illinois

• Jeffery W. Walk, The Nature Conservancy, Michael
  P. Ward and Steven D. Bailey, Illinois Natural
  History Survey, and Jeffrey D. Brawn, University
  of Illinois at Urbana-Champaign

Results Changes in land cover/land use have bee
n dramatic over the past century. Corn has
consistently been the dominant land use, with
soybeans becoming important after about 1930.
Forested areas have expanded steadily since 1920.
Small grains, hay, and pasture (collectively)
, have been reduced from 50 of the states ar
ea in 1900, to about 7 in 2000. Bird commu
nities within some habitats have changed
profoundly, particularly grasslands.
Meadowlarks, dickcissels, bobolinks, and
grasshopper sparrows (grasslanders, below,
left) were 40 of the birds found in grasslands
in the 1900s, 35 in the 1950s, and 13 at
present. In contrast, forest bird communities
have been relatively stable (below, right).
Other Interesting Notes The Rich Kee
p Getting Richer, the Poor Keep Getting Poorer
Just 5 abundant generalists red-winged
blackbird, European starling, common grackle,
American robin, house sparrow made up 55 of all
birds recorded. More than 40 species, present in
small numbers the 1900s and 1950s, went
undetected. Southern Birds Expand Northward Red
-bellied woodpeckers, Carolina wrens, northern
cardinals, and tufted titmice occur farther north
at great abundance than 100 years ago. Are land
use, practices such as bird-feeding, or climate
change behind these shifts? New to the Survey
Absent in the 1900s or 1950s, but again nesting
in Illinois, are sandhill cranes, bald eagles,
Canada geese, and wild turkeys. House finches and
Eurasian collared-doves are recently-introduced
birds, now found statewide.
Study Sites The locations surveyed 100 years ag
o are vaguely known. Gross and Ray typically
took trains to starting points, and walked for
several days to another railroad, counting and
collecting birds along the way, sleeping in
hotels, barns or homes when they were invited.
In the 1950s, the Grabers surveyed from 96 lo
cations (described with varying
precision), split evenly among northern,
central, and southern Illinois. We
originated our surveys from each of
these 96 areas, sampling all land cover
types within about 3 miles of that point.
The hand-held computers used for entering bird d
ata in real time during transects and
point-counts include a GPS receiver that logged
our location every 5 seconds.
Land Cover of Illinois, 1900-2000
Replicating Historic Surveys From 1906-1909, Al
fred Gross Harold Ray (right), directed by S
tephen Forbes, sampled birds in various habitats
throughout Illinois. These surveys were the
first quantitative descriptions of
the bird communities within various land cover t
ypes. Richard and Jean Graber used the same m
ethods to measure avian diversity and abundance
in habitat types in northern, central and
southern Illinois. Their work from 1956-1958
examined changes over the preceding 50 years, and
estimated statewide populations for several
common species. We repeated these surveys from
2006-2008, and are comparing distribution,
abundance and richness of bird species to results
from 50 and 100 years ago.
Sampling Effort, By the Numbers
20,164 individual birds Of 132 species Recorde
d on 963 transects Totaling 54,743 meters Repres
enting 23 habitat types.
Birds Encountered in Grasslands
Birds Encountered in Forests
Methods Forbes was an aquatic entomologist, and
apparently regarded sampling birds in the fiel
d similarly to sampling bugs in a stream.
He described the method he devised as
a gigantic sweep-net, 150 feet wide and 300
feet deep, so drawn across the country day by day
as to capture every bird which comes in its way
Two observers walk in parallel lines, often for
miles, recording birds seen between and up to
300 feet in front of them. Because more birds
are heard, but not seen, as vegetation height and
density increase, the Grabers dryly noted
the strip census is not well adapted to
woodland areas. To supplement the unusual trans
ect method, and to account for birds heard but
not seen, we conducted paired-observer, 5-minute
point-counts with distance estimation. These
results will be more comparable with other
contemporary surveys, such as the North American
Breeding Bird Survey.
Winners Birds of suburbs and forest edges, water
birds (herons, geese, gulls) and Losers Grassl
and, shrubland, savanna, and marsh birds
Funding for this study is from the State Wildlife
Grants Program, project T-16-P-1. Special thanks
to hundreds of landowners!