The Trelease Woods Research Area is a 60-acre remnant of a roughly 12-square mile prairie grove forest (known as Big Grove) that was present in Champaign County at the time of European settlement. Trelease Woods, along with the 60-acre UIUC owned Brownfield Woods Research Area, located a mile to northwest of Trelease Woods, are the only two high-quality, ecologically functioning woodlands left of the original Big Grove forest tract. The land for the Trelease Prairie Research Area, 18.3-acres of land adjacent to the south side of Trelease Woods, was purchased in 1943 to add another dimension for research. In 1968, a 130-acre farm across the road from Trelease Woods and Trelease Prairie was purchased to again add new dimensions for research and add to the protected area around Trelease Woods. In 2002, the University purchased 10.6 acres of farmland adjacent to the north and northeast sides of Trelease Woods to create a 50-meter deep buffer to protect the Woods edges from current farming practices and future development. Additional lands to add to the Trelease Woods area have long been of interest to the University but current land prices and development plans have probably eliminated most of those options.

Ornithological Summary

Research data at Trelease Woods spans nearly 90 years , making it likely the longest running data set from Illinois and probably one of the longest running in the Midwest. Records from those nine decades also detail physical and biological changes, which could have impacted avian use at the site. For example, the arrival of the Dutch elm disease at Trelease Woods and the loss of red and American elm trees has been documented in detail, as has the change in the distribution and composition of tree species before and after the event in the 1950s. Studies such as Paul Strode's 2004 dissertation tie some of this information together by using climate data, tree leaf out phenology, insect hatch timing by insect and tree species, and warbler migration timing and foraging time spent in different species of trees. Trelease Woods offers an incredibly unique setting for the study of birds in Illinois.

This site was chosen as an IBA becuase it met the criteria for a research site.

Conservation Issues

Adjacent agricultural land to the south and southeast sides is currently owned by a major local developer. Agricultural land to the north and northeast is currently for sale at development prices. Within 10 years the site may have major housing developments on three sides of it.


Trelease Woods Research Area is a University of Illinois Board of Trustees property. The woodland
was purchased in two parcels in 1917 and 1918. Management of the site is the responsibility of the
Committee on Natural Areas, a unit within the Office of the Vice Chancellor for Research, UIUC.


Habitat types consist of mature, mixed-mesophytic forest with a closed canopy. Sugar maple has become the dominant species over the past 60 years with a relatively rich herbal layer. The dominant species are sugar maple, northern red oak, Ohio buckeye, American basswood, hackberry, white ash, bur oak, red elm, chinkapin oak, black walnut, blue ash, black cherry, bitternut hickory, plus about 18 more species.

Land Use

The site is managed on a minimal human impact basis. Access is restricted to U of I and
affiliated agency personnel for research and teaching purposes. A usage permit system is in
place to control access and monitor potential ecological impacts due to usage.
Trelease Woods averages about 25 research projects annually by UIUC faculty and staff and affiliated researchers. Current research activities include (partial list) topics on forest phenology, variety of entomological topics, avian population dynamics, treefalls and gap formation, aquatic insects and zooplankton communities, small mammal studies, total tree census, soil and macrofungi communities, and West Nile virus studies involving mosquitoes and birds (passerine and raptors). The adjoining Phillips Tract Research Area, Trelease Prairie and the Trelease Buffers area add another 25 ? 30 research interests going on around Trelease Woods proper.

Stay abreast of Audubon

Our email newsletter shares the latest programs and initiatives.