About the Cook Arboretum

The Robert O. Cook Arboretum is part of a forest landscape in Rock County, Wisconsin, that runs from the Rock River northwest of Janesville and dissipates as it extends westward. The park is at the center of the image below. It is located at the intersection of Austin Road and County Road A, on the west edge of Janesville. Though the overall forested landscape is large, Cook Arboretum itself is a narrow rectangle of 160 acres. The park supports several breeding populations of birds sensitive to forest area and forest fragmentation. Unfortunately, the Arboretum is the only protected portion of the forest, is small, and is surrounded by land with high market value as residential development.

The Cook Arboretum officially is a Janesville city park, but is maintained and managed by the Janesville Public School District. It is the site of the Janesville Schools Outdoor Laboratory, where children learn about nature, biodiversity, and natural resources. Eighty-five acres of its hilly terrain were designated as a park in 1968, followed by purchases in 1979, 1987, and a recent land swap resulting in its current acreage. In 1986, the arboretum was officially certified as a School Forest. It is one of the largest such properties in Wisconsin. The park has an excellent network of trails, including a portion of the Wisconsin Ice Age Trial.

The forest-tree community in the Cook Arboretum is dominated by Shagbark Hickory, Black Walnut, Basswood, and White Ash. It is most mature in the southern two-thirds of the park. The forest floor contains a variety of native flowering plants and ferns, as well as, unfortunately, invasive species such as European Buckthorn, Garlic Mustard, barberry, and Multiflora Rose. On the northern edge of the park, along Marsh Creek, is a wetland, willow shrubland, and a small area maintained as prairie. The western border of the park is contiguous with mature forest in adjacent property. In contrast, the eastern edge of the park is separated from similar habitat by a wide powerline corridor.

Over 125 species of birds are known from the Cook Arboretum. It is one of the premier birding destinations of south-central Wisconsin. The breeding birds of the arboretum include three species listed as Threatened in Wisconsin (Cerulean Warbler, Acadian Flycatcher, and Hooded Warbler). In addition, three breeding species are listed as Species of Special Concern in Wisconsin: Red-headed Woodpecker, Common Nighthawk, and Yellow-billed Cuckoo. In addition, many additional species with the status of Threatened or Special Conservation Concern in Wisconsin appear sporadically in the park or only during migration. These include Kentucky Warbler, Olive-sided Flycatcher, Swainson's Thrush, Ruby-crowned Kinglet, Black-throated Blue Warbler, Cape May Warbler, Canada Warbler, Connecticut Warbler, Tennessee Warbler, Lark Sparrow, Yellow-breasted Chat, and White-eyed Vireo. This assemblage of species documents the importance of the Cook Arboretum and surrounding area to Rock County's forest species. Documenting the diversity and abundance of all forest-obligate species in the park is a major objective of the Birds of the Cook Arboretum Research Project.

Changes to the park in recent years have included a widening of the powerline corridor along the eastern edge of the park, a new woodland subdivision to the east and accompanying access road, the addition of several interpretive trails and trail markers, and an explosion of invasive plants on the forest floor.

Principle Investigators:

Dr. Tom Klubertanz, Professor of Biology, University of Wisconsin-Whitewater at Rock County, Janesville, Wisconsin.

Quentin Yoerger, Evansville, Wisconsin.