Washington County:
https://ebird.org/hotspot/L1170716?yr=all&m=&rank=mrec
Dodge County: https://ebird.org/hotspot/L10999087?yr=all&m=&rank=mrec
Habitat: Theresa Marsh State Wildlife Area is a seven mile long irregularly shaped 5,900 acresof state-owned lands and 300 acres of publicly accessible easements spread out over two counties. The East Branch of the Rock River flows north through the core of the wildlife area, 80% of which consists of wetlands (primarily emergent cattail marsh) and bottomland hardwood forest bordering the river water channels. The other 20% consists of restored native grassland, non-native upland grassland, successional oldfields, and upland hardwood forest interspersed with agricultural cropland. Due to private property restrictions and given the physical restrictions posed by dense stands of cattails, birding primarily takes place by car along the roadsides and overlooks. Other birding options consist of walking the dikes or by kayaking or canoeing the channels when the water level permits. These latter two options allow for greater access to the interior of Theresa Marsh where chances for observing more uncommon species are better.
Best Birds: Theresa Marsh has historically been referred to as a mini-version of Horicon Marsh due to the Rock River connection and the sharing of many of the signature species associated with Horicon. In the past 15 years, however, many signature breeding bird species in Theresa Marsh become uncommon or scarce when water levels are low, e.g., Sora, Virginia Rail, Black Tern, Common Gallinule, American Coot, Pied-billed Grebe, Least Bittern, and Yellow-headed Blackbird. Abundantly present in the cattail marsh are Swamp Sparrow and Marsh Wren. Sedge Wren, Willow Flycatcher, Horned Lark, and Bobolink can be found in dry or wet grasslands depending on the species. Spotted Sandpiper (uncommon), Great Blue Heron, Green Heron, Great Egret, Sandhill Crane, Double-crested Cormorant, and usually American White Pelican are regularly observed in the Marsh. Migratory shorebirds can be found in season whenever and wherever mudflats occur along the margins of emergent vegetation. Theresa Marsh is especially well known for hosting an abundance of diverse waterfowl and marsh birds with rarities occasionally present during migration. Look for Bald Eagle at any time of year and Northern Harrier, Rough-legged Hawk, and Short-eared Owl from late fall through winter. Woodland species include both cuckoos, Barred and Great-horned Owls, Blue-grey Gnatcatcher, three vireo species, Wood Thrush, Veery, and Scarlet Tanager.
Directions: The Theresa Marsh State Wildlife Area is located near the towns of Theresa and Allenton. Approximately half of the Theresa Marsh Wildlife Area is in northwestern Washington County and half in northeastern Dodge County. From Hwy 41, exit at State Highway 28 and proceed west a quarter of a mile where the highway intersects the Theresa Marsh. Birding the Dodge County portion of Theresa Marsh (43.53702,-88.41244) primarily occurs from both sides of Hwy 28 and/or by walking north along an open water channel on the "Legacy Marsh" dike. The traffic on Hwy 28 can be heavy! Be sure to be well off the road when parking and be observant when crossing the road. A second Dodge County birding site can be readily accessed by proceeding west .2 miles from the Legacy Marsh dike. After crossing the bridge over Lomira Creek, look for a gravel road marked by a posted sign specifying an address of W547 State Hwy 28, turn south on this road and drive .6 miles to a parking lot from which you can walk on a dike leading to the dam of the East Branch of the Rock River. This area can also be reached by driving .4 miles further west on State Highway 28, turning south on North Pole Road and then following the signage directing you to a boat launch at 9054 North Pole Road (43.52089, -88.39653) where a kayak or canoe can be launched near the dam.
The Washington County portion of Theresa Marsh (43.30520,-88.23479) can be accessed by turning south on Mohawk Road, the first road to the left after you have exited the Hwy 41 interchange. Travel south on Mohawk Road for 2.2 miles and turn right on a gravel road marked by State Wildlife Area signage. This road leads to an overlook of the marsh and an access to a Washington County boat launch area. Additional Washington County road access sites can be reached by continuing south on Mohawk Road (which transitions into County Hwy H going east.) Cross over Hwy 41, after which you should turn right on Midland Drive. Proceed three miles south and then turn right (west) on to County Hwy D. About a half mile after crossing Hwy 41 you will again be in the Theresa Marsh. There are several parking lots within a two mile long stretch of Hwy D and West Bend Road from which you can access the marsh, lowland woods, and potentially productive mudflats which can be well populated with shorebirds in season depending on water levels. The Theresa Marsh access off of West Bend Road is a gravel road through farmland which takes you about 1/4 mile east to a parking lot adjacent to a busy rail line which needs to be crossed on foot to gain entry to this southerly portion of the marsh. Be extra careful when crossing the RR tracks as trains come fast through here and often stop for a half-hour or more on a side track to let other trains pass in the other direction.
Site Address & Additional Information:
Dodge County: W 547 State Hwy 28, Theresa, WI
Washington County: 8905 Mohawk Road, Allenton, WI
Map: https://ebird.org/hotspots?hs=L1170716&yr=all&m=
John O’Donnell
