Birding Cone Marsh

by Carol Thompson
County Map

Cone Marsh State Wildlife Management Unit is located in NW Louisa County on a lowland between the Iowa and Cedar Rivers. This area, called the Lake Calvin Basin, was thought to be a glacial lake formed by the advance of Illinoian (300,000 years before present) ice into eastern Iowa which caused blockage of these SE flowing rivers. More recent studies have shown that the landscape is actually composed of younger Wisconsinan and Holocene (less than 30,000 years before present) deposits.

Alluvial features such as broad floodplains, terraces, and dunes are the dominant landform components, creating large areas of flat terrain. The marsh, located in the Iowa River floodplain, was formed from a series of abandoned meander loops (oxbow lakes).

Cone Marsh MapThe 701 -acre marsh was acquired by the State in 1960 with smaller purchases in 1968 and 1969. Much of the actual marshland is in private ownership belonging to two private hunting clubs. The boundary of the state land is indicated on Figure 1. There are no facilities at the marsh. Part of the area is diked to provide for artificial water control. The marsh can be especially productive for migrating waterfowl and shorebirds and, in some years, marsh birds (rails, herons, etc.). The habitat fluctuates with changing water level and ranges from numerous pools of open water to vegetation-covered mudflats. The pools at the north end are the deepest and tend to be permanent. The pools at the south end show more fluctuation and can provide excellent mudflats in late summer. Other habitats include old fields with a lot of brush, dense willow stands, and a small area of mature timber (mostly burr oak). Atlas efforts at the marsh and surrounding area yielded 76 species, 70 percent of which were in the probable and confirmed category.

To reach Cone Marsh, drive south out of Lone Tree on X-14 (this road becomes G-28 at the Louisa County line) for approximately six miles. At this point the paved road will turn east and there will be a gravel road to the south. This is the northwest comer of the map in Figure 1. If you are birding in the early morning it is usually best to continue east on the paved road for another 11/4 miles and then turn south on a gravel road. This allows a tour of the marsh in a clockwise direction with the sun behind you for the first few stops. Drive south along the road until you can overlook the marsh (#1 on Figure 1) which is all private property on this side. The old railroad car at the nearby farm has given this spot the colloquial name "caboose." Scoping of the marsh here can be very productive. Many ducks, geese (occasional White-fronted), shorebirds, and wading birds can be seen. There is a little drainageway leading down to the marsh where water pipits have been seen.

Proceed south to the intersection and turn west. During migration, longspurs (Smith's, Lapland) are sometimes found 'in the cultivated fields to the south (#2). Many of the other fields in the area should also be checked. Proceed west and you will drive down off the terrace and onto the floodplain. Park along the road (#3) and scan for waterfowl and shorebirds. This is usually a good area for large flocks of snipe (especially to the south) and can yield many other species when conditions are right (when the vegetation is high it can be extremely frustrating). Continue west to a small parking lot on the north side of the road (#4). There is a small dike over the southern part of Long Lake. A path parallels the lake along the east side and connects with the another dike to the north (#5). The path allows some looks at the marsh (if the water level is not too high and you can get through the bushes) and is often good for field/shrub birds. There is a low wet area just to the southeast of the parking lot where occasional rails and woodcock can be found. On the south side of the road at #4 is another oxbow which can be viewed from various points along the road. This is also a very good area for waterfowl and good views can be obtained. This area is private property, so do not trespass

Proceed west on the gravel road to a T-intersection and turn north. Approximately 1/2 mile to the north there is a gravel road to the east which leads to the main dike. Park at the parking lot on the top of the hill. The fields near the parking lot can be good for birds including Fox, Lincoln's, LeConte's, and Lark Sparrows, Brewer's and Rusty blackbirds, an occasional Woodcock, and even rarer Yellow Rails. A walk across the dike is usually worth the time, especially in spring and early summer (by late summer the weeds are taller than most people). In any season watch out for holes in the dike from burrowing animals. Waterfowl are usually abundant, Canada Geese nest at the north end of Long Lake, Black-crowned Night Herons can sometimes be seen, both bittems as well as Sora, Virginia, and King rails can be seen or heard, and other marsh birds such as Sedge Wrens, Marsh Wrens, Swamp Sparrow, and Common Yellowthroat can be common. There have been several Black Rail sightings in this area as well. Yellow-headed Blackbirds returned to nest in the marsh in 1989. The other side of the dike opens into some old fields where Bell's Vireo and Willow Flycatchers have nested. Sharp-tailed and LeConte's Sparrows can sometimes be flushed from the grass. The trees along the edge can be good for vireos and warblers during migration.

Return to the parking lot and the north-south gravel road and turn north. Go about 1/4 mile and turn onto a small gravel road (#6) that leads to a boat launch and parking area. The woods around the area are good during migration especially for woodpeckers, passerines, and occasional owls. To the south of the parking area, a trail leads to the south. Just inside the woods there is a seep area where Winter Wrens are often found. The trail leads to a dike along the edge of a small pool. Wood Ducks are often seen here and owls sometimes perch on the trees. The trail actually leads to the main dike (#5), but is fast reaching the point of being impassable. The woods west of the pool are fairly open and easy to walk through although not highly productive. The edge of the woods to the west is often a good spot for displaying woodcock. Just north of #6 is an east-west gravel road. This can be a very productive side trip from the main loop and can produce ducks, shorebirds, and birds such as shrikes, bluebirds, and sparrows.

As with any marsh area subject to the vagaries of weather patterns, the birding at Cone Marsh can be very good or very poor. During extended dry weather such as occurred in 1988-89 the marsh may have little or no water present. Some of the species mentioned as occurring at the stops are rare or uncommon and should not be expected. The area is a state wildlife area and hunting is permitted so fall birding is often not good. Overall, a trip to Cone Marsh can be an enjoyable birding experience.

Thanks are due to the members of the Iowa City Bird Club who provided many welcome comments and additions to this article including Bud Gode, Rick Hollis, Cal and Bernie Knight, and Jim Sandrock.

Basic waterfowl viewing tour of Cone Marsh

by Mike Dooley

Cone Marsh Waterfowl Viewing courtesy of Mike DooleyAt stops nos. 1 and 2, viewing is from roadside. No. 3 is a parking area from where you look north. No. 4 marks where you walk east from a parking area out onto the dike. No. 5 is a parking area from where you look generally east. At no. 6, viewing is from the roadside. Click on the map for a printable copy.

© Iowa Ornithologists' Union 1991