Birding Croton Unit, Shimek State Forest

by Bob Cecil
County Map

The Croton Unit of Shimek State Forest includes some 1,700 acres in three tracts in Lee County. The largest and eastern-most of these, known to Iowa birders and hereafter in this report as “The Croton Unit,” consists of middle-maturity, deciduous forest; small riparian corridors; conifer plantings; and overgrown pasture encompassing about 900 acres. The smaller units generally consist of similar habitats, although in different proportions.

In the 15 years since the first birding guide to the Croton Unit of Shimek State was published (Cecil 1993), many things have changed, but one has not. It remains one of Iowa’s premier birding locations, offering not only bird species that are scarce or absent in the rest of the state, but numerous other southeastern Iowa plant and animal specialties.

Route from West to Croton Unit

When visiting the area from the west, most birders go through the historic Van Buren County seat of Keosauqua. From there, continue south on Highway 1 to Highway 2. Go east to the small town of Farmington in eastern Van Buren County, and take the first road to the right on the north side of the Des Moines River bridge, which follows the river downstream. Continue through the hamlet of Croton, location of the most northerly battle, such as it was, of the Civil War. To go to the main unit, turn right just past Croton at the fork of Belfast Road from Croton Road (Figure 1.1), following the river valley, but perhaps stopping at the intersection to listen for Northern Parula and Yellow-throated Warbler in the sycamores and cottonwoods in the streambed. Continue along the river (watching for Lark Sparrow, Orchard Oriole, and, with luck, a Blue Grosbeak) to the curve at the “town” of Belfast, of which only a single house on the north side of the road remains. A short distance farther is the riparian forest that comprises a portion of the largest unit and a small bridge (Figure 1.2).

Route from North-central Iowa to Croton Unit

The newly completed “Avenue of the Saints” has greatly eased access to and from northern and central Iowa. From Mt. Pleasant or Iowa City, it is south on Highway 218/27. At the exit of Highway 218 to Keokuk, continue on Highway 27/394, approaching the Missouri border, and take the Argyle exit between mile markers four and five. Backtrack a short distance to the little town of Argyle, then go left (west) at the post office and church. Continue straight for about 2.5 miles to where the road begins to wind through a tiny settlement and Iowa’s most famous junkyard (Figure 1.3). Stop here in the spring or early summer and listen and watch carefully for what is sometimes the state’s only Bewick’s Wren(s), which has managed to generate an isolated dot on the range maps of modern field guides. Just beyond is a small parking area (Figure 1.4) and entrance to the first and largest of the three units, the Croton Unit, also known in the local vernacular as “The Thousand Acres.”

Birding Challenges in Croton Unit

Another unchanging aspect of birding the Croton Unit is the challenge it presents to birders. It is undeveloped, having few trails and no picnic areas, restrooms, or campgrounds. Ticks are abundant during the spring and summer, and birders are strongly encouraged to use repellant and wear tall rubber boots which, according to personal experience, can cut tick transmission from forest to birder by 90%. Lone Star and American dog ticks predominate, but the more dangerous deer ticks may occur. Chiggers can be abundant in summer, especially in grass, but can also be discouraged with repellant. Poison ivy is ubiquitous. Birders who are sensitive to it are encouraged to know the leaf and to avoid it. If that’s not enough, groves of stinging nettle carpet areas of the lowland forest––entering such an area wearing shorts is a mistake that is never repeated. All Shimek Forest units are public hunting areas, but this should be of little concern because the best birding is during spring and summer. Wild Turkey hunters may be present well into spring, but are rarely encountered. Finally, birders new to the area are often concerned about getting lost. A good rule of thumb for the largest and most visited tract, the Croton Unit, is to follow a stream downstream. They all ultimately lead back to the parking lot (Figure 1.4) or, if you strike out across country, to the small bridge (Figure 1.2). If exploring the other two tracts (Figures 1.5 and 1.6), it is advisable to have a good sense of direction, a GPS unit, or a compass.

Birding Trails in Croton Unit

Yellow-breasted Chat photo by Mark BrownTo enter the largest and easternmost of the three tracts (the Croton Unit), park in the small parking area (at the bottom of the hill on the north side of the road) (Figure 1.4), which most birders use. Before arriving at the parking area, on the immediate left just beyond the entrance sign, is an area that once was accessible but has become an impenetrable tangle of raspberries and multiflora roses among a stand of introduced white pines. This parking area (Figure 1.4) farther down the hill, however, provides the most well-known and productive access to this unit; in recent years, 10 warbler species have nested or been suspected of nesting here, and most nest annually. In addition, the Croton Unit is noted for vireos, Summer and Scarlet Tanagers, and other woodland species. In spring, when most birders seek the area’s specialties, the path accessed by crossing under the horizontal wooden pole-gate at the parking lot is easily passable because the weeds are not developed or are trampled down by seekers of morel mushrooms, Wild Turkeys, or birds. Just before the trail jogs to the left across the stream (Figure 1.7), the path will cross a usually shallow stream and then quickly angle off to the north again. The parking lot and this short stretch of trail can produce Acadian Flycatcher, Carolina Wren, Blue-winged Warbler, Northern Parula, Yellow-throated and Worm-eating Warblers, Ovenbird, Louisiana Waterthrush, Kentucky Warbler, Yellow-breasted Chat, and both tanagers; more occasionally, Hooded Warbler. From here, the once well-defined trails have become vague and overgrown but lead up the two main ridges to the left (west), reconnecting just before the single trail comes to a large planting of maturing White Pines, now pretty much a birdless monoculture. If you make it this far, you can turn right (north) at the pines and continuing through them and some thickets to the ATV trails described below.

A second option for birding from the parking lot is to simply follow the stream northward from the first stream crossing (Figure 1.7)––rubber boots are highly recommended. For the most part, the walking is relatively easy although sometimes you will need to clamber over fallen trees or bypass log-jammed hairpin turns by cutting through Equisetum or around multiflora rose thickets. This stream or its branches will take you past some excellent habitats for the region’s specialties as well as more expected southern Iowa species.

A third option for birding the Croton Unit is not well known to birders. A small number of clandestine trails are kept open by ATV riders. While their use is prohibited in state parks, and although they have caused localized erosion problems, there seems to be little abuse of the adjacent habitat with the exception of occasional beer cans, and they do create excellent walking trails. They are best accessed from the small bridge (Figure 1.2). The trail is not visible from 150th Avenue, the road on the west side of the Croton Unit. Walk to the Shimek State Forest sign just off the road, and then go on past it and look for the trail that heads rather steeply up the hill. After trudging to the top, you will come to the far end of the pine plantation noted above. This trail will continue for over two miles through excellent habitat ranging from middle maturity forest to old fields harboring Blue-winged Warbler and White-eyed Vireo. Kentucky Warbler, Ovenbird, and Eastern Towhee can be especially common, but watch and listen also for Acadian Flycatcher and Worm-eating Warbler. Hiking north about a mile along this trail, you will come to a fork to the right (Figure 1.8). This goes down to the main stream that can be followed back to the parking lot (Figure 1.4); you can then follow the often birdy Belfast Road back to the small bridge (Figure 1.2). Remaining on the main trail to the north will take you through additional forest and old fields, finally ending at an obscure entrance (Figure 1.9) to the road at the north edge of the tract.

For those birders reluctant to venture too deeply into the forest, a good sampling of the area’s birds can be found along Belfast Road between the parking lot (Figure 1.4) and the small bridge (Figure 1.2), and north of the small bridge where sycamores line the roadside. Watch and listen for White-eyed Vireo, Blue-winged Warbler, Northern Parula, Yellow-breasted Chat, and other good birds. Of special interest to most birders is Worm-eating Warbler. A good location, albeit on private property, is the deep ravine across the road from the parking lot (Figure 1.4).

Other Croton Unit Tracts

The remaining two tracts of the Croton Unit are virtually unvisited by birders. Note that the maps on the Iowa Department of Natural Resources web site are correct regarding their respective configurations, but misleading regarding access and the presence of hiking trails. Each unit has only one access that does not require crossing private property. Trails range from nonexistent at the central tract (Figure 1.5) to pretty good at the western tract (Figure 1.6). Regarding their respective locations, it is probably best to refer to the map (Figure 1), but both are easy to access from the largest unit or from the town of Croton.

Access to the central tract (Figure 1.5) is a short section of frontage along 140th Avenue, which is between Croton and Belfast Roads––a little pull-in offers limited parking. The young woodland is composed of shagbark hickory; black cherry; and shingle, Chinquapin, and other oaks, with an often impenetrable understory of raspberries, multiflora rose, and other thorny shrubs. Trails are inconspicuous and short and, overall, birding the area is difficult. The young forests can yield the more expected woodland species and the large, dense overgrown pastures adjoining 140th Avenue south of the parking area might be checked for White-eyed Vireo, Blue-winged Warbler, and Yellow-breasted Chat.

The western tract (Figure 1.6) is at the dead end of 130th Avenue off Croton Road, about 1.6 miles east of Croton. A trail continues south into the area, soon coming to a fork. The right (west) fork leads to a large wooded area that has recently had a selective timber harvest; this has opened the forest but rendered the area almost impassible due to fallen branches and treetops. The area is still worth checking for woodland species, however. The left (east) fork crosses a small stream, soon splitting again with a fork to the left that goes through one of the area’s dominant habitats––large areas of eastern red cedar thickets. The other fork goes straight and leads through young deciduous woodland and then to a small stand of young white pines. These pines probably offer southeastern Iowa’s most promising location for Prairie Warbler, at least for three or four years until the trees become too mature to appeal to the species. The area with the pines is part of a much larger section of old fields in various stages of regrowth. The cedar thickets should also be checked for Prairie Warblers––Shane Patterson discovered one here in the summer of 2006. Be alert also for White-eyed Vireo and Blue-winged Warbler. Depending on the Iowa Department of Resources’s plans for this tract, it will be interesting to watch this area’s maturation and the changing species to which it appeals.

Other Southeastern Iowa Birding Areas

Southeastern Iowa is rich in birding options. Another spring and summer birding favorite is Lacey-Keosauqua State Park just across the Des Moines River from Keosauqua; see “Birding Lacey Keosauqua State Park” (Sandrock 1986). While the Croton Unit is not especially productive during late fall and winter, nearby Pool 19 of the Mississippi River is one of Iowa’s premier fall and winter birding hotspots; see “Birding Pool 19 in Winter” (Dooley 2004) and updates on Lock and Dam 19.

Thanks to Stephen J. Dinsmore, Mike Dooley, Chris Edwards, and Shane Patterson for their review of this article, and thanks especially to John Cecil for his invaluable assistance during four days of rediscovering this Iowa treasure.

Literature Cited

Cecil, B. 1993. Birding the Croton Unit of Shimek State Forest. Iowa Bird Life 63:10–13.
Dooley, M. C. 2004. Birding Pool 19 in winter. Iowa Bird Life 74:158–171.
Sandrock, J. P. 1986. Birding Lacey-Keosauqua State Park. Iowa Bird Life 56:6–8.

© Iowa Ornithologists' Union 2007