Birds of the St. Croix River Valley: Minnesota and Wisconsin
Deciduous Forest Communities
Northern Hardwood Forest
This floristic community extends throughout the Northern Highland and much of the Central Plain north of St. Croix Falls (Polk and Chisago counties). Characterized by a mixture of coniferous and deciduous tree types, the Northern Hardwood Forest occurs on a wide range of topographic sites and on many soil types. Mesic sites support white birch, sugar maple, hemlock, basswood, and red oak. Important coniferous species of this habitat are red pine, white pine, and to a limited extent jack pine. Depending on the extent of early successional stages this is generally a climax or near-climax community.
Prevalent within the shrub layer and among ground layer species are beaked hazel, bracken fern, wood anemone, wild sarsaparilla, big-leaf aster, blue bead lily, northern bedstraw, ground pine, Canada mayflower, bishop's cap, Solomon's seal, twisted stalk, starflower, downy yellow violet, rice grass, and Pennsylvania sedge.
Characteristic breeding birds include broad-winged Hawk*, ruffed grouse*, great horned owl, barred owl, black-billed cuckoo*, common flicker, yellow-bellied sapsucker*, hairy woodpecker*, downy woodpecker, great crested flycatcher, least flycatcher*, eastern wood pewee*, blue jay, northern raven, black-capped chickadee, white-breasted nuthatch, American robin, wood thrush, veery*, solitary vireo, red-eyed vireo*, black-and-white warbler, chestnut-sided warbler, ovenbird*, American redstart, northern oriole, scarlet tanager, rose-breasted grosbeak*, and white-throated sparrow.
Lowland Deciduous Forest
This rich deciduous community occurs primarily along the floodplains of larger streams and rivers adjacent to the St. Croix in the Western Upland and Central Plain. The abundant soil moisture from river flooding and high water table is a principal microclimatic feature of this community. Because of its southern plant affinity, Lowland Deciduous Forest attracts some typically southern breeding bird species that occur in no other habitat type. Major tree species characteristic of this community are silver maple, American elm, green ash, red oak, basswood, and cottonwood.
Prevalent species in the shrub layer are black willow, box-elder, and gray dogwood. Depending on the amount of disturbance by grazing cattle, tartarian honeysuckle and prickly ash approach dominance in the shrub layer. Important among ground layer species are jack-in-the-pulpit, toothwort, Virginia waterleaf, wood nettle, poison ivy, germander, hedge nettle, jewelweed, and skunk cabbage.
Characteristic breeding bird species of the Lowland Deciduous Forest include great blue heron*, wood duck*, red-shouldered hawk*, yellow-billed cuckoo, screech owl*, barred owl*, pileated woodpecker*, red-bellied woodpecker*, downy woodpecker, eastern wood pewee, tufted titmouse*, white-breasted nuthatch*, blue-gray gnatcatcher*, yellow-throated vireo*, warbling vireo*, blue-winged warbler*, yellow warbler, cerulean warbler*, Louisiana waterthrush*, northern oriole*, scarlet tanager*, and rose-breasted grosbeak.
Southern Deciduous Forest
This habitat type includes a closed-canopy upland community that is generally restricted to the region south of the Tension Zone in the Western Upland and Central Plain. Southern Deciduous Forest occurs almost exclusively on dry, well-drained upland sites. Before settlement of this region, Southern Deciduous Forest existed as part of an oak forest intermixed with prairie giving the area aspects of a savannah. Currently, stands of Southern Deciduous Forest are primarily restricted to bluff tops and edges adjacent to the St. Croix River and in scattered farm woodlots, which are usually heavily grazed.
Important component trees in this community include red oak, white oak, Hill's oak, and bur oak. In more mesic sites, large-toothed aspen, sugar maple, basswood, and white ash become important. Shrubs indicative of this community include black cherry, common elder, gray dogwood, and hazelnut. Prevalent ground layer vegetation includes dogbane, wild sarsaparilla, rattlesnake fern, tick trefoil, Virginia strawberry, northern bedstraw, wild cranesbill, Jacob's ladder, sweet cicely, wild lettuce, false Solomon's seal, Solomon's seal, wild leek, blue cohosh, goosegrass, bloodroot, large-flowered trillium, and Pennsylvania sedge.
Very few breeding bird species are restricted to or reach their greatest density in the Southern Deciduous Forest in the Valley. Principal breeding species include Cooper's hawk, red-tailed hawk, ruffed grouse, great horned owl, whip-poor-will, common flicker, red-headed woodpecker*, hairy woodpecker, great crested flycatcher, eastern wood pewee, blue jay, common crow, black-capped chickadee, white-breasted nuthatch, house wren, brown thrasher*, American robin, yellow-throated vireo, ovenbird, American redstart, scarlet tanager, rose-breasted grosbeak, indigo bunting, rufous-sided towhee, vesper sparrow (in openings), and field sparrow (in openings).
Deciduous Clear Cuts
A major principle of wildlife management is the provision of a multitude of habitats in various successional stages. Suppression of wildfires and the tremendous reduction of logging that occurred after settlement of the Valley were responsible for allowing many upland sites to return to near climax conditions. Northern Hardwood Forest, dominated primarily by sugar maple and basswood, rapidly becomes prevalent in northern forests that are not managed. Although the mature hardwood forest is a primary habitat for several breeding birds, the lack of early successional stages creates a situation that is relatively unattractive to a number of other species.
Within the last 15 years, foresters and wildlife managers have taken steps to retard succession in several upland forest types. These management practices have been highly successful in providing a variety of successional stage forests and several age classes. Providing a variety of age classes has produced significant beneficial effects for many woodland breeding birds. The primary methods used to accomplish these practices are clear-cutting and selective cutting.
In general, these practices have been accomplished on upland sites in the northern areas of the Central Plain and throughout the Northern Highland. Trembling aspen is the primary tree species associated with Deciduous Clear Cuts. Additional tree and shrub species that are important components of clear cuts include ironwood, hazelnut, sugar maple, and basswood. Important ground layer species include black raspberry, big-leaf aster, rice grass, bottle-brush grass, Pennsylvania sedge, northern bedstraw, bracken fern, and wood anemone. In wet-mesic sites bunchberry and large-flowered trillium are also important.
Deciduous Clear Cuts and associated edge habitat probably support the greatest diversity of breeding birds among the habitats in the Valley. Principal breeding species include ruffed grouse, ruby-throated hummingbird, eastern kingbird, alder flycatcher*, house wren, gray catbird*, brown thrasher, eastern bluebird, golden-winged warbler*, Nashville warbler, yellow warbler, chestnut-sided warbler*, mourning warbler*, common yellow-throat*, Canada warbler*, brown-headed cowbird, rose-breasted grosbeak, indigo bunting*, American goldfinch, white-throated sparrow*, and song sparrow.
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