The St. Croix Lake IBA is located east/southeast of the Minneapolis-St. Paul metropolitan area, along the eastern border of Minnesota. It includes that portion of the St. Croix River that is in Minnesota, extending roughly 16 miles south from I-94 at the town of Lakeland to Point Douglas Park at the conjunction of the St. Croix and Mississippi Rivers. To the west it is defined on the north end by Neal Ave south to County Rd 18 east to County Road 21/St. Croix Trail south to US 10/Point Douglas Road south. Specifically, it includes all land and water within Afton State Park, Carpenter Nature Center, Belwin Conservancy, St. Croix Bluffs Regional Park, and Lost Valley Prairie Scientific and Natural Area.
The St. Croix River is contained within the St. Croix National Scenic Riverway, which is administrated by the National Park Service. While not a true lake, the widening of the St. Croix River here makes it ecologically distinct from other Important Bird Areas along the river just to the north and south. The IBA is within the hardwood forest ecoregion, and is primarily deciduous with some pine plantations and remnant (mostly restored) prairie found throughout. No large inland lakes are here, though there are scattered ponds and marshes. Along the river are glacial moraines and bluffland, with ravines dropping as much as 300 feet to the river and displaying sandstone and limestone outcrops. Oak, aspen, cherry, and birch are the predominant trees found here. Inland, a broad diversity of habitats are present, including: oak savanna, spring-fed cold water streams, floating bogs, potholes, maple and basswood forests, wetlands (floodplain forest, seepage meadow, fen) and grasslands (including dry sand-gravel prairie, tallgrass prairie, oak savanna, restored and remnant prairies). Also present are limestone ridges and lowlands featuring rare and unique plant communities in the region, including rock sandwort, Hill?s thistle, and many prairie wildflowers.
St. Croix Lake IBA has a mix of aquatic, woodland, and grassland habitats making it an important migratory route, wintering area, and breeding area for a wide variety of birds. Its location along the St. Croix River north of its junction with the Mississippi River, ensures that a large number and variety of birds utilize the area throughout the year. It is a part of the deciduous hardwood ecosystem but is in close enough proximity to the boreal forests to the north and grasslands to the west that birds from all regions can be found here. It is an important migration corridor for significant numbers of migrating raptors and waterbirds and open water on the river attracts wintering Bald Eagles and waterfowl. Its location and variety of habitats result in great species diversity with 268 birds documented within the IBA boundaries. The combination of its proximity to the Twin Cities and the natural areas within the IBA boundaries provide numerous outreach and research opportunities in this IBA.
Open water for much of the winter attracts waterfowl, waterbirds, and Bald Eagles who have few other places to find suitable habitat in the cold season. For this reason, the IBA hosts large numbers of ?winter ducks? like Common Goldeneye, Common Mergansers, plus small but regular numbers of American Black Duck, Red-Breasted Merganser, Barrow?s Goldeneye, Canvasback, and Redhead. Of course, the open water also draws gulls; the IBA has hosted a number of rarities in the past few years, including Lesser Black-Backed, Thayer?s, Iceland, Glaucous, and Slaty-Backed Gulls. Other rarities recently seen within the boundaries of this IBA include Whooping Crane, Surf Scoter, Harlequin Duck, Golden Eagle, and Black Vulture. The IBA is also host to a number of species of conservation concern: Henslow?s Sparrow, Red-Shouldered Hawk, Peregrine Falcon, Bald Eagle, American White Pelican, Hooded Warbler, Louisiana Waterthrush, and Loggerhead Shrike. Specifically the St. Croix Lake IBA is important as a migration corridor for significant numbers of migrating raptors and wintering Bald Eagles (MN-1d). The best documentation comes from a 2001 count (ref. 17) of 5,315 total raptors, which is above the minimum for Criteria 1d. Species high counts included 2,188 Bald Eagles, 90 Red-Shouldered Hawks, and 1,757 Red-tailed Hawks from March 11-April 15, 2001. This IBA also provides habitat for over 50 wintering eagles as recorded on Christmas Bird Counts at Afton and Hastings. With 268 species documented (Appendix 1), this IBA meets the criteria for species diversity (MN-1e). Carpenter Nature Center and Afton State Park recorded the highest number of species with 260 and 193 respectively (Appendix A). Warblers (33 species) and sparrows (17 species) are particularly well represented in this IBA. The extensive restored prairies of the Belwin Conservancy (more than 500 acres) have become an important breeding ground for the suite of grassland species native to this area, but whose populations are declining. Sightings of Red-headed Woodpeckers in the expanding oak savanna restoration areas are infrequent, but should be more common as the Belwin Conservancy?s restoration efforts progress. Louisiana Waterthrush, a species of Conservation Concern, is found in riparian areas along the St. Croix River Valley, which is near the northernmost extent of its breeding range (refs. 1, 12, 13, 18, 26). Prothonotary Warblers are also found here at the near northernmost extent of their breeding range (refs. 1, 12, 26). Rare, vagrant, or species with limited range within the state that have been seen in this IBA include: Yellow Rail, Caspian Tern, Boreal Owl, Long-Eared Owl, Burrowing Owl, Whip-poor-will, Three-toed Woodpecker, Black-backed Woodpecker, Tufted Titmouse, Townsend?s Solitaire, Northern Mockingbird, Bell?s Vireo, Summer Tanager, Barrow?s Goldeneye, Eurasian-Collared Dove, and Whooping Crane (ref. 13), Long-Tailed Duck, Black Vulture, Glaucous Gull, Thayer?s Gull, Lesser Black-Backed Gull, Iceland Gull, Slaty-Backed Gull, Greater Scaup, Cackling Goose, Golden Eagle, Surf Scoter, Bohemian Waxwing, Mute Swan, Gyrfalcon, Northern Goshawk, Upland Sandpiper.
Situated at the eastern edge of the Twin Cities metro area means that development is a top threat to conserving quality habitat in this IBA. Preserving existing wetland areas is important for flood control and filtering storm water runoff. Water quality is a concern because of both urban expansion and agricultural runoff from the many farms in the area. According to the DNR, 149 Species in Greatest Conservation Need (SGCN) are found in this subsection of the state; this is the second most of all the state?s subsections. Most of these (59) are birds, comprising of over 60 percent of the state?s SGCN (ref. # 25). It should be noted that SGCN only consider animals, but there are several at-risk plant species here as well.
According to the DNR?s Tomorrow?s Habitat for the Wild and Rare: An Action Plan for Minnesota Wildlife, the single biggest threat to the largest number of SGCN?s is habitat degradation in Minnesota. This is a problem for 87 percent of the SGCN?s in this subsection. Other top threats (by percentage of SGCN species affected) are: habitat loss in Minnesota (81), pollution (38), invasive species and competition (32), habitat loss/degradation outside of Minnesota (28), and social tolerance, persecution and exploitation (21). Smaller problems include: food source limitations (3), and disease (2). Among the SGCN?s, the DNR has determined that the greatest numbers of species use four habitats most within this subsection: prairie, oak savanna, grassland, and upland deciduous hardwood forest, respectively. Significant numbers of species also are found in shoreline/dune/cliff, aspen-oak upland forests, and even developed and cropland areas. Among birds, the greatest numbers of SGCN species depend on non-forest wetlands, which make up only about 3 percent of the subsection, making conservation of what remains very important (ref. # 25).