Important Bird Areas

St. Croix Bluffs IBA

Minnesota

Location:
This Important Bird Area is located west and northwest of Minneapolis/St. Paul on the eastern border of Minnesota along the St. Croix River. It extends roughly 25 miles north from Stillwater, MN to the Exel Energy dam at Taylors Falls, MN. Generally, it lies between Minnesota Highway 95 and the center of the St. Croix River or the border between Minnesota and Wisconsin. Specifically, it includes all land within the St. Croix National Scenic Riverway, Interstate Park, William O'Brien State Park, St. Croix State Game Refuge and Falls Creek State Natural Area.

Directions:
This area can be accessed either by boat or by car, generally from MN Highway 95 or US Highway 8. Parking areas are located in the state parks, at Falls Creek State Natural Area off MN Highway 95 and at the Boomsite Wayside, scenic overlook, boat ramp and historical marker just north of Stillwater. Boats can be launched all these locations as well as a small ramp at Franconia and Log House Landing in Copas, just north of William O'Brien State Park. A small canoe launching site is located in the village of Marine-on-St. Croix. Skiing and/or hiking trails are located in the state parks and an informal trail can be found at Falls Creek. A bike trail goes northward from Marine-on-St. Croix through William O'Brien State Park and terminates at the junction of MN highways 95 and 97. Several county and local roads also traverse parts of the area.

Prominent Features:
The St. Croix River is the most prominent feature of this IBA along with the associated wetlands and adjoining bluffs and cliffs. The views at Interstate are among the best in the state.

Ornithological Summary

The St. Croix River and adjacent riparian and upland habitats contains a diverse assemblage of birds that depend upon the area. It is a natural north-south migratory corridor.

Two great blue heron colonies are located within this proposed IBA with a combined total of 534 nests counted in 2004. Both rookeries have been active for over 15 years.
Eleven pairs of bald eagles nested along this stretch of the St. Croix River in 2004. This is the highest number recorded since counting began in 1982. This area contains the highest density of nesting bald eagles within the St. Croix National Scenic Riverway.
Red-shouldered hawks are common here though the number of nesting pairs is unknown. This is probably one of the best concentrations of breeding red-shouldered hawks in the state.
Pairs of Louisiana waterthrush can be found in nearly every stream valley dissecting the bluff, especially when permanent flowing water is present. It is likely that 25 pair may nest in these narrow ravines on this stretch of the St. Croix River. Louisiana waterthrushes reach their northern limit on the St. Croix River, but farther upstream than this site. This is probably an important migratory corridor for them both spring and summer.
MN-2b:
Prothonotary warblers are common on the St. Croix River and reach their northern limit in Minnesota here. They are number 10 on the list of species most frequently observed on the breeding bird surveys conducted here by National Park Service staff.
MN-3b:
This site contains extensive floodplain forests and support an assemblage of birds associated with that habitat. All the species listed in the criteria for MN-3 under floodplain forests are found here and, except for the cerulean warbler, are considered common and are regularly recorded on the NPS conducted breeding bird surveys.
This site contains extensive upland deciduous forests mostly protected by public ownership or easements owned by the National Park Service. Most of the birds listed in the criteria for MN-3 under upland deciduous forest are common here with the primary exception of those whose ranges do not reach this site. Those and others missing from this list include whip-poor-will, tufted titmouse, blue-winged warbler, golden-winged warbler, black-throated blue warbler, Mourning Warbler, Worm-eating Warbler, Kentucky Warbler and Hooded Warbler.
MN-4a:
Four programs of long-term bird monitoring is taking place at this location, three of which are conducted by National Park Service personnel. Nesting bald eagles have been monitored annually since 1982. Nests within great blue heron rookeries have been counted since 1973. Breeding bird surveys by boat on the St. Croix River have been conducted in 1982, 1998-2001, 2003 and are currently on a biennial schedule. These surveys have recorded over 85 species of birds in June. Finally, the St. Paul Northeast Suburban Christmas Bird Count (CBC) includes most of this site between Stillwater and Marine-on-St. Croix. That data may be useful as an indication of winter birds at this site, but not an absolute count as the CBC count circle only partly overlaps the proposed IBA site.

Conservation Issues

New cell towers, wind towers and power lines are proposed along the bluffs overlooking the St. Croix River each year. Deforestation, primarily linked to housing developments, and recreational use of the river with possible disturbance to colonial nesting birds and bald eaglesis are ongoing threats.
Several gravel pits operate within this area, just back of the bluff line. All the forests in this area are susceptible to infestation by common buckthorn and the plant already forms dense thickets. A 300+ acre patch of garlic mustard is located across the river from Arcola Mills. Purple loosestrife is present but mostly removed annually. Other exotic plants being monitored and/or controlled include Grecian foxglove and nodding thistle. Nodding thistle is spreading rapidly in Washington County and is found in scattered locations within this area.
Pesticides from agriculture and lawn management are a concern and are present in the river.

Ownership

Specifically, it includes all land within the St. Croix National Scenic Riverway, Interstate Park, William O'Brien State Park, St. Croix State Game Refuge and Falls Creek State Natural Area.

Habitat

Uplands are generally covered with maple-basswood forests in wet areas and oak forests in the drier areas. White and red pine are common at scattered locations. Riparian woodlands dominated by silver maple and green ash are typical in the floodplain and the islands within the St. Croix River. Exposed limestone bedrock and cliffs are commonly found along the bluff, occasionally down to the river's edge. Extensive wetlands are found primarily along the St. Croix River in the flood plain but large wetlands can also be found at William O'Brien State Park. The wetlands are typically sedge meadows or cattail marshes. Open treeless areas are scattered throughout the upland portion of this IBA. Primarily these consist of various agricultural areas but also include abandoned crop lands with typical old field vegetation. Parts of William O'Brien State Park are being actively managed and maintained as native prairie. Basalt balds are open areas with thin soils on top of basalt bedrock. These are found within and near Interstate Park. Typical vegetation here includes oaks and/or eastern red-cedar along with prairie plants. Native prairie is also found in scattered locations along the bluff throughout the proposed IBA.