The Lake Osakis IBA includes Lake Osakis, its shoreline, and surrounding upland areas to the north and south, which include many smaller lakes and wetlands (Figs. 1 and 2). These areas have been included in the IBA based on their value to breeding and or/migratory birds (Apps. A and B). Lake Osakis is a 6,269 acre (2,537 ha) lake located in both Todd and Douglas counties in west-central Minnesota. The lake contains 21 miles (34 km) of shoreline, is 11 miles (18 km) long, 3.5 miles (5.6 km) wide, has an average depth of 35 feet (10.7 m), and a max depth of 73 feet (26 m) (Fig. 3). The lake is rated as one of the premier fishing lakes in the state, featuring Walleye, Northern Pike, Large and Smallmouth Bass, Crappie and Sunfish. The lake is also known for other recreational activities such as boating, canoeing, camping, and hunting (Celebrating Osakis 2007).
Lake Osakis is an important wildlife lake in Minnesota. Its unique and dynamic habitat supports significant populations of several important colonial waterbird species, including the largest breeding population of Western Grebes (Aechmophorus occidentalis) in the state. In addition to colonial waterbirds, Lake Osakis and the surrounding area provide significant habitat for a variety of marsh birds and waterfowl (Apps. A and B).
The north/northwest boundary of the IBA briefly follows County Highway 10 before turning to include 2 wetland complexes associated with the Long Prairie River and Crooked Lake Ditch. The IBA boundary then rejoins County Highway 10 to Schelfhout Point, where the boundary includes the wetland to the west of the highway, a site with a documented rare bird feature (Figs. 1 and 2). From this wetland, the boundary continues south on County Highway 10 and County Highway 3 to the town of Osakis. The boundary then follows State Highway 127 south before heading west to include the North and South Units of Osakis WMA and Tenhoff WPA. Between these state and federally managed lands lies Clifford Lake (a.k.a. Swim Lake), the site of a known colonial waterbird nesting area (Figs. 1 and 2). At Interstate 94, the boundary continues south to include Herberger Lake WMA and West Union WPA along with their associated wetland complex. From there the IBA boundary heads northeast to include Aurzada, West Union, Quistorff, and Spohn WMAs; as well as Terfehr, Sogge, and Faber WPAs. Rare birds, mammals, and mollusks have been documented in this portion of the IBA (Figs. 1 and 2). The boundary then heads north and follows the east side of Lake Osakis along sections of State Highway 27 and County Highway 37. The boundary includes Battle Point County Park on the northeast lakeshore and 2 wetland areas to the east of the park: Stallcop Lake and Platt Lake (the site of an active Bald Eagle (Haliaeetus leucocephalus) nest). To the north of Lake Osakis the boundary includes 2 shallow lakes (Little Lake Osakis and Behim Lake) and adjacent wetland areas.
Not included in the IBA boundary, but an important area for visitors, the town of Osakis is located on the south end of Lake Osakis. Osakis offers a variety of recreational opportunities, including resorts and campgrounds, gift and antique shops, restaurants, and other family attractions. The economic base of Osakis is tourism, agriculture, and manufacturing. Two recreational trails, the Central Lakes Trail and the Lake Wobegon Trail meet in Osakis, featuring over 130 miles of paved surface, provide access to the prairie and lake scenery for which the region is known (Celebrating Osakis 2007).
Lake Osakis IBA supports major breeding populations of several important nongame bird species that are not well represented elsewhere in the state. Primarily known for its large number of nesting Western and Red-necked Grebes, a few Clark?s Grebes have also been documented. Historically, one of Minnesota?s largest colonies of Forster?s Terns, a species of special concern in the state, was also documented at Lake Osakis. This IBA is a unique wildlife habitat that provides a major source of human recreation and an important waterbird nesting area with sufficient emergent vegetation to be one of Minnesota?s premier colonial waterbird breeding locations. Because Lake Osakis and the surrounding area are currently given no special designation by the state or federal government, the area is extremely vulnerable to increasing levels of development and human disturbance. Clifford Lake, located south of Lake Osakis, has a documented colonial waterbird nesting site. Species observed included Double-crested Cormorant, Great Blue Heron, American White Pelican, and Black-crowned Night Heron. Other areas surrounding Lake Osakis in the IBA include WMAs, WPAs, and privately owned wetlands that support rare natural features.
Western Grebes have been nesting on the west side of Lake Osakis, for at least 25 years. In 1981, over 200 pairs of Western Grebes were estimated to nest at Lake Osakis, making it the largest of 29 active colonies known in Minnesota. Currently, the nesting colony of Western Grebes on Lake Osakis remains the largest in Minnesota, with more than 550 nesting birds recorded in 2006.
During ice out, the combination of ice and wind action on Lake Osakis can result in large chunks of cattail breaking off from the west shore and floating across the lake. There they become lodged in sparser bulrush or cattails, sink, and become prime emergent habitat for solitary nesting Red-necked Grebes. The habitat on the east side of the lake (where Red-necked Grebes primarily nest) is highly dynamic, with available nesting areas changing yearly. From 1995 to 1998, this colony contained 160-200 Red-necked Grebes, which is the largest documented nesting concentration known for this species in the state of Minnesota.
Historically, Lake Osakis contained one of the largest Forster's Tern colonies in Minnesota; in 1981 and 1983 an estimated 1,000 pairs nested there. In 1992, over 132 nesting pairs were documented, and in 1993, 158 pairs were documented. Since 1994, 30-60 pairs have been documented each year on Lake Osakis. Although poor nesting documentation is available for Minnesota in recent years, Lake Osakis continues to support one of the largest Forester?s Tern colonies in the state.
Several Clark?s Grebes have also been documented at Lake Osakis. This grebe is extremely rare in Minnesota, and may be expanding its range eastward from populations further west. Lake Osakis is the most eastern nesting location known to date. Numerous other nongame birds have been documented breeding within the beds of emergent vegetation found on the lake including Common Loon, Least Bittern, Virginia Rail, Sora, Black Tern, American Coot, Yellow-headed Blackbird, Marsh Wren, and Sedge Wren.
Along with providing important breeding habitat, Lake Osakis serves as an important stopover area for numerous waterbird species that use the lake during migration periods. Species that use the lake during migration include, but are not limited to: over 20 species of ducks, geese, and swans, Horned Grebes, several heron species, shorebirds such as Black-necked Stilts, Lesser Yellowlegs, Ruddy Turnstones, Semipalmated Sandpipers, Least Sandpipers, Baird's Sandpipers, Dunlins, and Short-billed Dowitchers, American White Pelicans and Double-crested Cormorants. In addition to waterbird species, many migrating songbirds can be observed at Battle Point County Park, located on the northeast shore of Lake Osakis.
Bald Eagles have been observed on numerous occasions within the Lake Osakis IBA boundary. Active nesting has occurred since 1992 just east of Lake Osakis at Platt Lake, with the most recent nest documented in 2005. Marbled Godwits were first observed within the IBA boundary in 1995. Subsequent breeding season observations have been documented, most recently in 2004.To date; there has been no documented nesting within the IBA boundary.
The MNDNR first documented waterbird colonies on Lake Osakis in 1964. Data from subsequent monitoring of the colonies can be found in the Colonial Waterbird Database maintained by the Division of Ecological Resources. Studies conducted by the Department of Biological Sciences at NDSU from 1990 to 2005 focused on several colonial waterbird species that nest on the lake, primarily Western Grebes, Red-necked Grebes, and Forster?s Terns. A number of professional papers have been published as a result of this research, as well as several reports to the MNDNR and Master?s theses by graduate students.
Agricultural intensification/ expansion: Intensive row crop agriculture has resulted in nutrient loading, and algal blooms are common during the growing season. Pesticide use from local agriculture and homeowners may impact Lake Osakis.
Disturbance to Birds: Negative public perception is one of the biggest threats to grebes at Lake Osakis. There has been some negative sentiment toward the grebes and other waterbirds, from people concerned that as fish-eaters they may be affecting the status of fish populations in the lake.
Predators: Predators may have considerable impacts on reproductive success, and could be the most significant threat to nesting birds within the IBA. Main predation is seen by Great Horned Owls, Great Blue Herons, Black-crowned Night Herons, and Mink.
Recreation/tourism: The population of Osakis nearly triples with the influx of tourists during the summer months. Watercrafts can be particularilly dangerous to the birds of Lake Osakis especially if users deliberately persecute the birds, or create wakes that flood nests or uproot emergent vegetation.
Wetland loss: Changes in hydrology to existing wetlands may cause shifts in the composition of plant species and decrease habitat suitability for animals. With this change in vegetation, a decline in species diversity has been observed in most prairie wetlands in Minnesota, including this IBA.
Industrialization/urbanization: Loss of valuable shoreline and shallow-water habitat is one of the biggest concerns with future development. If more lakeshore is developed, vegetation may be removed, which could lead to declines in waterbirds that need extensive beds of emergent vegetation to successfully breed and nest.
Introduced animals or feral pets: The Common Carp was intentially introduced into Midwest waters in the 1880s. The feeding habits of the Carp disturb shallow-rooted vegetation and cause murky water conditions. The effect that this species has on birds is still unknown.