The Mille Lacs IBA includes the entire water body and islands (Spirit and Hennepin) of Lake Mille Lacs, the surrounding shoreline, and significant areas adjacent to the lake. The IBA is located about 100 miles north of the Twin Cities in three counties (Mille Lacs, Aitkin and Crow Wing) and several townships. Lake Mille Lacs has a surface area of 207 square miles (132,500 surface acres) and is Minnesota?s second-largest lake. The total watershed area is 249,000 acres, making the ratio of land to water in this lake less than 2:1. The lake is rather shallow for its size with a maximum depth of about 43 feet and average depth of 21 feet. The current water quality of the lake overall is good, although some water quality parameters indicate the potential to develop serious problems. The Rum River flows out of Lake Mille Lacs through Lakes Ogechie and Shakopee in Mille Lacs Kathio State Park, winding through central Minnesota where it ultimately connects with the Mississippi River around Anoka.
Significant lands within the IBA boundaries include two state parks (Mille Lacs Kathio and Father Hennepin), the Lake Mille Lacs Indian Reservation, state forestry lands, six wildlife management areas, and county forestry lands (Crow Wing and Aitkin).
The two small islands, Spirit and Hennepin, in the south and southeast parts of the lake, comprise the Mille Lacs National Wildlife Refuge, the smallest National Wildlife Refuge in the country. This National Wildlife Refuge has one of only four Common Tern nesting colonies in Minnesota. The Common Tern is currently a state-listed Threatened species.
The land on the west side of Lake Mille Lacs was identified as an area of high biodiversity by the Minnesota County Biological Survey and the Brainerd Lakes Area Conservation Collaborative. This primarily hardwood forest area also was identified as containing a significant population of Red-shouldered Hawks, a state-listed Species of Special Concern.
The Mille Lacs IBA is especially important for the Common Terns nesting on Hennepin Island, as a fall staging area for Common Loons and Bonapartes Gulls, for Red-shouldered Hawks that nest in the hardwood forest on the west side of the lake, for Bald Eagle nest sites, and during migration, for a variety of waterfowl, gulls, marsh birds, and passerines. Of the 231 species of birds recorded for this IBA, there are 62 Species of Greatest Conservation Need.
The land on the west side of Lake Mille Lacs was identified as an area of high biodiversity by the Minnesota County Biological Survey and the Brainerd Lakes Area Conservation Collaborative. This primarily hardwood forest area also was identified as containing a significant population of Red-shouldered Hawks, a state-listed Species of Special Concern. Hennepin Island was added in 1920. A project to increase Common Tern nesting success on Hennepin Island was initiated in 1993 with the assistance of the Mille Lacs Band of Ojibwe Department of Natural Resources. The project includes annually installing a gull exclosure (deterrent) grid over the gravel beach portion of Hennepin Island during the nesting season. The grid acts as a barrier to Ring-billed Gulls that compete for nest sites with terns. The Mille Lacs Band of Ojibwe support a Environment Wildlife Program that aid in the conservation for declining and threatened species such as Purple Martins and Common Terns. The main species of concern on the Mille Lacs IBA are the Common Tern, Bald Eagle, Red-shouldered Hawk, and the Yellow Rail. Although the Purple Martin is not listed as a SGCN, this species has shown a substantial population decline in Minnesota according to the Breeding Bird Survey for the period from 1966-1994.
Lake Mille Lacs may be the most popular walleye fishing lake in the state and is recognized nationally as a premiere walleye lake. Large numbers of anglers increase the threat to birds of boater harassment, entanglement in fishing line, and lead poisoning from ingestion of lead sinkers and jigs.
Erosion on Hennepin Island is a serious problem for the nesting Common Terns. A habitat enhancement project is being pursued to reduce the erosion and increase the area for nests.
Development around the lake is continuing at a rapid pace. The shore length is 76 miles with more that 70% of it developed with seasonal and year-round homes, businesses and other commercial interests. The greater majority of these developed parcels are not sewered and rely on on-site treatment systems.