The four largest islands, Gull, Sugar, Big Charity, and Thunder Bay, all have similar habitat types. The islands have either a flat sandy beach or steep rocky face surrounding their perimeter. The pitcher’s thistle, a federally listed threatened plant, can be found growing in the sand dunes on these islands. The interiors of the islands consist of paper birch, red maple, sugar maple, northern white cedar, balsam fir, white spruce, and trembling aspen. The groundcover is dominated by Canada yew, mountain ash, red osier dogwood, elderberry, willow, and juniper as well as a host of woodland wildflowers. These islands provide habitat for American bitterns, black-crowned night-herons, bald eagle, northern harrier, and American woodcock. Piping plovers, a federally listed endangered species, also have the potential to nest on these islands and have done so in the past.