Guide to Significant Wildlife Habitat - Door County Web Map

Horseshoe Island
Horseshoe Island, named for its distinctive shape, is 37 acres and is located approximately onehalf
mile from the mainland of Peninsula State Park. The island is a favorite anchoring spot for boaters
who often wade ashore with picnic lunches (Judziewicz and Kopitzke 1999).
• The island is owned and administered by the WDNR as part of Peninsula State Park and is located in
the geographic boundary of the Town of Gibraltar.
• Land use is primarily low impact recreation.
• Soils are sloping glacial till plains underlain by dolostone bedrock. Rock outcrops are common
(USDA SCS 1978).
• No surface water resources are present on the island.
• Stands of white cedar are found along the dolostone cliffs on the north and west coast. Younger
balsam fir and white birch are common. Climbing fumitory and weedy garlic mustard are abundant
understory plants (Judziewicz and Kopitzke 1999).
• There are no known rare plant or animal species on the island.
• The aesthetic value of Horseshoe Island is mainly as a favorite scenic area used by boaters. It also
has value as a natural area for various plants and animals.
Sister Islands
Sister Islands are two uninhabited bird islands separated by a shoal, located approximately 1.5
miles northwest of Sister Bay in the waters of Green Bay (Judziewicz and Kopitzke 1999). These islands
are sometimes above water and sometimes below depending on water fluctuations of Green Bay.
• Sister Islands are in the Town of Liberty Grove. The islands are State Natural Areas that are owned
and managed by the WDNR.
• Soils are nearly level to sloping on old glacial lake beach ridges. Dolostone bedrock is at a depth of
40 or more inches (USDA SCS 1978).
• Vegetation has not been surveyed since William E. Tans of the WDNR visited the islands in 1977.
Common plants were box elder (Acer negundo), orange jewelweed (Impatiens capensis), red-osier
dogwood, bittersweet nightshade (Solanum dulcamara) and stinging nettles (Urtica dioica)
(Judziewicz and Kopitzke 1999).
• Cormorants and gulls dominate the islands.
• No rare plant or animal species have been documented on the island.
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Grand Traverse Islands