U.S. Fish & Wildlife Service logo A Unit of the National Wildlife Refuge System
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Gravel Island
National Wildlife Refuge


double-crested cormorant standing on rock

Door County, WI   
E-mail: gravelisland@fws.gov
Phone Number: 920-387-2658
Visit the Refuge's Web Site:
http://www.fws.gov/refuge/gravel_island/
Double-crested cormorants nest on both Gravel and Spider islands.
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  Overview
Gravel Island National Wildlife Refuge

Gravel (4 acres) and Spider (23 acres) islands comprise the Gravel Island National Wildlife Refuge. These islands are located in Lake Michigan, approximately 1 mile east of the northern tip of the Door County peninsula, Wisconsin.

The islands were set aside by Executive Order in 1915 as a preserve and breeding ground for native birds.

Gravel Island National Wildlife Refuge and Hog Island, one component of Green Bay National Wildlife Refuge, comprise the Wisconsin Islands Wilderness Area, which, at 29 acres, is one of the smallest wilderness areas in the country. The refuge is managed by staff at Horicon National Wildlife Refuge, in Mayville, WI. Public use is not allowed due to ground nesting by migratory birds and limited access.


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Wildlife and Habitat

Neither Gravel nor Spider Island have an overstory vegetation layer.

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History
The limestone and dolomite rocks that make up the base of Gravel and Spider islands formed from compacted sediments of marine life that were deposited over 500 million years ago, when the area was covered by an ancient ocean.

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    Note
Public use not permitted to ensure necessary protection of ground nesting migratory birds.




Recreation and Education Opportunities
Environmental Education
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Management Activities
Resource values are maintained by natural processes. The refuge is monitored to ensure that these values have not been compromised.

Several studies involving double-crested cormorants, red-breasted mergansers, and black-crowned night herons have used Gravel Island Refuge as a study site. Activities have included sampling eggs, embryos, adults, and juveniles for various toxicants; counting nests; sampling blood for genetic purposes; and banding.

The most recent study was initiated in 2001. Through banding and re-sighting efforts, researchers are trying to better understand the population of double-crested cormorants and its growth. The study continued through 2006.