Seasons of Wildlife
Plum Island essentially functions as its own small ecosystem and retains natural characteristics absent on the nearby mainland. This habitat type contains a wide range of forest conditions, from those composed primarily of early successional species such as aspen, to forest dominated by sugar maple, basswood and eastern hemlock. The interior of Plum Island is dominated by a sugar maple and basswood forest. White cedar is dominant near the coast, especially where dolomite rock formations are visible along the ground. The habitat provides valuable rest stops for birds migrating across open water. In late spring, densities approaching 60 birds/hectare (up to 17 species/hectare) have been recorded. Seven species of wood warblers and up to 25 yellow-rumped warblers per tree, in some locales, have been observed.
Hog Island provides nesting habitat for colonies of herring gulls, great blue herons, black-crowned night herons and great egrets. Pilot Island provides nesting habitat for herring gulls and a large colony of nesting double-crested cormorants. Plum and St. Martin Islands contain ecotypes and habitat rare elsewhere in Wisconsin, including the coastal fens and alvars (e.g. limestone barrens). These communities support rare plants such as dwarf lake iris (Iris lacustris) and Canada yew (Taxus canadensis), making the refuge a unique opportunity for conservation and management.
Dwarf lake iris
Islands provide important habitat for plants and wildlife and their seclusion helps support populations of a variety of threatened and endangered species. The dwarf lake iris, found on Plum Island, is on the endangered species list and is only found in select habitats in the Great Lakes region.
Removed from the endangered species list in 2007 due to rising populations, the recovery of the bald eagle is listed as one of the greatest conservation success stories in the nation. Eagles actively nest on Plum Island and are often visible to passing boaters as they sun in trees along the island perimeter. You can help protect bald eagles by maintaining a 1/4 mile distance from their nests when hiking or boating, as they are often sensitive to disturbance.
Herring gulls are large gulls with stout bills. Adults have light-gray backs, black wingtips and white heads and underparts. Juveniles are mottled brown. The legs are dull pink at all ages. Herring gulls breed on islands in the Great Lakes and can be found following fishing boats and feeding in habitats as diverse as open water, mudflats, plowed fields and garbage dumps. They are loud and competitive scavengers, happy to snatch another bird's meal and are often found in large congregations.
These colonial nesting birds make nests of soft soil, sand or short vegetation. To protect the nest from prevailing winds and hide it from predators, it is usually placed next to a rock or vegetation. This also hides it from the nearest neighbors. Crevices may be used as nest sites in rocky areas. After chicks hatch, both parents feed them day and night for up to 12 weeks, splitting foraging shifts to offer each chick up to half a pound of food per day as it nears fledging.
Young herring gulls are more migratory than adults. In the Great Lakes, most adults remain near their breeding grounds, but the nonbreeders move farther south in the fall.