Threatened in the state of Michigan, both Caspian and common terns are known to nest in colonies on the gravel and sand beaches of Michigan Islands National Wildlife Refuge. Both species of terns can be seen in the Great Lakes Region during the spring, summer and fall months. Although similar in appearance, they can be distinguished by looking for a few telltale trademarks. The Caspian tern is the largest of all tern species sporting a dark red bill graying at the tip and black legs. The common tern’s breeding plumage is very similar to the Caspian tern; however, it is significantly smaller than the Caspian tern and has a bright red-orange bill with a black tip and red-orange legs. Both terns have black caps, white bellies and gray backs. Terns can be quite entertaining to watch and are easily differentiated from other species of birds by the way they hunt. Terns will hover several feet over the water searching for prey, then in a quick aerobatic flourish, they will dive into the water often coming up with a shimmering fish in their beak.

The ring-billed gull can be seen throughout the Great Lakes Region in the spring, summer and fall months. An opportunistic feeder, it will eat everything from fish and insects to seeds and mice, and is known to eat garbage and beg for food when habituated to people. The ring-billed gull is similar to Caspian and common terns in that it nests on the ground. The three species are frequent neighbors. Adult ring-billed gulls have a black band near the tip of their beak which gives them their name and makes them fairly easy to distinguish from other species of gull. Young herring gulls can resemble an adult ring-billed gull as they also have a black band around their beak as well. However, they generally have more of a brownish cast to their feathers. A number of the islands that make up Michigan Islands Refuge are home to large colonies of these gulls, some are several thousand strong.

Gull and Scarecrow Islands, part of Michigan Islands NWR, have small colonies of nesting black-crowned night-herons. These short, stocky herons prefer to feed during the twilight hours and overnight, especially on bright moonlit nights. By feeding at these times, after other herons have gone to roost for the evening, they avoid competition for choice feeding grounds. Black-crowned night-herons may stalk their prey, much like other species of herons, by wading, standing watch or walking slowly through shallow water. Then with one quick motion they pluck their prey from the water. This little heron has several other tricks up its sleeve, including plunging in head or feet first after prey and even swimming in pursuit of their prey in water too deep for them to wade. These herons have even been known to raid the nests of nearby terns, eating the chicks.

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.

Several of the smaller islands consist of cobblestone or sandy spits scattered with vegetation varying from brush to patches of grasses and flowers. These sparsely vegetated islands are important nesting sites for ground nesting colonial waterbirds such as common terns, Caspian terns, ring-billed gulls, and herring gulls.

Thunder Bay Island has a rare, distinctive, alvar ecological community with a little bluestem alvar grassland, alvar pavement, and a limestone bedrock lakeshore. An alvar is an area with thin or no soil over limestone bedrock where various plants may be able to take root and survive. Plants that live on alvars need to be able to survive in extreme environments. During the summer, the hot sun beats down on the thin soils, causing them to dry out. In the winter, freezing temperatures and cold blowing winds pose their own challenges. These hardy, yet fragile ecosystems are home to the dwarf lake iris, a federally listed threatened species, and various other rare plants. Several species of birds, mainly grassland and shoreline birds, such as savannah and field sparrows may utilize this type of habitat.