Ecoregions of Michigan

Glaciation has had a profound influence on the landforms, as well as vegetation cover, throughout Michigan.  No portion of the state has escaped the forces of glacial activity.  The most obvious product of the last (Wisconsonian) period of glaciation was the formation of the five Great Lakes; four of which – Superior, Michigan, Huron, and Erie – surround Michigan, forming two distinct peninsulas.  Throughout the state, the topography consists primarily of a variety of glacial formations.  Broad till plains with thick and complex deposits of drift, paleobeach ridges, relict dunes, morainal hills, kames, drumlins, meltwater channels, and kettles occur.

Much of the state is rather low in elevation, and flat, particularly in the southern Lower Peninsula.  The only truly mountainous areas of Michigan are in the western Upper Peninsula, including the Huron Mountains west of Marquette, the Porcupine Mountains northeast of Ironwood, and the Keweenaw Ridge along the Keweenaw Peninsula, which juts northward into Lake Superior.  These mountainous areas sit on Precambrian bedrock that is part of the Canadian Shield.  Michigan’s highest point is Mt. Arvon (1,979-foot elevation), located in the Marquette highland west of the Huron Mountains.

In general, Michigan straddles the zone where southern deciduous forests gradually give way to coniferous forests to the north.  About mid way up the Lower Peninsula, running at about 43° north latitude, or roughly from Muskegon to Saginaw, is a boundary described by early ecologists in Michigan as a “zone of tension.”  To the north of this zone, conifers are more frequent in forested areas, while south of this zone conifers are infrequent, except in some coastal dune areas.  While deciduous forests clearly dominate the southern Lower Peninsula, coniferous forests are not uniformly distributed in the northern Lower or Upper Peninsulas.  As travelers move north through the state, it is easy to detect the increasing presence of conifers, as well as the subtle change in deciduous forests.  Birches in particular become more common to the north as they thrive in areas where the soil tends to remain frozen throughout the entire winter.  Many southern plants reach the northern limits of their distribution at the tension zone.

Nearly all of Michigan’s magnificent forests, which never completely covered the state, were logged in the 1800s, with only a few isolated fragments of virgin timber remaining.  Among these fragments of old growth include a virgin stand of White Pine at Hartwick Pines State Park and, surprisingly, a patch of about 200 acres of old growth on Belle Isle in the Detroit River.  Thus, older second growth and successional areas predominate in most of the state.  Large portions of Michigan are under cultivation.  Most of the southern Lower Peninsula is dominated by agriculture, as well as by human settlements and urbanization.  Most of Michigan’s large cities, and more than half of the state’s more than 8 million people are in the southern Lower Peninsula.

The Great Lakes and Coastlines

One of the most distinctive ecoregions of Michigan certainly must be the Great Lakes, four of which border on the state.  These lakes are a great influence on Michigan’s bird life.  Many islands provide breeding habitat for ground-nesting waterbirds.  These include some large colonies of Herring and Ring-billed Gulls, smaller breeding colonies of Caspian, Common, and Forster’s Terns.  In the trees on these islands Double-crested Cormorants often form large nesting colonies as they have begun to recover from steep declines in the 1960s and 1970s due to DDT thinning their eggshells.  Lying offshore, these islands provide some measure of protection from predators due to their isolation from the mainland, and closer proximity to food sources of these mainly fish-eating birds.

The open waters of the lakes provide resting and feeding areas for many thousands of migrating diving ducks, sea ducks, geese, swans, loons, grebes, gulls, terns, and rarely jaegers.  Among the five diving duck species occurring regularly in Michigan, canvasback, and greater scaup occur mainly on the Great Lakes in migration. Redhead and lesser scaup migrate on the large lakes but are also found on smaller lakes, and ring-necked duck occurs much more frequently on smaller lakes though sometimes near the shorelines of the Great Lakes.  From shore it is possible to see waterfowl only a couple miles away, yet there are often large flocks that occur even farther out.  Canvasbacks are one of the specialties of the Great Lakes and in many years the largest counts in North America, sometimes tens of thousands, are found on Lake St. Clair or Lake Erie during the annual Christmas Bird Count.

The sea ducks include three species of scoter, common goldeneye, bufflehead, and long-tailed duck.  The Great Lakes provide a migration corridor for these species, as well as a wintering area for many when the lakes don’t freeze all the way across.  Goldeneyes and buffleheads occur frequently on smaller lakes as well, but the scoters and long-tailed ducks are almost completely confined to the Great Lakes, where their main food is shellfish.  The unfortunate introduction of zebra mussels into the Great Lakes ecosystem has at least had one short term benefit, because in recent years large rafts of hundreds of scoters and thousands of long-tailed ducks have over-wintered in northern and central Lake Michigan.  These species apparently feed on the abundance of these invasive shellfish.  The greater scaup seems to have benefited from the presence of zebra mussels as well.

Large rafts of red-breasted mergansers in migration, and common mergansers in late fall through winter (ice conditions permitting) can be found on the Great Lakes and shorelines.  Flocks of thousands of birds are not uncommon.  Mergansers feed primarily on small fish, including shiners, minnows, and suckers.  Both species can also be found on smaller lakes, where their relative the hooded merganser is almost exclusively found, though the common merganser is much more often found on the Great Lakes, especially in winter.

Michigan’s more than 3,000 miles of shoreline is longer than that of any state except Alaska.  The character of the shoreline varies from rocky to sandy to marshy.  Many of the state’s dabbling ducks migrate along the shorelines, and breed in the coastal marshes.  Migrant shorebirds use most of Michigan’s shorelines to varying degrees.  Rocky shores attract few shorebirds, mainly small numbers of ruddy turnstone and black-bellied plover.  The rare purple sandpiper prefers rocky areas, but is most often found on man-made jetties on Lake Michigan in late fall.  Sandy shorelines are found mostly along Lakes Michigan and Huron, where they sometimes attract several species of shorebirds and provide breeding habitat, where undisturbed, for the federally threatened piping plover.

At various points along the Great Lakes it is possible to conduct what could be called, for lack of a better name, a seawatch.  These waterbird counts have been conducted at Whitefish Point for many years, and other productive sites include Port Huron, Alpena, and South Haven.  In addition to numbers of ducks and geese, these sites are good places to watch migrant loons and grebes, as well as gulls and terns.  At these sites, species that are rarely encountered elsewhere in Michigan can almost be expected, usually in small numbers, including red-throated loon, red-necked grebe, harlequin duck, black-legged kittiwake, little gull, Sabine’s gull, and jaegers (often too distant to identify to species, though parasitic is the most common).

Southern Lower Peninsula

This most intensely settled region of Michigan also provides the greatest diversity of habitat types in the state, though much of it is fragmented.  The major cities of Detroit, Flint, Ann Arbor, Lansing, Grand Rapids, Battle Creek, and Kalamazoo provide habitat for only the most tolerant bird, primarily introduced species including mute swan, Canada goose (native populations do not breed in Michigan), ring-necked pheasant, rock pigeon, European starling, house finch, and house sparrow.  Native species that are tolerant of man’s presence in cities and agricultural areas include mourning dove, killdeer, red-tailed hawk, American kestrel, downy woodpecker, blue jay, American crow, black-capped chickadee, Carolina wren, American robin, song sparrow, northern cardinal, red-winged blackbird, common grackle, and American goldfinch.

Agricultural areas account for a significant proportion of the land area in the southern Lower Peninsula.  Horned larks, field sparrows, vesper sparrows, western meadowlarks, and bobolinks are found in agricultural areas and fallow fields.  If these fields are left to regenerate for several years, they can become suitable for less common species including upland sandpiper, and grasshopper and Henslow’s sparrows.

These neglected and fallow fields resemble prairie habitats, which are now quite rare in Michigan, and require frequent burning to maintain.  Most of Michigan’s remaining prairies are in the southwestern corner of the state, and even there they are extremely fragmented.  More extensive prairies in the past allowed species like greater prairie chicken to breed in the state, but by 1981 they had died out.  These prairies and grasslands also allowed the brown-headed cowbird to invade the state in large numbers during the last century, which negatively affected many songbirds that had never encountered this species before, and were not adapted to counter their parasitic habits.  Most severely affected by the increase in cowbird numbers was the always range-restricted Kirtland’s warbler in the northern Lower Peninsula.

The rivers and streams in the southern Lower Peninsula provide riparian forest corridors where woodland birds can find refuge and breeding habitat.  Belted kingfishers build their nests in steep banks along these rivers, while eastern phoebes nest under bridges over these streams.  A few species found more often in larger stands of deciduous forest can often eke out a living in these narrow corridors of habitat.  This habitat also provides feeding and resting areas for migrating songbirds.  Riparian areas with southern affinities, which often include stands of sycamore, provide breeding areas for southern bird species such as prothonotary warbler and, much more rarely, yellow-throated warbler.  The latter is primarily restricted to the riparian areas of the Galien River in the southwestern corner of the state.  The woodlands in southern Michigan support one of the healthiest breeding populations of cerulean warblers in North America.

Successional areas include shrubby fields, shrub wetlands, and early stages of second growth woodlands.  Birds found breeding in these habitats include yellow warbler, blue-winged warbler, gray catbird, brown thrasher, swamp sparrow, song sparrow, indigo bunting, Baltimore oriole, and many others.

Nearly all the woodland in Michigan is second growth, and in the southern Lower Peninsula this woodland is dominated by deciduous species.  As successional areas mature into woodland, larger areas of forest have provided opportunities for species requiring larger tracts to recolonize areas they inhabited before deforestation, including pileated woodpecker and barred owl, which are now found closer to urbanized areas than previously.  These woodlands provide food and shelter for migrating songbirds.  Breeding species in these southern deciduous woodlands include wood duck, ruffed grouse, yellow-billed and black-billed cuckoos, downy, hairy, and red-bellied woodpeckers, eastern wood-pewee, great crested flycatcher, Acadian flycatcher, red-eyed vireo, yellow-throated vireo, tufted titmouse, veery, wood thrush, and scarlet tanager.

Marshlands are patchy in distribution in the interior portions of the southern Lower Peninsula, but along the shore of Lake Erie some large areas have been reclaimed.  Some portions of the Lake Erie Lakeplain provide habitat for a number of rare an threatened plant species, and is an extremely rare habitat anywhere in the world.  Areas of cattail are all too frequently invaded by phragmites and purple loosestrife in this region, which are far less productive for birds.  Cattail marshes provide breeding habitat for sora and Virginia rails, common moorhen, American bittern, mallard, blue-winged teal, marsh wren, swamp sparrow, and many other species.

Northern Lower Peninsula

Larger stands of deciduous and mixed forest, with less agricultural and urban development, characterize the northern Lower Peninsula.  The Huron-Manistee National Forest contains a good variety of deciduous, mixed, and coniferous (both wet and dry) habitats, where a number of warbler species can be found breeding.  In the western portion (primarily the Manistee section), maples, oaks, and hickories intermingle with red and white pine and cedars, providing a varied habitat for many breeding species.  In these areas black-throated blue, chesnut-sided, yellow-rumped, magnolia, black-and-white warblers, and American redstarts, and northern waterthrushes are fairly common.  Mourning warblers are widespread and uncommon.  Forest floor inhabitants include wood thrush, veery, Swainson’s thrush, and ovenbird.  In areas where conifers dominate, black-throated green, Blackburnian, and pine warblers, as well as dark-eyed juncos can be found.  In addition to the abundance of breeding warblers in this habitat, ruffed grouse, wild turkey, red-shouldered hawk and barred owl can also be found.

The eastern portions of the Huron-Manistee National Forest are dominated by jack pine areas on sandy soil, the preferred habitat of the Kirtland’s warbler.  Although jack pines occur from northern Alberta south through Minnesota and Michigan and east into the Canadian Maritimes, only north-central Michigan provides the Kirtland’s warbler with its primary breeding habitat.  Occasionally, individuals have been found breeding in Minnesota, Wisconsin, and Ontario, but not in recent years.  A few Kirtland’s warblers do nest in scattered locales in the Upper Peninsula in drier jack pine plains.  Other species that can be found breeding in these areas include Nashville, yellow, yellow-rumped, and black-and-white warblers, Swainson’s and hermit thrushes, Lincoln’s and clay-colored sparrows, and in the more open areas, Brewer’s blackbirds.

Successional areas, which sometimes include alder, and conifers, are good breeding areas for eastern towhee and both blue-winged and golden-winged warbler.  The golden-winged seems to prefer older shrubby fields, before woodland takes over, and often with a coniferous wetland component.  The golden-winged warbler is more specialized than the blue-winged warbler, and is thus being crowded out as the blue-winged has been increasing its range northward.  These two species hybridize with each other where they come into contact, which is more of a threat to the less common and more specialized golden-winged warbler.  These mixed alder-cedar wetlands are also breeding habitat for white-throated sparrows.

One of the state’s best wetland areas occurs along Saginaw Bay.  The extensive marshes here provide breeding habitat for many waterfowl, as well as sora and Virginia rails, American coots, black terns, American and least bitterns, and one of the most reliable breeding colonies of yellow-headed blackbird in the state.  Large areas of mudflat provide feeding grounds for migrant shorebirds, and the waters of Saginaw Bay host thousands of migrating waterfowl.  One of the premier bird watching sites in the Midwest is Tawas Point, where the narrow peninsula provides a resting place for thousands of northbound migrant songbirds in the spring, as well as in fall.  The trees and shrubs are short here due to the sandy soil, so observing migrant warblers here is a pleasant experience, with no complaints of “warbler neck” so common where the trees are taller.

In the northwestern portion of the Lower Peninsula, there are some quality areas of grassland where upland sandpipers, grasshopper sparrows, and bobolinks may be easily found.  Also in these areas, Savannah and field sparrows, and eastern meadowlarks can be quite common, with an occasional western meadowlark in areas where the grass is shorter.

Along Lake Michigan, the dominant habitat is forested dunes, a large portion of which have been preserved in the Sleeping Bear Dunes National Lakeshore.  Here, among some of the tallest sand dunes in North America, there are forested dunes which are dominated by conifers.  This habitat provides breeding areas for one of Michigan’s rarest breeding warblers, occurring in even smaller numbers than Kirtland’s warblers; the prairie warbler.  The beaches here and farther to the north provide an undisturbed and protected breeding ground for the federally threatened piping plover.  These areas of forested dunes occur along the entire length of Lake Michigan and into the southernmost portions of Michigan, where breeding species from farther north, including black-throated green and Canada warblers, can be found in isolated patches.

Sandy areas also occur along the Lake Huron shore, and Piping Plovers have been found breeding recently around Alpena.  The sandy regions also reach to the tip of Michigan’s “Thumb”, which is typically considered part of the southern Lower Peninsula.  Standing on the sandy shores of Lake Michigan or Lake Huron gives one a feeling of standing on the Atlantic seashore.  This illusion is reinforced by the huge dimensions of the lakes, both of which are more than 50 miles wide, but also by some of the plants on the beaches.  Some species of grass and other plants, including Marram grass, sand reed grass, beach pea, sea rocket, and wormwood are found principally on the Atlantic Coast, but have disjunct populations along the sandy Great Lakes shorelines.  A unique feature of these shores is the presence of three localized Great Lakes endemic plants, the Lake Huron tansy, Houghton’s goldenrod, and Pitcher’s thistle, found nowhere else in the world.

Upper Peninsula

Upper Peninsula is truly “up north” for many Michiganians, providing large areas of relatively unspoiled habitat and isolation.  The eastern portion of the Upper Peninsula is somewhat different in character from the western portion, being more heavily forested, and more dominated by mixed and coniferous forests.  Also, the eastern portion holds a few open areas as well as patches of boreal forest and spruce bogs.  The western portion has more open areas as well as a greater proportion of deciduous and mixed forest than the eastern, though there are probably more patches of boreal forest in the western Upper Peninsula.

The eastern Upper Peninsula has received much more attention from bird watchers, so we have a better idea of which birds occur there.  The large Hiawatha National Forest consists of much mixed and coniferous forest and wetlands that provides breeding habitat for many warblers also found in the northern Lower Peninsula.  The patches of boreal forest are perhaps the most unique feature of the Upper Peninsula, with spruces and cedars dominating, with isolated bogs that are attractive to a number of species, although there are also isolated patches of boreal forest in the northernmost portions of the Lower Peninsula.  Breeding songbirds in this habitat include olive-sided and yellow-bellied flycatchers, ruby-crowned and golden-crowned kinglets, hermit thrush, and pine siskin.  A few less common to rare breeding warblers include Cape May, bay-breasted, palm, and Wilson’s, while the bog areas themselves are places where the secretive Connecticut warbler breeds.  These bogs are also excellent places to look for rare plants, as well as rare dragonflies.  The ebony boghaunter and ringed boghaunter dragonflies have recently been found in bogs in the Upper Peninsula.  Other boreal forest inhabitants, which can be found throughout the Upper Peninsula, include spruce grouse, black-backed woodpecker, gray jay, boreal chickadee, and sometimes white-winged and red crossbills.

Throughout the Upper Peninsula there are open areas and jack pine plains where a few Kirtland’s warblers have been found nesting.  Also, the more open patches provide breeding display grounds for sharp-tailed grouse.  In winter these openings and their edges provide hunting grounds for northern owl species, including snowy owl, northern hawk owl, and great gray owl, which invade the Upper Peninsula about once every three to five years when the populations small northern mammals, especially voles, crashes.  These owls must then wander much more widely in search of food.  Often accompanying these cyclical irruptions are rough-legged hawks and northern shrikes.  Another cycle which causes irruptions is the cone crop cycle, which bring what are known as “winter finches” into the Upper Peninsula, and in some years throughout the state.  Common and hoary redpolls, red and white-winged crossbills, pine and evening grosbeaks, and pine siskins are the species involved in these irruptions, though the siskin, the crossbills, and the evening grosbeak also breed in the northern parts of the state.

Wetlands in the Upper Peninsula are varied and include the previously mentioned spruce bogs, as well as tamarack bogs, alder swamps, cattail marshes, sedge marshes, and open lakes.  Common loons and bald eagles often nest on the more isolated and undisturbed lakes.  Sedge marshes are home to species that are rather uncommon to rare elsewhere in Michigan, including Yellow rail (state threatened), sedge wren, and Le Conte’s sparrow.  The large man-made wetlands of Seney National Wildlife Refuge provide breeding habitat for Michigan’s largest breeding population of trumpeter swans, which were introduced here through the 1990s.

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