Old Man's Cave in the Hocking Hills of Ohio. Photo by Jaknouse / Wikimedia

Ecoregions of Ohio

Ecoregions are geographically distinct areas of land, characterized by distinctive climates, ecological features, and plant and animal communities. Ohio is covered by three broad ecoregions and two of these are further subdivided. Each has its own distinctive characteristics, which are most obvious in regards to the plant communities. As birds are heavily dependent upon plants, and many species are closely associated with specific plants, each ecoregion tends to favor certain birds.

Appalachian Plateaus Province

Geographers break this province into seven subregions, of which Ohio is included in two: the Unglaciated Allegheny Plateau, and the Glaciated Allegheny Plateau. This region is basically the foothills of the Appalachian Mountains, the great chain of mountains that begin in New England and run south into the Carolinas. 

In Ohio, this region stretches from Adams County along the Ohio River northeastward to extreme northeastern Ohio. The Appalachian Plateaus cover more than one-third of the state’s land mass, and contain the rugged hill country that many people associate with southern and eastern Ohio.

The defining feature of this ecoregion, other than the rugged topography, is forests. At the time of European settlement, Ohio was cloaked with dense woodlands that covered about 95 percent of the state. Soon after settlement, efforts began in earnest to open the forest primeval for agriculture and other development, and by the early 1900’s very little remained. 

Forest conservation efforts began to take shape in the 1920’s and 30’s, and today, Ohio is nearly one-third forested. The vast majority of woodlands are found in the Appalachian plateaus, and consequently this ecoregion harbors the biggest populations of our forest birds.

Probably the best place to get a sense for what pre-settlement Ohio would have looked like is Shawnee State Forest in Scioto County, near the city of Portsmouth. This 63,000+ acre woodland is the state’s largest contiguous forest, and supports big populations of many birds associated with mature woodlands. One species, the cerulean warbler, is intimately associated with oak-hickory woodlands that carpet the dry ridge tops, and this bird is plentiful in Shawnee. 

Other birds that are strongly associated with Appalachian Plateaus forests in Ohio and are abundant in Shawnee include worm-eating warbler, ruffed grouse, and broad-winged hawk. All told, this magnificent forest harbors more than 100 species of breeding birds, and probably supports the largest populations of woodland species in Ohio.

One of the most popular tourist destinations in the state is imbedded within the Appalachian Plateaus – the scenic Hocking Hills region, which is mostly in Hocking County. The most significant plant communities here are the hemlock gorges, which are steep-sided ravines and valleys carved from the sandstone bedrock by water erosion. 

These gorges have distinct microclimates, often remaining as much as ten degrees cooler than surrounding uplands. The cool temperatures allow hemlock trees—a northern plant—to flourish, and they blanket the sides of the gorges. A small suite of northern birds, here at the southern edge of their range, is dependent upon the hemlock community and they occur in small numbers in the Hocking Hills. 

These species include hermit thrush, blue-headed vireo, and Canada, magnolia, and black-throated green warblers. A few of the better places to see this habitat include Old Man’s Cave and Cantwell Cliffs state parks, Conkle’s Hollow State Nature Preserve, and Clear Creek Metropark.

Ohio’s only National Park is found in the Appalachian Plateau – the 33,000-acre Cuyahoga Valley National Park. Situated midway between Akron and Cleveland, mostly in Summit County, much the park is heavily forested and supports a wide diversity of breeding birds. Bisected for 22 miles by the Cuyahoga River, CVNP harbors many different forest types, and almost 200 species of birds have been documented within its boundaries, and well over half of them are breeders. 

Southern birds near their northern limits here, like Kentucky and worm-eating warblers, while northern species are at the southern edge of their range, such as purple finch and chestnut-sided warbler. Obligate forest birds, such as scarlet tanager, ovenbird, and wood thrush can be found in abundance, and rarer nesting species like sharp-shinned hawk occur.

Central Lowlands

This is the largest ecoregion in Ohio, covering more than half of the state. This physiographic region has been divided into six subregions, two of which are found in Ohio. The Central Lowlands cover much of western Ohio, from Brown County on the south and extending north and east to include the borders of Lake Erie. The defining event that shaped the topography of this region was glaciation. 

When the Wisconsin glacier reached its southernmost advance some 12,000 years ago, it covered the part of Ohio defined by this ecoregion, flattening most of the landscape like a pancake. After the glacier receded, much of the terrain was poorly drained and swampy and cloaked with swamp forests Glacial rock debris was deposited here and there in the form of eskers and moraines. 

In places, kettle lakes were formed by large ice blocks calving off the glacier’s face, and these eventually developed into bogs. In areas too wet or otherwise not conducive to tree growth, prairies eventually formed, and covered approximately 1,000 square miles of Ohio at the time of settlement.

Today, the great majority of the Central Lowlands subregion known as the Till Plains section—covering most of western and central Ohio—has been converted to agriculture. Once settlers discovered how fertile the prairie soil was and invented a plow that could turn it, prairies rapidly disappeared from the Ohio country. Today, it is perhaps our rarest habitat, as more than 99 percent of the original prairie has been destroyed. 

An excellent place to get a taste for the former prairies are the Big Island and Killdeer Plains wildlife areas, which are located about seven miles apart near the city of Marion. These sites protect remnants of the formerly expansive Sandusky Plains wet prairie, and are important habitat for many birds. Prairie birds like dickcissel, upland sandpiper, and Western meadowlark nest regularly. Large wetlands within the wildlife areas attract great numbers and diversity of waterfowl, and in recent years sandhill cranes have nested at Killdeer Plains. 

Bald eagles have active nests at both areas, and some years, northern harriers and short-eared owls breed. About 1,000 acres of wet prairie has been restored at Big Island since 1996, and these wetlands have already lured nesting Wilson’s phalaropes, and in 2004, black-necked stilts attempted to breed—an Ohio first.

An excellent example of one of Ohio’s few remaining glacial kettle lakes can be found just west of the city of Circleville, Calamus Swamp. Kettle lakes began life when an enormous chunk of ice split from the glacier, and plopped into the wet muck with tremendous force. Visualize dropping an ice cube into a bowl of jello; the result would be similar. Initially – in the case of Calamus Swamp, this would be 12,000 years ago – glacial lakes would have been cold, clear water bodies with little life. 

Over time, plants began to colonize them, and as they died their organic debris built up peat layers in the lake. Eventually, their fate is to fill with decomposed plant material and succeed to swamp forest, as most of these lakes in Ohio have done. Calamus has not reached that stage, and displays classic kettle lake zonation of open water, mixed-emergent marsh, and swamp forest buffering the margins of the lake. 

Many wetland birds are found here, and sora and Virginia rails breed, as do green heron, willow flycatcher, and common yellowthroat. Numerous migrant waterfowl use Calamus, and the surrounding wet woods attract many songbirds and swamp woods specialists like rusty blackbird in migration.

The other Central Lowlands subdivision is the Lake Plains, which borders Lake Erie. At the eastern end of the lake, from Ashtabula to the Cleveland area, the Lake Plain is quite narrow – only five miles wide in places. Near Sandusky Bay, the plain flares out and encompasses about seven counties in the northwest corner of the state. Obviously, Lake Erie is the dominant feature of the Lake Plain, and this region encompasses many very important bird habitats.

Just west of Toledo lies one of Ohio’s most unusual ecosystems, the Oak Openings, which cover about 130 square miles. This habitat is characterized by the sandy soil that remains from when Lake Erie was much larger, and its shores extended far past the modern boundaries. The water table is very high here, creating a fascinating juxtaposition of dry sandy knolls grown over with oak savanna adjacent to low swales carpeted with wet sedge meadows. 

More species of rare plants occur here than any other Ohio locale, and bird diversity is also exceptional. Oak Openings Metropark’s dry, sandy fields and savannas support Ohio’s only remaining lark sparrow population, and red-headed woodpeckers are common. Southern species like summer tanager and blue grosbeak have northern outposts here, and whip-poor-wills are locally common. 

The wet sedge meadows, such as are found at Irwin Prairie State Nature Preserve, harbor breeding Wilson’s snipe, American bittern, and swamp sparrow. Wet thickets have supported rare nesters like mourning and golden-winged warblers, and Bell’s vireo.

The enormous coastal marshes that buffer Lake Erie’s western basin are amongst the most biologically significant habitats in the Central Lowlands. Most of these marshes have been “tamed” by dikes, which have cut them off from the lake, but nevertheless they support a vast array of both migrant and nesting birds. 

These marshes extend interruptedly from Sandusky Bay to Toledo, and the best place to get a flavor for these wetlands is Magee Marsh Wildlife Area. More than 300 species of birds have been documented from this 2,000-acre site. The marshes support huge numbers of most species of ducks that traverse the Mississippi Flyway, and many of them breed here in lesser numbers. 

There are fantastic movements of migrant tundra swans, and this is a critical area for bald eagles. Many waterbirds occur, including unusual species like king rail, snowy egret, and common moorhen, all of which breed here.

Interior Low Plateau Province

By far the smallest physiographic region of Ohio, a tiny portion of a subregion of this province juts into Adams County, in the southernmost part of the state. Known as the Bluegrass section, this ecoregion may be small, but it is very significant. Pioneering Ohio botanist Lucy Braun conducted landmark ecological studies of the vegetation in Adams County, and was among the first to recognize the significance of the rare prairie communities of the Bluegrass Region.

This area is underlain with limestone bedrock, which is quite near the surface in many areas, creating alkaline soil conditions that favor certain plants. The most obvious manifestation of this is the prevalence of red cedars, which is a dominant tree in reverting old fields and around prairies. These cedar glades are excellent habitats for birds that favor successional plant communities, such as prairie warbler, yellow-breasted chat, and field sparrow. 

Southern birds at the northern edge of their range are well known here, too, such as Chuck-will’s-widow, black vulture, and blue grosbeak. Adams County is also one of the last regular locales where loggerhead shrikes are found in the state. Northern bobwhites, which have declined significantly in Ohio, can still be found reliably within this region.

One of the highest quality rivers in the state flows through the heart of Ohio’s Bluegrass Region. Ohio Brush Creek has its headwaters in southern Highland County and winds its way south until it meets the Ohio River. In recognition of the significance of this watershed, The Nature Conservancy and the Cincinnati Museum began to protect land along the stream in the 1960’s, and to date own more than 15,000 acres. 

This bioreserve is called the Edge of Appalachia Preserve, and is a vital conservation area for birds. More than 100 species breed in the diverse forest communities and other habitats within the Edge, including more than half of the neotropical species that migrate north to breed in Ohio. 

This is the area where chuck-will’s-widow was first discovered in Ohio, in 1932, and the Ohio Brush Creek valley has long been known as one of the state’s few strongholds for black vultures. Red-shouldered hawk, northern parula and yellow-throated warblers are common in the streamside forests, and cerulean warblers and pileated woodpeckers occupy upland oak-hickory woodlands.

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