Ecoregions of Louisiana

Geologically, Louisiana is quite a young place, with the majority of the state’s surfaces having been sculpted by late Pleistocene sediments (approximately 1.8 million to 11,000 years ago) and glacial melt-water. Only the northwestern quarter of the Louisiana exhibits older surface sediments, predominately in the form of Tertiary deposits (around 26 to 66 million years ago). Within this region, Louisiana’s highest elevation is reached; a dizzying 535-feet above sea level at Driskill Mountain (located just south of Interstate 20 between Shreveport and Monroe). Precious few rock formations find surface expression in Louisiana, with the majority of the bedrock being buried under as much 20,000 feet of Pleistocene mud, sand, and gravel deposits.

Basically, Louisiana is divided into six eco-regions, each of which is discussed below:

Marsh Region

Makes up nearly 13 percent of Louisiana’s total landmass, mostly confined to the coastal zone, encompassing the coast itself and extending northward (inland) 40 to 60 miles. This region is subdivided into three distinct marsh types, based on salinity levels in the associated waters. Salt marshes exist in relatively small pockets located at various points directly on the coast. Predominate herbaceous vegetation includes oyster grass, salt meadow grass, black rush, couch grass, sea-oxeye, glasswort, and saltwort. Woody vegetation is sparse. When found, it is usually in the form of black mangrove, groundsel, rattlebox, and marsh elder. Though numerous birds use salt marshes on a temporary basis, only a few actually call it their home, including reddish egret, clapper rail, Nelson’s sharp-tailed sparrow (winter), and seaside sparrow.

Fresh marshes contain the highest diversity of plant and animal species. Herbaceous plant growth is dense, and dominated by species such as cattail, bulrush, common reed grass, American lotus, water lily, swamp lily, parrot’s feather, alligator weed, water hyacinth, water lettuce, and several species each of arrowheads and irises. Interesting bird species include snowy egret, little blue heron, tricolored heron, roseate spoonbill, white-faced ibis, king rail,  sora, purple gallinule (summer), common moorhen, black-necked stilt, Wilson’s snipe, gull-billed tern, marsh wren, and red-winged blackbird, along with numerous species of waterfowl (winter). During the summer months, a few nesting waterfowl species can be found, such as fulvous whistling-duck, mottled duck, and blue-winged teal.

Brackish (a mixture of freash and saltwater) marshes are the most common type and are populated with plants and animals common to both salt and fresh marshes. During the winter months, brackish marshes are probably the best places to look for birds such as roseate spoonbill, greater scaup, Virginia rail, and American avocet.

Prairie Region

This triangular-shaped area in the southwestern corner of Louisiana once held 2.2 million acres of coastal tallgrass prairie, filled with big bluestem and other grasses, mints, Indian plantain, blazing stars, compass plant, sunflowers, and false-indigos. Unlike midwestern prairies, which maintain their grassland character due to deep, porous soils and little rainfall, woody plant growth on Gulf Coast prairies is discouraged due to the presence of a thick clay-pan layer found only a few inches below the topsoil layer.

By the mid to late 19th century, most of this region was cleared for rice-farming and cattle ranching, resulting in the total extirpation of several indigenous animals including Attwater’s prairie chicken, the Louisiana prairie vole, and the red wolf. Today, only a few relict native prairie communities remain, mostly in small patches adjacent to the east-west rail line which traverses the region. The good news is that a number of successful prairie restoration initiatives are presently underway, providing much needed nesting habitat for northern bobwhite, scissor-tailed flycatcher, eastern kingbird,  dickcissel, and eastern meadowlark, among others.

By the same token, the rice farms which replaced native prairie habitat have themselves provided outstanding foraging and resting habitat for wading birds, waterfowl, raptors,  shorebirds, sparrows, and other species. In fact, data from the Crowley Christmas Bird Count, located right in the center of this region, has documented some of the highest densities for selected species of wading birds, raptors, and shorebirds in the entire nation. Unquestionably, the “rice country” is the place to go for those birders desiring to study any of the above-mentioned bird groups, especially during fall, winter, and spring.

Longleaf Pine Region

This region represents the western end of an historical longleaf pine belt which once extended nearly uninterrupted from the coastal zone of the Carolinas westward through the Gulf Coast states and terminating in extreme eastern Texas. As was the case with many other U.S. tree species, longleaf pine was simply too valuable a resource for its construction-quality wood to be left untouched by European settlers. Consequently, only the dampest, most inaccessible stands of longleaf pine escaped timbering. Fortunately, longleaf pine restoration projects have been initiated throughout the belt, mostly in response to the endangered red-cockaded woodpecker, which prefers building its nest cavities in living longleaf pine.

In Louisiana, the longleaf pine region runs east to west, directly through the middle of the state, being interrupted midway by the wide floodplain of the Mississippi River. Within the region, longleaf pine occurs both on hillsides mixed in with slash or loblolly pine, oaks, hickories, flowering dogwood, huckleberries and other shrubs, and as savannahs where near-pure stands of longleaf pine exist over a grassy, prairie-like understory.  During the spring and summer months, the wildflower show within this layer can be astonishingly beautiful. Common species include poppy mallow, false-foxglove, orange butterfly weed, larkspur, purple coneflower, spotted horsemint, and a few species of sunflowers and blazing stars, amply dotted throughout a dense carpet of bracken fern, little bluestem, dropseed, and toothache grass.

Throughout the region on hillsides possessing impermeable clay-pans and in low lying areas,  acidic bogs develop featuring plants such as red bay, sweetbay magnolia, poison sumac, gallberry, swamp cyrilla, summer sweet, snowbell, red butterfly weed, pitcher plants, pipewort, rose gentian, meadow beauty, and fringed orchids.

Longleaf pine forests also feature interesting birds! Red-cockaded woodpecker, brown-headed nuthatch, pine warbler, and Bachman’s sparrow are year round residents. Spring, however, is the best time of year to search for the usually reclusive Bachman’s sparrow, since the males are sitting up atop mid-story trees and shrubs at that time, singing their hearts out. During the winter months, longleaf pine forests are the best places to find Henslow’s sparrow, another shy species that likes to hide out among dead grass tufts within the soggier areas.

Shortleaf Pine-Oak-Hickory Region

Limited primarily to the drier tertiary hills of northwestern and north-central Louisiana, this forest type averages only 45-inches of rainfall per year (compared to the 60+ inches received within the remainder of the state). Over the years, the more adaptable loblolly pine has come to dominate throughout this region, in all but the driest ridgetops where shortleaf pine continues to thrive along with sassafras, black hickory, black gum, post oak, and southern red oak. Bottomlands at the bases of the hills possess basswood, hawthorns, redbud, red buckeye, flatwoods plum, red honeysuckle, and wild azalea. Also residing in this region are Louisiana’s rarest wildflowers, including Drummond rain-lily, trout lily, yellow violet, bloodroot, and wind flower.

Much of this region retains a wild, pre-settlement air about it. Its dry, open character has attracted several western birds such as roadrunner, scissor-tailed flycatcher, Bell’s vireo, and western kingbird, all of which nest there. Louisiana’s only records of Clark’s nutcracker, a far-western species, and ringed kingfisher, a Rio Grande Valley specialty, have come from this region. Additionally, interesting mid to late summer reports of species such as scarlet tanager and American goldfinch, with known nesting ranges well north of Louisiana, continue to intrigue local birders. Northern bald eagles reside in many of the region’s reservoir-lakes during the winter months. McCown’s, Smith’s, and chestnut-collared longspurs also turn up each winter with some regularity.

Bottomland Hardwood/Swamp Region

Characterized by low, damp, deciduous forests interlaced with permanently flooded bald cypress-tupelo gum swamps, this is the eco-region for which Louisiana is best known to the outside world. Bottomland hardwood forests are among the youngest natural habitats in Louisiana, created for the most part as residual floodplains of the post-Pleistocene Mississippi and Red Rivers and their various tributaries. The Mississippi River in particular created millions of acres of bottomland hardwood and swamp habitat as it eased back 50 to 80 miles eastward into its present-day channel at the end of the last ice age, only 5,000 years ago. It was within this vast north to south tract of forest that the ivory-billed woodpecker made its last North American stand. Early twentieth century timbering, along with mid-twenthieth century cotton and soybean farming reduced this massive ecosystem to a mere shadow of its former self. Fortunately, numerous reforestation initiatives in recent years have begun to patch the forest back together.

Bottomland hardwood forests are deciduous in character, dominated by varying percentages of sweet gum, American elm, water oak, live oak, Nuttall oak, overcup oak, hackberry, green ash, sycamore, cottonwood, and water hickory, along with a number of smaller trees such as common persimmon, green hawthorn, deciduous holly, and rough-leaf dogwood. Because these forests are inundated with floodwater at various times of the year, there is no true shrub layer beneath the canopy, except for scattered colonies of dwarf palmetto. The vine community, on the other hand, carries much of the forest’s fruit-bearing load, which is of crucial year-round importance for birds and other wildlife. Common vine species include poison ivy, trumpet creeper, crossvine, Virginia creeper, supplejack, muscadine, and other wild grapes. The herbaceous plants that constitute the forest-floor community are all obviously flood-tolerant species, and provide a beautiful spring bloom show. These include short-stemmed iris, spiderwort, spider lily, wild petunia, southern shield fern, and green dragon, to mention a few.

Throughout Louisiana, bottomland hardwood forests are the strongholds of Mississippi kite, red-shouldered hawk, barred owl, red-bellied woodpecker, downy woodpecker, Acadian flycatcher, great-crested flycatcher, white-eyed vireo, red-eyed vireo, yellow-throated vireo, prothonotary warbler, northern parula, hooded warbler, Kentucky warbler, Swainson’s warbler, yellow-breasted chat, and eastern towhee. Indeed, annual breeding bird census data collected over the past few decades within the bottomland hardwood/swamp habitats of south-central Louisiana’s Atchafalaya Basin has consistently shown the highest U.S. breeding densities for these species. Other locally-common species of interest include wood stork (summer only), swallow-tailed kite, wood thrush, American redstart, indigo bunting, and painted bunting.

Bottomland hardwood forests grade almost imperceptibly into permanently-flooded bald cypress –tupelo gum swamps. Additional swamp-dwelling plant species include swamp red maple, pumpkin ash, water elm, swamp privet, copper iris, blue Louisiana iris, swamp lily, yellow-top, and water hyacinth. Typical breeding birds include wood duck, osprey, pileated woodpecker, and yellow-throated warbler, along with a whole host of wading bird species including anhinga, great blue heron, great egret, snowy egret, little blue heron, tricolored heron, green heron, yellow-crowned night-heron, black-crowned night-heron, green heron, white ibis, and roseate spoonbill. Over the past two decades, observers are also noting a very gradual increase of black-bellied whistling-duck, a tropical American species which nests in tree cavities.

Southern bald eagles also nest in swamp habitats, prolifically so in the swamps of southern Louisiana near Franklin, Morgan City, Houma, and New Orleans. These birds generally arrive in September, raise young in mid to late winter, and depart by mid-May. Other common winter birds in the swamp include double-crested cormorant, neotropic cormorant, American white pelican, lesser scaup, hooded merganser, American robin, yellow-rumped warbler, white-throated sparrow, and American goldfinch.

Coastal Woodlands

Taken together, these miscellaneous forests – all found within the Louisiana’s coastal zone – are technically classed as bottomland hardwood types. However, due to the crucial importance of these coastal forests to all of eastern North America’s migratory songbird population, we have separated them out for more detailed discussion. Basically, three types of coastal woodlands occur: chenier, salt-dome, and generalized riparian. All are dominated by live oak and hackberry, with lesser amounts of small acacia, prickly ash, honey locust, mulberry, red bay, and prickly-pear cactus. Physiographically, coastal woodlands are most often associated with slight elevational rises (5 to 10 feet), either human-made or natural, above surrounding marshlands.

Chenier (from the French cheniere, or “oak grove”) forests are naturally occurring woodlands located upon old Pleistocene beach ridges which became effectively “stranded” due to continual accretion of land seaward during successive interglacial periods. Salt-dome forests rise up on the outcrops of massive subterranean salt-dome formations which are widely scattered throughout the coastal zone. Riparian forests occur naturally upon the banks of rivers and bayous as they approach the gulf shore, or artificially upon the spoil banks of dredged canals.

Together, these coastal woodlands serve as important “stop over” habitat for neotropical migrants during spring (March through May) and fall (August through October) migration periods, especially during periods of inclement weather when the migrational procession is  temporarily halted. During the spring months, these forests are typically loaded with the “worms” of larval butterflies and moths, and with adult insects and fruiting trees and vines during the fall months, furnishing a ready supply of food upon which migrant birds can fatten up. The tree foliage itself allows safe resting for the songbirds, protecting them from the elements and predators (hawks, falcons, owls) alike.

Upland Hardwood Region

This eco-region habitat occurs in relatively thin “slivers” of higher blufflands associated with the banks of selected rivers. The best developed of these exists on the east bank of the Mississippi River through West Feliciana, East Feliciana, and East Baton Rouge parishes just above Baton Rouge, Louisiana. This is the only forest type in Louisiana in which eastern chipmunks may be found. The soils are overlain with varying thicknesses of loess, a wind-blown sandy silt possessing the consistency of flour, which was deposited across the region 10,000 years ago. Over the centuries the loess has differentially eroded, resulting in high ridges and steep ravines. Upon the slopes and ridgetops, the forests are dominated by black cherry, winged elm, coastal pignut hickory, pecan, water oak, and cherrybark oak, with lesser amounts of swamp chestnut oak and live oak. Down in the ravines, a majestic, cathedral-like American beech—southern magnolia transitional forest predominates.

Birdlife within the upland hardwood region is almost identical with that of surrounding bottomland hardwoods. Within the breeding bird community, however, one major difference exists in the form of the worm-eating warbler, which nests solely within upland hardwood habitats. As with bottomland hardwoods, upland hardwoods feature  especially well-developed woodpecker and woodland raptor components. Mississippi kite and red-shouldered hawk are particularly abundant, and Cooper’s hawk is fairly common as well. With the exception of the red-cockaded woodpecker, every woodpecker species native to Louisiana is densely distributed within this region.

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