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Habitats of the Heard Wildlife Sanctuary

The Heard sanctuary has five habitats including Blackland prairie, wetlands, bottomland forest, upland forest and white rock escarpment. Each habitat is unique and offers a variety of plants and animals that live in specific environments.

A trail leading into a wooded area

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Blackland Prairie

A prairie habitat is an ecosystem dominated by grasses, small broad-leaved plants and wildflowers. Prairies are level or hilly grasslands usually characterized by deep, fertile soil with almost no shrubs or trees. Trees may be present, but less than 10% of the area in these broad tracts of land has a tree canopy. Typical grasses of the North Texas native grassland such as here at the Heard Wildlife Sanctuary are big bluestem, little bluestem, switch grass and yellow Indian grass. You may see good examples of these on the Bluestem Trail.


Prairies were maintained naturally for thousands of years in part by grazing animals such as bison and pronghorn, and browsers like deer. Natural prairie fires burned off the dry brown thatch that the grazing animals missed. The fires killed the woody saplings that otherwise would have encroached upon the prairies.


Natural prairie areas with bison and other prairie animals disappeared as human settlers developed and inhabited this community. Bottomland woodland habitats, such as seen on the Hoot Owl Trail, were generally left alone since the occasional flooding of these areas meant the land was not good for farming. The rolling expanse of open prairie was the most desirable land to farmers and settlers. Prairies were plowed under and changed into farmland and homesteads. Once humans were established, they also disrupted the prairie’s natural cycle of rebirth and succession by aggressively controlling fires whenever possible. Non-native grasses were introduced for livestock to graze. As suburban development and businesses replaced the farming communities, again the prairie land was the most logical and desirable place for building. Due to human factors, the famous, once-expansive North Texas native prairie is now the rarest of habitats in the area.

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In 1990, the Heard created a 50-acre wetland area within the floodplain of Wilson Creek. These wetlands have expanded and increased the quality of wildlife habitat for wetland species, lessened the impact of floodwaters from upstream areas of Wilson Creek and provided a venue for public education.  


Water from heavy rain runs into the wetlands bringing with it pollutants like motor oil and gas that accumulate on roads, chemicals like fertilizer, and litter from roadsides. Not only do the wetlands help slow down flood water and help protect property down-stream, all the organisms from the microscopic phytoplankton to the aquatic plants begin the process of cleaning up all of the man-made pollution in the water.


A boardwalk allows visitors to experience much of the wetlands and its resident wildlife. Increased presence of migratory shorebirds, wintering waterfowl and breeding neo-tropical songbirds has also been recorded at the Heard wetlands in the years since its establishment. 


Wetlands serve as nurseries for fish. Many birds, especially waterfowl, build nests and raise their young in wetlands. Migratory birds depend on food from the wetlands that lie on the way of their route, and in the south, many birds winter in the wetlands.


Amphibians and reptiles make wetlands their homes. Salamanders, frogs and toads, turtles, alligators, and snakes live in wetlands. Insects and spiders, butterflies and moths, along with mammals from the tiny mouse to the ferocious bobcat or the gigantic moose—all these creatures are supported by the different wetlands.


Over 50% of North America’s wetlands have been destroyed for farming, housing developments, roads and shopping.

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Bottomland Forest

Bottomland hardwood forests are found along rivers and streams of the southeast and south central United States, generally in broad floodplains. In the case of the Heard, it is found around our wetlands and our Heron Slough and along Wilson Creek. These ecosystems are commonly found wherever streams or rivers at least occasionally cause flooding beyond their channel confines. They are deciduous forested wetlands, made up of various species that have the ability to survive in areas with variable water levels. These forests serve a critical role in the watershed by reducing the risk and severity of flooding to downstream communities. In the case of our bottomland forest, it is also critical because it provides areas to store floodwater originating upstream in McKinney. In addition, these wetlands improve water quality by filtering and flushing nutrients, processing organic wastes, and reducing sediment before it reaches open water.

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Upland Forest

Though it occupies very little of the Heard’s nature preserve, we do also have upland forest habitat.

White Rock Escarpment

The rocks underlying most of the Heard Wildlife Sanctuary and the surrounding area are part of the Austin Chalk Limestone formation locally called white rock.  The white rock layer is most visible along the escarpment called “Old Baldy” on the Hoot Owl Trail, and also along the ridge the Science Resource Center is built upon. This rock is actually made up of billions of microfossils.  These are the shells of tiny protozoans, which settled to the ocean bottom and compacted into thick solid layers of sediment.  These sediments were deposited about 70-80 million years ago during the Cretaceous Period, when Texas was in the middle of an ocean covering most of the central United States.  Also found here are fossils of the larger forms of ocean life, oysters, clams, sea urchins, coral, shark teeth, and burrows of worms and clams. 


A fossil is any evidence of life that lived a long time ago. Fossils of mastodons and prehistoric bison are also frequently found in north central Texas.  They are in deposits of a later age, the Pleistocene Period, approximately 75,000 years ago.  Most of these deposits have been eroded through the centuries, leaving only remnants as gravel deposits.  Minerals found in Austin Chalk include calcite and iron pyrite.  Iron Pyrite is commonly known as fool’s gold, because it is yellow, hard, shiny, and heavy like real gold.


The Heard welcomes groups to assist with special service projects. Picking up trash from our grounds and trails is always an available project option for groups of all sizes. Other projects such as trail and sanctuary maintenance, habitat restoration, and handiwork jobs may be available. All service projects must be pre-scheduled. Ages: 10 through adult.