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Habitats of the Llano Estacado
Human Created Environments

Introduction

People have always modified the environment to suit their wants and needs. We grow crops and plant gardens. We build cities, suburbs, parks and cemeteries. We pamper lawns and golf courses, and keep houseplants. We also use millions of gallons of water to irrigate the modified landscape. This building, planting, and watering forms a new type of habitat – the “urban forest.”

Many of the plants in the urban forest come from nurseries and greenhouses from great distances. Often these plants carry non-native hitchhiking animals. Frequently the soil that comes with the plants brings the seeds of “weeds.” Urban forest habitat will attract insect pests as well as migrating songbirds. Native animals also adapt to new habitat. Populations of foxes, skunks, and many songbirds are all much higher in town than out in the country.

Runoff from excessive watering forms new habitat when park playas fill. Many people have small backyard fountains, birdbaths and bird feeders. Ranch stock ponds attract plants and animals that are not normally found in the surrounding landscape. Streetlights attract many kinds of insects. Even sewage ponds and garbage dumps form habitat away from town.

Reptiles and Amphibians

The Mediterranean gecko is an Old World lizard that has traveled widely by stowing away on ships but has escaped in southern port cities of America. It has taken up residence in many plant nurseries in the southern United States. Geckos hide in the soil or cling to plants and are shipped in refrigerated trucks and delivered to air-conditioned nurseries. The Mediterranean gecko arrived in Midland in the 1980s. They are mainly nocturnal, and on warm evenings can be found on buildings, window screens, or near lights where insects congregate.

The green anole lizard is native to the southern United States. It is often called the American chameleon. It has the ability to change color from green to brown, but its color-changing ability is poor compared with the true chameleons of the Old World. Like the Mediterranean gecko, the green anole extended its range to the Llano Estacado by arriving on plant shipments.

The bullfrog is the largest North American frog. It prefers larger bodies of water than most other frogs. Its tadpoles are often sold in bait shops and are frequently released. It is not a good idea to release them into natural waterways, for they will eat the native fauna, including the leopard frog.

Ornate box turtles are frequently “rescued” and kept as backyard pets. They readily adapt to their urban homes and routine feeding. It tolerates arid conditions and burrows to escape heat; rainstorms sometimes result in the appearance of large numbers of box turtles.

Mammals

Families of fox squirrels were introduced to Midland in the early 1990s clinging to large trees dug up with heavy machinery in Central Texas. The branches of the root-balled trees were bound with netting and loaded onto truck trailers. After arrival in West Texas the netting was cut, the trees planted, and the squirrels ran free. Fox squirrels are adaptable to a wide variety of forest habitats. Attitudes about fox squirrels are polarized among city dwellers: their antics may be entertaining, but they can do a tremendous amount of damage to the electrical wiring of homes.

The gray fox inhabits wooded areas, particularly areas of mixed hardwood. It is adept at climbing trees. They are not strictly nocturnal, but they are most active at night. They have been observed on many occasions in the daytime. Gray foxes are omnivorous – the food varying with the season and availability. In town, gray foxes scavenge for food scraps in alleys and pet food left outdoors. They often den in attics, under dumpsters, and in outbuildings. Red foxes are not native to Texas, but were introduced for hunting around 1895. Today red foxes occur throughout Central and Eastern Texas and have gradually spread westward, but are not as common as gray foxes. They prefer mixed wooded uplands interspersed with farms and pastures. Like the gray fox, the red fox is an opportunist.

House mice are small rodents with scaly tails. (Native mice have hairy tails). They were accidentally introduced to North America at seaport towns as stowaways on ships. They are widely distributed over Texas either as commensal or feral animals in practically all parts of the United States. As commensals, house mice live in close association with humans – in houses, outbuildings, stores, and other structures. Feral house mice may be found in fields, along watercourses, and in other places with dense vegetation. Prolific breeders, house mice can produce as many as 13 litters, with an average of six young, per year. Although destructive when allowed to run free, house mice are widely used in laboratories as subjects for biological, genetic, and medical research.

Birds

The natural occurrence of birds in an area with regard to the seasons is seasonal distribution. In any part of North America the bird population is subject to changes as a result of seasonal migration. The avifauna present at one time of year may be very different at another time of year. Regional bird checklists are readily available to see which species to expect at any given time of the year. The urban forest in and around Midland, Texas provides habitat for about 150 species of migrating birds that otherwise would not stop. Bird species may be grouped into the following seasonal categories:

  • Summer Residents: Species in an area during the summer, coming from the south in the spring to breed and returning in the fall.

  • Transients: Species stopping temporarily in an area during their northward migration in the spring and again during their southward migration in the fall.

  • Winter Visitors: Species in an area during the winter, having come from their northern nesting grounds to pass the winter in a less rigorous climate and traveling north in the spring.

  • Permanent Residents: Species not undergoing a regular seasonal migration and staying in the same area the year round.

Oak acorns form a major portion of the diet of blue jays, but they also eat the eggs of other birds, insects, and other plant seeds. They became permanent residents on the Llano Estacado when humans provided oak habitat. One of the blue jay’s outstanding characteristics is its wide vocal repertoire. They are curious and often travel together in noisy family groups.

The Mississippi kite is a summer resident that nests in tall trees along watercourses. They eat thousands of grasshoppers and cicadas every year. They are very protective of their nest site and will attack any perceived predator that comes near. In the fall, hundreds and even thousands gather to make the long flight to South America for the winter. In recent years the number of Mississippi kites has diminished.

On March 16, 1890 sixty European starlings were released in Central Park in New York City as a tribute to the birds mentioned by William Shakespeare. The next year forty more starlings were released. From these 100 starlings sprang unnumbered millions that now flourish throughout North America as introduced residents. They are hardy, prolific, aggressive, and compete with native birds for nesting sites.

The American widgeon (wigeon) is a winter visitor. It is also known as the “baldpate” because of the shining white crown of the male. It is a wary dabbling duck that provides an early warning system for other ducks. It often feeds on scattered debris floating on the water’s surface brought up by the feeding activities of diving ducks.

The western tanager is a bird of pine and oak forests of the Rocky Mountains. Because of the introduced urban forest habitat of West Texas, the western tanager is a transient that may be seen in the spring and fall migrations. The western tanager feeds mostly on insects and fruit.

Plants

Texas was no longer a wild frontier with the successes of the cattle industry, agriculture, the railroads, and the discovery of oil. Prosperity came for the middle class. Time and resources were available to plant things to make homesteads more comfortable and attractive. For the most part homesteaders chose plants and landscape designs they or their parents had known before coming to Texas. Texans of Mexican or Spanish descent enclosed their yards with walls and built patios. They adorned their landscapes with drought-tolerant trees, shrubs, vines, and perennials from south of the Rio Grande. Anglo settlers preferred the traditions of northern Europe with tightly clipped hedges, manicured lawns, and isolated flower gardens that require tremendous amounts of water. It is important that in drought-prone areas such as the Llano Estacado to use plants adapted to the soils, rainfall, and temperature. Even under the best of circumstances, when soils are disturbed for cultivation, the opportunity exists for the growth of “weeds.” Plant species are considered as weeds when they interfere with human activities or welfare. Weeds can be any types of plants that grow where they are not wanted.

The common dandelion is native to Europe and Asia, but is now cosmopolitan. It grows in moist sites, including lawns, meadows, pastures, and overgrazed areas. Dandelions are considered as weeds in lawns and gardens, but are good forage on cattle and sheep ranges. They do have several culinary and medicinal uses as well.

Poison ivy arrived in Midland on the root balls of large trees excavated from further east and then transplanted in home landscapes. Birds have transported the seeds after eating the berries and accidentally planted seeds in other home landscapes. If the plant oil or dried residue of poison ivy comes in contact with the skin, many people develop a severe skin rash within a few hours.

Pigweed, also known as carelessweed, is commonly found in cultivated lands, gardens, and waste areas. It is a prolific seed producer and the seed can be spread great distances with the wind.

Ailanthus, or the tree-of-heaven, is a native of China where it has medicinal uses. It is cultivated in the United States for ornament. It is very hardy and sometimes escapes cultivation and grows well under adverse conditions of dust, smoke, and poor soil. It is often found in waste places, trash heaps, vacant lots, cracks of pavement, and crowded against buildings.

Mistletoe is a semi-parasitic shrub that grows on trees. They have evergreen leaves that carry out some photosynthesis, but they mainly rely on their host trees for water and mineral supplies. Most mistletoes are spread when birds eat the fruit and later deposit the seeds on another tree. If mistletoe growth is heavy, it can be fatal for a tree, but usually it only results in growth reduction of the host tree. Mistletoe has recently become recognized as ecologically important. It figures prominently in the mythologies and customs of many cultures, and is being studied for medicinal uses.

Plant galls are numerous, widespread, and varied. A gall arises as a result of parasitic attack. It represents the growth reaction of the plant host to the chemical attack of a parasite---a bacterium, fungus, mite, or insect. A gall develops either by abnormal increase in the number of plant cells or by the cells becoming abnormally enlarged. Whatever the form of the gall, it is derived entirely form the tissues of the plant and not the parasite. Usually gall formation is closely associated with the reproduction of the parasite.

Invertebrates

Many species of invertebrates, especially insects, may be classified into two groups based on their relationship to humans: beneficial and harmful. We benefit from insects in many ways; without them, human society could not exist as it is now. Without the pollinating services of bees and other insects, we would have few fruits and vegetables. Many insect species are predators or parasites and are important in keeping pest species under control. Others help to control undesirable weeds. Still others clean up refuse.

Conversely, some species are destructive. They attack crops and ornamental plants, attack human possessions like homes, clothing, furniture, and food. Some insects transmit diseases to humans, livestock, pets, and plants. And some are an annoyance because of their presence, odors, bites, or stings. The good, however, done by beneficial insects far outweighs the harm done by injurious ones.

Aphids form a large group of insects that are frequently found in large numbers sucking the sap from the stems or leaves of plants. Many species are serious pests of cultivated plants. They can cause a plant to wilt by their feeding, and some are vectors of many serious plant diseases.

The bodies of mealybugs are covered with waxy secretions. They may be found on almost any part of a host plant. Several species are serious pests of citrus crops and many occur in greenhouses where they attack a variety of plants.

Braconid wasps are a beneficial family of parasitic wasps. Many have considerable value in the control of insect pests. The larvae are parasites of a great variety of insects. Many species pupate in silken cocoons on the outside of the body of the host.

Ladybird beetles (“ladybugs”) are predaceous, as both larvae and adults, and mainly feed on aphids; they are frequently common on vegetation where aphids are numerous. Ladybird beetles are sometimes imported into infested areas to serve as a means of biological control of insect pests.

The brown garden snail is native to the Mediterranean region. It was introduced to the United States in the 1850s as an edible delicacy. It has become a major agricultural pest in many areas and feeds on many types of fruit trees, vegetable crops, garden flowers, and cereals. Another mollusk, the decollate snail, was introduced from North Africa as a biological control agent. It is a voracious predator of the brown garden snail.

Dog-day cicadas came to West Texas in the 1920s with the introduction of the Siberian elm tree. Cicada nymphs live underground feeding on plant juices from roots, sometimes not emerging as adults for several years depending on the species. Males have the ability to produce conspicuously loud sounds by a pair of tymbals on their abdomen. Each species of cicada has its own characteristic songs. Female cicada wasps (cicada killers) are large solitary wasps that nest in the ground and provision their nests with stung and paralyzed cicadas.

Related Resources

The following resources for learning more about the Human Created (Urban) Environments are available on this website:

Photo Essays

Essays

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Sibley Nature Center
1307 E. Wadley, Midland, Texas 79705
phone 432.684.6827
email info@sibleynaturecenter.org