Matt Wagner, Texas Parks and Wildlife Department, and Felipe Chavez Ramirez, World Wildlife Fund, Chihuahuan Desert Program,San Pedro Garza Garcia, Nuevo Leon.

The Taumalipan Biotic Province extends southward from the Balcones Escarpment in Texas into northern Mexico approximately 350 km. In Mexico, it is bordered by the Sierra Madre Oriental on the West, the Sierra San Carlos to the South, and the Gulf of Mexico marshes to the East. The Taumalipan Region encompasses some 4.5 million hectares in Texas alone. The region is dominated by a diversity of woody plants including mesquite, various acacias, graneneo, foresteria, cenizo, whitebrush, condalia, prickly pear, and tasajillio. This characteristic thorn scrub habitat creates a fairly homogeneous vegetation structure and composition throughout the region, except where river basins dissect the area (Blair 1950).

The river systems consist chiefly of the Nueces, Rio Grande, and Rio Soto la Marina, each with a different assemblage of riparian vegetation. The Nueces and it's tributaries contain a well developed live oak gallery forest, while the Rio Grande Valley is characterized by retama, Texas ebony, anaqua and other species. Introduced salt cedar is also a major component in many areas along the Rio Grande. Of course, much of the Lower Rio Grande Valley has been transformed by intensive agriculture practices, so that what habitat remains is of critical importance to wildlife. Along the Rio Corona, which feeds the Rio Soto la Marina, Montezuma bald cypress and sycamore can be found (Wauer 1992). In addition to these riparian corridors, palm groves occur infrequently in the region, and lend yet another unique habitat association to the Tamaulipan Region.

This diversity of habitats and associated vegetation, supports a wide variety of wildlife species. The vast majority of these are classified as "nongame". This means that they are not hunted as game, nor are they endangered. Nongame wildlife is not a biological or technical term, rather it is an administrative term that lumps all wildlife species whose take (hunting for recreation, food or fur) is not legally regulated, although in Mexico it is usually prohibited. In biologic terms it includes most biodiversity of any political unit. However, commonly it refers primarily to birds, mammals and reptiles. There are differences between the two countries that share the Tamaulipan Region in that a species considered nongame in the US can be regulated as a food species in Mexico (i.e. pack rats, Neotoma spp.). In addition, an exotic species, such as wild boar, is not regulated in the US, however in Mexico it is regulated in the hunting calendar as a game species.

The objective of this paper is to increase awareness of landowners to issues of biodiversity and nongame animals including the diveristy of nongame and endangered species and opportunities for managment in the Tamaulipan Region. Management in the sense of potential opportunities for use as well as the discussion of some established techniques. Nongame wildlife includes the most common birds such as northern mockingbird to the most elusive mammals such as the mountain lion. In fact, approximately 90% of all the wildlife species in Texas and Mexico are considered as nongame, which increasingly can be an important aspect of diversification for landowners. As our urban population grows, more people are demanding more diverse forms of outdoor recreation. Hiking, camping, and wildlife watching are now among the fastest growing recreation activities. Management practices that will enhance a diversity of wildlife are an important consideration for landowners. Even more important is to sensitize this new group of outdoor users to the fact that private land stewardship is the key to sustaining wildlife populations into the next millennium.

TAMAULIPAN REGION BIODIVERSITY

Put simply, biodiversity is the variety of living organisms and their ecological roles in the environment. Due to the scope of these proceedings, we will present basic information only on the vertebrate component of the biodiversity of this region. The Tamaulipan Region is rich in all terrestrial vertebrate groups as exemplified by a survey of existing information for the states comprising this region (Table 1).

Table 1. Species of different vertebrate groups reported in 3 Mexican states in the Tamaulipan Region and the state of Texas (Mexican data from Conabio 1998, Texas information from Blair 1950, Damude 1999, Garrett and Barker 1987)

Following is a general discussion of the main vertebrate groups with treatment of some of the most salient features within each group.

BIRDS

Most of the 600 species of birds in Texas migrate through or breed in the Tamaulipan Region. The great diversity of birds in the region has attracted birders from around the country in pursuit of species found nowhere else in the U.S.. In Texas, 28 species of nongame birds are endemic or confined to the Tamaulipan for breeding, and at least 16 are neotropical birds that reach their northern breeding limits here (Fisher 1984). These include such specialties as ringed kingfisher, red-billed pigeon, Altamira oriole and brown jay. A relatively common neotropical migrant, painted bunting, is one of North America's most beautiful birds. Resident birds such as pyrrhuloxia are more closely tied to a general area, whereas long distance migrants such as the painted bunting are more apt to move to more suitable nesting sites depending on local rainfall. Water-dependent birds such as the great blue heron are obviously closely tied to water for their food source. Breeding pairs of these and other colonial nesters can be reduced to half of their historic nesting sites when surface water is reduced due to drought conditions.

MAMMALS

Although overlooked by many, nongame mammals are a vital and interesting component of the Tamaulipan fauna. At least 61 species of mammals occur in the Tamaulipan of Texas. Fifteen are considered to be neotropical (Blair 1950). In the Mexican states of the Tamaulipan, more than 100 species are present. Many rodent species are adapted to drought conditions, which make them well suited to the Tamaulipan Region. Many of the rodents are nocturnal and burrow to escape the daytime heat. Flying mammals, bats are also a common element of the mammalian fauna in the Tamaulipan. Common predators such as the bobcat and more rare ones such as ocelots and jaguars are present. During drought years there is a decrease in cover for small mammals. This may make them more susceptible to predation which may account for the higher observation of feline predators during dry conditions. Although mountain lions are quite widespread throughout the region, research in South Texas reveals that they are closely tied to riparian areas (Harveson 1997).

REPTILES AND AMPHIBIANS

Of the over 200 reptiles and amphibians (herpetiles) in Texas, 19 species of lizards, 6 snakes, 4 frogs, 1 toad and 1 tortoise occur only in the Tamaulipan Region (Blair 1950). In Mexico, there are 290 amphibians and more than 70 reptiles reported, with approximately 60 and 15 reptiles and amphibians, respectively, present in the state of Coahuila, Nuevo Leon and Tamaulipas. Most of the species include snakes and lizards, but also turtles and frogs, in addition to some larger species such as sea turtles and alligators.

STATUS AND CONSERVATION

Rare and endangered Species

The Tamaulipan Region is home to many species currently considered threatened or endangered by either the U.S. and/or Mexico. Threatened and endangered are designations given to species, that due to a decrease in population and/or threats to the survival of a population, are legally recognized for their protection. Some mammals, such as the ocelot and jagaurundi have received federal endangered status in the United States and Mexico, while the white-nosed coati, Coue?s rice rat, and southern yellow bat are considered state-threatened in Texas. Other interesting reptiles such as the Texas horned lizard, reticulate collared lizard, Texas tortoise, and Texas indigo snake (the largest snake in the state with a length of over 8 feet), are state-threatened species and protected from sale or possession because of their relative rarity. Many other species are considered to be endangered or threatened in both countries including some birds, such as the Aplomado falcon, bat falcon, reddish egret, and many smaller passerine birds.

Habitat fragmentation and loss is the primary cause for species populations declines and eventual listing as an endangered or threatened species. Therefore, special consideration should be given when conducting habitat manipulations in the range of a listed species in either country. Prior approval by the appropriate regulating agency may be required before substantial modifications are made to endangered species habitat. Proper grazing, the discretionary use of broadcast pesticides, the creation of patchy habitats and cover, and the reduction in feral predators such as cats and hogs can benefit threatened reptiles such as the horned lizard (Henke and Fair 1998).

Effect of Exotics species on Native Wildlife

Introduced mammals such as feral cats and hogs are changing the ecological relations of this and many other biological regions in Mexico and the U.S. Increasing feral cat populations may benefit potential predators like great horned owls, however, the most significant impact is that of predation on songbirds and small mammals. It is believed that there are an estimated 60 - 70 million cats in the U.S. today. Free ranging domestic cats are estimated to kill about 39 million birds annually in the state of Wisconsin alone (Coleman and Temple 1993). Feral hogs are increasing in many areas of the region, but are limited by water availability. Although they are considered to be an unofficial game animal, they compete directly with native wildlife for food, and cause considerable property damage. Feral hogs are also significant predators of ground nesting birds. While in Texas hogs may be hunted at anytime, their take in Mexico is regulated as a game species, with hunting season and bag limits announced in the annual hunting calendar.

Conservation Problems with Native Nongame Wildlife

The wide diversity and unique herpetofauna of the Tamaulipan Region attracts reptile enthusiasts or ‘herpers' from many parts of the U.S as well as other parts of the world. The commercial collection of reptiles for the meat and pet trade in Texas has led to efforts by the Texas Parks and Wildlife Department to establish a permit program for the sale and commercial possession of certain important species such as softshelled turtles, diamondback rattlesnakes, and Mexican milk snakes. Food importers in Taiwan have been documented to obtain over 27,000 kg of softshell turtles in a single shipment from South Texas sources. These turtles were being sold live at a rate of nearly $5.00 per kg for a total of almost $130,000. Many articles have focused on animals such as box turtles, which are popular in the pet trade, retailing for around $25. At least 64 other species of native reptiles and amphibians have been identified in the Texas food and pet trade with some retail values ranging from $3 for green anoles to $100 for Mexican milk snakes. Many of the specialty snakes sold in Texas are captive-bred, using brood stock from popular Texas locations (Wagner 1997a).In addition, Texas Parks and Wildlife Department staff have received reports of buyers driving circuits to buy diamondback rattlesnakes for the commercial trade in specialty skins or rattlesnake parts. In 1992, at least 2 large-scale dealers in live rattlesnakes claimed multiple processing facilities throughout the state. At least 12 commercial buyers of rattlesnakes and rattlesnake parts were identified in 1992 and 1993. In 1986, 5 dealers were collectively estimated to have processed between 300,000-500,000 rattlesnakes. The 1989 harvest estimate by 7 dealers was almost 230,000 kg of meat and/or products from at least 400,000 snakes. One USFW agent reported 4,500 kg of whole-frozen rattlesnakes in a Gulf Coast fish house in late 1989. The market value at that time ranged between $7.00 and $26.00 per kilogram for live snakes (Jester 1992, Jester and Adams 1990). The range of nongame species and the number of animals traded indicates a potential significant impact on some local nongame populations (Jester 1992). However, under controlled conditions, the commercial harvest of some reptiles may be an incentive for private landowners to maintain habitat for economically important species. Many avian species in the Tamaulipan region are bought and sold in the pet trade market. Parrots are the primary species collected in the wild and are generally smuggled across the border to the U.S. While actual numbers are lacking, it is estimated that in the 1980´s 150,000 birds, mostly parrots were being smuggled across the Mexico-Texas border (Fitzgerald 1989). It is considered that up to 60% of parrots collected for export in Mexico die before reaching the U.S. border (Inigo-Elias and Ramos 1991). In recent years (1990´s), the average number of parrots seized per year has been 616. Several songbirds are common as cage birds in many parts of Mexico, which are collected legally from the wild via collection and commercial permits. However, besides the issuing of permits to collect birds, there are no regulations or enforcement in the actual collection and/or transport of these species and it is widely recognized that there are many collectors without permits.

Nature Tourism

The average person today is unaware of the great diversity of wildlife that can be found outside the home and office. In the U.S., most wildlife information is usually obtained through television or magazine articles. This is especially true of young people learning to appreciate nature without access to wild places. Teaching children the difference between a bird and a butterfly seems absurd to most of us with a natural resource background, but in reality, that is the level of exposure many children have, especially in urban settings. Today, there is a growing number of people seeking access to wildlife and wild places for the simple enjoyment of being in natural surroundings. Wildlife viewing, particularly birding, is a potential economic option for many landowners seeking additional revenue streams.

World-wide, nature-based tourism has been increasing about 30% annually since 1987 (World Tourism Organization 1992), with total economic value of about $238 billion in 1994 (Eco-tourism Society 1994). This can only be expected to increase in the years ahead. In the future, wildlife watching may become the largest outdoor activity. In fact bird watching grew about 150% from 1983 to 1995 according to the 1994-95 National Survey on Recreation and the Environment (NSRE). This growth has led to the development of the Great Texas Birding Trail, a road system winding through 41 Texas counties along the Texas Coast. When completed, the Trail will feature over 300 distinct wildlife-viewing sites. In association with the Birding Trail is the Texas Birding Classic. This event is a week-long competitive birding tournament which is billed as the biggest, longest, and wildest birdwatching tournament in the U.S. Winners of the Birding Classic share a total of $50,000 to be used for conservation projects in Texas. Finally, the World Birding Center, a major education facility with an international scope, is being planned for the Lower Rio Grande Valley of Texas. It is intended to be a world class destination featuring many varied exhibits and urban wildlife programs making it the gateway for birding the Texas Gulf Coast, the Lower Rio Grande Valley, and Mexican borderlands.

From an economic standpoint, there are about a million hunters in Texas today (8% of the population). They spend over a billion dollars per year in pursuit of that activity. Anglers number nearly 3 million or 21%, spending over one and a half billion per year. The number of people who enjoy wildlife watching however, number 4 million, or nearly on third of the population. They are contributing only about as much as hunters.

There are several reasons for this discrepancy, not the least of which is an adequate funding mechanism to support ‘nonconsumptive' wildlife management programs, much like hunting licenses and the Pittman-Roberstson Act work for hunters in the U.S. In fact, there is a movement today called ‘Teaming with Wildlife' that seeks to develop new funding mechanisms to accomplish nongame management and tourism infrastructure on a national level. In addition, the amount of private land available to wildlife watchers may not be as great as hunters, but the demand is growing rapidly. Several South Texas ranches are already catering to birders. However, nature tourism is not a panacea for every ranch, and will not even be feasible for most. Unless the land supports some unique feature such as a wetland, oak forest, native prairie, or other natural resource that attracts a rare assemblage of species, marketing is difficult. Those properties with specialized habitats will harbor specialized forms of wildlife not found on other ranches, and in effect create a niche market. Other natural phenomenon such as the South Texas ‘Hawk Alley' raptor migration, monarch butterfly roosts along the Nueces River, and Mexican free-tailed bat flights are temporal in nature, and cannot always be reliable from a commercial standpoint. Yet, there are over a dozen festivals in Texas today associated with particular resident and migratory wildlife that could be used to promote tours on local ranches.

Habitat

Habitat refers to the combined needs of a species for its survival, that is the area (generally referenced as a vegetation association) where it satisfies its needs for food, shelter, and reproduction. For simplicity, we will describe habitats as distinctive vegetation associations where one expects large number of nongame species to occur. Whether birdwatching, hunting or just being outdoors, the common element is sufficient habitat quality and quantity to pursue these activities. The principles for managing for nongame species are the same as for game species - habitat management is the key. Providing the proper levels of food, water and cover for nongame will attract and maintain wildlife diversity on the land. Following are four major habitat types of the Tamaulipan Region in Texas, the nongame assemblages, and best management practices used to enhance or maintain the habitat. Nongame assemblages have been selected to characterize the main habitats of the region, and to serve as indicator species that could be found in the area. In most cases, their presence is not limited solely to a particular vegetation composition, but rather is indicative of habitat structure.

Thorn Scrub/Mixed Brush

Typical of much of the Tamaulipan, thorn scrub habitat is dominated be a great diversity of woody plants that provide food and cover for many nongame species. Fruits, seeds, and flowers of cactuses, leguminous shrubs, and a variety of other beneficial shrubs and forbs provide food for birds, small mammals, some reptiles and insects. The quality and extent of habitat will determine which species will occur, and how well wildlife populations will be sustained through stress periods like drought. Many times, thorn scrub is a successional landscape, supporting brush species of lower stature usually after some form of mechanical brush control like roller chopping or root plowing. Periodic management is required to maintain a mosaic of habitat structure throughout a particular land tract. This will prevent brush from growing beyond the point of usefulness to the species that require a lower growth form, while allowing other areas to mature. Brush management practices like rollerchopping may be effective in achieving this goal without the detrimental effects of rootplowing. Rootplowing typically creates a less diverse plant community, dominated many times by mesquite. Studies have shown that depending on the size of the cleared blocks and juxtaposition with other blocks of habitat on a landscape scale, bird diversity and density will change (Fulbright 1996). A less diverse plant community generally means a decrease in wildlife diversity on a particular site, but diversity on a landscape level (i.e. county level) may actually increase depending on what species have benefitted from a particular land practice. Some species also require large blocks of undisturbed habitat. These species will decrease when habitat is fragmented. Leaving connective corridors between cleared patches may reduce the effects of fragmentation. Restoration of thorn scrub habitat has been conducted by the Texas Parks and Wildlife Department in the Lower Rio Grande Valley for almost 50 years. Transplanting seedlings of high-quality shrubs can re-establish vital habitat, and link remaining tracts of sizable acreage to form a viable corridor for wildlife. The nongame assemblage for the thorn scrub/mixed brush habitat includes: lark bunting (early succession), blue grosbeak, verdin, elf owl, black-tailed gnatcatcher, Texas pocket gopher, southern plains woodrat, southern earless lizard, Texas tortoise and Texas indigo snake.

Mesquite Savannah/Park Habitats

Mesquite savannahs can be described as having a canopy cover of mesquite, granjeno, lotebush, prickly pear and other shrubs of less than 70%, characterized by a dominant grass and forb layer. The land use history of many tracts has changed this savannah condition, resulting in a ?thicketized? understory with an increase in brush species. Although these plants have wildlife value as food and shelter for many nongame species, they may become detrimental when over-abundant, and begin to out-compete native grasses and forbs that are essential components in savannah habitats. For example, scissor-tailed flycatchers require relatively open mesquite savannah for nesting as a defense against predators (Nolte and Fulbright 1996).

Savannahs are transitional between open grasslands and thorn scrub habitats. This mosaic type of habitat supports a more diverse vegetation community for a greater diversity of wildlife. Active management is required to mimic the natural disturbances historically caused by wind and fire, and create the habitats in large enough areas for the species adapted to them (DeGraaf and Rappole 1995). Savannah habitats should be integrated into an overall management scheme for a particular site based upon what the potential vegetation is, and what other habitats are present. Practices to restore, maintain, or enhance a savannah may include thinning undesirable or exotic plants by using selective herbicides on individual plants, mechanical treatments, and prescribed burns to control young brush species. In some cases, native woody plant establishment may be required. If brush is cut and removed, the appropriate herbicide should be applied to the stump surface to prevent re-sprouting. Cut debris should be stacked into piles to provide cover for small mammals and reptiles. Clumps of scattered brush interspersed with herbaceous vegetation will create ?mini-mottes? containing a diversity of plant species and structural layers. This, in turn, benefits a wider variety of nongame species. As shrubs mature, it will be necessary to top-kill them before they reach a height beyond the usefulness of the target species for nesting or cover. Fire is generally the best way to achieve this, but mechanical treatment may be more applicable where burning is not possible or does not create the desired results. Late summer burns provide optimum conditions if fuel moisture levels are low enough to create sufficient heat. However, managers need to be aware that the risk of a fire escaping from the target area is greater in the summer. Late summer also follows the breeding season for most all grassland birds and should not interfere with their nesting success. Follow-up burns will further reduce the energy reserves and re-sprouting ability of many established plants (Wagner 1997b). Late summer burns are being investigated as a means of re-creating mesquite savannah in North Central Texas (Ansley 1997).

Limiting the amount of savannah burned in a given year will insure that wintering sparrows and other wildlife will find refuge in adjacent cover. It is recommended that burns take place every 4-5 years with approximately 25% of the total amount of savannah burned each year. Use of pastures by wintering sparrows such as savannah sparrow, as well as other birds including western meadowlark, and sedge wren can be reduced following a burn. Other birds like long-billed curlew, long-billed thrasher, white-tailed hawk, American Kestrels, mourning dove, and killdeer are attracted to open, post-burned areas for foraging. Higher bird density and diversity were present on burned-unburned edge compared to interior of post-burned area (Tewes 1982). Burning reduces litter and standing dead material and may increase forb density and production.

High-intensity, short duration grazing can also be used to create a mosaic of habitat patches. Guthery et al. (1990) compared nongame bird population dynamics of several grazing systems. Heavy short duration grazing (HSDG) was the only grazing system to show an increase in bird species diversity between years compared to moderate continuous grazing, heavy continuous grazing, and heavy deferred-rotation. Richness decreased in all systems in 1984, but the decline was lowest under HSDG. Increased bird richness and diversity on the HSDG treatment were attributed to a combination of plant species composition and higher variance in structural measures. The HSDG treatment showed more stability in both plant and bird community composition. Meadowlark density was higher under moderate grazing compared to heavy grazing in the Coastal Bend area of Texas (Baker and Guthery 1990). Mountain plovers and lark sparrows, and horned larks require short vegetation, and respond positively to grazing. Other species such as Cassin's sparrow require heavy leaf litter and grass cover, and respond negatively to grazed versus ungrazed grasslands. Still other species require intermediate levels of ground cover, and respond positively to moderate grazing in tall grass communities. Species in this category include grasshopper sparrow, dickcissel, and bobolink (Finch and Stangel 1993). Grazing may also enhance habitat for other species such as the black-tailed jackrabbit, and some rodent species. Preliminary research on the Chaparral Wildlife Management Area indicated that there was no difference in herpetofauna species richness between grazed and ungrazed pastures. Species diversity was greater on grazed sites, and total numbers were greater on ungrazed sites (Ruthven et al 1998).

As with prescribed burning, it is desirable to rest a portion of the total amount of savannah during the year. The rest-rotation grazing system (Stoddart et al. 1975) is particularly suited to prairie-dependent species in that the deferred part of the range is given complete rest for an entire year. This allows seed production and dispersion, sufficient leaf litter accumulation, and undisturbed conditions for wintering, transient, and breeding birds. Approximately 25% of the total amount of prairie should be rested in a given year, on a rotational basis. The 75% of remaining prairie should be rotationally grazed, moving livestock between pastures when approximately 50% of the available forage is removed. This practice of "taking half and leaving half" is an objective measure based on the land managers ability to judge the desired condition of the range to benefit plants and animals. Degree of use can also be estimated by using small exclosures to compare grazed and ungrazed forage height. Introduced grasses such as buffelgrass, Wilman's lovegrass, and a number of other exotics have accounted for substantial acreage conversion from native conditions, to the detriment of wildlife.

The species assemblage for mesquite savannah habitats are white-tailed hawk, blue grosbeak, Botteri's sparrow, northern grasshopper mouse, Gulf Coast kangaroo rat, Texas horned lizard, Schott's whipsnake, Mexican racer, and Couch's spadefoot frog.

Woodland and Riparian Areas

Woodlands are forested habitats (i.e. bosques) occurring in large blocks, small patches, or irregular corridors. They typically support a diversity of overstory trees and understory shrubs that provide food in the form of fruits, nuts and berries. Woodlands also provide vertical layers important for nesting and cover for a wide variety of nongame birds. The amount of plant canopy cover, height, and species diversity are important factors in determining which bird species will use wooded habitats. In general, a higher structural and plant diversity will support a greater diversity of wildlife.

Some woodlands occur along the margins of rivers, creeks, oxbow lakes or other water features. These specialized riparian habitats represent some of the most biologically rich and unique habitats in Texas. Riparian areas also act as filters for excess nutrient runoff, and prevent erosion when vegetation is properly managed. Although less than 4 % of Texas' land area is made up of riparian-type vegetation, higher numbers of wildlife and a greater diversity of species are found in these areas than in other habitats. Dominant trees of Tamaulipan riparian areas were listed in the introduction according to river basin. Other species include cedar elm, sugar hackberry, black willow, and Mexican ash.

In woodlands, habitat patch size can be a limiting factor for successful reproduction of many interior-nesting bird species. When large openings are created in woodland habitats, nest predators and the brown-headed cowbird, a nest parasite, are more likely to gain access to interior-nesting species. Depending on the goals of the land manager and the amount of contiguous woodlands in close proximity to the property, it may be desirable to re-forest existing openings with native trees to create a continuous closed canopy. On the other hand, highly fragmented wooded patches surrounded by openings in various successional stages may not become suitable tracts for interior species no matter what the management strategy is. Leaving or restoring connective corridors between cleared patches may reduce the effects of fragmentation. Where needed, plant a diversity of native food-producing trees. Consider using simple techniques such as setting fence posts connected with a single smooth wire 120 centimeters above the ground. This will provide perching sites for birds to deposit seeds in the appropriate area. In addition, buffer zones of wooded habitat along riparian areas should be at least 46 meters on each side of the stream. This not only provides cover for wildlife movement between tracts of habitat, but serves to stabilize stream banks and filter runoff. Protect young, establishing trees and shrubs from over-browsing by livestock using temporary electric fencing, or construct permanent fencing to control the intensity, timing, and location of grazing in woodlands and riparian areas (Wagner 1997b).

In woodland, riparian or other sensitive habitats, the selective control of exotic plants or other undesirable species can be conducted by hand-cutting, girdling or selective herbicide applications. Apply the appropriate herbicide directly to the cut stump surface to prevent re-sprouting. Basal bark treatments, or the ‘hack and squirt' method can be used to kill undesirable trees without impacting surrounding plants. This also creates snags for cavity-nesting species. Six snags and/or den trees per acre of woodland is considered adequate for most kinds of wildlife (Missouri Department of Conservation 1985).

The golden-fronted woodpecker is a resident species typical of woodland and riparian areas of South Texas, while the vermillion flycatcher and Audubon's oriole breed in similar habitat. Curve-billed thrasher can be found nesting in mature upland thorn woodlands, while Bell's vireo uses the more brushy-type riparian habitats. Other key species of the Texas Tamaulipan woodlands and riparian areas include gray hawk, Altamira oriole, ferruginous pygmy-owl, Coue's rice rat (adjacent to grassy marsh areas), coati, mesquite lizard (Rio Grande), Ruthven's whipsnake, northern cat-eyed snake, and sheep frog.

Palm Groves

Sabal palms are believed to have once extended continuously from Northern Mexico into South Texas. As the climate became drier, palms became restricted to locations providing adequate moisture, typically along rivers or in the valleys of the mountain foothills of Mexico. The Sabal Palm is very rare in Texas. The largest grove is slightly over 200 hectares near Brownsville, Texas, and is managed as a sanctuary by National Audubon Society.

Wildfires probably affected some areas of the historical palm woodlands, but it is unlikely that a natural fire would have burned all the palms along the Rio Grande River in one event. While some species were eliminated by fire, they were survived by others. When the burned area recovered, those species could re-establish from the unburned adjacent areas. Although Sabal palms are somewhat fire resistant, other plants and animals, and the protective insulating blanket of leaf litter that insures survival of some tropical species in the winter could be eliminated by fire.

Exotic plants such as nephitis now threaten the survival of young palms and native shrubs by shading out seedlings. Efforts are now underway to restore the Sabal Palm Sanctuary to a more natural condition. As exotics are removed, native species will be seeded and transplanted to accelerate the return to a natural state (Sabal Palm Sanctuary 1998)

The nongame assemblage for Palm Grove habitat is buff-bellied hummingbird, southern yellow bat, Mexican spiny pocket mouse, Central American speckled racer, and Rio Grande chirping frog.

Water

In the Tamaulipan Region, drought is a common occurrence, and is a temporal limiting factor for most wildlife. Even though native wildlife are adapted to dry conditions and can survive periodic drought, poor habitat quality may exasperate negative effects on wildlife during prolonged dry conditions. For example, during drought, many birds will establish territories and attempt to nest, but may not produce eggs or fledge young. When new vegetation growth is inhibited due to drought, the insects that feed on new growth will be suppressed, which will affect reproductive success of some species that feed on insects.

It is no secret that the provision of livestock water has greatly benefited wildlife, in particular nongame species. Generally, one water site per 80 - 120 ha is sufficient (Guthrey 1985). There are several techniques to modify livestock troughs for wildlife. They range from simple concrete ramps or placing rocks inside a trough, to large floating platforms used in open water storage tanks (Payne and Bryant 1994). Portable devices can be moved to provide alternate watering sites for wildlife. A water depth of about 7-8 cm is sufficient for most nongame wildlife.

Stock pond management is another consideration. Restricting livestock access by partial fencing provides protection for vegetation along the pond edge for waterfowl and wading birds, while creating bare ground on the grazed portion. Bare edges around ponds are important for many small birds and other wildlife to gain access. It may also be possible to completely fence off some ponds while allowing unrestricted access to others. Since many stock ponds dry up during dry conditions, the design of areas accessible to cattle even during low water is important to consider. The design by DUMAC of ?minihabitat? for waterfowl is an efficient model.

Most arid rodents and reptiles are not dependent on surface water for their metabolic needs. They obtain water mostly through plant or animal food sources. Conversely, wading birds, fresh water turtles and amphibians are obviously tied to permanent surface water sources for part or all of their life cycle.

Nesting and Escape Cover

An important consideration to enhance habitat for nesting birds is the use of nest boxes for cavity nesting species. Nest boxes are an easy way to increase nesting success while providing an educational opportunity for children. Nest boxes help offset the loss of natural snags which are becoming less common in managed landscapes. Snags are standing dead trees that provide feeding and nesting opportunities for many species. They are extremely important to everything from woodpeckers to some bats. The elf owl, the smallest owl in North America and the Ferruginous Pygmy Owl will readily use nest boxes, as will barn owls, purple martins, bluebirds, wrens, titmice, and chickadees. Nest box plans are available from the Texas Parks and Wildlife Department for almost every cavity nesting or denning animal.

Brush piles are an effective management practice to enhance small mammal populations as well as quail and other birds. Generally, 2-10 piles per hectare, spaced 30-60 m apart is recommended for small wildlife (Giles 1978, Martin and Steele 1984). Brush piles can be used to provide cover between blocks of wooded habitat, and they will get more use in proximity to water.

SUMMARY

The perpetuation of secure habitat on private lands lies in maintaining production agriculture on suitable land, and in controlled, sustainable commercialization (i.e. hunting and nature tourism) of key resident wildlife (DeGraaf and Rappole 1995) . Refining these practices will provide landowner incentive to protect and restore large tracts of remaining habitat, and create a demand for thoughtful planning as development continues to occur in the region.

One of the greatest threats to wildlife habitat in Texas and Mexico today is the subdivision of large land holdings into smaller tracts. Changes in estate and property tax structure, incentives for habitat conservation, and alternative economic uses of key resident wildlife will slow this trend With the passage of Proposition 11 in 1995, Texas landowners can now retain their agricultural property tax valuation if their land use changes to active wildlife management. Ultimately, this will have a positive effect on wildlife as small land holdings, forced to carry livestock for tax purposes, receive much needed deferment. Cooperative efforts involving multiple landowners within managed units such as a landowner associations or watersheds must become commonplace if strategies for the future of wildlife in the Tamaulipan Region are going to be successful. Technical guidance for Tamaulipan habitat management in Texas is available through Texas Parks and Wildlife biologists, the Texas Agricultural Extension Service, the Natural Resource Conservation Service, and other organizations.

Finally, if wildlife management is going to be successful in the 21st century, private/public partnerships are essential. In addition to changing land use and threats from habitat fragmentation, changing values toward wildlife and associated management issues will challenge wildlife professionals to seek new strategies for reaching new constituents.

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