Wilderness Study Report Us Department of the Interior

LAGUNA ATASCOSA WILDERNESS STUDY AREA Laguna Atascosa National Wildlife Refuge Cameron and Willacy Counties, Texas

WILDERNESS STUDY REPORT

U. S. DEPARTMENT OF THE INTERIOR Fish and Wildlife Service Bureau of Sport Fisheries and Wildlife CONTENTS

Preface ...... I. Introduction ...... II. Objectives ...... 6 III. History ...... A. Early Stage ...... 7 B. Conquest and Colonization ...... » C. Revolution and Republic ...... «J D. Texas in the United States ...... >4 IV. Land Status ...... 20 V. Physical Characteristics ...... 24 A. General ...... 24 B. Climate ...... 28 C. Geology ...... 29 D. Ecology ...... 31 VI. Resources ...... • ...... 35 A. Wildlife ...... 35 1. Manuals ...... 35 2. Birds ...... 36 3. Reptiles and Amphibians ...... 41 4. Fish ...... 44 B. Wetlands ...... 45 C. Vegetation and Soils ...... 47 D. Mineral ...... 61 E. Recreation ...... 62

VII. Socio-Economic Considerations ...... 66

A. General ...... 66 B. Grazing ...... 68 C. Navigation ...... 69 D. Agriculture ...... 69

VIII. Development ...... ' ...... ;g

IX. Management ...... ,-. . 74

A. Wildlife and Vegetation ...... 7/1 B. Minerals - Mining ...... 4 ] * " 74 C. Recreation ...... - ° * 7fi D. Navigation ...... ] .'.'.';!!.' I 76

X. Summary and Conclusions . , , . .««••.., . /y7 0i, Appendix I .*.... * ...... 83 PREFACE

The following report is presented in fulfillment of the require- ments of the Wilderness Act (P.L. 88-577).

The Laguna Atascosa National Wildlife Refuge, located in southern Texas, is a biotic community representative of the South Texas Coast. The entire refuge was examined for its wilderness potential. Artificial impoundments, farming for wildlife, improved pastures and public use facilities eliminated from consideration all but the northern one-fifth of the refuge. This unit, North Island, consists of tidal flats, low vegetated ridges and old stream channels. Nu- merous species of plants and animals are present, many occurring in the United States only in southern Texas. The complex community is a seeming fusion of seashore, desert and subtropical elements.

In view of rapidly disappearing coastal waterfowl habitat and the important role the refuge assumes in providing such habitat, the va7ue of North Island was also considered in this respect. The old stream channels and adjacent ridges interlace to provide considerable potential for fresh water impoundments. The refuge Master Plan recognizes this potential and recommends that such potential be developed.

While North Island meets the qualifications of the Wilderness Act and thus must be found suitable for consideration, wilderness designa- tion would preclude full development for wildlife.

iii I. INTRODUCTION

Laguna Atascosa National Wildlife Refuge is located on the South Texas Coast about 25 miles north of the Mexican border (Figure 1). The eastern boundary of the refuge fronts on the Laguna Madre, a large, shallow, 100-mile-long embayment formed by Padre Island and lying along the Texas Coast from Corpus Christi to the mouth of the Rio Grande. The refuge was established in 1946 when the first tract of land was purchased with Duck Stamp monies. It is the southernmost link in the chain of waterfowl refuges along the Central Flyway and contains 45,050 acres, including about 7,000 acres of marsh and open water and 14,600 acres of mud flats. Its name is derived from its largest lake, Laguna Atascosa.

A headquarters is situated on the refuge and an office is maintained in the town of San Benito about 25 miles southwest. U. S. Highway 77, the main coastal route, passes through San Benito. Other nearby towns of importance include Rio Hondo, 12 miles; Harlingen, 27 miles; and Brownsville, 25 miles from the refuge. The Harlingen Ship Chan- nel bisects the refuge into two unequal parts. The main channel of the Intracoastal Waterway skirts the refuge a short distance offshore in the Laguna Madre and a small stretch crosses the refuge on the northeastern tip.

The major objective of the refuge is to develop, maintain, and manage waterfowl habitat to support up to 500,000 ducks and 20,000 geese. LAQUMA ATASCOSA ' NATIONAL. WU-.DL-IRE

WILLACV CAMERON co

IMPKOVEO DI»T UNIMPROVED COUNTY L.INE BOONOAieY MUD WATER HOLE - txCAVA-re Other objectives are: To preserve habitat for animals rare or endangered in the United States; to provide for public use and enjoy- ment of the wildlife resource; and to manage for the greatest number of migratory and indigenous species within the capabilities of available habitat.

For management purposes the area is divided into eight units (Figure 1). All units except Unit IV are south of the Harlingen Ship Channel.

Unit I (1,385 acres) is separated from the rest of the refuge by a paved road. It is a scenic walk-in area.

Units II and III (15,930 acres) include almost 6,000 acres of water surface. They contain the bulk of the high-quality waterfowl habitat. A guided-tour road traverses the length of Unit II. Additional developments for waterfowl are planned including an impoundment between Cayo Atascoso and the Harlin- gen Ship Channel.

Unit IV, North Island (9,440 acres), is isolated from the rest of the refuge by the ship channel. The only surface access is by boat. There are no roads and virtually no developments on the.area. Developments for waterfowl are planned.

Unit V, Horse Island (3,770 acres), fronts on the Laguna Madre and the Harlingen Ship Channel. It is proposed to operate this unit as a saline habitat with an impoundment to provide resting habitat for water birds.

Units VI and VIII (6,040 acres) contain 1,500 acres of farmlands, 400 acres of improved pastures and headquarters facilities. They contain the primary deer and goose browse areas.

Unit VII (8,485 acres), once part of a military gunnery range, contains a self-guided auto tour. Some evidence of military occupation still remains. It is planned to further develop this unit to the extent that water supplies will permit. The auto tour will also be more fully developed.

Unit IV, North Island (Figure 1), is the only roadless area of 5,000 acres or more on the refuge. The relative lack of development and the isolation coupled with the nearly "natural" aspect of the.landscape combine to qualify this tract for consideration as a wilderness area. The remainder of the report deals primarily with this area. Unit IV is hereafter referred to as North Island (Figure 2). Figure 2. North Island is representative of the South Texas coastal community and is the only sizable, roadless and undeveloped block of land on the refuge. II. OBJECTIVES

The objectives of this study are to gather and present for review such information as necessary for determining the suitability or non-suitability of portions of the Laguna Atascosa National Wild- life Refuge for inclusion in the National Wilderness Preservation System under Public Law 88-577, the Wilderness Act. III. HISTORY

A. Early Stage Excavations in several northern counties reveal the existence of man in Texas at least 12-15,000 years ago. Archaeology suggests that a basic way of life was typical over a wide area and a long period of time^and was also similar to patterns to the south in Mexico. The manifestations are probably derived from the Desert Culture.

It would appear that assemblages of the early stage were inland and represented hunting-collecting peoples in small to large groups having an essentially nomadic way of life. Later peoples occupied the coastal zone and relied considerably more on sea- food. Although precipitation is not unusually low on the coast, it is spasmodic and not seasonally patterned to farming without irrigation. In the absence of agriculture the native peoples depended on a variety of natural resources. Along the shore, fish and shellfish were caught; inland the diet consisted of seeds, nuts, fruits and roots. Hunting was pursued throughout the area.

The middle or Archaic State is marked by the advent of ceramics and small arrow points. Shoreline cultures of this stage were represented by small nomadic bands with widespread contact with other, often larger, groups inland and along the Rio Grande. Pottery was almost certainly not a local product but a result of trade with more developed neighbors to the south. It is most likely that these phases relate to the historic Coahuiltec Indians. Coahuiltec is a name adopted to include a group of small, supposedly cognate tribes on both sides of the Rio Grande. The name is geographic rather than ethnic.

The Historic stage saw a general breakdown in native Indian culture when European colonization was seriously undertaken. The aboriginal population, sparse to begin with and not accustomed to political or religious domination or a sedentary way of life, did not adapt well to mission induction of the Spanish ecomienda system. Disease, intertribal strife and abandonment of native crafts all contributed to the cultural decline, and by the 1850's the remaining groups had retreated across the Rio Grande to Mexico.

There is some disagreement concerning the area occupied by the cannibalistic Karankawa Indians. The literature suggests that this colorful group centered along the coast from Galveston to Corpus Christi, although there are reports of occupation along the entire Texas coast. One source refers to a sizable village on Padre Island approximately 25 miles north of the refuge. Like the Coahuiltec Indians, the Karankawas were semi-nomadic and divided into small groups. Although there are more fanciful accounts, including group suicide, the last of the Karankawas were probably driven into Mexico amid intensive white settlement of the lower Texas coast.

B. Conquest and Colonization 1519-1835 The first white man to visit south Jexas probably were members of the Pineda expedition of 1519. Alonzo Alvarez de Pineda, in command of four vessels, set out from Florida to explore the gulf coast. At one point he put into a natural harbor between two islands and named the pass Brazos Santiago (Figure 3). This harbor was to play a major role in the future of the Lower Rio Grande.

Pineda's report to Francisco Garay, Governor of Jamaica, prompted an attempt at settlement. Diego de Camargo reached the Rio Grande, then known as the Rio de las Palmas, and pushed inland. Although well received by the natives, harmony did not last. The Indians revolted, presumably against the tyranny of the Spaniards, • and Carmargo was forced to flee. Meanwhile, Garay, assuming success by Carmargo, set out with 16 ships and plans to construct a permanent settlement. When his explorers reported the land unsuitable for settlement he proceeded to Vera Cruz.

In the years to follow, tragedy and failure stalked those who attempted to settle 'Rio de las Palmas'. Texas was officially a Spanish province by 1691, but South Texas was yet to see a OL

Q) successful permanent settlement.

In the 1750's, Jose Escandon was commissioned to establish a colony at the mouth of the Rio Grande, probably somewhere between the present svtes of Brownsville and Harlingen. There were three other parties inspired by Escandon. Braz de la Garza came over the mountains of northern Mexico and down the San Juan River to the Rio Grande. At the same time Miguel de la Garza Flacon was sent out of the state of Coahuila and came down the north bank of the Rio Grande. He recommended that no settlement be made on the north side of the river as it was "too high and dry for irrigation". (Today the Lower Rio Grande valley is one of the most intensively irrigated farming areas in the nation.) Juan Bazaterra outfitted his expedition in Texas and traveled south over a route closely following the present U. S. Highway 77 from Kingsville.

The four expeditions met, compared notes and returned to Quere- taro, Mexico, where they assembled 758 soldiers and 2500 settlers. These pioneers reached the Rio Grande in 1760, and established several settlements along the river. Following Spanish custom, the land around each settlement was common property. This was changed in 1769 when the Spanish Government decided to give land titles to its citizens. Residents of each settlement were granted the land around their towns. The result

11 was the "porciones", long narrow strips straddling the river near Reynosa, and the larger land grants to the east. Some of the porciones have never been divided and remain to this day in the ownership of the family to which they were granted over 200 years ago. All of the larger grants have since been divided.

As the 19th century began, Portuguese Priest Nicholas Balli and his nephew were granted the narrow strip of sand which sheltered the South Texas coast from the Gulf of Mexico. Is!a de San Carlos de las Maraguitas became the site of a ranch that thrived for more than three decades. A ranch headquarters was established approximately 26 miles north of the island's southern tip, a point directly east of the refuge. The island came to be known as Padre Balli's Island. Usage cut the name simply to Padre Island.

For the early colonies, frontier hardships were accepted as a way of life. Spanish rule, however, was not so readily accepted. A decline in Spanish influence (1793-1821), marked by general disruption and additional hardships, culminated in the Republic which replaced Spanish rule. Under Mexican rule, chaotic as. it was, life on the Lower Rio Grande returned to 'normal'—for a short time. The opening of the river to commerce and thus to Anglo-American colonization was to kindle yet another struggle.

12 In 1835 Texas was seeking independence from Mexico.

C. Revolution and Republic 1835-1845 A successful but costly revolution gave Texas the status of an independent republic which was set up in 1835 and officially recognized by the U. S. Government in 1837. From the start the Republic had a rocky time. The country south from the Nueces River to the Rio Grande became a "formal excuse" for the Mexican War. Referred to as the Wild Horse Desert, this disputed strip of territory extended along the Rio Grande for more than 200 miles, its big end butted against the Gulf for 130 miles.

In 1842, following several attacks by Mexican forces on San Antonio, Victoria, Refugio and other places, there was wide public sentiment for an expedition against Mexico. A force marched to the Rio Grande under command of General Alexander Somervelle, but turned back under orders of the Provisional Government. However, an independent expedition of about 300 men, organized under Colonel W. S. Fisher, crossed the Rio Grande and attacked Mier, a strategic point with a strong ' garrison. After a bloody battle the Texans were defeated and captured. They were started as prisoners toward Mexico City.- At Sol ado they escaped but were recaptured. As a result of the famous 'drawing of the black beans', every tenth man was executed. Captain Ewen Cameron, for whom Cameron County is

13 named, was also executed for having headed the break for liberty.

The task of firmly establishing the Rio Grande as the Internation- al boundary was a difficult one. Although the Republic of Texas had obtained recognition by a number of leading world powers, no treaty was ever signed. An armistice was signed in 1844 but was annulled by Mexico in 1845 when annexation to the United States was effected.

D. Texas in The United States The contention did not end. Mexico gave warning and withdrew her envoy from Washington. Despite motions toward settlement the Mexican Government agreed to nothing and President Polk was constrained to accept the Texan view that the Rio Grande was indeed the boundary line of Texas. He ordered Brigadier General Zachary Taylor to the Rio Grande to defend what was now claimed as part of the United States. In March of 1846, Taylor's army constructed an earthen breastworks at a point opposite the Mexican town of Matamoros. There are several versions of the battles that ensued, but the following is a particularly interesting account:

There were two battles which might be called 'major1 on Texas soil. These were the twin battles of Palo Alto and Resaca de la Palma (May 1846). Palo Alto is a prairie between Brownsville and the mouth of the Rio Grande. The U. S. forces were under Zachary Taylor and the Mexican General was a red-headed officer named Maria.no Arista. Taylor had 2,200 men. Arista about twice that many and the prettiest cannons.

14 It was said that the Mexican artillery was 'artistically wrought'. It was also obsolete and lobbed cannon balls so lazily that Taylor's men could dodge them if they were alert. Mostly the infantry on both sides stood at attention while an artillery duel went on. Some of the Mexican cannons were 80 years old, while Taylor had some new models in artillery and his gunners were experienced. While his infantrymen stood at attention his artillery tore great gaps in the Mexican ranks. Of the four Americans killed in the battle of Palo Alto at least one was hit while standing at attention when a Mexican cannon ball rolled up like a bowling ball. The Mexicans retreated to Resaca de la Raima, just east of the Rio Grande and just north of Brownsville. Next day Taylor whipped them soundly and ran them across the river. Arista had 547 casualties, while Taylor's losses were only 33 killed and 89 wounded. After that the war shifted to Mexican soilJ

When Taylor's army was dealing with the enemy at Palo Alto and Resaca de la Palma, 500 men of the 7th Infantry and 2 batteries under the command of Major Jacob Brown were left facing Matamoros. They were besieged and withstood heavy cannonfire until Taylor returned. Taylor renamed the breastworks Fort Brown, later to become the town of Brownsville, after Major Brown who fell mortally wounded.

In the years to follow many prominent military figures were stationed on the Lower Rio Grande at some time during their careers. Among them were Jefferson Davis, Robert E. Lee, U. S. Grant, Lew Wallace and Phillip Sheridan.

Holbert, F. X. 1951. An Informal History of Texas. Harper Bros, Pub. N.Y., p. 184. 15 Perhaps a basic reason for the fighting on the Lower Rio Grande was the location of the port of Brazos Santiago, the only prac- tical funnel through which commerce poured into northern Mexico. El Paso de los Brazos de Santiago - the Pass of the Arms of Saint James - was the main staging area for U. S. Troops during the Mexican War. It was also to play an important role during the Civil War.

For more than 25 years, riverboats had been a key factor in the economy of the Lower Rio Grande, carrying their cargo from the Gulf Coast to points upriver. During the Civil War, Union ships blockaded every southern port including Brazos Santiago. Yet, throughout the conflict, European cargo ships anchored off the mouth of the Rio Grande to receive cotton which maintained a huge textile industry abroad. Cotton, the backbone of the Confederacy, was shipped from the Rio Grande under the guise of Mexican ownership. In fact, most of the war activity in South Texas centered around the shipment of cotton, much of it hauled overland from points as far as Louisiana. In the later stages of the war, even high level Confederate thinking opposed exportation, now too profitable to be stopped, hoping the foreign demand would exert pressure on the Union.

Activity was not restricted to shipping, however. "Enganchados", or Mexican guerrillas, were paid by Union agents to ride into

16 Texas and make trouble. To balance this there were many Latins fighting for the Confederacy along the Rio Grande. The Texans1 best defender was a former mayor of Laredo named Santos Benavides, who became a Confederate General. Benavides defeated enganchado Juan N. Cortina, a 'rascal' on the Rio Grande for many years.

The scene of the last land engagement of the Civil War, the Battle of Palmito Hill, is on a rise of brush and cactus-covered plain about eleven miles east of Brownsville. The battle was fought after the official end of the war and was considered a confederate victory.

Following the war, cattle ranching became the major enterprise in South Texas. Wild cattle, escaped from Mexican ranches, roamed the prairie land of the Wild Horse Desert. From 1836-1840, the Texas Government could not pay its soldiers and had given them furloughs to go live off the land. Many of those who had been driving cattle from south of the Nueces River for the Texas Army decided to continue such operations on a strictly private basis, a somewhat questionable practice. The thieves were mostly young men who had served in the army and whose fathers had lost their personal property in the fight for Texas independence. They went about in bands referred to as "Cow Boys", thus the origin of the popular name cowboy. Much of Central and West Texas was stocked by Mexican cattle from south of the Nueces.

17 In the turbulent years to follow, cattle ranching became in- creasingly important. In 1863-64,'a prolonged drought and severe northern storms caused a phenomenon referred" to as The Big Drift. Tens of thousands of cattle from central and northern Texas, with no fences to hold them, drifted south hunting warmth and grass, many of them reaching the coastal prairies north of the Rio Grande delta. A wartime shortage of help made it impossible for owners to locate and move stock. The drifters stayed, they and their increase to vastly multiply the cattle numbers on south Texas ranges. By the end of the war it is estimated by some sources that 200,000 cattle, some with brands as far north as Austin, had come into this country. They became a highly profitable resource. By 1886 South Texas cattle drives were terminating at Kansas railheads.

In 1873, Richard King, founder of the famed King Ranch, took steps toward acquisition of the huge San Juan de Carricitos grant which borders Laguna Atascosa Refuge on the north. It was finally acquired and is still part of the King Ranch complex.

Ranching continued as the primary industry on the Lower Rio Grande until 1892, when Lt. Wm. H. Chatfield undertook to interest local and outside capital in irrigating the fertile soils with Rio Grande waters. It took 10 years for his ideas

18 to become active. By 1910 there was enormous capital investment in land, clearing brush, constructing canals, and building towns, schools and roads. Winter vegetables and citrus were the primary interests at this time. It was not until World War I that cotton became an important crop. With the advent of the tractor, cotton and sorghum became leading commodities.

The beginnings of the vast petroleum industry of Texas is lost in antiquity but the use of crude oil by Europeans was recorded as early as 1543 (DeSoto). The first producing oil well in Texas was founded in Nacogdoches County in 1866.

The turn of the century brought the end of the Wild Horse Desert. In 1904 the St. Louis, Brownsville and Mexican Railway was completed through Cameron County. The Southern Pacific lines were completed in 1927, with Harlingen at the crossroads.

The year 1953 saw the completion of Falcon Dam, the first major change in the flow of the Rio Grande in over 400 years of written history. Port Isabel, after prolonged wrangling in Congress, became a deep water port in 1935. The Intracoastal Waterway and the Harlingen Ship Channel were opened in 1949.

Laguna Atascosa Refuge was established in 1946 as the largest waterfowl refuge along the Texas Gulf coast. Administered primarily as a wintering area for ducks and geese, it also offers a haven for great numbers of other wildlife.

19 IV. LAND STATUS

The refuge was originally part of the Potrero del Espiritu Santo Grant, a patent for 59 leagues from the Spanish Government in Mexico to Jose Salvaso de La Garza in 1781. This grant was later divided into shares and passed into other ownership. The shares are of unequal width and are separated by parallel lines running completely through the area in a north-south direction at an angle of about N 2° E. Land for the refuge was purchased by the Federal Government in two tracts, the Continental Tract including shares 29, 30, and 31, and the Luttes Tract including share 32. The western edge of share 29 forms the western boundary of the refuge. The purchase included recognition of mineral right reservation, easement rights for the Harlingen Ship Channel and prior rights of the Intracoastal Waterway.

The grantors (former owners) reserved for themselves, their successors and assigns, the right to prospect for, mine or remove oil, gas, or other minerals from the lands for a period of 30 years from the date of land transfer. Should oil, gas, or other minerals be discovered, the grantor is entitled to continue production beyond the 30-year limitation until production ceases.

In the event oil, gas, or other minerals are discovered and developed, 40 percent of one-eighth royalty of same that is removed and saved shall be paid to the Federal Government until royalties shall equal

20 the purchase price of said land (total purchase price of land under the purchase agreement). The 30-year mineral reservation on the Continental Tract expires in 1976 and on the Luttes Tract in 1979.

The Harlingen Ship Channel* forms the southern boundary of North Island. The Arroyo Colorado Navigation District holds in fee title a 300-foot-wide channel through the Luttes Tract (Figure 4). In addition, the District holds easement rights for spoil deposition on a 350-foot-wide strip of land parallel to and north of the channel on both tracts. This land is contiguous with the 300-foot channel and runs, as does the channel, completely through the refuge. The Federal Government holds in surface ownership the channel on the Continental Tract and the 350-foot strip on both tracts. That part of the channel on the Luttes Tract is in turn leased from the Navi- gation District by the Fish and Wildlife Service for refuge purposes.

The Corps

21 HAI?LlNG,EN SHIP CHANNEL. - OWNERSHIP: UUTTES, TFcV^CT — AKJ^OYO COLORADO NAViqATlON CONTINENTAL. TF2ACT — U.S.GOV'T. • l^lQHT- of - WAV HEuO BY DISTRICT U.S. QOVT. EASEMENT HEL.D by N A V I Cj AT I r>ig CXSTEICT 300 Y//A OWNERSHIP: U.S. QOV'T. UNDER "t. COeRSof '» ' '•• F=v-ic» cpv.il Oe:POSiT\OfsJ.

HI | | |1 OWNERSHIP". U.S.QOV'T. UWDE'F? PEl^Ninr "/« CORRS »t EN/aiWEE(?S WATEI? DEPOSITION j &IICT DEPOSITION) WOT to •exceso 4 INCHES OWNEESH/P: U.S.GiOV'T. UWDE-re PETS.M IT "t CORPS «feoQ 4^ XJ N^OOi2INCj FAClt-iT/- OVERLAYS KJAVICi^TlOM

OVS.TSJ_AVS that when additional spoil area is necessary, lands will be made available.

The Corps also holds a permit to construct, operate and maintain a barge mooring facility along the north edge of the Harlingen Ship Channel in the Luttes Tract. It is described as a tract of land 150 feet in width, 3,000 feet in length, contiguous to the north boundary of the channel, and situated between Station 9+250 and Station 12+250 as located by the Corps of Engineers. In addition the Corps has the right to deposit spoil on land 250 feet in width north of and contiguous to the mooring area. This parcel of land overlays and its northern border coincides closely with the 350-foot-wide strip mentioned earlier that is under easement to the Arroyo Colorado Navigation District.

When the Luttes Tract was acquired the actual boundary between the tract and waters of the Laguna Madre was in question. No formal agreements or permits have been made between the BSFW and the Corps relative to the Intracoastal Waterway as the Waterway was constructed prior to acquisition. However, the Corps' right-of-way and channel maintenance needs are recognized. An official boundary map of the coastal borders of the refuge was recently filed in the County records to more clearly delineate refuge limits.

North Island includes the lands and waters subject to the aforemen- tioned easements and spoil deposits along the Intracoastal Waterway.

23 V. PHYSICAL CHARACTERISTICS

A. General Description North Island lies within the Lower Rio Grande Valley and is part of a small delta formed by the Arroyo Colorado. It is naturally bordered on the south by the Harlingen Ship Channel, on the east by the Laguna Madre and on the west and north by the Arroyo Colorado (Figure 1). The Arroyo Colorado, formerly a principal flood channel of the Rio Grande, is the only sizable permanent stream other than the Rio Grande in the lower valley.

The area comprises 9,440 acres and can be described generally as flat. It is an area of low ridges crossed by a number of old stream channels, broad flats with no natural drainage, and coastal mud flats occasionally inundated by wind tides (Figure 5). The elevation varies from sea level to 34 feet. A single excavated stock tank supplies the only dependable fresh water although the old channels and depressions may contain water following floods or heavy rains. The Arroyo Colorado is brackish as far inland as Harlingen because the bottom of the ship channel is below sea level.

The ridges are covered with a thick growth of medium sized to small thorny trees which constitute the dominant vegetation (Figure 6). They are associated with a dense growth of thorny

24 Figure 5. Over half of North Island is covered by coastal mud flats. Onshore winds often inundate these flats with several inches of water.

Figure 6. The better soils on ridge tops support a variety of shrubby trees and brush. This is in sharp contrast to the low vegetation of poorer drained soils, 25 bushes and shrubs, some cacti and a more or less continuous cover of native or introduced grasses. The lower sites support a more open growth while the poorly drained sites containing considerable alkali salts support only coarse salt grasses, cordgrass and alkali weeds (Figure 7). Occasional drifts of wind-blown sand add to the diversity.

A few dunes coursing north-south through the center of the area mark the eastern limit of tide-free land (Figure 8). To the east only spoil piles break the monotony of the barren mud flats which cover nearly half of the area. This coastal area is pro- tected by Padre Island which is separated from the mainland by the shallow waters of the Laguna Madre.

The Laguna Madre, because of its restricted connection with the Gulf, has no periodic tide. Rise and fall of water at any particular locality is largely dependent upon wind conditions. Extreme wind can cause a tidal range of 3 to 4 feet and put a considerable portion of North Island under water.

The area contains no roads and is accessible only by boat. There is almost no evidence of man except for a small group of corrals, hurricane debris and spoil located along the ship channels, and a minimum of fencing (Figure 1). Viewed from inside the area, the spoils piles along the eastern boundary appear to be large dune islands. Numerous fishing shanties line the Intracoastal

26 Figure 7. Soils of the poorly drained lowlands support only salt-tolerant vegetation. The floristic variety is considerably less than that of the ridge tops.

Figure 8. The eastern and southern boundaries of North Island are marked with numerous piles of channel dredgings, These spoil piles are easily eroded and difficult to contain. 27 Waterway just off the refuge and are quite conspicuous from parts of the area. Several oil drilling platforms are also visible some distance offshore.

B. Climate The climate of Cameron County can be described as mild with features of a dry subhumid (semitropical) climate on the one hand and of semi arid on the other. The mean temperature for the winter months is about 62°f; the mean summer temperature is 84°F. Extremes run from a low of 12°F to a high of 104°F. Mean annual relative humidity is 80 percent. Annual precipitation averages 26.60 inches with extremes of 12.15 inches (1917) and 60.06 inches (1886). It is the seasonal distribution of temperature and precipitation accompanied by high relative humidity that yields the semi tropical-arid features (Table 1). The spring and fall months, May-June and September- October, receive more than half of the annual precipitation; the remainder is'distributed rather evenly throughout the year. Despite this apparent even distribution, prolonged drought is not uncommon. The prevailing winds are from the Gulf of Mexico at 12 mph. The normal growing season is 336 days.

Northern storms accompanied by rapid temperature change, rain, and wind are not uncommon from October to March. Hail is unusual although occasional destructive hailstorms do occur. The South

28 and brush control began for farmers and ranchers alike. When the refuge was established in 1946, land clearing operations were still going on; the valley was now based on a farming economy. Today the refuge remains as an example of brush country now scarce in this part of Texas.

North Island occupies the northeast corner of the Rio Grande Delta and itself forms the mouth of the Arroyo Colorado. It can also be associated with the Gulf Coastal Plain, the recognized physiographic province extending north along the Gulf coast. Although South Texas was historically a grassland, it is doubtful that this particular area was ever exclusively so. As a delta it has undergone continual change. Gulf storms and floods as well as slower changes in stream channels all result in periodic disturbances. Old stream channels are particularly evident and greatly influence topography and the resulting vegetation.

The coastal prairies in general were converted by overgrazing into a disclimax characterized by mesquite and cacti or by a mesquite and a variety of shrubby associates. Over much of the former prairies the two disciimaxes actually became one. In essence, grazing produced a short grass sod in a savanna of mesquite and cacti, an ecotone between two climax formations. The resulting shrubs and trees, once established with roots

32 at a greater depth than those of the grasses, may persist indefinitely. Because of its location, North Island was probably not extensively grazed during this period but periodic disturbances over time had already produced similar effects. Although the area has a recent history of grazing, the effect has been not so much an increase in brush as changes in composition of the major vegetative types and an obvious invasion of introduced grasses.

By reason of its proximity to the Gulf, the refuge is signalized by higher rainfall than similar associations further inland. The result is a climate of both subtropical and semiarid features. Water is not scarce but rather unreliable; seasonal drought is not uncommon. Perhaps the most significant feature is the relatively warm winters which favor the presence of subtropical vegetation. Legumes and warm climate grasses dominate the flora. The area is also rich in perennial forbs due chiefly to the long growing season and high temperatures. The vegetation is more an indi- cation of climate than soils. The entire area is bordered on the coastline by broad mud or saline flats which receive accretions, slowly with normal drainage and rapidly following floods or tropical storms. The mud flats provide a striking contrast to the coastal ridges and are maintained by the constant interaction of erosion and deposition.

33 The Harlingen Ship Channel has replaced the Arroyo Colorado as the principal runoff channel. This will influence the future evolution of flood channels and of the vegetation since the old channels now receive flowing water only under the most extreme flood conditions.

Changes over the last 100 years have also affected wildlife. For example, the pronghorn, never plentiful, was excluded as brush increased. The range or habitat of others, such as the turkey and the white-winged dove, was increased. While it is likely that the invasion of brush provided deer advantage in the presence of expanding human population, early travelers report that deer were common even on the open plains where the amount of cover was quite limited. When land clearing began, the trend was reversed. Animals were forced into smaller and smaller areas, and poaching became widespread. Today the limited brushland provides vitually the only habitat for many indigenous species.

34 VI. RESOURCES

A. Wildlife 1. Mammals. Thirty-one species of mammals are known to occur on the refuge; most can be found on North Island. The following are considered common: the opossum, coyote, cottontail, black-tailed jackrabbit, raccoon, Mexican ground squirrel, white-footed mouse, cotton rat, striped skunk, bobcat, and white-tailed deer.

Two subtropical cats, the ocelot and jaguarundi, are occasionally seen. Both occur in the United States only in southern Texas and a limited area in southern Arizona.

The peak deer population on the refuge has averaged about 550 for the last 5 years. During the same period peccary have averaged about 140. Only a small portion of both populations is attributable to North Island. In addition, inter- change occurs between the area and private lands west of the Arroyo Colorado channel.

The following list includes only mammals observed or collected on the refuge. Common names follow: A Field Guide to Mammals, Burt-and Grossenheider, Houghton Mifflin Co., 1952. Scientific names are after: List of North American Recent Mammals, Miller and Kellogg, U. S. Nat'l Mus. Bui. 205, 1955.

35 Opossum Pi del phis marsupial is Least shrew Cryptotis parva Cave myotis Myotis velifer Evening bat Nycticeius humeral is Mexican freetail bat Tadarida brasiliensis^ Armadillo Dasypus novemcinctus Blacktail jackrabbit Lepus californicus Eastern cottontail Sylvilagus floridanus Mexican ground squirrel Citell us mexicanus Spotted ground squirrel Citellus spilosoma Texas pocket gopher Geomys personatus Merriam pocket mouse Perognathus merriami Fulvous harvest mouse Reithrodontomys fulvescens White-footed mouse Peromyscus leucopus^ Northern grasshopper mouse Qnychomys leucogaster Hispid cotton rat Sigmodon hispidus Southern plains woodrat Neotoma micropus Norway rat Rattus norvegicus House mouse Mus musculus Nutria Myocaster coypus^ Coyote Canis latrans^ Raccoon Procyon lotor Longtail (bridled) weasel Mustela frenata Badger Taxidea taxus Striped skunk Mephitis mephitis Ocelot pardalis Mountain lion Felis concolor Jaguarundi Felis yagouaroundi Bobcat Lynx rufus Peccary Pecari angulatus Whitetail deer Qdocoileus virginianus

The preceding is probably not a'complete list. Eleven bats occur in this part of the United States but only three are listed on the refuge. In addition, the refuge lies in the recognized distribution of 17 other mammals that are also not listed.

2. Bir;ds. The primary purpose of the refuge is to provide migration and wintering habitat for migratory waterfowl.

36 Each year the refuge supplies the life needs of many thousands of birds. In addition, it is especially well located on north-south migration routes and accommodates large numbers of birds passing through during the spring and fall.

There are few places in the United States where the bird variety of Laguna Atascosa can be rivaled. About 45 percent of the 725 bird species found in the Continental 48 States have been seen on the refuge. Southern Texas is the northern limit for about 23 subtropical species. Twelve of these nest on the refuge including the black-bellied tree duck, white-tailed hawk, pauraque, golden-fronted woodpecker, green jay, groove-billed ani, and jacana. Southern Texas shares an additional 15 subtropical species with parts of Florida and extreme southern Arizona.

The refuge is heavily used by waterfowl migrating to and from Mexico and points south and is the terminus for large flocks of wintering birds. Peak numbers in 1968 were 211,000 ducks and 13,000 "yeese. About 75 percent of the continental redhead population winters on the Laguna Madre; a significant portion of these utilize the fresh-water supplied by the refuge. The peak redhead population on the refuge in 1968 exceeded 160,000 and accounted for about 50 percent of the

37 total duck use. Pintails are a strong second followed by ruddy ducks, American widgeon, lesser scaup and canvas- backs. The Canada goose is the most common of the four goose species regularly using the refuge and accounted for 75 percent of the 500,000 use-days in 1968. North Island logs about 10 percent of the duck use and 5 percent of the goose use experienced by the refuge.

Waterfowl use both the refuge and surrounding habitat. Ducks utilize the extensive offshore beds of shoal grass in the Laguna Madre. Redheads spend considerable time feeding on the abundant crustaceans associated with these beds. Geese roost and feed on the refuge with half frequenting nearby pastures and cropland.

The southern bald eagle and the American peregrine falcon, both considered endangered by the Committee on Rare and Endangered Wildlife Species, have been seen on the refuge. Until recently, the peregrine was considered common in the spring. In the last decade, however, populations have taken a nosedive and the occurrence of a peregrine on the refuge today is considered a rare event.

The following birdlist contains 315 species which represent observations since 1946. The following species have been recorded on the refuge as accidentals, having been observed

38 Birds nesting locally are preceded by a •. S S F w Symbols indicative of seasonal abundance of each species are used as follows: Redhead c o a BIRDS OF THE Ring necked Duck 0 o S - March-May a - abundant Canvasback u c S • June-August c • common Greater Scaup r LAGUNA ATASCOSA F - September-November u - uncommon Lesser Scaup u c W - December-February o - occasional Common Goldeneye r - rare Bufflehead u c NATIONAL WILDLIFE REFUGE Surf Scoter Ruddy Duck u c S S F W Masked Duck r r r Common Loon r r r Hooded Merganser r Horned Grebe o o Red- breasted Merganser o u Eared Grebe u o c c •Turkey Vulture a c a •Least Grebe u c u u Black Vulture c c c Western Grebe r r •White-tailed Kite u u c •Pied-billed Grebe c u a a Mississippi Kite r White Pelican c c c c Sharp-shinned Hawk u 0 u Brown Pelican r r r r Cooper's Hawk u o u u Double-crested Cormorant u c c a Red-tailed Hawk u u c Olivaceous Cormorant u u u u Red-shouldered Hawk o o 0 0 Anhings o o o Broad-winged Hawk u u Frigate-bird r r Swainson's Hawk c 0 c 0 •Great Blue Heron c c a c Zone-tailed Hawk r Green Heron u u 0 0 •White-tailed Hawk c c c c Little Blue Heron u c c u Ferruginous Hawk 0 o u Cattle Egret u c c u •Harris' Hawk a c a a Common Egret c u c u Black Hawk r Snowy Egret c c c c Golden Eagle r LAGUNA ATASCOSA NATIONAL WILDLIFE REFUGE, estab- Reddish Egret c c a c Bald Eagle r lished in 1946, contains about 45,000 acres and is located on the lower Louisiana Heron c c c c Marsh Hawk a o a a •Black -crowned Night Heron u o u u Gulf Coast northeast of San Benito, Cameron County, in the southern Osprey u u •Yellow-crowned Ntfit Heron u 0 u o •Caracara c c c c tip of Texas. It is administered by the Bureau of Sport Fisheries and Least Bittern o u o o Prairie Falcon r Wildlife, U.S. Fish and Wildlife Service, in the Department of the American Bittern 0 0 u Peregrine Falcon c u u Interior. Wood Ibis u u u Aplomado Falcon r The refuge embraces coastal prairies, salt flats, low vegetated ridges White-faced Ibis u c u u Pjgeon Hawk o 0 0 supporting thick thorny shrubs, brushlands composed of mesquite, White Ibis u c u u Sparrow Hawk c o a a huisache, and granjeno, with scattered cacti and yuccas in the more Roseate Spoonbill u u u r •Chachalaca u u u u open spots. Water areas consist of Laguna Atascosa (3,200 surface Canada Goose a a c •Bobwhite a a a a White-fronted Goose 0 c c acres). Laguna de los Patos (250-300 acres), Cayo Atascosa (some 300 Sandhill Crane c c c Snow Goose a a c •King Rail o o 0 0 feet to .5 mile wide and 6 miles long), western reaches of the Laguna Blue Goose c c c Clapper Rail r r Madre, and several potholes and resacas. There are no extensive •Black -bellied Tree Duck c c o o •Sora u r c u marshes. Fulvous Tree Duck u u 0 u •Purple Gallinule o o This folder lists 315 species seen on Laguna Atascosa Refuge since Mallard u u u •Common Gallinule o o o o 1946. Another 15 species have been recorded on the refuge as •Mottled Duck c c c c •American Coot a u a a accidentals, having been seen only once or twice: American flamingo, Gadwall c 0 c c Jacana r Ross' goose, black duck, European widgeon, Marian's hawk, turkey, Pintail u u a a American Oystercatchw r a beardless flycatcher, blue jay, red-breasted nuthatch, canyon wren, Green-winged Teal u 0 u Piping Plover u 0 0 u •Blue-winged TM) u u u Semi pal mated Plover u u u brown thrasher, western tanager, black-headed grosbeak, lazuli bunting, • Cinnamon Teal u o u •Wilson's Plover a a c o and Harris' sparrow. The 80 or more nesting species include several that American Widgeon u o a a Mountain Plover 0 u 0 are restricted in the United States to south Texas. Shoveter c 0 a c •KilkJeer c c c c Wood Duck r American Golden Plover u r Refuge Leaflet 125-R4 • June 1969

39 S F S S F W S w S S F W S S F w

Black-belt.cd Plover a c a c »Horned Owl u u u u Sage Thrasher o o o •House Sparrow c c c c Ruddy Turnstone u 0 u u Burrowing Owl u U [ Robin u c u •Eastern Meadowlark c c c c Common Snipe u u u Short-eared Owl u i Wood Thrush u Western Meadow lark 0 u Long-billed Curlew c c a c Chuck-will's-widow u u Hermit Thrush u u u Yellow headed Blackbird o o o WhimWe i c o 0 Whip-poor-will r Swainson's Thrush u •Red-winged Blackbird a a a a Upland Plover u u •Pauraque c c c c Gray-cheeked Thrush u Orchard Oriole u o o Spotted Sandpiper M* u u u •Common Nighthawk a a Veery r •Black -headed Oriole u u Solitary Sandpiper u u u o •Lesser Nighthawk u u Eastern Bluebird 0 0 u •Hooded Oriole c c •Wiilet c a a c Chimney Swift c 0 Mountain Bluebird r r Baltimore Oriole c u Greater Yellowlegs a U a c Ruby-throated Hummingbird c c Blue-gray Gnatcatcher u 0 u u •Bullock's Oriole u u Lesser Yellowlegs a u a c Black-chinned Humnnngbtrd u Golden-crowned Kinglet u Brewer's Blackbird c u c c Knot u u Buff-bellied Hummingbird r Ruby -crowned Kinglet 0 u u •Boat-tailed Crackle a a a a Pectoral Sandpiper c o c o Belted Kingfisher u u Cedar Waxwing u u •Brown-headed Cowbird c c a a White-rumped Sandpiper u u Green Kingfisher r ; Water Pipit o c c •Bronzed Cowbird c c u u Baird's Sandpiper o o Yellow shafted Flicker o o Sprague's Pipit u Scarlet Tanager r Least Sandpiper c u c u Red-shafted Flicker r Loggerhead Shrike c c c •Summer Tanager 0 0 a Dunlin u a c •Golden-fronted Woodpecker a a a a Starling o o •Cardinal c c c c Long-billed Dowitcher 3 u a c Yellow-bellied Sapsucker o O : •White-eyed Vireo c c c c Pyrrhuloxia o r 0 o Stilt Sandpiper U c u o 'Ladder-backed Woodpecker a a a a Ye How- throated Vireo u Rose-breasted Grosbeak u Semipalmated Sandpiper a a a c Eastern Kingbird a a Solitary Vireo u u •Blue Grosbeak c c c Western Sandpiper a u c c 'Tropical Kingbird u u 0 Yellow-green Vireo r Indigo Bunting a u Buff-breasted Sandpiper u 0 u Western Kingbird u Red-eyed Vireo u •Varied Bunting r r Marbled Godwit u u u u •Scissor-tailed Flycatcher a c a Philadelphia Vireo u •Painted Bunting a u u Hudsonian Godwit r •Kiskadee Flycatcher u u u u j Warbling Vireo u •Dickcissel a o c Sanderling 0 u u u Great Crested Flycatcher u u Black-and-white Warbler c c u White-collared Seedeater r r r r •American Avocet c 0 c c 'Wied's Crested Flycatcher c c Prothonotary Warbler u Pine Siskin u •Black -necked Stilt u c u o Eastern Phoebe c C J Worm-eating Warbler u American Goldfinch u u u Red Phalarope r Say's Phoebe u u U 1 Blue-winged Warbler u Lesser Goldfinch r r Wilson's Phalarope u c u Acadian Flycatcher u u Tennessee Warbler u •Olive Sparrow u u u u Northern Phalarope r Least Flycatcher c c Orange-crowned Warbler c 0 Green-tailed Towhee u Herring Gull c o c c Eastern Wood Pewee a a Nashville Warbler L° u Rufous-sided Towhee r Ring-billed Gull c o c a Western Wood Pewee u u Parula Warbler u Lark Bunting o o o • Laughing Gull a a a c Olive-sided Flycatcher u u Yellow Warbler c Savannah Sparrow a a a Franklin's Gull a a •Vermilion Flycatcher c c u Magnolia Warbler u Grasshopper Sparrow o u u Bonaparte's Gull o u r »Horned Lark c c c c Myrtle Warbler c a c Baird's Sparrow r •Gull-billed Tern c c c u Tree Swallow c c u Black-throated Green Writer o u u Le Conte's Sparrow u • Forster's Tern c u c c Bank Swallow u u u Cerulean Warbler o Sharp-tailed Sparrow r Common Tern c c u Rough-winged Swallow a u c Blackburnian Warbler u Seaside Sparrow o • Least Tern c c c O Barn Swallow a o a Yellow-throated Warbler o Vesper Sparrow c c c • Royal Tern u u u o Cliff Swallow u u 0 Chestnut-sided Warbler r Lark Sparrow c c c c Sandwich Tern u u u o Purple Martin u o Bay-breasted Warbler r •Botteri's Sparrow c c c Caspian Tern c c c c 'Green Jay u u u u Btackpoll Warbler r •Cassin's Sparrow c c c 0 Black Tern c c a o *White-necked Raven o u 0 o Palm Warbler 0 •Black -throated Sparrow c c c u • Black Skimmer c c c u 'Black -crested Titmouse u u u u ! Northern Waterthrush u Slate-colored Junco r Red-billed Pigeon r r r •Verdin c c c c Louisiana Waterthrush r Chipping Sparrow u u •Mourning Dove a a a a House Wren c c Kentucky Warbter o o Clay-colored Sparrow u r u u •White-winged Dove c c u •Bewick's Wren c c c c •Yellowthroat c c u Field Sparrow 0 o u •Ground Dove c c c c 'Carolina Wren u u u u •Yellow-breasted Chat u c White-crowned Sparrow u u u f Inca Dove r •Cactus Wren c c c c Hooded Warbler u White-throated Sparrow 0 u White-fronted Dove u u u u Long-billed Marsh Wren u u Wilson's Warbler u Lincoln's Sparrow o c c Yellow-billed Cuckoo c c 0 L Short-billed Marsh Wren u u Canada Warbler u u Swamp Sparrow u o u Black -billed Cuckoo o L_ Rock Wren r American Redstart c 0 Song Sparrow u u u •Roadrunner c c c c •Mockingbird a a a a •Groove-billed An! u u u o Catbird u u UNITED STATES DEPARTMENT OF THE INTERIOR u •Long-billed Thrasher u u u u •Barn Owl u u u FISH AND WILDLIFE SERVICE •Screech Owl u u u u •Curve-billed Thrasher a II a • BUREAU OF SPORT FISHERIES AND WILDLIFE 6P 0 B7*<*1*

40 but once or twice: American flamingo, Ross1 goose, black duck, blue jay, European widgeon, Harlan's hawk, beardless flycatcher, red-breasted nuthatch, canyon wren, brown thrasher, western tanager, black-headed grosbeak, lazuli bunting, and Harris1 sparrow. The list, using species names, is in accordance with the Fifth (1957) A.O.U. Check- list.

3. Reptiles and Amphibians. Mild climate and moderate rainfall produce conditions well suited to many reptiles and amphibians. Frogs and toads representing 15 species and snakes representing 29 species are especially diversified. Eighteen of the 67 species of herpetiles occurring in this area are limited to southern Texas in their distribution within the United States.

The western diamondback rattlesnake is common on the area. This is probably the most dangerous snake in the United States and is responsible for more fatalities than any other North American serpent. It is unusually pugnacious and, if threat- ened or sufficiently annoyed, will vigorously defend itself. In this area diamondbacks often exceed 6 feet in length and individuals over 7 feet are known. The bite of this snake is very serious even to adults in excellent physical health.

The endangered American alligator was once present along the entire Gulf Coast of Texas. Except for one individual

41 discovered near Weslaco after the 1967 hurricane, none have been seen in South Texas in many years.

A listing of reptiles and amphibians has not been compiled for the refuge. However, the following list abstracted from A Field Guide to Reptiles and Amphibians, by Roger Conant, includes all species whose range overlaps Laguna Atascosa National Wildlife Refuge. Species marked with an asterisk (*) are found nowhere in the United States except this part of southern Texas. A number of these have extensive ranges in Mexico.

Salamanders Rio Grande siren Siren intermedia texana * Barred tiger salamander Ambystoma tigrinum mavortium Black-spotted newt Diemictylus meridional is * Toads and Frogs Hurter's spadefoot Scaphiopus hurteri Couch's spadefoot Scaphiopus couchi Mexican white-lipped frog Leptodactylus labial is * Rio Grande frog Syrrhophus campi * Rocky Mountain toad Bufo woodhousei woodhousei Gulf coast toad Bufo valliceps Texas toad Bufo compactilis Eastern green toad Bufo debilis' debilis Blanchard's cricket frog Acris crepitans blanchardi Green treefrog Hyla cinerea Mexican treefrog Hyla baudini * Spotted chorus frog Pseudacris clarki Sheep frog Hypopachus cuneus cuneus Bullfrog Rana catesbeiana Rio Grande leopard frog Rana pi pi ens berlandieri

42 Turtles Yellow mud turtle Kinosternon f1ayescans Texas diamondback terrapin Malaclem.ys terrapin littoral is Texas slider Pseudemys concinna texana Red-eared turtle Pseudemys scripta elegans Big Bend turtle Pseudemys scripta gaigeae * Ornate box turtle Terrapene ornata ornata Texas tortoise GopherusTberlandieri * Texas softshell Trioriyx spinifer emoryi Lizards Keeled earless lizard Holbrookia propinqua propinqua * Texas rose-bellied lizard Seeloperus" variabilTs marmoratus i Texas spiny lizard Sc eloper us" o1ivaceus~ Northern fence lizard Seel operus undulatus^ hyacinthinus Texas horned lizard Phrynosoma cornutum Eastern spotted whiptail CnemidopEorus sacki^ gularis Six-lined racerunner Cnemidophorus sexlineatus Ground skink Lygosoma late rale ~" Great Plains skink Eumeces obsoletus Four-lined skink Eumeces tetragrarnmus * Short-lined skink Eumeces Brevilineatus Western slender glass lizard Ophisaurus attenuatus attenuatus Snakes Plains blind snake Leptotyph 1 ops^ du lei's dulei's Texas brown snake Storeria dekayi texana~~" Gulf salt marsh snake Natrix sipedon clarki" Eastern checked garter snake Thamnophis marcianus marcianus Western ribbon snake ThamnophTT sauritus proximus Mexican hognose snake Heterodon nasicus Fennerlyi Black-striped snake Coniophanes imperial is.imperial is * Rio Grande racer Coluber constrictor stejnegerianus * Schott's whipsnake Masticophis taeniatus schptti~~" Ruthven's whipsnake Masticophis taeniatus ruthveni * Western coachwhip Masticophis flagellum' tes^taceus * Speckled racer Drymobius margaritiferus margaritiferus Texas indigo snake Drymarchon corai sTerebennus Rough green snake Opheodrys~aes ti vus Texas patch-nosed snake "Salvadora lineata Bullsnake Pituophis melanoleucus sayi Great Plains rat snake Elaj)h(5 guttata emoryi Texas long-nosed snake RHinochei1 us 1econtei tessallatus Mexican milk snake Lampropeltis doliata annulata~

43 Sonoran kingsnake Lampropeltis getulus spi endida South Texas ground snake Sonora episcopa^ tayl ori * Mexican hook-nosed snake Ficimia olivacea streckeri * Texas night snake Hypsiglena torquata texana Texas cat-eye snake Leptodeira se p t e n_t r i o n a 1 i s septentrional is * Texas black-headed snake Tantil la nigriceps fumiceps Northern flat-headed snake Tantill a gracilis ha11 owe11i Texas coral snake Micrurus fulvius tenere Desert massasauga Sistrurus catenatus^ edwardsi Western diamondback rattlesnake Crotalis atrox

4. Fish. The lower Laguna Madre is unique among Texas bays in that there is little pollution and few man made disturbances, although both are on the increase. This relatively undisturbed condition is believed to.be an important factor in the excellent fish production of the Laguna. Fish are present in the North Island Unit only during the higher wind tides but are trapped in intermittent lakes after hurricanes or floods. A complete list of the fish occurring in refuge waters is not available but it presumably would include all major species of the Laguna.

Spotted seatrout Cynoscion nebulosus Red drum or redfish Sciaenops ocellata Black drum Poqonias cromis Shipjack herring Al os a chrysochloris Pinfish Lagodon rhomboides Killifish Fundulus S£p_. Striped mullet Mugil cephalus Flounder Para lich thy s Interior fresh and brackish lakes and ponds are populated by: Carp Cyprinus carpio Striped mullet Mugil cephalus

^Common and scientific names used here are in accordance with Report ojf the. Committee on Names of fish, Special Pub!ication Number 2, American Fisheries Society7T960. 44 Alligator gar , Lepisosteus spatula Smallmouth buffalo Ictiobus bubal us_ Freshwater drum Aplodinotus grunniens Catfish Ictalurus sp.

Extensive stands of shoal grass interspersed with widgeongrass and other aquatics provide spawning, nursery, and forage areas for bay fishes. They are also the summer nursery for young brown shrimp (Penaeus aztecus) which as adults make up about 80 percent of the commercial shrimp catch along the Gulf of Mexico.

B. Wetlands The term wetlands commonly refers to lowlands covered with shallow and sometimes temporary or intermittent waters. In this report, we are dealing with the salt flats which reach out from the Laguna Madre into the grass- and brush-covered ridges of the mainland (Figure 9).^ Periodic flooding keeps the sparse vegetation in stages of both progressive and retrogressive succession.

Most of the vegetation occurs near the margins with only a few plants, primarily glassworts, invading the salt-incrusted flats. Saltgrass, saltflat grass, seablite, saltwort, cordgrass and . sea oxeye occupy the border areas or the occasional low dunes.4

3Classed as Type 15, Coastal Salt Flats, in Wetlands of the United States. USDI, Fish & Wild!. Ser. Cir. 39. The Laguna Madre can be classed as Type 19, Sounds and Bays. a list of common and scientific names see Ser. Cir. 39.

45 Figure 9. Few plants can tolerate almost constant submersion in saltwater. Many of the lowest areas are virtually devoid of vegetation.

46 These expanses provide little food but are used as resting areas by waterfowl and shorebirds feeding on the richness of the Laguna Madre. Fish-eating birds feed here at high tides.

Upland areas of North Island contain no permanent free water with the exception of one small dredged stockpond. The pond contains no emergent vegetation but is used quite extensively as a source of fresh-water.

C. Vegetation and Soils One of the most interesting aspects of North Island is the pattern and dynamics of the coastal vegetation. Surprisingly little ecological work has been done in southern Texas and even less is pertinent to the coastal environment of the Laguna Madre. A text adequately covering South Texas flora has apparently never been prepared, although one is under prepara- tion at the present time. During the present study only one article of significance dealing with the plant ecology of this area was discovered.5 This article was heavily relied upon in developing the vegetational and ecological comments in this report.

Seemingly, the vegetation is an amalgam of semiarid, tropical and seashore elements. Plants like acacia, palo verde, mesquite and the several species of cacti argue semiarid, while species

5Clover, E.U. 1937. Vegetational Survey of the Lower Rip Grande Valley, Texas. Madrono IV(2): 41-66; TD"TT7^f007

47 like Texas lantana, wild crepe myrtle and yaupon have generally tropical distribution. Seashore plants such as moss flower, sea oxeye, and glasswort complete the triangle. The predominance of legumes among the woody plants is typical of warm climates. The point is further emphasized by the prevalence of warm climate grasses; 65 percent of the grass species are members of the tribes Andropogoneae, Chlorideae, and Paniceae. Genera such as Bromus, Poa, Festuca, Agropyron and Muhlenbergia, so well represented in more northern areas, are completely absent.

Figure 10 delineates the pattern of principal vegetation types on the area. Three general types are recognized: salt flat, sacahuistal and mesquital. Subdivision of these types is possible but the additional detail is of little value in portraying the general character of the area. The three types can be correlated to some extent with three soil types recognized by the Soil Conservation Service. Some species appear to be restricted to a particular soil; others are more tolerant and overlap soil types considerably.

Salt flats cover over half the area. They.are periodically inundated by water from storms or wind tides and are essentially barren except near the margins or where topography is a few inches higher than the surrounding flat (Figure 11). The soils are heavily saline, and usually wet on or a few inches

48 o o

c CJ *O 7} £PI ?^- N frf r I c n o vo >0 I OJ

W 0 C r 5 Is o > 3 q 5 fr o CP o m o r r en -i r? < a- -1 T> X m .P r > -< r o > 3 Figure 11. A few inches increase in elevation above the inundated flats is sufficient to permit survival of most of the species present on the saline flats.

50 below the surface. Vegetation is dominated by sea oxeye and glasswort. Knotgrass and shoregrass are prominent on the better drained margins.

The sacahuistal, so called for the dominant Gulf cordgrass or sacahuiste, is prevalent along the coast and inland for several miles (Figure 12). This type is variable and intergrades into a mesquite dominant on higher ground. The sacahuistal's most

V. typical development occurs on the poorly drained soils. On North Island it conforms closely with the distribution of dark brown to brownish Lomalto Clay soils. These soils are low and salty with a water table at 2 to 4 feet. Standing fresh water occurs in depressions after storms. Apart from cordgrass, common plants include sacaton, dwarf screwbean, western ragweed, nightshade, verbena, Berlandier croton, seepweed, glasswort, silver beardgrass, and Hartweg paspalum. Other, grasses are Angleton, red grama, Bermuda, seashore saltgrass, blue panic, and Texas needlegrass. A few trees, mainly retama and huisache, are also present.

Mesquite is the dominant species on higher well-drained sites. Association with various other woody plants is referred to as mesquital or mesquital-chaparral (Figure 13). On North Island this type is confined to the numerous small mounds locally known as clay dunes. The "dune" soils are Point Isabel silty

51 Figure 12. Sacahuiste (Gulf cordgrass) occupies an intermediate position between the salt flat and the ridge top. In places it occurs in monotypic stands.

Figure 13. Mesquite is the dominant species on ridge tops. It may occur in virtually pure stands but is usually accompanied by granjeno, brasil and other small trees. 52 clay loams, a crusty and saline loamy soil with dense subsoils. These are the most fertile soils on the area and support the greatest variety of plant life. Woody growth is dense and usually 5 to 8 feet tall (Figure 14). Mesquite, granjeno and brasil are the most prominent species. Other trees include Texas ebony, haujillo and coma. Shrubs are led by snakeeye and white-brush and include Spanish dagger, coyotillo, Texas lantana, ceniza and prickly pear. Sacaton is the most prevalent grass with four-flower trichloris, buffalo, windmill and Bermuda also important. Other grasses include red grama, bur- grass, crowfoot, tanglehead and brown-top millet. Herbs include western ragweed, milkweed, sunflower and rainlily. Devil's head and hedgehog cacti are also prominent.

Two minor communities lie along the edges of the area. The first includes those areas that are constantly under salt water. Here shoalgrass and widgeongrass dominate. Other aquatic plants include manatee grass, turtle grass, and Halophilia englemannii. The second community is that developing on spoil piles along the ship channel (Figure 15). In many ways these are similar to permanent dunes and associated with a prairie phase of coastal vegetation. The vegetation is most evident along the base of the pile, since the upper reaches of the pile are periodically disturbed by dredgings and subject to severe erosion. Species commonly found in this situation include seashore

53 Figure 14. Plant variety and density of growth are greatest on the ridges. Thorny trees, cacti and other woody plants sometimes form impenetrable stands.

Figure 15. Revegetation of spoil piles is slow. While similar in elevation to the ridges of the interior, the sand soils will not support a similar growth. 54 saltgrass, Gulf cordgrass, saltwort, seepweed, Matamoros saltbush, sea purslane, wedgeleaf prairie clover, Indian mallow, sea oxeye, Indian blanket and moss flower.

As described earlier, the course of plant succession along the coastal areas is open to question. Probably, the vegetational aspect of North Island has changed very little in the last 150 years. A number of plants have been introduced either unintentionally, as in the case of North Island, or in an effort to improve grazing. Notable among these are the following grasses: Bermuda, Angleton, blue panicum, buffel grass, Rhodes grass, silky bluestem, crowfoot, jungle rice, Mediterran- ean lovegrass, bur bristlegrass and Johnson grass.

The more prominent plants present on the refuge are listed below. Also included is a list of the genera and number of species in each genera (in parenthesis). Since this is a listing for the entire refuge, a few of the plants included may not actually be present on the area. Common and scientific names of grasses are according to Texas Plants, A Checklist and Ecological Summary, b$ F. W. Gould, 1969 revised, Bur. Exten., Texas A&M University.

TREES (16 species in 13 genera) Athel Tamarix aphylla Berlandier ash Fraxinus berlandieriana

55 Black willow Sal ix^ nigra Brasil Condalia hop_keri Coma Burne 1ia celastrina Granjeno Celtis pallida Hackberry .Celtis laevigata var. laeyigata Huajillo Pithecellobium pallens Huisache Acacia farnesiana Mesquite Prosopi s^ julif 1 ora var. glandulosa Palo verde CercidiutTi mac rum Retama Parkinsorna aculeata Schaffner acacia Acacia schaffneri Tepehuaje Leucaena pulverulenta Texas ebony Pi thecen obi urn flexi caul e Wild olive Cordia boissien "~

SHRUBS (67 species in 55 genera) Prominent species Berlandier croton Croton humilis Bush morning glory Ipomea fistulosa Ceniza LeucophylluLeucppnyl m frutescens Coyotillo Karwinskiia humboldtiana Dwarf screwbean Prosppsis reptans var. cinerascens False willow Baccharis neglecta Indian mallow Abu ti 1 orii ncanum Panalero Forestiera angustifolia Rubber plant Jatropha dio|ca Saltwort Batis maritima Sea oxeye Borrichia frutescens Shrubby blue sage Sa 1 via "bal 1 o ta ef o 1 i a Snake-eye Phaul othainnus spinescens Spanish dagger Yucca treculeana Texas lantana horrida Texas persimmon Diospyros texana Texas randia Randia tfiagocaypa Tubercled saltbush Atriplex acanthocarpa White brush Alpys^ia gratyssima Wild crepe myrtle Malpfgia glabra Vaupon Schaefferia cuneifolia Croton soliman

56 SHRUBS (continued) Genera (number of species) Abutilon (2) Forestiera (1) Oenothera (1) Acalypha (1) Gymnosperma (1) Palafoxia (1) Aloysia (1) Hibiscus (1) Phaulothamnus (1) Amyris (2) Heimia (1) Phoenix (1) Atrip!ex (2) Hydrolea (2) Phorandendron (1) Baccharis (2) Ipomea (1) Prosopsis (1) Batis (1) Isocoma (2) Randia (1) Bernardia (1) Jatropha (1) Ricinus (1) Borrichia (1) Karwinskia (1) Rivina (1) Capsicum (1) Lantana (3) Salicornia (1) Cassia (2) Leucophyllum (1) Sal via (T) Castela (1) Lippia (1) Schaefferia (1) Clitharexyllum (1) Lycium (2) Sesbania (1) Condalia (1) Malpigia (1) Sophora (1) Croton (2) Malyastrum (1) Wissadula (1) Dalea (2) Maytenus (1) Xanthoxylum (1) Diospyrps (1) Mimosa (1) Yucca (1) Eupatorium (1) Nicotiana (1) Zexmenia (1) Eysenhardia (1)

CACTI (7 species in 6 genera) Barbwire acanthocereus Acanthocereus pentagonus Devil's head cactus Homalocephla texansis Engelman prickly pear Opuntia lindheimeri Hedgehog cactus Hamate-cactus setispinus Pi chilingo Mammil 1 aria~hemi sphaen ca Tasajillo Opunti a 1eptocaulis Echinocereus blanckii

SALTWATER AQUATICS (5 species in 5 genera) Manatee grass Cymodocea mar^atorum Shoal grass Pi pi antheri a wr^ighti i Turtle grass Thai a s s i a tes tud i num Widgeongrass Ruppia maritima Ha1ophi1i a englemanni i

57 GRASSES (70 species in 31 genera) Prominent species Angleton grass D i c h a nth i um a r i s ta turn Bermuda grass Cy nod on dactyl on Blue panic grass Panicum antidotal e Browntop panicum Pa ri'i clirn T as c i cu 1 a turn Buffalo grass Buchloe dactyl pi des Buffel grass Penni setum ci Bur-bristlegrass Setaria VerticTl lata Bur-grass Cenchru^ echi na€us Crowfoot grass Dactyl octenium aegyptium Four-flower trichloris Tri ch 1 or~ i~^ s^ pi u ri f 1 bra" ' Gulf cordgrass (sacahuiste) Sparti na s~parti nae Hartweg paspalum Paspalum hartwegiFnum Johnson grass Sorghum hal epense Jungle-rice E cFi noc h 1 oa co 1 prium Knotgrass Pas pal um d i s ti chum Mediterranean lovegrass Eragrpsti s barrel i eri Red grama Bouteloua trifida Rhodes grass Chlorfs gayana Sacaton Sporobolus wrightii Seashore saltgrass Pi s ti ch 1 i s s pi ca ta Shoregrass Monanthochloe 1ittoralis Silky bluestem Dichanthium sericeum " Silver beardgrass BpthriochTora saccaroides Slim-spike windmill grass Ch Ion's andropogonojdes ~~ Tanglehead Heteropogon contortus Texas needlegrass Stipa leucotricha Willkommia texana Genera (number of species) Agrostis (1) Eragrostis (8) Paspalum (5) Andropogon (5) Eriochloa (3) Pennisetum (1) Aristida (2) ' Heteropogon (1) Setaria (2) Bouteloua (1) Leersia (1) Sorghum (1) Buchloe (1) Leptochloa (5) Spartina (1) Cenchrus (2) Leptoloma (1) Sporobolus (4) Chloris (6) Limnodea (1) Stipa (1) Cynodon (1) Monanthochloe (1) Tridens (2) Dactyloctenium Panicum (6) Trichloris (1) Distichlis (1) Pappophorum (1) Willkommia (1) Echinochloa (2)

58 GRASSLIKE PLANTS (16 species in 4 genera) Prominent species Roundstem cyperus Cyperus articulatus Common spikerush Eleocharis calva" Square-stemmed spikerush Eleochari s quadrangu1 a ta California bulrush Scirpus californicus Saltmarsh bulrush Scirpus robustus ~ Cattail Typha donnngensis Genera (number of species) Cyperus (8) Scirpus (3) Typha (1) Eleocharis (4)

FORBS (227 species in 168 genera) Prominent species Bluebell Eustoma exalta tus Deer apple Ibervil'ea tenel Te Duckweed Lemna minor Evening primrose Oenothera laciniata False flax Gilia incfisa Glasswort Salicorma sp_. Goosefoot ChenopjDduiin sp. Indian blanket Ga j 11 oTdTa~puTchel 1 a var. pi eta Matamoros saltbush Atri piex~matamorensis Mi 1kweed Asclepias sp. Moss flower Portujaca pilosa Nightshade Sol anum sp_. Pigweed Amaranthus sp. Rain lily ZephryanthesDrazosensis Russian thistle Sal^sola ka^li var. tenuifolia Sea-purslane Sesuvium verrucosum ~ Slender vervain Verbena Halei Seepweed Suaeda conferta Sunflower Helianthus anniis Verbena Verbena sp~. Water shamrock Marsijea uncinata Wedge!eaf prairie clover Petalostemum emargi natum Western ragweed Ambrosia psilostachya Wild lettuce Lactuca hirsuta var. sanguinea Genera (number of species) Abutilon Aeschynomene (1) Ambrosia (1) Acalypha (lIf') Alternanthera (1) Ammannia (1) Acleisanthes (1) Amaranthus (4) Amoreuxia (1) 59 FORBS (continued) Ammoselinura (1) Gaillardia (2) Pluchea (1) Anredera (1) Galactia (1) Polanisia (1) Anthericum (1) Gaura (2) Polygala (1) Anoda (2) Gilia (1) Polygonum (1) Aphanostephus (1) Gnaphalium (1) Portulaca (2) Apium (1) Gomphrena (1) Pseudoabutilon (1) Argemone (1) Gossypianthus (1) Psoralea (1) Argythamm'a (1) Hedyotis (1) Pyrrhopappus (1) Asclepias (2) Helem'um (2) Ratibida (1) Aster (T) Helianthus (1) Rhynchosia (1) Astragalus (1) Heliotropium (2) Ruellia (1) Atrip!ex (2) Heteranthera (2) Rumex (2) Boerhavia (1) Houstonia (1) Sagittaria (1) Bogenhardia (1) Ibervillea (1) Salvia (1) Bacopa (1) Indigofera (1) Samolus (1) Calyptocarpus (1) Ipomea (2) Sanvitalia (1) Callitriche (1) lya (2) Salicornia (1) Cardiospermum (1) Jatropha (1) Salsola (1) Centaurium (1) Jussiaea (1) Satureja (1) Celosia (1) Kallstroemia (1) Sedum (1) Chamaesaracha (1) Lactuca (1) Senecio (1) Chenopodium (3) Lemna (1) Sesuvium (2) Cirsium (1) Lepidium (1) Sibara (1) Cissus (2) Lesquerella (2) Sida (8) Clappia (1) Limnosciadium (1) Simsia (1) Clematis (1) Linomium (1) Siphonoglossa (2) Cleome (2) Lythrum (1) Sisymbrium (1) Coldenia (1) Machaeranthera (1) Solanum (4) Cooperia (1) Malvastrum (2) Sonchus (1) Commelina (3) Marsilea (1) Spermacoce (1) Conyza (1) Margaranthus (1) Stachys (2) Coreopsis (1) Menodora (1) Stellaria (1) Crotalaria (1) Metastelma (1) Suaeda (2) Croton (3) Mollugo (1) Talinum (2) Cuscuta (2) Najas (1) Teucrium (1) Dalea (3) Nama (1) Thamnosma (1) Daucus (1) Nothoscordum (1) Tidestromia (1) Desmanthus (1) Nymphaea (1) Tillandsia (1) Dichondra (1) Oenothera (3) Tradescantia (1) Diodia (1) Orobanche (1) Trianthema (1) Dyschoriste (1) Oxalis (3) Trichocoronis (1) Dyssodia (2) Palafoxia (1) Trixis (1) Elytraria (1) Parietaria (1) Urtica (1) Echinodorus (2) Parthenium (1) Urticularia (1) Eclipta (1) Passiflora (2) Verbena (5) Erigeron (1) Perezia (2) Verbesina (1) Eryngium (1) Perityle (1) Veronica (1) Euphorbia (1) Petalostemum (1) Vicia (1) Eustoma (1) Petunia (1) Wissadula (1) Eupatorium (1) Physalis (1) Xanthocephalum (1) Evax (2) Phyla (2) Ximenesia (1) 60 FORBS (continued) Evolvulus (2) Phyllanthus (1) Zannichellia (1 Florestina (1) Plantago (1) Zephryanthes (1

D. Mineral For many people Texas means flatland and oil. While all of Texas is not flat, oil has greatly influenced the economy of the entire state. The rich oil fields which dominate the economy of East Texas extend southward along the coast to the Rio Grande where their importance is overshadowed by the equally rich farmlands.

Oil and natural gas constitute the mineral potentials of North Island. Although some exploration has been carried out on the refuge proper, no producing wells have been established. Any positive results of a single "dry" hole drilled in 1968 immedi- ately across the Harlingen Ship Channel have not been revealed. Just what potential the refuge has for oil is not certain but test holes, production and offshore drilling point towards continued interest.

As stated in a previous section, mineral rights on refuge lands have been retained by the previous landowners but are due to expire on North Island within 10 years. Until expiration, the area is open to serious exploration by the previous landowners or their leasees.

61 Cameron and Willacy counties combined are responsible for about 0.2 percent of statewide oil production. By 1966, the total production for Cameron County was 84,000 barrels. There is no oil production in the county at the present time. Willacy County had produced over 57 million barrels by 1966. v There are currently five fields producing natural gas in eastern Cameron County. All of these are within 10 miles of the refuge . (See Appendix I, letter from University Texas, Bur. Econ. Geology). The five fields constitute 23 wells and produced approximately 10.6 billion cubic feet of gas in 1968.

E. Recreation Amid intensive agriculture and activities, including recreation, centered on the Gulf of Mexico, the refuge offers a variety of wildlife-oriented recreation. Table 2 lists these and the amount of use attributed to each for the entire refuge. Observation of the multitude and variety of bird life on Laguna Atascosa and its nearby sister refuge, Santa Ana, is one of the most outstanding quality recreation opportunities in this part of Texas. It is truly a place for birdwatchers to "do their thing". Although none of the listed activities are unique to North Island, opportunities for wildlife observation, photography and hiking exist in forms more "remote" than on surrounding lands. Inaccessibility and lack of permanent water will limit most activities. In general, North

62 Island is not for the average pleasure seeker, but can provide the student, the avid observer, or photographer a unique experi- ence. Recreation and its impact on the community are discussed in the following section.

Table 2. Recreational Activities and Related Use, Laguna Atascosa National Wildlife Refuge, 1968.

ACTIVITY NUMBER OF VISITS

Fishing 14,570 Scenic Auto Tour 3,450 Wildlife Observation 2,360 (non-designated areas) Picnicking 938 Camping 334 Wildlife Guided Tours 283 Wildlife Trail Walks - 203 Wildlife Photography 51 Bird and Animal Calling 5 Miscellaneous - Wildlife 72 Peak Load Day 1,320

Total Wildlife-Oriented 22,266 Total Nonwildlife 721 Grand Total 22,987

According to the Bureau of Outdoor Recreation, there are over

100 recreation areas administered by Federal, State and local entities within a 100-mile radius of Laguna Atascosa National- Wildlife Refuge. These areas encompass a total of approximately 139,OOO6 acres of land and water. Relatively little of this

^Does not include Laguna Atascosa National Wildlife Refuge lands.

63 acreage is intensively developed for recreation purposes.

Of the above total, approximately:

— 460 acres, or less than 1 percent, are classified as BOR Class I "high density recreation areas";

— 2,970 acres, or 2 percent, are classified as BOR Class II "general outdoor recreation areas";

— 135,365 acres, or 97 percent as BOR Class III "natural environment areas"; and

-- 205 acres, or less than 1 percent, as BOR Class IV "outstanding natural areas".

Land administered by the National Park Service in Padre Island National Seashore accounts for a significant portion of the above acreage—especially Class III lands. The National Sea- shore is over 133,000 acres in size and is 10 miles northeast of Laguna Atascosa National Wildlife Refuge. Sizable portions of the Gulf of Mexico and Mexico are found within the limits of the Laguna Atascosa National Wildlife Refuge 100-mile radius influence area.

Other important recreation areas within the above area include the Brazos Island State Scenic Park near Port Isabel and the Nueces County Parks near Corpus Christi. The Aransas National

64 Wildlife Refuge and Falcon Reservoir are situated just outside the influence area.

There are no designated wilderness, primitive or roadless areas within a 100-mile radius of the Laguna Atascosa National Wildlife Refuge.

Population within the influence area was approximately 712,000 in 1967.

65 VII. SOCIO-ECONOMIC CONSIDERATIONS

A. General In the last 60 years Cameron County has been converted from a brush covered delta into an area of intensive farming. Over 70 percent of the total land acres is currently under production. Yet, despite the farming economy, 140,000 people reside in the county, 80 percent in three major cities. Visitors also see the Lower Rio Grande as a desirable fall and winter retreat.

Despite the potential visitor use the refuge received fewer than 25,000 visits annually (Tables 2 and 3). This is not due entirely to the offering, however, as the refuge must compete with Padre Island National Seashore, the Gulf with its boating, swimming and deep-sea fishing, and of course, attractions only Mexico can offer.

The Texas Outdoor Recreation Comprehensive Plan indicates that demand for all outdoor recreation activities will continue to increase in this region because: (1) warm temperatures prevail most of the time; (2) Padre Island National Seashore will attract more tourists to the area; and (3) this area is the gateway to Mexico for those people living in the East and Mid-west.

Fishing accounts for more than half of the refuge visits even though it is permitted only along the Harlingen Ship Channel. The Channel also acts as a waterway for pleasure boaters,.some

66 of whom have permanent or vacation homes at nearby Arroyo City (Figure 1). The 14,500 fishing visits in 1968 represent only a small portion of the total fishing in the area. The great bulk of the sport fishing is done from boats on the Gulf or along the Intracoastal Waterway. Trot lines and shanties are evident along the coastal boundary. The Intracoastal Waterway which passes through the northeast corner of the refuge is a major travel route for sport and commercial fishermen as well as for shipping.

Although several game species are present, the refuge has never been open to hunting at the time of this study. It is, however, a wintering area for a variety of waterfowl and acts to stock surrounding areas. When consistent with policy, the refuge may offer opportunity for 'quality' waterfowl, deer and dove hunting.

The demand for additional hunting areas is not easily measured. Many surrounding landowners either close their land or lease hunting rights to private individuals or clubs. Clean farming practices have reduced available habitat throughout the valley. It is likely that local hunters would take advantage of a public hunting area.

North Island supplies none of the use listed in Tables 2 and 3, due to lack of access. There is essentially no demand since the refuge proper offers similar opportunity. Thus, the

67 recreation potential of the area must be considered low.

Table 3. Estimated man-day use, Laguna Atascosa National Wildlife Refuge, 1951-1968.

YEAR ESTIMATED MAN-USE DAYS 1951 18,000 1955 23,200 1961 25,000 1962 25,000 1963 - 12,500 1964 15,000 1965 15,500 1966 18,900 1967 18,000 1968 23,000

B. Grazing The refuge contains seven grazing units; North Island is synonymous with refuge Unit IV. Following is a breakdown of the broad land types and the current grazing permit: North Island (Unit IV) Grazing lands. 4,765 acres Marsh and water 300 acres Salt and mud flats 4,375 acres Total area 9,440 acres . Minimum acres per cow 27 Maximum number of head 130 Period of use. . * year-long Grazing fee $0.50 per AUM Number of permittees one

The permit allows year-long grazing for 130 head for a total of 1,560 AUM's; the grazing fee is .$780.00 per year at present. No special provision is made for cow-calf or yearling classes and excess numbers are removed every six months.

68 A grazing study currently being made may change some of these factors. The impact of changes in grazing policy would not be great economically and operational changes would affect only one permittee.

C. Navigation The situation concerning the Intracoastal Waterway and the Harlingen Ship Channel has been outlined in previous sections. Their effect on wilderness from an aesthetic viewpoint is apparent. No further navigational facilities are planned. However, it is implied in the written agreement that if the Corps of Engineers requires additional lands for spoil deposition, such lands will be made available. Such an event is not anticipated but would encroach upon the North Island Unit.

D. Agriculture North Island is totally unsuited for farming and there is no consideration from this standpoint.

69 VIII. DEVELOPMENT

There are no developments for waterfowl or other wildlife on North Island. However, old stream channels and adjacent ridges interlace to provide considerable opportunity for fresh-water impoundments. The refuge Master Plan recognizes this potential and states that a number of small ponds similar to those developed along the west side of Laguna Atascosa and Cayo Atascoso could be realized with construction of five miles of low dikes with earthen spillways (Figure 16).

Although planned developments are limited to numerous small catchments, water resource projects in South Texas offer the possibility for a permanent supply of fresh-water (see The Texas Gulf Coast. A Special Report, Div. Wildlife Refuges, Region 2; May 1964). Such a possibility would have a bearing on long-range planning efforts.

There is little doubt that the South Texas coast will undergo dramatic changes in the years to come. Most of these changes will act to reduce existing waterfowl habitat. But even as waterfowl habitat disappears so do other natural features. The brushlands and native grasses, also constrained by "progress", are no less valuable in the natural scheme and should not be ignored. In view of this, retention of North Island as either wilderness or developed waterfowl habitat is imperative.

70 Figure 16. The meandering action of the Arroyo Colorado was the principal force in sculpturing the landscape. Diking across these channels to provide fresh water catchments for waterfowl is an element of the Refuge Master Plan.

71 Existing developments for grazing include several miles of fence, one stock pond, and a loading chute along the ship channel (Figures 1, 17 and 18). The fencing is conspicuous and not in keeping with wilderness characteristics but is apparently needed for livestock removal. The western and northern refuge boundaries from the Laguna Madre to the Harlingen Channel are also fenced. No additional facilities are needed with the possible exception of additional stock ponds to better distribute grazing.

Further development of the previously described navigation facilities is not foreseen, although spoil will continue to be deposited.

72 Figure 17. This fence is used to aid cattle management on North Island. It is several miles long and quite conspicuous on the open flat.

Figure 18. The single excavated stock pond on North Island appears "natural" except for the heavy use by cattle around the perimeter. 73 IX. MANAGEMENT

A. Wildlife and Vegetation The principle of plant succession is basic to wildlife as well as vegetation and it is often not climax but a serai stage that commands attention. It was brought out in a previous section that vegetation on North Island can be termed a 'permanent' disclimax representing a balance between brush and grassland. Historically, grazing has been the primary management tool uti- lized on the area but has not been geared specifically to main- taining this balance. Initially, the stocking rates were the same as those practiced by former landowners but these were considered heavy and cutbacks were soon made on most refuge units. Since 1948, the annual stocking rate on North Island has remained constant at about 25-30 acres per animal unit. Grazing has always been year-long.

The current program places emphasis on close cropping of grasses to attract wintering geese (Figure 19). However, year-long grazing and recent hurricane damage have decreased the amount of available goose browse. As a result, a grazing study is being conducted to set priorities based on development plans and long-range objectives for the area.

B. Minerals-Mining Mineral rights have been reserved by the former owners of the

74 Figure 19. The current grazing program emphasizes close-cropping of grasses to attract wintering geese.

75 two tracts composing North Island. They will expire in 1976 and 1979. Until these dates, access for exploration and development by mineral right owners and their agents must be permitted. If discovery and production occur prior to the expiration dates, mineral reservations will remain in effect "indefinitely". Petroleum and natural gas are the only known mineral potentials of the area, and the possibility of discovery is very real. Producing wells would mean not only drilling and pumping equipment but roads and or channels for servicing.

C. Recreation Virtually no recreation occurs on the area at present. Future recreational use will increase but is not expected to approach the public use of the more attractive areas. Since use will be low and confined primarily to hunting and nature study, no active management for other forms of recreation is contemplated. . The large number of diamondback rattlesnakes on the area demands that visitors be adequately informed and prepared to cope with the danger.

D. Navigation Both the Harlingen Ship Channel and the Intracoastal Waterway have an effect on the area (Figure 20). The Harlingen Ship Channel effectively isolates the area from the rest of the refuge and limits access for public use (Figure 21). The Water- way cuts across the northeast corner of the unit. Conspicuous

76 Figure 20. "Fishing shanties and trot lines" is the theme along the Intracoastal Waterway. Neither is permitted within refuge boundaries.

Figure 21. The 300-foot-wide Harlingen Ship Channel places North Island in "quarantine". The area can be reached only by boat. 77 piles of channel dredgings line both channels and boat movements in the channels are easily visible from many places on the area. Maintenance dredging will add to the present spoil sites. Channel maintenance is under the jurisdiction of the Corps of Engineers.

78 X. SUMMARY AND CONCLUSIONS

The Laguna Atascosa National Wildlife Refuge lies on the South Texas Coast about 20 miles north of the Mexican border. Its eastern boundary fronts on the Laguna Madre, a large shallow embayment formed by Padre Island and lying along the coast from Corpus Christi to the mouth of the Rio Grande. Only the northern one-fifth of the refuge, a roadless tract of about 9,440 acres, qualifies for consideration as wilderness.

This tract, North Island, is bordered on the east and north by the Laguna Madre and the Intracoastal Waterway, on the west by the old Arroyo Colorado channel, and separated from the remainder of the refuge by the Harlingen Ship Channel. It was originally part of a Spanish land grant of the late 18th century. Surface rights were acquired by the Federal Government with the establish- ment of the refuge, but the former owners retained mineral rights for a period of 30 years. The last of these rights revert to Federal ownership in 1979 unless mineral discovery and development occur prior to that date. There are no surface right inholdings, although the Corps of Engineers and the Arroyo Colorado Navigation District do retain various rights and easements along the ship channels primarily for deposition of channel dredgings.

North Island is part of a small delta formed by the Arroyo Colorado, a former flood channel of the Rio Grande. It is an area of low

79 ridges dissected by a number of old stream channels, broad flats with no natural drainage, and coastal mud flats occasionally inundated by wind tides. The small trees and brush dominating the ridgetops are among the area's most attractive features. Tidal flats covering over half of the area are sparsely vegetated or completely barren.

Much of South Texas was formerly grassland broken only by patches of brush along stream courses. In the 19th century, overgrazing and drought triggered an extensive invasion of brush. Today the brushlands are rapidly giving way to cultivation and pasture improvement. It is likely that North Island was never itself grassland and that the general aspect of the area has changed little since early Spanish exploration.

The climate is mild with features of both dry and subhumid and semiarid types. Erratic precipitation patterns, mild temperatures and coastal exposure combine to support a complicated and highly interesting flora. Desert plants exist side by side with tropical and seashore species. Over 400 species of plants are known to occur on the refuge.

The primary purpose of the refuge is to provide migration and wintering habitat for migratory waterfowl. In this respect, it is admirably located as an important link in the National Wildlife Refuge System. An estimated 75 percent of the continental redhead

80 population winters on the Laguna Madre. A significant portion of these birds utilize the fresh-water supplied by the refuge. In addition there are few places in the United States where bird variety of Laguna Atascosa can be rivaled. Large numbers of shorebirds utilize the mudflats for resting and feeding while the interi- or brushlands provide habitat for a great variety of small birds.

Southern Texas is also an area rich in peripheral species. Numer- ous plants and animals make their only appearance in the United States in this region. Several of these occur on North Island.

The refuge offers a variety of wildlife-oriented recreation. Visi- tation over the past 8 years has averaged about 19,000 with over half devoted to fishing. Due to limited access virtually none of this use occurred on North Island.

North Island has been subjected to nearly continuous grazing since the refuge was established. It currently carries 130 head of cattle on a year-long basis under one permit. The program emphasizes close use of grasses to attract wintering geese. A reevaluation of the grazing program is currently being conducted.

No developments have been made on the area for waterfowl or other wildlife. Developments for grazing include several miles of fence, one stock pond and a loading chute. No additional developments for grazing are contemplated. Piles of dredging spoil line both ship

81 channels and will continue to be periodically deposited. The refuge Master Plan recognizes the need for additional fresh-water impoundments for waterfowl. These structures would be low-level dikes across old drainage channels, similar to structures on other parts of the refuge.

North Island qualifies for consideration as wilderness; it is roadless and relatively undisturbed. However, private mineral development is a real, if immeasurable, possibility. Petroleum exploration and production could create conditions completely incompatible with wilderness. Also there is concern with the trend toward increasing industrialization and urbanization along the Texas Gulf Coast. Coastal waterfowl habitat is rapidly being lost. With further development Laguna Atascosa National Wildlife Refuge can play an even more important role in providing resting and wintering habitat for migratory birds.

82 APPENDIX I

83 THE UNIVERSITY OF TEXAS AT AUSTIN BUREAU OF ECONOMIC GEOLOGY AUSTIN, TBXAS 78712

University Station, Box X September 5, 1969 Pbont 312-GR 1.1)34

Mr. Gerald E. Duncan Assistant Refuge Manager United States Department of the Interior Fish and Wildlife Service Bureau of Sport Fisheries and Wildlife P. O. Box 1032 0 Yuma, Arizona 85364

Dear Mr.' Duncan:

Following is the information regarding oil and gas in Cameron County, Texas that you requested.

- The mainland portions of northeastern Cameron County and adjacent areas are underlain by Pleistocene and Holocene Rio Grande deltaic deposits which consist of sand and mud. The eastern margins of the mainland, along Laguna Madre, and Padre Island, a barrier island composed of sand deposited by longshore currents, are mantled by windblown sand. The mineral potential of this area is essentially zero except for sand which is available all along the Texas coast.

At the present time there is no oil production in Cameron County. There are 0 five fields producing natural gas in the eastern and northeastern part of the county. All produce from sands of Miocene age and range , in depth from 3500 to 7500 feet.

The five fields are:

1. HOLLY BEACH, Located two miles northwest of Port Isabel and in Laguna Madre. Eleven wells produced 6.33 billion cubic feet of gas in 1968.

2. PADRE ISLAND, located eighteen miles north of Port Isabel, on Padre Island. One well produced 359 million cubic feet of gas in 1968.

3. EAST THREE ISLANDS, located twelve miles north of Port Isabel, in Laguna Madre. Two wells produced 1.9 billion cubic feet of gas in 1968.

84 ,.. J L .

Mr. Gerald E. Duncan Page 2 September 5, 1969

4. L/UTTES, located three miles west of Three Islands. Three wells produced 1.15-billion cubic feet of gas in 1968.

5. PARKS FARM, located fifteen miles north of Los Fresnos. Six wells produced 860 million cubic feet of gas in 1968.

In regard to future prospects for oil and gas, based upon past exploratory drilling in the area, which has been neither widespread or particularly successful, such prospects would not appear to be promising. However, Cameron County lies within the deepest part of the Rio Grande Embayment. Deeper exploratory drilling, (15, 000 to 20, 000 range) of which there has been little to date, may develop production in the future.

Hoping this information is helpful to you, I am O

:TER Director

PTFrjpv

85 . THE UNIVERSITY OF TEXAS AT AUSTIN AUSTIN, TEXAS 78712

The Department of Botany September 10, 1969

Mr. Claude F. Lard, P. 0. Box 1032 Yuma, Arizona 85364 Dear Mr. Lard: I just returned from 13 months in Europe to find your letter of June 11, 1969, inquiring about plants on the.laguna Atascosa National Wildlife Refuge. I am very much interested in your program on wilderness O areas and especially in the much-abused Laguna Atascosa Refuge, where the very unfortunate practice of government-sponsored overgrazing has taken a terrible ecological toll. I would like to be of any help I can. Miss Clover's 1937 paper was a good one, but the nomenclature is sadly out of date. Unfortunately there is no good reference for you^ to turn to. That is no published reference. My advice is to try to obtain a xerographic or microfilm copy of my dissertation "Vegetation of the eolian plain and associated coastal features.of southern Texas" The University of Texas, 1955. 167 pp. I believe you can obtain this by writing the Librarian, The University of Texas at Audlin, Austin, Texas 78712. You could enclose this letter so that the librarian would know that copying the thesis is all right with me. —Unfortunately after Li years the nomenclature in this thesis is also slightly out of date; not nearly so much as Miss Clover's, of course. Some information might be obtained in my paper in Ecology 4-4:456-—4.66, but o not much. (I have no more reprints). Even earlier I wrote a master's thesis on the vegetation of eastern Cameron County, and you might want to get a copy of that from our library; it was dated 1952. I have made some marks on the plant list you sent; I hope they are informative. Perhaps if you could send me a draft of your report I could go through it and try to bring the names up to date as far as I can. • The Manual of the Vascular Plants of Texas by D.S. Correll and me is in manuscript still and printing will not commence until October, 1969. The appearance of the book is probably still almost a year in the future. If I can be of any help, please do not hesitate to call on me. Sincerely,

Marshall C. Johnston 86