Texas Parks And Wildlife Department Research Articles

Relative Abundance of Bobwhites in Relation to Weather and Land Use

Weather and land use are important factors influencing the population dynamics of northern bobwhites (Colinus virginianus) in Texas and elsewhere. Using an artificial neural network, we studied the effects of these factors on an index of bobwhite abundance (hereafter, index) in 6 ecoregions in Texas. We used roadside-count data collected by the Texas Parks and Wildlife Department (TPWD) during 1978-1997. Weather variables were June, July, and August mean maximum temperatures, and winter (Dec-Feb), spring (Mar-May), summer (Jun-Aug), and fall (Sep-Nov) rainfall. We also included the proportion of county area in cultivation, the number of livestock per hectare of noncultivated land, and the previous year's bobwhite count in the analyses. The data were partitioned into training and validation data sets prior to analyses. The neural model explained 65% of the variation in the training data (n = 72) and 61% of the variation in the validation data (n = 17). The most important variables contributing to network predictions were July temperature, fall rainfall, cattle density, and the previous year's bob-white count. State-level simulation results indicated that the bobwhite index decreased with increasing June temperature and livestock density. The bobwhite index increased with July and August temperature, fall rainfall, and the previous year's bobwhite count. Bobwhite abundance increased with the proportion of county area in cultivation up to approximately 20% cultivation and then declined. Winter, spring, and summer rainfall had little effect on the bobwhite index. Although many relationships appeared approximately linear or were decelerating, proportion of county area in cultivation and livestock density on noncultivated land showed strongly curvilinear responses. Therefore, cultivation up to approximately 20% of county area was beneficial, but the benefits disappeared as cultivation increased beyond this level. Further, at low livestock densities, between 0.15 and 0.40 head/ha, small increases in head/ha resulted in a decrease in the bobwhite index of 156.4%/head/ha. The results also indicated that a potential bias might exist in the survey protocol resulting in artificially inflated counts under some weather conditions.

Differential Influence of Weather on Regional Quail Abundance in Texas

Although weather variables are known to influence quail abundance in some habitats, most studies have addressed only limited geographic areas and indices to weather conditions. The few replicated studies addressed relatively similar climate zones. We used 21 years (1978-98) of quail abundance data collected by the Texas Parks and Wildlife Department (TPWD) biologists to address the relationship between both simple precipitation and Palmer drought indices and Northern Bobwhite (Colinus virginianus) and Scaled quail (Callipepla squamata) abundance in 6 ecological regions of Texas. Three 12-month Palmer indices were more highly correlated with changes in Northern Bobwhite abundance in the South Texas Plains ecological region than was raw precipitation alone. The 12-month Modified Palmer Drought Severity Index (PMDI) was correlated (r s ≥ 0.78, P ≤ 0.001) with the mean number of Northern Bobwhites visually observed per survey route in the Rolling and South Texas Plains ecological regions, while a 12-month, raw precipitation index was correlated (r s = 0.64, P = 0.002) with Northern Bobwhite abundance in only the South Texas Plains. The PMDI and raw precipitation were correlated (r s ≥ 0.67, P ≥ 0.001 and r s ≤ 0.57, P ≤ 0.007, respectively) with the mean number Scaled Quail observed per survey route in the Edwards Plateau, South Texas Plains, and Trans-Pecos Mountains and Basins ecological regions. There was no relationship (P ≥ 0.437) between changes in quail abundance and the PMDI or raw precipitation in the Gulf Prairies and Marshes physiographic region, where precipitation was relatively high. The monthly PMDI was a better indicator of changes in both northern bobwhite and Scaled Quail abundance among years than was monthly precipitation alone. Both monthly and 12-month precipitation-based weather indices were more correlated with changes in Northern Bobwhite and scaled quail abundance among years in relatively dry as opposed to wet ecological regions. Our approach should help wildlife biologists and managers better account for annual variability in quail productivity in semi-arid environments so that long-term populations trends can be better elucidated.

Archaeological Testing of Site 41BX1199, Government Canyon State Natural Area, Bexar County, Texas

In May 2001, the Center for Archaeological Research (CAR), The University of Texas at San Antonio, tested two areas of site 41BX1199 in the Government Canyon State Natural Area. The Natural Area is located in northwest Bexar County and is under the ownership and management of the Texas Parks and Wildlife Department (TPWD). In advance of opening the Natural Area for public use, TPWD contracted with the CAR to conduct a 100 percent pedestrian survey of proposed trail systems within the property and to carry out National Register eligibility testing of site 41BX1199. CAR personnel conducted the testing of 41BX1199 under Texas Antiquities Permit 2582. This report discusses only the results of the test excavations performed at 41BX1199. Two spatially isolated portions of site 41BX1199 were to be impacted by the construction of picnic locations and camping facilities. The two areas covered 7 acres (2.8 hectares) and 11.6 acres (4.7 hectares), respectively. The CAR testing efforts focused on these areas. Thirty-five shovel tests and one 1-x-1- meter test unit were excavated in the larger area, while 14 shovel tests were dug in the smaller area. Testing efforts identified a low-density, disturbed surface scatter of artifacts and a modern hearth feature. No temporal diagnostic artifacts were recovered. The sparse collection of lithic artifacts, the lack of temporal diagnostics, the deflated character of some of the deposits, and the modern hearth feature suggested that the examined portions of 41BX1199 have low research potential and are not eligible for listing on the National Register of Historic Places or designation as a State Archeological Landmark. It is recommended that the area connecting the two impact zones be periodically examined for exposed artifacts that may come to light as a result of pedestrian and equestrian traffic. It is further recommended that an archaeologist monitor the work to be carried out in the impact zones and document any intact cultural materials encountered during construction.

1999 Excavations at Mission Rosario

Mission Nuestra Senora del Rosario founded in 1754, is located four miles west of modem-day Goliad, Texas. Established for the Karankawa Indians, it was finally abandoned in 1808. Archaeological investigations have been conducted at the site in the 1940s, 1970s, and 1990s. This body of work, the most recent, was conducted by the Center for Archaeological Research at The University of Texas at San Antonio (CAR) (UTSA) under the auspices of the Texas Parks and Wildlife Department (TPWD). In July through September 1999, CAR excavated 105 units, cleared some above-ground walls, and probed for buried walls or foundations. A geophysical survey complementing the archaeological investigations was conducted by Baylor University geophysicists. Archival research combined with extensive field mapping using an electronic Total Data Station has resulted in a visual synthesis of mission features and the previous investigations associated with them.

Law enforcement personnel needs of a state natural resource agency

In this study, we assess personnel needs of the Law Enforcement Division (LED) of the Texas Parks and Wildlife Department (TPWD). The LED's mission is to enforce Texas’ laws and regulations regarding hunting, fishing, and other uses of wildlife resources for recreational and commercial purposes. Texas is a leading state nationally in outdoor recreational use of natural resources. It ranks second in the number of anglers and hunters, fourth in the number of boaters, fourth in size of the population, and fifth in the number of citations issued per warden in the southeastern United States. Operational, demographical, and ecological data were obtained from several Texas state agencies and from a mail—out survey of all Texas game wardens (n = 397) and their captains (n = 33). Maximum R‐square variable selection and general linear model procedures were conducted to estimate the numbers of game wardens needed per county. The regression model explained 78% of the total variation in the distribution of game wardens and estimated that there was a statewide excess of 17 game wardens. In a mail survey conducted in May of 1997, TPWD game wardens expressed a perceived need for 157 more game wardens. Over half (59%) of the differences between observed and perceived needs occurred in three of 10 LED regions. Differences between the model and perceived estimates for game warden personnel indicated the difficulty of determining where and how many game warden personnel are to be assigned and a need for additional consumer and other demand types of data at the county level.

Effect of the Colorado River Diversion on Matagorda Bay Epifauna

The effect on epifauna of the Colorado River diversion, which restored river flow to Matagorda Bay, Texas, U.S.A. was assessed using three independent data sets and analytical approaches. A monitoring study conducted by the Galveston District, U.S. Corps of Engineers, revealed lower croaker and brown shrimp abundances for 3 years following the diversion compared to their abundances during 3 pre-diversion years. No changes in the abundances of white shrimp, blue crabs and spot were evident in this monitoring study. The relative distributions of these common epifaunal organisms within the eastern arm of the bay, where the redirected river-mouth empties, did not change following the diversion. Analyses of data (1982–1995) from a long-term trawl-survey programme conducted by the Texas Parks and Wildlife Department (TPWD) indicated that the catches of common epibenthic organisms in the eastern arm of the bay following the diversion were also within the range of historic variation. Species richness decreased significantly at the eastern stations where salinities were lower following the diversion. Commercial fishery landings of most species in the post-diversion period were within the range of historic variation. Oyster landings, however, were consistently low for the 4 years for which post-diversion data were available, probably because previously harvestable reefs were lost to sedimentation and burial close to the redirected river mouth. Prior to the diversion (1970–1991), oyster landings were negatively associated with the same year's maximum annual river flows and the duration of low flows (<14m3s−1) 2 years previous (r2=0·63,P<0·001). The regression results indicate that post-diversion increases in freshwater inflows during low flow periods will likely benefit oyster harvests 2 years later Increases to oyster yields may take several more years to be realized and will be contingent upon the success of harvests from the newly created oyster reefs along the northern bay arm.

Boat-Propeller–Related Injuries—Texas, 1997

Approximately 78 million persons engage in recreational boating annually in the United States. Several types of injury can occur during boating recreation, including drowning, falls, burns, and propeller-related injuries. Injuries from the propeller are typically multiple, deep, parallel lacerations that can result in permanent scarring, substantial blood loss, traumatic or surgical amputation, or death. Persons sustaining injuries from boat propellers can require long periods of hospitalization, recovery, and rehabilitation. In Texas, the extent of boat-propeller-related injuries is unknown; however, the existence of approximately 600,000 motorboats in the state exposes many Texans to the potential risk for propeller-related injury. To characterize the occurrence of boat-propeller-related injuries in Texas, the Texas Department of Health (TDH) and the Texas Parks and Wildlife Department (TPWD) investigated boat-propeller-related injuries that occurred in four lakes in Texas during May 24 -September 1, 1997, the time of year when boating activities are most common. This report summarizes the results of the investigation.

Development of Tagging Techniques for Monitoring Fish Populations at Texas Artificial Reefs

Texas Parks and Wildlife Department (TPWD) has used a broad range of methodologies to monitor the social, economic, and biological impacts of artificial reefs in the Gulf of Mexico. Social and economic issues have been addressed through charter boat and diver mail-in questionnaire surveys and on-site creel surveys. Biological issues have been investigated through hook and line tagging, diver-based visual transects, and video traps. Assessments of hydroacoustic and remotely operated vehicle (ROV) biological survey techniques are also planned for deepwater reef sites. There is also a need to develop inexpensive biological monitoring methods to track target fish populations such as red snapper over time at specific reef sites. The Department has been investigating the use of collapsible traps to tag fish underwater as a potential long-term monitoring tool for assessing reef fish populations. The cost effectiveness and efficiency of this gear type was compared to hook and line capture techniques. During the initial effort, 223 red snapper were tagged underwater by divers after capture by three collapsible traps, and 291 red snapper were tagged on the surface by anglers after capture by hook and line techniques. The collapsible traps appeared to be more size selective for smaller sized red snapper than hook and line techniques. Fish tagged underwater had a higher recapture rate of 25.45 percent compared to the 11.89 percent recapture rate for fish caught and tagged on the surface. Although three recapture periods were used to evaluate tag return data, our findings suggest that future efforts directed at monitoring artificial reef fish populations should use multiple gear types with equal effort applied to account for size-selective capture patterns and logistical constraints.

Breeding Biology of the Eastern White-Winged Dove in Southern Texas

coast of Tamaulipas, Mexico (Bent, 1932; Saunders, 1968). In the lower Rio Grande Valley (LRGV) of Texas, an estimated 4,700 ha of riparian forest and chaparral plus 11,760 ha of citrus groves are currently available to whitewings as nesting habitat (G. L. Waggerman, pers. comm.). Because >99% of their prime native nesting habitat has been modified (Cottam and Trefethen, 1968; Marion, 1974), whitewings have become increasingly dependent on citrus for nest sites. Unfortunately, citrus trees are killed during severe freezes, such as occurred in 1951, 1962, and 1983 and numbers of breeding doves also decreased markedly following freezes (Cottam and Trefethen, 1968; Waggerman, in litt.). Native vegetation remains relatively undamaged by freezing (Cottam and Trefethen, 1968; Lonard and Judd, 1985, 1991). The Texas Parks and Wildlife Department (TPWD) has made acquisition, re-establishment, and management of native nesting habitat the top priority of the white-winged dove management program (Brown, 1977; G. L. Waggerman, pers. comm.). TPWD assumes that whitewing breeding populations will increase by increasing the amount of available nesting habitat. This assumption is based on the premise that density-dependent factors (e.g., intraspecific competition for nesting territories) control the size of the breeding population. That assumption had not been tested prior to this study. Thus, our objective was to determine effects of intraspecific competition for nesting territories on breeding population sizes of white-winged doves in south Texas.

Accuracy of Trip Durations Reported by Marine Sport-Boat Fishermen

Abstract The Texas Parks and Wildlife Department (TPWD) conducted surveys to determine the accuracy of trip durations reported by marine sport-boat fishermen. The surveys were conducted at boat ramps on 21 d during May-August 1982. The fishermen's reported trip duration (nearest 0.5 h) was compared to TPWD's observed trip duration (nearest 0.1 h). No significant differences were found between the reported and observed trip durations by sport-boat fishermen. Eighty-six percent of all differences between reported and observed trip durations were within ± 1.0 h of zero, and 68% of those differences were within the precision desired (nearest 0.5 h). Therefore, the mean trip duration reported by sport-boat fishermen during 1-d fishing trips is an empirically unbiased estimate of actual mean trip duration. The accuracy of trip duration reported by sport boaters was not influenced by the actual trip length.

Evaluation of the Accuracy and Precision of Volunteered Size Data from Tagged Red Drum Returns

Abstract The accuracy and precision of total lengths and weights from recaptured tagged red drum (Sciaenops ocellatus) reported by Texas Parks and Wildlife Department (TPWD) biologists, anglers, and commercial fishermen were compared. No differences were found in the total length-weight regressions of data reported by sport and commercial fishermen, but there were significant differences found between data reported by fishermen and data collected by TPWD biologists (F, = 6.312; P < 0.05). Fish lengths reported by fishermen were not biased but they were more variable than lengths reported by TPWD due to rounding to the nearest whole or partial English unit. Weights reported by fishermen were more variable than weights reported by TPWD biologists. A significant difference between regression coefficients was found and a comparison of confidence limits of the regression lines showed that fishermen overestimated the weight of small fish; therefore, growth estimates calculated from red drum weights provided by ...