John T. Baccus

δ13C food web analysis of a Texas sand dune community

Abstract Stable carbon isotope ratios ( δ 13 C) were determined for 31 plant and 16 animal species from a sand dune community on the south Texas coast. Plants and insects had similar δ 13 C values, forming two distinct groups, while herbivorous rodents formed a third intermediate group. This suggests that insects at the study site are specialists which feed on C 3 or C 4 plants, while the rodents are generalists, feeding on plants of both groups.

A comparison of effects of radiotransmitter attachment techniques on captive white-winged doves

Abstract We experimentally evaluated alternative techniques of attaching radiotransmitters to captive white-winged doves (Zenaida asiatica) in Kingsville, Texas during 1998. Our evaluation consisted of monitoring physiological, pathological, and behavioral parameters in doves subjected to 6 radiotransmitter attachments (backpack harnesses, adhesive, subcutaneous implants, intracoelomic implants, subcutaneous surgeries without implantation, intracoelomic surgeries without implantation). We analyzed physiological parameters across 2 pretreatment and 4 post-treatment periods using a model-selection approach of mixed-effect models. Birds did not differ in physiological variables among treatment groups and a control. Time-activity budgets analyzed using nonparametric Friedmans tests did not differ in any activity category among treatment groups and a control. Subcutaneous implants were the most effective method of attachment based on retention rates, lack of mechanical difficulties associated with external attachment techniques, and minimum levels of pathology reported following necropsies.

Freshwater Turtle Conservation in Texas: Harvest Effects and Efficacy of the Current Management Regime

ABSTRACT The collapse of Asian turtle populations led to the creation of a worldwide freshwater turtle market in the 1990s. Texas is one of several states in the United States that has capitalized on this market. The Texas Parks and Wildlife Department (TPWD) recently instituted regulations designed to protect turtles from commercial harvest in public waters. Two counties in the Lower Rio Grande Valley (LRGV) accounted for 66.1% of known wild turtle harvest in 1999, with no reported harvest in subsequent years. We sampled 60 sites in the LRGV to determine if we could detect harvest effects. We also investigated the potential for sustainable harvest under the new harvest guidelines using source-sink dynamics implemented in a Geographic Information System (GIS) approach. We detected differences congruent with harvest effects for red-eared sliders (Trachemys scripta) and Texas spiny softshells (Apalone spinifera). Based on a GIS analysis of water bodies throughout the entire state, we estimated that only 2.2% of water bodies are protected under the current commercial harvest regulations. We determined source water bodies could supply 30.5% of sink water bodies in the LRGV, and we concluded that long-term sustainable turtle harvest is unlikely under the current management regime due to the intensity of commercial harvests, the low number of protected water bodies, and non-robust or non-interactive protected populations. One solution to this would be modification of the regulations to include season and bag limits, a management strategy currently implemented in various forms by 14 states in the eastern half of the United States.

BREEDING ECOLOGY OF WHITE-WINGED DOVES IN A RECENTLY COLONIZED URBAN ENVIRONMENT

Abstract Using field-implanted subcutaneous radio transmitters, we monitored the breeding biology of White-winged Doves (Zenaida asiatica) in a recently colonized urban area (Waco, Texas). We implanted transmitters in June 2002 (n = 39; 16 males, 23 females) and February and March 2003 (n = 40; 17 males, 17 females, 6 unknown sex), and tracked radio-tagged doves every 3rd day until transmitters no longer functioned (90–120 days). We tracked 26 doves to 36 nests in nine tree species. The maximum number of nesting attempts was four. Nest success of first and second nesting attempts was 62 and 24%, respectively, and overall nest success for both years combined was 52%. Mean nest height—as a proportion of tree height—ranged from 0.31 to 0.75. Urban White-winged Doves had an extended breeding season; nesting attempts occurred both before and after the traditional dove breeding period in native brush habitats of the lower Rio Grande Valley of Texas. Field-implantation of subcutaneous radio transmitters was a viable technique for monitoring nesting activities of White-winged Doves.

Representativeness of Land Cover Composition along Routes of the North American Breeding Bird Survey

ABSTRACT. The North American Breeding Bird Survey (BBS) is an annual transect point-count survey of >500 species and >3,500 survey routes (transects). Observers drive and record birds seen and heard within a radius of 400 m of 50 survey points (“stops”) evenly spaced along a 39.4-km survey route. Thus, the land area along both sides of a route composes a linear or curvilinear landscape. Although BBS data have been used in many studies and conservation plans, there have been few attempts to determine how well the landscapes along BBS routes represent landscapes at larger spatial extents, particularly with regard to land-cover composition. Using data from the 2001 National Land Cover Database, we conducted a study of representativeness of 3,230 routes by comparing the differences in percent cover of 15 land-cover types in BBS landscapes (buffer width of 0.4 km surrounding a route) to larger local landscapes (10 km buffer width) and regions. At the local level, BBS landscapes were representative for most of the cover types except open water, which was underrepresented, and lightly developed open space, which was overrepresented. At the regional level, the collective composition of BBS landscapes was very similar to the composition within entire Bird Conservation Regions. Overall, these results should encourage the continued use of BBS data in ornithological and ecological research and in conservation planning.

MOBILE ANESTHESIA UNIT FOR IMPLANTING RADIOTRANSMITTERS IN BIRDS IN THE FIELD

Abstract We designed a mobile anesthesia unit for surgically implanting radio transmitters in birds in the field. This minimizes the amount of time individuals undergoing the procedure are kept from their normal activities. Two units were designed and tested. In 2000, we successfully implanted radio transmitters in 40 white-winged doves in Kingsville, Texas, using a surgical unit carried in the bed of a truck. In 2002, we successfully implanted 39 white-winged doves in Waco, Texas, using a surgical unit carried in the cargo area of a minivan. The success of both trials indicates this method has great potential for use for numerous avian species while minimizing impacts to individuals being studied.

BEHAVIORAL INTERACTIONS BETWEEN AXIS AND FALLOW DEER AT HIGH-VALUE FOOD PATCHES

Abstract We classified displacements between axis deer (Axis axis) and fallow deer (Dama dama) by age, sex, species, and intensity (contact, non-contact) at high-quality, supplemental food patches on a Texas ranch. Axis deer males performed significantly fewer interspecific displacements than fallow deer males in fall and winter, whereas fallow deer males performed significantly fewer interspecific displacements than axis deer males in summer. Fallow deer males required significantly less intensity to displace axis deer males than conspecifics in both fall and winter. Fallow deer females engaged in significantly fewer displacements than axis deer females in winter and spring, and axis deer females required significantly less intensity to displace fallow deer females than conspecifics in winter. Heterospecific displacements between axis deer and fallow deer males correlated with the proportion of fallow deer males in hard antler. Fallow deer female displacements correlated with season. We concluded that interspecific dominance interactions between males of these 2 species are resolved by differences in the developmental stage of antlers and aggressiveness.

Horizontal and Vertical Movements of the White-Ankled Mouse (Peromyscus pectoralis) in Central Texas

We traced the three-dimensional movements of Peromyscus pectoralis in the absence of potential competitors by the fluorescent-pigment technique. P. pectoralis left 89.5% of pigment trails on ground, 9.5% on cliffs, and 1.0% in shrubs and trees. The infrequent use of trees by P. pectoralis in the absence of Peromyscus attwateri , a syntopic species in portions of the distribution of P. pectoralis , provides evidence that the pattern of habitat use by P. pectoralis is related to inherent selection rather than competitive interactions.

Potential Positive Effects of Fire on Juvenile Amphibians in a Southern USA Pine Forest

Prescribed fire is a common tool used to conserve and manage the integrity of forest ecosystems. We investigated shortterm juvenile amphibian capture and body condition changes subsequent to fire (i.e., one prescribed burn and two wildfires) in a southern United States pine forest. We surveyed amphibians and predatory invertebrates before and after fires occurring during summer 2010. We tested for treatment (i.e., control, wildfire, or prescribed burn) and status (i.e., preburn or postburn) differences in 1) genus-level captures, 2) amphibian health (inferred through a body condition index), and 3) predatory invertebrate captures. Bufo and Scaphiopus captures increased in the prescribed burn treatment; whereas, no differences in Gastrophryne captures were observed. We did not detect a burn status effect on amphibian body condition. Predatory invertebrate captures were higher postburn in the control and wildfire treatments. Neither a low-intensity prescribed burn nor high-intensity wildfires negatively impacted short-term juvenile amphibian captures. Further, we speculate that Bufo and Scaphiopus survivorship may have been higher after the prescribed burn.

Seasonal Diet and Foraging Preference of Greater Kudu Tragelaphus Strepsiceros in the Llano Uplift of Texas

Abstract The greater kudu Tragelaphus strepsiceros, a large African herbivore, occupies the browser trophic niche. This species has been introduced into selected areas of Texas inhabited by the white-tailed deer Odocoileus virginianus, a native browser. Based on similar trophic function, potential interspecific competition could exist between these two species. The objectives of our study were to: 1) describe the seasonal diets of greater kudu in Texas and 2) determine if greater kudu show preference for plants that might create competition with white-tailed deer. We documented the seasonal diet and forage preference of greater kudu at Mason Mountain Wildlife Management Area from 15 May 2001 to 25 February 2002 by identifying epidermal fragments of plants in faecal pellets. We identified and quantified 49 species of plants eaten by greater kudu. Annually, browse made up 80.2% of the diet, while 7.6% mast, 6.5% grasses, 3% forbs and 2.7% unidentified material comprised the remaining parts of their diet. Important browse species included Texas/blackjack oak Quercus buckleyi/Q. marilandica, plateau live oak Q. fusiformis, Ashe juniper Juniperus ashei, mesquite Prosopis glandulosa, prickly pear Opuntia sp., flameleaf sumac Rhus lanceolata, and Texas persimmon Diospyros texana. We measured availability of forage plants by quadrat and line intercept methods concurrent with faecal pellet collection. We compared plant use (dietary composition) with plant availability and assessed forage preference by greater kudu using log-likelihood χ2-tests with Bonferroni corrected confidence intervals and Manlys alpha indices. We detected statistically significant differences between plant use and availability (P < 0.05). Purple horsemint Monarda citriodora, Canada wildrye Elymus canadensis, mesquite, flameleaf sumac, Texas/blackjack oak and Ashe juniper were preferred species. Relative preference of general forage categories by greater kudu in Texas was similar to that reported from Africa. Based on our findings, greater kudu could compete with white-tailed deer for browse forage.