Corpus Christi, TX, United States
Corpus Christi, TX, United States

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Randklev C.R.,Texas A&M University | Wang H.-H.,Texas A&M University | Groce J.E.,Monash University | Grant W.E.,Texas A&M University | Wilkins N.,East Wildlife Foundation
Journal of Fish and Wildlife Management | Year: 2015

We assessed the influence of geology, land use, and other features on the occurrence of the rare freshwater mussel smooth pimpleback, Quadrula houstonensis, in the Leon River, Texas. Boosted regression trees were used to assess the relationships between the species’ occurrence and potential explanatory variables based on field data from 52 sampling locations. The individual variables that best explained prevalence for this species were downstream distance from reservoirs, percentage of shrubland within the riparian buffer, and percentage of alluvium and aquifer bearing rock-types. These results indicate that smooth pimpleback may be sensitive to flow modification and changes in land use that increase sedimentation. The application of similar modeling efforts to other rare species in this region could help in their management and conservation. © Citation of the source, as given above, is requested.


Campbell T.A.,University of Florida | Campbell T.A.,East Wildlife Foundation | Long D.B.,University of Florida | Shriner S.A.,National Wildlife Research Center
Environmental Management | Year: 2013

Given the popularity of feeding white-tailed deer (Odocoileus virginianus) in Texas and the increasing amount of corn that is distributed, more information is needed on the impacts of this activity on non-target wildlife. Our objectives were to report visitation, intra- and interspecific contact, and contact rates of wildlife at artificial feeding sites in Texas. Our study was conducted at three sites in Kleberg and Nueces counties, Texas. We trapped animals from February to April and August to September, 2009 and marked animals with passive integrated transponder (PIT) tags. At each site and season, we placed one feeder system containing a PIT tag reader within 600 m of trap locations. Readers detected PIT tags from a distance of 25 cm. We determined a contact event to occur when two different PIT tags were detected by feeder systems within 5 s. We recorded 62,719 passes by raccoons (Procyon lotor), 103,512 passes by collared peccaries (Pecari tajacu), 2,923 passes by feral swine (Sus scrofa), 1,336 passes by fox squirrels (Sciurus niger), and no passes by opossums (Didelphis virginiana) at feeder systems. For site-season combinations in which contact events occurred, we found intraspecific contact rates (contacts per day) for raccoons, collared peccaries, and feral swine to be 0.81-124.77, 0.69-38.08, and 0.0-0.66, respectively. Throughout our study we distributed ~2,625 kg of whole kernel corn, which resulted in 6,351 contact events between marked wildlife (2.4 contacts per kg of corn). If 136 million kg of corn is distributed in Texas annually, we would expect >5.2 billion unnatural contact events between wildlife would result from this activity each year in Texas. Consequently, we do not believe that it is wise for natural resource managers to maintain artificial feeding sites for white-tailed deer or other wildlife due to pathogen transmission risks. © 2013 Springer Science+Business Media New York (outside the USA).


Collier B.A.,Texas A&M University | Farrell S.L.,Texas A&M University | Long A.M.,Texas A&M University | Campomizzi A.J.,Texas A&M University | And 4 more authors.
Auk | Year: 2013

Abstract.-Relating population density to spatially explicit habitat characteristics can inform management by directing efforts to areas with lower densities or focusing conservation and land protection on high-density areas. We conducted point-transect surveys for the endangered Golden-cheeked Warbler (Setophaga chrysoparia) and Black-capped Vireo (Vireo atricapilla) in the live-fire region of Fort Hood, Texas. We used mark-recapture distance sampling and combined a Horvitz-Thompson estimator with a habitat-based, resourceselection gradient to estimate spatially explicit density for both species. We detected Golden-cheeked Warblers at 120 locations (202, 197, and 89 detected by primary, secondary, and both observers, respectively) and Black-capped Vireos at 173 locations (241, 255, and 107 detected by primary, secondary, and both observers, respectively). For Golden-cheeked Warblers, the average (± SE) composite detection probability estimate within a 100-m point-sample radius was 0.57 ± 0.14, and for vireos it was 0.24 ± 0.02. Estimated mean density (singing males ha-1) was 0.14 ± 0.03 (95% confidence interval [CI]: 0.08-0.23) and 0.47 ± 0.05 (95% CI: 0.38-0.60) for Golden-cheeked Warblers and Black-capped Vireos, respectively. Our analysis suggested evidence of heterogeneity in the detection process for both species, as well as imperfect detection at distance g(0), both of which would bias estimated densities if ignored. Additionally, both species exhibited spatial variability in estimated densities, with those areas that had higher occurrence probabilities typically having higher estimated density. In the absence of spatially explicit density prediction, managers must treat all losses of potential habitat for endangered species uniformly, despite likely differences in conservation value. Our approach could be used to ascertain areas of changing density in relation to changing habitat conditions over time and space.© 2013 by The American Ornithologists' Union. All rights reserved.


Stewart L.R.,Texas A&M University | Stewart L.R.,United Road Services | Morrison M.L.,Texas A&M University | Hutchinson M.R.,Texas A&M University | And 3 more authors.
Wildlife Society Bulletin | Year: 2014

Oak wilt is a fatal forest disease caused by the fungus Ceratocystis fagacearum. Loss or degradation of habitat caused by oak wilt may negatively affect forest songbirds, including the federally endangered golden-cheeked warbler (Setophaga chrysoparia), a species that breeds exclusively in the Ashe juniper-oak woodlands (Juniperus ashei-Quercus spp.) of central Texas, USA. During 2010 and 2011, we investigated the influence of oak wilt on golden-cheeked warbler habitat selection and quality at 25 study sites that each contained forest affected by oak wilt and unaffected forest. We assessed habitat selection in terms of use versus availability at 2 scales: within the patch and within the territory. Wealso assessed post-breeding use of affected forest by comparing detection densities in affected and unaffected forest. To assess the influence of oak wilt on habitat quality, we compared the reproductive outcome of territories in unaffected and affected areas. We assessed within-patch habitat selection for 67 ritories and found that golden-cheeked warblers used affected forest significantly less than its availability. We found use of affected forest to be variable within the 14 territories that contained affected forest in >10% of their area. Post-breeding use of affected forest was also variable. Pairing success was 27% lower for males whose territories contained >10% affected forest but fledging success was not affected. Our results suggest that the presence of oak wilt negatively influences habitat selection and quality for golden-cheeked warblers, likely due to reduced canopy cover in susceptible oak species. © 2013 The Wildlife Society.


Stewart L.R.,Texas A&M University | Stewart L.R.,United Road Services | Morrison M.L.,Texas A&M University | Appel D.N.,Texas A&M University | And 2 more authors.
Wildlife Society Bulletin | Year: 2014

Research suggests the presence of oak wilt in Ashe juniper-oak (Juniperus ashei-Quercus spp.) woodland has a negative effect on habitat selection and quality for the federally endangered golden-cheeked warbler (Setophaga chrysoparia). We used aerial imagery and an occupancy model to estimate the amount of golden-cheeked warbler habitat within our study region in Texas, USA, that was affected by oak wilt over a 10-year timeframe, 2008-2018, and to assess the current probability of warbler occupancy in areas affected by oak wilt prior to 1983. We also quantified vegetation characteristics to assess regeneration in areas affected by the disease. Our results indicate that oak wilt frequently occurs in golden-cheeked warbler habitat and will continue to spread into warbler habitat in the coming years. We estimated that 6.9% of golden-cheeked warbler habitat within our study region in the southwestern portion of the warbler's range was affected by oak wilt in 2008. By 2018, we predict that 13.3% of golden-cheeked warbler habitat will be affected by the disease. Areas affected by oak wilt prior to 1983 were less likely to be classified as current potential warbler habitat than were unaffected areas. We found no differences between the understory vegetation of affected and unaffected areas but, in general, oaks were more common in the overstory than in the understory, suggesting that species composition in affected areas may shift following an outbreak of oak wilt. Future management efforts should address the threat oak wilt poses to golden-cheeked warblers by incorporating applicable preventative measures. © 2013 The Wildlife Society.


Campomizzi A.J.,Texas A&M University | Farrell S.L.,Texas A&M University | Mcfarland T.M.,Texas A&M University | Mathewson H.A.,Texas A&M University | And 3 more authors.
Wildlife Society Bulletin | Year: 2012

Research conducted near the time a species is listed as threatened or endangered can help inform management guidelines. However, these studies are typically limited in temporal and spatial scope and typically address a limited set of ecological questions. Application of such information can result in misleading management guidelines or ineffective conservation if species-habitat relationships vary across space or if preliminary information fails to provide reliable assessments of habitat quality. We evaluated existing management guidelines that addressed reproductive success of the golden-cheeked warbler (Setophaga chrysoparia), a federally endangered songbird endemic to central Texas, USA. We monitored 1,382 territories in 87 patches of woodland across the breeding range from 2007 to 2011. Ours was the first evaluation of management guidelines addressing reproductive success with data collected across the warbler's breeding range. Our results did not consistently confirm the commonly accepted management guidelines that habitat quality, based on the presence of offspring in a territory, was positively associated with patch size and territory canopy cover, and negatively associated with patch edge. The relationship between probability of a territory fledging ≥1 offspring and patch size, patch edge-to-area ratio, and territory canopy cover varied by geographic region (level-IV eco-region). Our results suggested future conservation plans that address habitat quality should consider variation among regions to improve conservation efforts and that habitat associations identified with warbler occurrence were not necessarily indicative of reproductive success. © 2012 The Wildlife Society.


Farrell S.L.,Texas A&M University | Collier B.A.,Texas A&M University | Skow K.L.,Texas A&M University | Long A.M.,Texas A&M University | And 5 more authors.
Ecosphere | Year: 2013

Advances in remotely sensed data for characterizing habitat have enabled development of spatially explicit predictive species distribution models (SDM) that can be essential tools for management. SDMs commonly use coarse-grain metrics, such as forest patch size or patch connectivity, over broad spatial extents. However, species distributions are likely driven in part by local, fine-grained habitat conditions. Conservation and management are often planned and applied locally, where coarse predictions may be uninformative or not sufficiently precise. We investigated the integration of high-resolution LiDAR (Light Detection and Ranging) with avian point sampling data to develop a detection-corrected occupancy model to quantify habitat-occurrence relationships for two species with different habitats: the endangered golden-cheeked warbler (Setophaga chrysoparia) and black-capped vireo (Vireo atricapilla) on a military installation in central Texas. We compared occupancy models that used only the more conventional, coarse remotely sensed metrics to models that also incorporated high-resolution LiDAR-derived metrics for vegetation height and canopy cover, to assess their use for predicting distributions. Models including LiDAR-derived vegetation height and canopy cover metrics were competitive for both species, and models without LiDAR-derived vegetation height had substantially lower model weights and explanatory strength. Area under curve estimates for the highest ranked models were high for warblers (0.864) and moderate for vireos (0.746). Using the best supported models for each species, we predicted the occurrence distribution for both species. The resulting predictions provide a decision support tool that enables assessment of the status, impacts, and mitigation of impacts to endangered species habitat on the installation due to land management and military training activities that is more standardized and accurate than current assessment approaches based on visual gestalt of habitat and expert opinion. Additionally, although previous species distribution models have been created for our focal species, most fail to match the grain and extent of most management actions or include local, fine-grained metrics that influence distributions. In contrast, we demonstrate that use of LiDAR with species occurrence data can provide precision and resolution at a scale that is relevant ecologically and to the operational scale of most conservation and management actions Copyright: © 2013 Farrell et al.


Pope T.L.,Texas A&M University | Pope T.L.,Utah Division of Wildlife Resources | Morrison M.L.,Texas A&M University | Wilkins R.N.,Texas A&M University | Wilkins R.N.,East Wildlife Foundation
Journal of Wildlife Management | Year: 2013

Identifying vegetation types that result in the highest quality habitat will help direct management and conservation activities designed to recover endangered species. Shrubland is considered to result in high quality habitat for black-capped vireos (Vireo atricapilla), whereas deciduous and oak-juniper woodlands are considered to result in marginal habitat (i.e., lower quality). We investigated differences in nest and fledgling survival among shrubland and woodland vegetation types. We monitored 302 black-capped vireo nests in 259 territories from 2008 to 2010 in Kerr County, Texas and collected vegetation data at each nest. We also resighted 350 fledglings to estimate individual survival. Nest survival and fecundity did not differ statistically among vegetation types. Although nest-site characteristics differed among vegetation types, none affected nest survival. Nests that were parasitized were less likely to survive and parasitism was the only variable to affect survival of those measured. Parasitism frequency was nearly twice as great in shrubland (22%) than in either woodland type (12% in each) and varied by year (31% in 2008 to 0% in 2010). Vegetation type and proximity of the nest to oak-juniper woodland did not affect fledgling survival. Our results suggest woodlands may result in good quality habitat in areas with large populations of black-capped vireos. Recognizing woodlands as non-typical, yet good quality, habitat will allow managers to incorporate these vegetation types into management plans and make recommendations for conservation incentive programs directed at private landowners. © 2013 The Wildlife Society.


Pope T.L.,Texas A&M University | Pope T.L.,Utah Division of Wildlife Resources | Conkling T.J.,Texas A&M University | Conkling T.J.,Mississippi State University | And 6 more authors.
Condor | Year: 2013

Predation is the leading cause of nest failure for many bird species. Most studies associate risk of predation with vegetation characteristics of the nest site. Alternatively, the Skutch hypothesis suggests that adults' activity at the nest can attract the attention of predators and lead to an increased risk of predation. We investigated whether vegetation characteristics surrounding nest sites affected nest attentiveness and visitation and if these behaviors affected nest survival. We used 1-hr nest observations and 8-hr video observations at Black-capped Vireo (Vireo atricapilla) nests in three regions of Texas to quantify nest attentiveness and visitation during incubation and the nestling stage. Females spent 80% more time on nests during incubation and 250% more time on nests during the nestling stage than did males, but visitation was similar for each sex. In general, nest behavior did not appear to be affected by vegetation characteristics, except males' attentiveness during incubation increased as average cover from 0 to 2 m increased. Adults' activity did not appear to increase the risk of nest predation. Despite visitation being more frequent during the nestling stage than during incubation, visitation during either stage did not affect nest survival. Overall, nest survival improved with attentiveness during incubation. © The Cooper Ornithological Society 2013.


Marshall M.E.,Texas A&M University | Morrison M.L.,East Wildlife Foundation | Wilkins R.N.,East Wildlife Foundation
Condor | Year: 2013

Vegetation characteristics affect avian reproductive success for a variety of reasons, including predators, nesting sites, song perches, and food availability. We investigated the relationship between habitat composition and prey availability and the effect these variables have on reproductive success in the Golden-cheeked Warbler (Setophaga chrysoparia). Our objectives were to determine differences in pairing and fledging success of Golden-cheeked Warbler territories in two distinctive vegetation types and to explore the relationship between reproductive success and tree species composition, arthropod density, and foraging effort. We sampled in 2009 and 2010 at Fort Hood, north-central Texas, within 347 territories of two vegetation types: post oak (Quercus stellata) habitat and Texas oak (Q. buckleyi) habitat. Pairing and fledging success of territories was significantly higher in Texas oak habitat. The birds' rate of movement was considerably higher in post oak habitat, indicating a difference in prey-encounter rate. Golden-cheeked Warblers clearly switched substrates on which they foraged from oaks in April to juniper in May. Arthropod sampling revealed a correlation between preferred foraging substrates and arthropod density. Our study of foraging indicates that the interplay between tree species and the arthropod communities they support is a crucial element driving the Golden-cheeked Warbler's reproductive success. © The Cooper Ornithological Society 2013.

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