Francisco J. Vilella
Mississippi State University
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Featured researches published by Francisco J. Vilella.
American Midland Naturalist | 2005
Leslie W. Elmore; Darren A. Miller; Francisco J. Vilella
Abstract Forest managers are increasingly expected to incorporate biodiversity objectives within forest landscapes devoted to timber production. However, reliable data on which to base management recommendations for bats within these systems are extremely limited. Although the red bat (Lasiurus borealis) is a widespread common species in temperate forests of North America, little is known of its ecology within intensively managed pine (Pinus spp.) forests of the southeastern United States. Therefore, we investigated size of foraging areas and habitat use by red bats during summer 2000 and 2001 in an intensively managed pine landscape in east-central Mississippi, USA. We captured bats using four-tier mist nets placed over water and attached radiotransmitters to red bats. Radiotagged red bats (n = 16) used habitat types randomly at the study area and foraging area scale. Mean size of foraging areas and mean maximum distance traveled between diurnal roosts and foraging locations were not different (P < 0.05) among adult male, adult female, juvenile male or juvenile females (n = 18). Most foraging areas contained a reliable source of water and all but one diurnal roost was located within foraging areas. Location of diurnal roosts may dictate location of foraging areas. Open canopy conditions in intensively managed pine stands (young, open canopy stands, thinned stands and riparian hardwood stands) likely provide appropriate foraging habitat for red bats. Landscape context may influence size of foraging areas and commuting distances of red bats. Provision of appropriate aged forest stands for diurnal roosts may be the best management action for red bats within intensively managed pine landscapes.
The Condor | 2005
Thomas H. White; Jaime A. Collazo; Francisco J. Vilella
Abstract We report first-year survival for 34 captive-reared Puerto Rican Parrots (Amazona vittata) released in the Caribbean National Forest, Puerto Rico between 2000 and 2002. The purpose of the releases were to increase population size and the potential number of breeding individuals of the sole extant wild population, and to refine release protocols for eventual reintroduction of a second wild population elsewhere on the island. After extensive prerelease training, we released 10 parrots in 2000, 16 parrots in 2001, and eight parrots in 2002 ranging in age from 1–4 years old. All birds were equipped with radio-transmitters to monitor survival. The overall first-year survival estimate for the 34 parrots was 41% (CI = 22%–61%). Only one parrot died within the first week postrelease, with most (94%) surviving for at least eight weeks after release. Most (54%) documented mortalities were due to raptor predation, which claimed 21% of all released parrots. A captive-reared bird (male, age one), released in 2001, paired with a wild female and fledged two young in 2004. We also calculated survival based on 0% and 50% of observed predation losses and found hypothetical survival rates of 72% and 54%, respectively. Rigorous prerelease training and acclimation was believed to have improved initial postrelease parrot survival, and releasing mixed age-class groups suggests the potential for shortening the time to recruitment. Supervivencia de Individuos de Amazona vittata Criados en Cautiverio y Liberados en el Bosque Nacional del Caribe Resumen. Determinamos la supervivencia de 34 individuos de cotorras Amazona vittata criados en cautiverio y liberados en el Bosque Nacional del Caribe, Puerto Rico entre el 2000 y el 2002. El propósito de las liberaciones era aumentar el tamaño de la población y el número potencial de individuos reproductores en la única población silvestre remanente, y refinar los protocolos de liberación para eventualmente establecer una segunda población silvestre en la isla. Después de un adiestramiento extensivo, liberamos 10 cotorras en el 2000, 16 cotorras en el 2001, y ocho cotorras en el 2002 fluctuando en edades entre uno y cuatro años. Cada individuo se liberó con un radio transmisor para determinar su supervivencia. La tasa general de supervivencia para 34 cotorras después de un año fue de 41% (IC = 22–61%). Sólo una cotorra murió durante la primera semana post-liberación, con la mayoría (94%) sobreviviendo por lo menos ocho semanas después de liberadas. La mayoría (54%) de la mortandad se debió a la depredación por aves rapaces, la que reclamó 21% de todas las cotorras liberadas. Una cotorra criada en cautiverio (macho, un año de edad), y liberada en el 2001, se apareó con una hembra silvestre y produjeron dos volantones en el 2004. Reduciendo la mortandad por aves rapaces informada en este estudio en un 100%, o en un 50%, resultó en tasas hipotéticas de supervivencia del 72% y 54%, respectivamente. Creemos que el adiestramiento y la aclimatación rigurosa pre-liberación mejoraron la supervivencia inicial post-liberación, y que la liberación de grupos de cotorras de edades mixtas sugiere el potencial de acortar el tiempo de reclutamiento.
Journal of Wildlife Management | 2004
Jacob L. Bowman; Bruce D. Leopold; Francisco J. Vilella; Duane A. Gill
Abstract Understanding human attitudes often is vital to the success of restoration projects, especially those involving controversial species such as carnivores. Support for restoration activities may differ depending on residence location of the respondent; thus, understanding the spatial distribution of attitudes is important when selecting suitable restoration sites. We used black bear (Ursus americanus) restoration as an example of how to calculate and use a spatially explicit model of human attitudes based on demographic variables to select restoration sites in Mississippi, USA. We sampled 2 populations (5,975 landowners adjacent to 10 public land areas and a random sample of 490 Mississippians) to determine human attitudes toward black bear reintroduction in Mississippi. We chose a series of reintroduction and demographic questions to develop 2 logistic regression models to predict support for reintroduction, and we validated the models. One model was developed on all demographic variables (how many acres respondents owned in Mississippi and for how long, as well as their age, sex, education, income, community size, and race) to determine the relationship between support for reintroduction and demographic variables. The second model used only age, race, and sex demographic variables. Age, community size, race, sex, and number of years of landownership were significant predictors of support for bear restoration for the first model; and age, race, and sex were significant predictors for the second model. Using the second model and the U.S. Census Bureau (1990) block group data, we predicted the proportion of each block group supporting restoration. Most of Mississippi had block groups with >50% support for bear restoration. We were able to determine a statewide distribution of attitudes. Additionally, we documented that attitudes of landowners immediately adjacent to public land may differ from those of residents of the area surrounding the public land (both adjacent and not). We suggest using our approach for other restoration projects to better integrate human attitudes into the restoration program.
Biological Conservation | 2000
Thomas H. White; Jacob L. Bowman; Bruce D. Leopold; Harry A. Jacobson; Winston P. Smith; Francisco J. Vilella
American black bear (Ursus americanus) populations were significantly reduced throughout their range, particularly in southeastern North America. Currently, populations in this region are very fragmented, resulting in concern over possible barrier effects of rivers to normal bear movements and dispersal. This is particularly true for Mississippi, where black bear dispersal into the state is critical if populations are to be recovered. Thus, we studied the relative effects of rivercourses on bear movements and dispersal patterns in southeastern Arkansas, 1992–1996. We captured, radiocollared, and uniquely tagged 40 bears and used radiotelemetry to determine their movements. The Mississippi River (width ≈1600 m) deflected bear movements, whereas the White River (width ≈200 m) was not a barrier to bear movements or dispersal patterns. Frequency of river crossing differed by gender (P=0.007) and season (P<0.001). Male bears crossed rivers more frequently than females. Rivers were crossed less from December to March compared to other seasons. Rivers acted as a semipermeable barrier to bear movements and dispersal patterns, which may have major implications for conservation of large mammal metapopulations. Males appear to be influenced less by rivers, so female translocations across rivers may be necessary to recover fragmented bear populations. We provide an example describing direct implications of this study to the recovery of the threatened Louisiana black bear (U. a. luteolus).
The Condor | 2003
Jaime A. Collazo; Thomas H. White; Francisco J. Vilella; Simón A. Guerrero
Abstract We report first-year survival rates of 49 captive-reared Hispaniolan Parrots (Amazona ventralis) released in Parque Nacional del Este, Dominican Republic. Our goal was to learn about factors affecting postrelease survival. Specifically, we tested if survival was related to movements and whether modifying prerelease protocols influenced survival rates. We also estimated survival in the aftermath of Hurricane Georges (22 September 1998). Twenty-four parrots, fitted with radio-transmitters, were released between 14 September and 12 December 1997. Twenty-five more were released between 29 June and 16 September 1998. First-year survival rates were 30% in 1997 and 29% in 1998. Survival probability was related to bird mobility. In contrast to birds released in 1997, none of the 25 parrots released in 1998 suffered early postrelease mortality (i.e., 3–5 days after release). Two adjustments to prerelease protocols (increased exercise and reduced blood sampling) made in 1998 may have contributed to differences in mobility and survival between years. The reduction of early postrelease mortality in 1998 was encouraging, as was the prospect for higher first-year survival (e.g., 30% to 65%). Only one death was attributed to the immediate impact of the hurricane. Loss of foraging resources was likely a major contributor to ensuing mortality. Birds increased their mobility, presumably in search of food. Survival rates dropped 23% in only eight weeks posthurricane. This study underscores the value of standardized prerelease protocols, and of estimating survival and testing for factors that might influence it. Inferences from such tests will provide the best basis to make adjustments to a release program. Supervivencia de Amazona ventralis Criadas en Cautivero y Liberadas en el Parque Nacional del Este, República Dominicana Resumen. Determinamos la supervivencia de 49 individuos de Amazona ventralis criados en cautiverio y liberados en el Parque Nacional del Este, República Dominicana. El proyecto se diseñó para aprender sobre los factores que pueden influenciar la supervivencia de las cotorras dominicanas. Específicamente, pusimos a prueba si la supervivencia estaba relacionada a movimientos y si modificaciones al protocolo de pre-liberación influenciaron la supervivencia. También estimamos la supervivencia de las cotorras después del paso del huracán Georges el 22 de septiembre 1998. En 1997 se liberaron 24 cotorras con radio transmisores entre el 14 de septiembre y el 12 de diciembre. Otras 25 se liberaron entre el 29 de junio y el 16 de septiembre de 1998. La estimación de la supervivencia en 1997 fue de un 30% y en 1998 de un 29%. La probabilidad de supervivencia estuvo relacionada a la movilidad del ave. En comparación con las cotorras liberadas en 1997, ninguna de las cotorras liberadas en 1998 murió durante los primeros 3–5 dias post-liberación. Dos ajustes a los protocolos de pre-liberación en 1998 contribuyeron probablamente a las diferencias en movilidad y supervivencia entre años. Este resultado fue alentador, así como el prospecto de alcanzar tasas más altas de supervivencia (e.g., 30% a 65%). La muerte de sólo una cotorra se atribuye al impacto directo del huracán. La pérdida de recursos alimenticios probablemente contribuyó fuertemente a la mortandad subsiguiente. Las cotorras exhibieron mayor movilidad, presumiblemente en búsqueda de frutos. La tasa de supervivencia disminuyó un 23% en solo ocho semanas después del huracán. Este estudio enfatiza el valor de protocolos de preliberación estandarizados y de estimaciones de tasas de supervivencia que ponen a prueba factores que la puedan influenciar. Las inferencias de dichas pruebas proveerán un mejor fundamento para ajustar los programas de liberación.
Journal of Herpetology | 2002
Jarrod H. Fogarty; Francisco J. Vilella
Abstract Various aspects of population structure and dynamics of Eleutherodactylus coqui in two forest reserves (Maricao and Guilarte) of the central mountain range of Puerto Rico were determined between July 1997 and June 1998. Adult density ranged from 8–25 animals/100 m2 for the wet season and 3–19 animals/100 m2 for the dry season. Abundance of froglets and juveniles was also greater in the wet season compared to the dry season. By contrast, egg mass counts were greater in the dry season compared to the wet season. Adult body size increased from wet to dry season as population density declined and was found to differ significantly between forests. Adult E. coqui trapped at similar elevations were larger in Guilarte compared to those in Maricao. Average body size for Maricao and Guilarte populations were smaller than those reported for populations in eastern Puerto Rico. Comparing average snout–vent length among frogs from the Luquillo Mountains, Guilarte Forest, and Maricao Forest, a gradient of decreasing body size was observed from east to west across the island.
Bird Conservation International | 1995
Francisco J. Vilella
Summary The reproductive ecology and behaviour of the endangered Puerto Rican Nightjar Caprimulgus noctitherus was studied at the Guanica Forest, located in south-western Puerto Rico. From 1985 to 1987 a total of 23 nightjar nests were located. Nests were initiated between 24 February and 2 July. Nightjar males were mostly responsible for parental duties. An elaborate nest-relief ceremony was discovered for this species. Courtship and laying activities were most common during the new moon and last quarter phases. Hatching dates were centred 3-5 days around the first quarter and during full moon. A total of 87% of the nests were successful in producing at least one fledgling. Locomotory activity of radio-tagged nightjar males was higher during periods of twilight, and averaged 61.5 m/movement. Area of primary utilization (i.e. home range) averaged 5.2 ha/nightjar during the period of transmission. A large portion of the speciess current range is privately owned forestland that could be subjected to changes (i.e. deforestation), rendering it useless for nightjars. The sedentary nature and nesting habits of this species make it particularly sensitive to the physical and ecological alteration of mature dry forest. Conservation of existing reserves, reforestation of disturbed areas with native and selected plantation species, and acquisition of privately owned tracts of mature dry limestone forest will help to insure the long-term survival of the species throughout its range.
Journal of Wildlife Management | 2003
Jarrod H. Fogarty; Francisco J. Vilella
We examined population densities, movements, and habitat use of common coqui (Eleutherodactylus coqui), the most common and widespread species of frog in Puerto Rico, in native forest and eucalyptus plantations in 2 forest reserves of the Cordillera Central between July 1997 and June 1998. We established 4 grids of bamboo retreat sites on stands of native forest and eucalyptus plantations in each reserve. We established sampling points within trapping grids to quantify vegetation and determine habitat use. Sampling was conducted during the wet and dry seasons. We used mark-recapture for population estimation. Population estimates and maximum distances moved were determined using program CAPTURE. During the dry season, common coqui population densities were similar in 3 of the 4 study grids, but 1 eucalyptus site had significantly lower densities. We found no differences in adult frog density among study sites during the wet season. Horizontal movements differed between forests, albeit not significantly. Our results indicate that plant species richness did not affect common coqui density. Coqui density was influenced more by vegetation structure than by plant species composition. Five habitat variables (midstory epiphyte load, midstory stem count, ground-cover stem count, total epiphyte load, total basal area) were correlated with adult common coqui density. Eucalyptus plantations in montane regions of Puerto Rico provide suitable habitat for the common coqui. However, suitability may be linked to threshold basal area levels of 18-28 m 2 /ha.
The Wilson Journal of Ornithology | 2010
Francisco J. Vilella; Guy A. Baldassarre
Abstract The Llanos is a significant waterbird site in the Western Hemisphere, but abundance and distribution of waterbirds across this vast region are poorly known, which hampers conservation initiatives. We used point counts along road routes in the Llanos region of Venezuela to examine abundance and distribution of waterbirds during 2000–2002 within five ecoregions across the Llanos. We detected 69 species of waterbirds and recorded 283,566 individuals, of which 10 species accounted for 80% of our observations. Wading birds (Ciconiiformes) represented the largest guild both in numbers of species (26) and individuals (55%), followed by waterfowl (26%), and shorebirds (11%). Five species comprised 62% of all individuals: Cattle Egret (Bubulcus ibis), White-faced Whistling Duck (Dendrocygna viduata), Black-bellied Whistling Duck (D. autumnalis), Great Egret (Ardea alba), and Wattled Jacana (Jacana jacana). Wading birds were particularly ubiquitous with at least 21 of 26 species recorded in each of the ecoregions. Species richness (66), proportion of waterbirds detected (54%), and mean number of birds per route (1,459) were highest in the Banco-Bajio-Estero savanna ecoregion. Our study provides the most comprehensive data set available on waterbirds in the Llanos of Venezuela and highlights regions of special conservation concern.
The Wilson Journal of Ornithology | 2012
Kristina L. Mitchell; Samuel K. Riffell; L. Wes Burger; Francisco J. Vilella
Abstract We used video cameras in 2008–2009 to record provisioning activities at Dickcissel (Spiza americana) nests in and around Conservation Reserve Program field buffers in north-central Mississippi, USA. We simultaneously observed foraging flight distances of parents. Provisioning rate (P = 0.412), biomass (P = 0.161), and foraging distance (P = 0.159) did not increase with nestling age. Parents delivered larger items to meet demand associated with older nestlings (P = 0.010–0.001). This suggests energetic costs of changes in prey selection were less than costs of increasing the number or distance of provisioning trips. Presence of male helpers increased provisioning rate (P < 0.001) but not biomass (P = 0.992) because males brought smaller prey items (P = 0.001–0.021). Presence of observers 30 m from the nest reduced provisioning rates (P = 0.005) and biomass delivered (P = 0.066). Lack of habitat effects for any aspect of provisioning suggests grass field buffers provided nestling food resources similar to surrounding habitats. Use of continuous video monitoring of nest activity allows well-concealed activities including provisioning and male helping to be directly observed and better quantified.