Francisco García

Linking sanitary and ecological requirements in the management of avian scavengers: effectiveness of fencing against mammals in supplementary feeding sites

In order to ensure that the objectives behind the conservation of biodiversity are fulfilled it is essential that policies of all stakeholders are compatible. This is the case of the application of sanitary measures for the management of animal by-products and the negative effects that such restrictions had on the population dynamics and behavioural ecology of the avian scavengers’ guild. Thus, measures that allow these species to feed and that reduce risks of disease transmission must be put into practice. This study aims to improve the technical implementation of one of the commonest tools employed in the conservation of avian scavengers: supplementary feeding stations. We evaluated the permeability of three types of fences in experimental feeding stations to determine which of the models prevent non-target species from accessing the food provided. We compared results from fenced-off feeding stations with those from random points in unfenced-off sites. The results showed that two of the models (high and low nets) were the most effective avoiding facultative mammal scavengers from gaining access into the exclosure for over two months and for 7–8 inputs of food. Avian scavengers were able to access food regardless of the type of exclosure, which did not determine the abundance of birds or the species present. The carrion consumption by non-target species can be reduced by affordable and sustainable means. We suggest proposals to optimize the management of supplementary feeding stations for threatened avian scavengers and for the design of fenced exclosures.

Is It Necessary Managing Carnivores to Reverse the Decline of Endangered Prey Species? Insights from a Removal Experiment of Mesocarnivores to Benefit Demographic Parameters of the Pyrenean Capercaillie.

Mesopredator control has long been used to alleviate the effect of elevated predation pressure on vulnerable, threatened or valuable species. However, the convenience of using mesopredator controls is technically questionable and scientifically-sound research is therefore required to evaluate the impact of predation on prey case by case. In this study we evaluated the effect of the alteration of terrestrial mesopredator dynamics on the demographic parameters of a relict capercaillie Tetrao urogallus aquitanicus population currently in decline for which the impact of predation has not previously been assessed. We used a six-year mesocarnivore removal experiment (2008–2013) together with seven-years of previous demographic information on capercaillies (1999–2007) within a before-after control-impact (BACI) design to evaluate the effect of mesocarnivore removal on capercaillie demographic parameters and on spatial behaviour of the most frequent predatory mesocarnivores of the capercaillie (Martes spp. and red fox Vulpes vulpes). Using a dynamic site-occupancy approach, the reduction of mesocarnivore population levels as a result of removal was clear for marten species, mainly during key months for capercaillie reproduction, but not for the red fox. Our results show that the breeding success of capercaillies was enhanced in areas where carnivores were removed and was inversely related to the occupation level of the studied mesocarnivores, although being only significant for Martes spp. Moreover, capercaillie predation rates were lower and adult survival seemingly higher in treatment during the removal phase. Cost-effective, long-term management interventions to ensure the recovery of this threatened capercaillie population are discussed in the light of the results. At our study area, the decision for implementing predation management should be included within a broader long-term conservation perspective. In this regard, a more feasible and sustainable management intervention in ecological and economic terms may be to balance the impact of mesocarnivores on capercaillies through the recovery of apex predators.

Mechanistic Model for Eccentric Annular Gas-Liquid Flow in Horizontal Pipelines

A mechanistic model for the prediction of pressure drop in horizontal pipelines is presented for annular flow. A new empirical correlation for the liquid/wall interfacial friction is proposed, where the effects of the annular flow eccentricity, due to the difference between the fluid density and viscosity, are accounted for. The model is compared to three different correlation models and five mechanistic models in current use. Its accuracy has been validated against experimental data for annular gas-liquid flow in horizontal pipelines, taken from different sources. A number of 240 experiments were carried out with superficial liquid velocities between 0.003 and 5.96 m/s, superficial gas velocities between 9 and 69.6 m/s, liquid viscosities between 1 and 1200 cP, and pipeline diameters between 0.0261 and 0.0953 m. We find that the mechanistic model proposed here reduces the absolute error of the pressure drop prediction by approximately 20 % compared to other mechanistic models.

Efecto de la Viscosidad y de la Densidad de Mezcla en el Gradiente de Presión de Flujo Homogéneo Gas-Líquido en Tuberías Horizontales

En este trabajo se evalua la precision de 76 modelos homogeneos de gradiente de presion para determinar el gradiente de presion experimental reportado en una base de 2415 datos de flujos bifasico gas-liquido en tuberias horizontales. Estos modelos se formularon a partir de 4 ecuaciones de densidad de mezcla combinadas con 19 ecuaciones de viscosidad de mezcla. Al estudiar el efecto de la viscosidad y de la densidad de mezcla en el gradiente de presion, utilizando el modelo homogeneo, se observa que el mejor modelo obtuvo un error absoluto promedio de 25.7%, mientras que el peor modelo obtuvo un error cercano al 2000%. Los resultados obtenidos indican que la precision del modelo homogeneo de gradiente de presion de flujo bifasico gas-liquido, depende significativamente de la adecuada seleccion de las ecuaciones de viscosidad y de densidad de mezcla.

Estudio Experimental de Patrones de Flujo Bifásico Aire-Agua en Tuberías Horizontales y Ligeramente Inclinadas

An experimental study in horizontal and slightly inclined pipelines was performed. A total of 493 airwater two-phase flow experiments were carried out, of which 191 correspond to horizontal pipelines and 302 correspond to upward flow. The space distributions of the experiments include the smooth and wavy stratified, slug, annular and dispersed bubble flow patterns. Experimental maps of the flow patterns for each inclination angle are developed and the prediction capability of four mechanistic models and two correlating models commonly used in the literature for determining flow patterns are evaluated. Comparison between calculated and experimental values indicates that the selected models have a success percentage greater than 75%.