Search results for "gull"

Molecular and morphological evidence for three species of Diplostomum (Digenea: Diplostomidae), parasites of fishes and fish-eating birds in Spain

2014

Background Recent molecular studies have revealed high species diversity of Diplostomum in central and northern Europe. However, our knowledge of the distribution of Diplostomum spp. in the southern distributional range in Europe of the snail intermediate hosts (Lymnaea stagnalis and Radix spp.) is rather limited. This study aims to fill this gap in our knowledge using molecular and morphological evidence. Methods Nineteen fish species and six fish-eating bird species were sampled opportunistically in three regions (Catalonia, Extremadura and Aragon) in Spain. All isolates of Diplostomum spp. were characterised morphologically and molecularly. Partial sequences of the barcode region of the …

Morphometric and hydraulic geometry assessment of a gully in SW Spain

2016

Abstract Gully erosion represents one of the most significant types of land degradation in the Mediterranean areas, giving place to important on- and off-site effects. In this paper, a second-order gully located in SW Spain is analyzed. Along the gully, 28 cross-sections were established and measured with a Leica TCRM1102 laser total station, approximately every 6 months from 2001 to 2007. The sections were located at variable distance, placing them in areas where active erosion was evident. In total, 13 field measurements were carried out, and the geometric characteristics of 28 cross-sections were obtained. Morphometric analyses were carried out in both the main gully and a tributary reac…

Contamination by trace metals and their trophic transfer to the biota in a Mediterranean coastal system affected by gull guano

2013

Transitional environments are vulnerable interface systems, ecologically connected with adjacent systems by several biotic or abiotic flows. The coastal system of the Marinello ponds (Tyrrhenian Sea, Italy) is affected by a colony of yellow-legged gulls Larus michahellis (Naumann, 1840), resident on the cliff beside the ponds. To investigate the role of the gull colony as a potential source of allochthonous non-essential trace metals (As, Cd, Pb and total mercury, THg) and the consequent metal trophic transfer to the biota in the ponds, we collected guano, surface sediment and biota from 3 ponds with different levels of avian input. The highest concentrations were observed in guano and surf…

Effects of a small seagull colony on trophic status and primary production in a Mediterranean coastal system (Marinello ponds, Italy)

2012

Abstract Colonies of seabirds have been shown to influence nutrient cycling and primary production of coastal areas, but knowledge is still limited above all for smaller colonies. This study evaluates the influence of a small resident seagull colony (Larus michahellis Naumann, 1840) on a Mediterranean coastal system (Marinello ponds, Sicily, Italy). The presence of ornithogenic organic matter from seagull guano was first assessed at increasing distances from the colony using δ15N to indicate the effects of guano on the trophic status and primary production. The pond directly affected by guano deposition showed an anomalous water and sediment chemistry, especially regarding physico-chemical …

Using topographical attributes to evaluate gully erosion proneness (susceptibility) in two mediterranean basins: advantages and limitations

2015

Empirical multivariate predictive models represent an important tool to estimate gully erosion susceptibility. Topography, lithology, climate, land use and vegetation cover are commonly used as input for these approaches. In this paper, two multivariate predictive models were generated for two gully erosion processes in San Giorgio basin (Italy) and Mula River basin (Spain) using only topographical attributes as independent variables. Initially, nine models (five for San Giorgio and four for Mula) with pixel sizes ranging from 2 to 50 m were generated, and validation statistics were calculated to estimate the optimal pixel size. The best models were selected based on model performance using…

Comparison of differences in resolution and sources of controlling factors for gully erosion susceptibility mapping

2018

Abstract Gully erosion has been identified as an important soil degradation process and sediment source, especially in arid and semiarid areas. Thus, it is useful to identify the spatial occurrence of this form of water erosion in the landscape and the most vulnerable areas. In this study, we explored the effects of different pixel sizes on some controlling factors extracted from a digital elevation model and remote sensing data when producing a gully erosion susceptibility map (GESM) of Ekbatan Dam Basin, Hamadan, Iran. An inventory map of the gully landforms was prepared based on global positioning system routes of the gullies, extensive field surveys, and visual interpretations of satell…

Argullol a vueltas con la opinión pública

2007

Ring species – Do they exist in birds?

2007

Abstract According to current theory, the splitting of a single species into two is best observed by a ring of intergrading populations which occupy a ring-shaped distribution area and whose terminal populations not only meet but overlap and co-occur without or with only little hybridization. The three most discussed examples in birds are revisited here. The great tit complex ( Parus major s. l.) turned out to be an assemblage of four subspecies groups forming a secondary ring of population. The herring gull/lesser black-backed gull complex ( Larus argentatus s. l.) forms a circumpolar circle of intergrading populations, but lacks the crucial cornerstone, the geographical overlap. The green…

De Vargas Llosa a Argullol

2007

Enfermedad, hundimiento, derrota. La caída de Albert Camus

2017

La enfermedad fue un acontecimiento importante en la vida de Albert Camus, que fue marcado por la tuberculosis desde su juventud y se vio obligado a luchar contra ella hasta su muerte. A pesar de ello, los efectos de la enfer- medad en sí misma en la obra literaria de Camus no han sido estudiados como se podría esperar. Este texto está centrado en La Caída (La Chute), una pequeña novela donde la enfermedad tiene un fuerte contenido simbólico que abarca el terreno de la antropología, la moral y la política. Illness was a major event in the life of Albert Camus. He was marked by tuberculosis since his youth and he had to fight the disease till his death. Despite this fact, the effects of the …