SEXENIO 2001-2006

(datos tomados de ISI Web of Science; 10-05-2011)



1    De La Montaña, E.; Rey Benayas, J.M.; Carrascal, L.M. 2006. Response of bird communities to silvicultural thinning of Mediterranean maquis. Journal of Applied Ecology 43:651-659.

      Land owners in some European Mediterranean regions receive subsidies to thin dense maquis. This practice consists in the elimination of most shrubs and saplings and the pruning of the tallest trees to favour more opened woodland stands. We investigated how this practice affects the structure of bird communities. We designed a large scale ‘natural experiment’ that included 21 paired thinned and un-thinned maquis stands in Central Spain. Thinning was responsible for a significant increase in species richness, but did not have any effect on total bird density. Average body mass of species in thinned stands was significantly larger than in un-thinned, more densely vegetated, stands. This is the first time that a large-scale experimental manipulation of habitat structure and vegetation volume demonstrates the predicted allometric effect of habitat structural complexity on the average body mass of a bird community. Thinned areas allow the occupation with higher densities of bird species whose European conservation status is of higher concern. Winter density of game birds was higher in thinned stands. Thinning of dense Mediterranean woodland also enhances habitat heterogeneity and suitability for several bird, although some un-thinned patches should be preserved to provide refuge for the few species that are impacted by thinning (mainly the widely distributed and abundant foliage gleaners).

      J. Appl. Ecol.: 7º puesto en Ecology (n=112 revistas JCR-2005), 10 citas.



2    Carrascal, L.M.; Polo, V. 2006. Effects of wing area reduction on winter body mass and foraging behaviour in coal tits: field and aviary experiments. Animal Behaviour 72:663-672.

      Theoretical and experimental evidence suggests that an increase in flight costs will decrease flight performance, and that birds should trade-off the benefits of body reserves to minimize these costs. Alternatively, birds could avoid starvation by increasing food intake, thereby maintaining body reserves, and/or decreasing flight activity to compensate for the greater per unit flight costs. To test the effect of increased flight costs on body mass regulation and on flying and feeding activity, we experimentally manipulated wing area in a free-ranging wintering population of coal tits, Periparus ater, and in captive birds living in a less restrictive environment (large outdoor aviaries). In the field, body mass decreased when wing area was reduced, but heavier birds lost more weight than lighter birds as a consequence of an allometric increase in flying costs. However, wing area reduction had no effect on body mass in the aviaries. Birds also flew less when wing area was reduced and those with higher wing loadings decreased flying frequency more markedly.We suggest that the goal of small resident birds living in a Mediterranean montane climate would be to maintain daily fat reserves within narrow limits during autumn and winter, even under contrasting ecological conditions.

      Anim. Behav.: 6º puesto en Zoology (n=114 revistas JCR-2005), 6 citas.



3    Carrascal, L.M.; Alonso, C.L. 2006. Habitat use under latent predation risk. A case study with wintering forest birds. Oikos 112: 51-62.

      We test the prediction that predation risk is a foraging cost affecting the spatial niche of birds within habitat. Using specially designed feeders containing the same amount and kind of food, we control for interspecific differences in food preferences and in foraging postures related to ecomorphological constraints, and for differences in natural food availability among foraging substrata. Small tree gleaning passerines avoided feeding on dark inner forest places far from edges, distant from protective cover, outside the tree canopy and near the ground; they preferred deciduous, relatively clear forest plots. These effects were highly predictable and remained invariable across years and weather conditions. There was a common pattern of selection of foraging locations: distance to cover (negatively), and height above ground and over the lowest branches of the tree canopy (positively) markedly determined the use of feeding places. According to these patterns, the vigilance proportion of species was significantly higher when feeding far from cover than when birds were feeding near pine foliage. These results demonstrate that the selection of feeding locations within habitat (i.e., spatial niche) follows a pattern minimizing predation risk. The interspecific dominance hierarchy of the species was negatively correlated with the use of the most exposed feeders (feeders nearer the ground and more distant from cover and below the lower branches of tree canopy), being the converse with the safest ones. Therefore, interspecific dominance hyerarchies can lead to the exploitation of unfavourable risky patches by subordinate species.

      Oikos: 21º puesto en Ecology (n=112 revistas JCR-2005), 7 citas.



4    Seoane, J.; Carrascal, L.M.; Alonso, C.L. y Palomino, D. 2005. Species-specific traits associated to prediction errors in bird habitat suitability modelling. Ecological Modelling 185:299-308.

      Although there is a wide range of empirical models applied to predict the distribution and abundance of organisms, we lack an understanding of which ecological characteristics of the species being predicted affect the accuracy of those models. However, if we knew the effect of specific traits on modelling results, we could both improve the sampling design for particular species and properly judge model performance. In this study, we first model spatial variation in winter bird density in a large region (Central Spain) applying regression trees to 64 species. Then we associate model accuracy to characteristics of species describing their habitat selection, environmental specialization, maximum densities in the study region, gregariousness, detectability and body size. Predictive power of models covaried with model characteristics (i.e., sample size) and autoecological traits of species, with 48% of interspecific variability being explained by two partial least regression components. There are species-specific characteristics constraining abundance forecasting that are rooted in the natural history of organisms. The better predicted species had high environmental specialization and reached higher maximum densities. We also detected a measurable positive effect of species detectability. Thus, generalist species and those locally scarce and inconspicuous are unlikely to be modelled with great accuracy. Limitations caused by those species-specific traits associated with survey work will be difficult to circumvent by either statistical approaches or increasing sampling effort while recording biodiversity in extensive programs.

      Ecol. Model.: 43º puesto en Ecology (n=112 revistas JCR-2005), 31 citas.



5    Carrascal, L.M.; Díaz, J.A.; Huertas, D.L.; Mozetich, I. 2001. Behavioral thermoregulation by treecreepers: trade-off between saving energy and reducing crypsis. Ecology 82:1642-1654.

      We hypothesized that, in temperate latitudes of cold winter climate with low cloudiness and under windless conditions, birds should select sunlit sites to reduce the metabolic cost of thermoregulation. At a within-habitat scale, a hypothesis of "only metabolic benefits" predicts that birds should select sunlit patches at temperatures in the shade (Tshade) below the lower critical temperature (Tlc), and shift to a random use of sunlit and shaded patches at temperatures above Tlc. Nevertheles, if higher visibility leads to diminished crypsis at sunlit patches ("trade-off with predation risk hypothesis"), birds should select only shaded patches at Tshade values above Tlc (to enhance crypsis), and their selectivity for sunlit patches should gradually increase as Tshade decreases below Tlc. We tested these hypotheses with the Short-toed Treecreepers Certhia brachydactyla inhabiting a montane coniferous forest during winter. Results obtained are indicative of a trade off between the energy savings (due to higher operative temperature and reduced metabolic costs) and the increased risk of predation (due to higher visibility and diminished crypsis) afforded by sunlit foraging patches. Treecreepers were selective in their use of sun-shade patches. This result holded at different spatial scales and can be interpreted as a behavioral thermoregulation strategy allowing birds to save energy. The selection of sunlit trunk patches at low temperatures was not a by product of their higher food availabilty. However, the results obtained lead to the rejection of the "only thermal benefits" hypothesis because although treecreepers preferred to forage on sun exposed surfaces when Tshade was lower than 4 ºC, they tended to forage on shaded surfaces when Tshade was higher than 9 ºC, a temperature that is considerably below the lower critical temperature (Tlc). Photometric measurements of treecreeper taxidermic mounts realistically positioned on trunk surfaces, detection times by simulated (human) predators and scanning behaviour of focal birds, suggest that treecreepers were more detectable under direct solar radiation than in deep shade. Thus, the observed temperature dependent variation in the selection of sunlit substrata is consistent with the "trade-off with predation risk hypothesis" predicting that prey should avoid patches where they are more detectable to potential predators.

      Ecology: 8º puesto en Ecology (n=112 revistas JCR-2005), 21 citas.