(ISI Web of
Science 22-01-2007)
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), SCI=4,59, HL (half-life)=8,5 años.
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), SCI=2,67, HL (half-life) >10 años.
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), SCI=3,31, HL (half-life)=8,4 años.
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), SCI=1,70, HL (half-life)=5,9 años. CITAS RECIBIDAS: 5 en 1 año.
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), SCI=4,51, HL (half-life) >10 años. CITAS RECIBIDAS: 13 en 5 años.