PRINCIPALES PUBLICACIONES CIENTÍFICAS (desde 1990)
MAIN SCIENTIFIC PUBLICATIONS (since 1990)

Luis M. CARRASCAL
Profesor de Investigación
Dept. Biodiversidad y Biología Evolutiva
Museo Nacional de Ciencias Naturales
Consejo Superior de Investigaciones Científicas

 

Lista completa de publicaciones

Carrascal, L.M.; Seoane, J.; Palomino, D.; Polo, V. 2008. Explanations for bird species range size: ecological correlates and phylogenetic effects in the Canary Islands. Journal of Biogeography doi:10.1111/j.1365-2699.2008.01958.x [SUMMARY] [pdf].

Seoane, J.; Carrascal, L.M. 2008. Interspecific differences in population trends of Spanish birds are related to habitat and climatic preferences. Global Ecology & Biogeography 17:111-121. [SUMMARY]  [pdf]

Polo, V.; Carrascal, L.M.; Metcalfe, N.B. 2007. The effects of latitude and day length on fattening strategies of wintering coal tits (Periparus ater L): a field study and aviary experiment. Journal of Animal Ecology 76:866-872. [SUMMARY] [pdf]

Bosch, J.; Carrascal, L.M.; Durán, L.;  Walker, S.; Fisher, M.C. 2007. Climate change and outbreaks of amphibian chytridiomycosis in a montane area of Central Spain; is there a link? Proceedings Royal Society London B 274:253–260 [SUMMARY] [pdf]

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. [SUMMARY] [pdf]

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. [SUMMARY] [pdf]

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

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. [SUMMARY] [pdf].

Carrascal, L.M. 2004. Distribución y abundancia de las aves en la Península Ibérica. Una aproximación biogeográfica y macroecológica. P.p. 155-189. La Ornitología hoy. Homenaje al Profesor Francisco Bernis. Editorial Complutense, Universidad Complutense de Madrid, Madrid. [pdf]

Carrascal, L. M.; Lobo, J. L. 2003. Respuestas a viejas preguntas con nuevos datos: estudio de los patrones de distribución de la avifauna española y consecuencias para su conservación. Pp. 645-662 y 718-721 en Martí, R., Del Moral, J.C. (Eds.). Atlas de las Aves Reproductoras de España. Dirección General de la Conservación de la Naturaleza-Sociedad Española de Ornitología, Madrid. [pdf]

Belliure, J.; Carrascal. L.M. 2002. Influence of heat transmission mode on heating rates and on the selection of patches for heating in a Mediterranean lizard. Phys. & Bioch. Zool. 75(4):369-376. [SUMMARY] [pdf]

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 [SUMMARY] [pdf]

Carrascal, L.M.; Polo, V. 1999. Coal tits, Parus ater, lose weight in response to chases by predators. Animal Behaviour 58:281-285. [SUMMARY] [pdf]

Polo, V.; Carrascal, L.M. 1999. Shaping the body size distribution of passeriformes: habitat use and body size are evolutionarily and ecologically related. Journal of Animal Ecology. 68:324-337. [SUMMARY] [pdf]

Carrascal, L.M.; Senar, J.C.; Mozetich, I.; Uribe, F.; Domenech, J. 1998. Interaction between environmental stress, body condition, nutritional status and dominance in mediterranean great tits (Parus major) during winter. Auk 115:727-738. [SUMMARY] [pdf]

Carrascal, L.M.; Díaz, M. 1998. Utilidad científica y difusión internacional de Ardeola: un análisis bibliométrico - Scientific utility and international diffusion of Ardeola: a bibliometric analysis. Ardeola 45:221-239. [SUMMARY] [pdf]

Moreno, E.; Barbosa, A.; Carrascal, L.M. 1997. Should congruence between intra- and interspecific ecomorphological relationships be expected? A case study with the Great Tit Parus major. Proceedings of The Royal Society London: B 264:533-539. [SUMMARY] [pdf]

Belliure, J.; Carrascal, L.M.; Díaz, J.A. 1996. Covariation of thermal biology and foraging mode in two mediterranean lacertid lizards. Ecology 77:1163-1173. [SUMMARY] [pdf]

Carrascal, L.M.; Moreno, E.; Mozetich, I. 1995. Ecological plasticity of morphological designs. An experimental analysis with tit species. Canadian J. Zoology 73:2005-2009. [SUMMARY] [pdf]

Carrascal, L.M.; Moreno, E.; Valido, A. 1994. Morphological evolution and changes in foraging behaviour of island and mainland populations of Blue Tit, Parus caeruleus. A test of convergence and ecomorphological hypoteses. Evolutionary Ecology 7:25-35. [SUMMARY] [pdf]

Tellería, J.L.; Carrascal, L.M. 1994. Weight-density relationships between and within bird communities. Implications of niche space and vegetation structure. American Naturalist 141:1083-1092. [SUMMARY] [pdf]

Moreno, E.; Carrascal, L.M. 1993. Leg morphology and feeding postures in four Parus species: an experimental ecomorphological approach. Ecology 74:2037-2044. [SUMMARY] [pdf]

Díaz, J.A.; Carrascal, L.M. 1993. Variation in the effect of profitability on prey size selection by the lacertid lizard Psammodromus algirus. Oecologia (Berl.) 94:23-29. [SUMMARY] [pdf]

Carrascal, L.M.; López, P.; Martín, J.; Salvador, A. 1992. Basking and antipredator behaviour in a high altitude lizard: implications of heat-exchange rate. Ethology 92:143-154. [SUMMARY]

Carrascal, L.M.; Moreno, E. 1992. Proximal costs and benefits of heterospecific social foraging in Great Tit Parus major. Canadian Journal of Zoology 70:1947-1952. [SUMMARY]

Carrascal, L.M.; Tellería, J.L.; Valido, A. 1992. Habitat distribution of canary chaffinches among islands: competitive exclusion or species-specific habitat preferences? Journal of Biogeography 19:383-390. [SUMMARY] [pdf]

Carrascal, L.M.; Tellería, J.L. 1991. Bird size and density: a regional approach. American Naturalist 138:777-784. [SUMMARY] [pdf]

Díaz, J.A.; Carrascal, L.M. 1991. Regional distribution of a Mediterranean lizard: influence of habitat cues and prey abundance. Journal of Biogeography 18:291-297. [SUMMARY] [pdf]

Carrascal, L.M.; Moreno, E.; Tellería, J.L. 1990. Ecomorphological relationships in a group of insectivorous birds of temperate forests in winter. Holarctic Ecology 13:105-111. [SUMMARY] [pdf]

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Carrascal, L.M.; Seoane, J.; Palomino, D.; Polo, V. 2008. Explanations for bird species range size: ecological correlates and phylogenetic effects in the Canary Islands. Journal of Biogeography

Aim To explore the determinants of island occupancy of 48 terrestrial bird species in an oceanic archipelago, accounting for ecological components while controlling for phylogenetic effects.

Location The seven main islands of the Canary archipelago.

Methods We obtained field data on density, habitat breadth and landscape distribution in Tenerife, Fuerteventura and La Palma, trying to sample the whole availability of habitats and the gradient of altitudes. In total 1,715 line transects of 0.5 km were carried out during the breeding season. We also reviewed the literature for data on occupancy, the distance between the Canary Islands and the nearest distribution border in the mainland, body size and endemicity of the 48 terrestrial bird species studied. Phylogenetic eigenvector regression was used to quantify (and to control for) the amount of phylogenetic signal.

Results The two measurements of occupancy (number of occupied islands or 10x10 km UTM squares) were tightly correlated and produced very similar results. The occupancy of the terrestrial birds of the Canary Islands during the breeding season had a very low phylogenetic effect. Species with broader habitat breadth, more intense preferences for urban environments, smaller body size, and lower degree of endemicity had a broader geographical distribution in the archipelago, occupying a larger number of different islands and 10x10 UTM squares.

Main conclusions The habitat generalist species with a tolerance for novel urban environments tend to be present in more islands and to occupy more area, while large-sized species that are genetically differentiated within the islands are less widespread. Therefore, some properties of the ranges of these species are explicable from basic biological features. The positive relationship with local abundance, previously uncovered in continental studies, was not found, probably because it relies on free dispersal on continuous landmasses that may be short-circuited in oceanic island scenarios.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Seoane, J.; Carrascal, L.M. (2007). Interspecific differences in population trends of Spanish birds are related to habitat and climatic preferences.  Global Ecology & Biogeography 17:111-121.

1. Aim Animal monitoring programs have allowed analyses of population trends, most of which recently comment on the possible effect of global climate change. However, the relationship between the interspecific variation in population trends and species’ traits such as habitat preferences, niche breadth or distribution patterns have received little attention, in spite of its usefulness in the construction of ecological generalizations. The objectives of this study were to (1) determine whether there are characteristics shared among species with upwards or downwards trends, and (2) assess whether population changes agree with what could be expected under global warming (a decrease of species typical of cooler environments).

2. Location The Spanish part of the Iberian Peninsula (ca. 500,000 km2) in the south-western part of the Mediterranean Basin.

3. Methods We modelled recent breeding population changes (1996-2004), in areas without aparent land use changes, for fifty-seven common passerine birds with species-specific ecological and distributional patterns as explanatory variables.

4. Results One-half of these species have shown a generalized pattern towards the increase of their populations, while only one-tenth showed a significant decrease. One half (54%) of the interspecific variability in yearly population trends is explained considering species-specific traits. Species showing more marked increases preferred wooded habitats, were habitat generalists and occupied warmer and wetter areas, while moderate decreases were found for open country habitats living in drier areas.

5. Main conclusions The coherent pattern in population trends we found disagree with the proposed detrimental effect of global warming on bird populations of Western Europe, which is expected to be more intense in bird species inhabiting cooler areas and habitats. Such pattern suggests that factors other than the increase in temperature may be brought to discussions on global change as relevant components to explain recent changes in biodiversity.


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Polo, V.; Carrascal, L.M.; Metcalfe, N.B. (2007). The effects of latitude and day length on fattening strategies of wintering coal tits (Periparus ater L): a field study and aviary experiment. Journal of Animal Ecology  doi: 10.1111/j.1365-2656.2007.01270.x

1. Cyclic daily fattening routines are very common in wintering small wild birds, and are thought to be the consequence of a trade-off between different environmental and intrinsic factors. According to theory, these trajectories should range from accelerated (i.e. mass increases exponentially towards dusk) when mass-dependent costs are the most important cause of mortality, to decelerated (i.e. the rate of mass gain is highest at dawn and decreases afterward) when starvation is the greater risk.

2. We examine if geographically separate populations of coal tits, wintering in Scotland and Central Spain under contrasting photoperiods, show differences in their strategies of daily mass regulation. We describe population differences in wild birds under natural conditions, and experimentally search for intrinsic interpopulation variation in diurnal body mass increase under common, manipulated, photoperiod conditions (9 h Light:15 h Dark vs 7L:17D) , controlling for temperature, food availability, predator pressure and foraging arena.

3. Winter diurnal mass gain of wild coal tits was more delayed towards the latter part of the daylight period in Central Spain (i.e., the locality with longer winter days) than in Scotland. In both localities, the pattern was linked to the average mass at dawn, with mass increasing more rapidly in lighter birds. However, under the controlled photoperiod situation the pattern of daily mass gain was similar in both populations. Diurnal body mass gain was more accelerated at the end of the day, and the increase in body mass in the first hour of the day was considerably lower under the long (9 hours) than under the short (7 hours) photoperiod in both populations.

4. Wintering coal tits show patterns of mass gain through the day that are compatible with current theories of the costs and benefits of fat storage, with birds at lower latitudes (with longer winter days) having a greater tendency to delay mass gain until late in the day. The experimental study revealed that these patterns are plastic, with birds responding directly to the photoperiod that they experience, suggesting that they are continually making fine-scale adjustments to energy reserves on the basis of both intrinsic (e.g. state-dependent) and extrinsic cues.


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Bosch, J.; Carrascal, L.M.; Durán, L.;  Walker, S.; Fisher, M.C. (2007). Climate change and outbreaks of amphibian chytridiomycosis in a montane area of Central Spain; is there a link? Proceedings Royal Society London B 274:253–260

Amphibian species are declining at an alarming rate on a global scale in large part due to an infectious disease caused by the chytridiomycete fungus, Batrachochytrium dendrobatidis. This pathogen of amphibians has recently emerged within Europe, but knowledge of its widespread effects on amphibian assemblages remains poor. Importantly, little is known about the environmental envelope that is associated with chytridiomycosis in Europe, and the potential for climate change to drive future disease dynamics. Here, we use long-term observations on amphibian population dynamics in the Peñalara Natural Park, Spain, to investigate the link between climate-change and chytridiomycosis. Our analysis shows a significant association between local climatic variables and the occurrence of chytridiomycosis within this region. Specifically, we show that rising temperature and humidity are linked to the occurrence of chytrid-related disease, and that these local variables are driven by general circulation patterns, such as the North Atlantic oscillation. Given that the chytrid is known to be broadly distributed across Europe, there is now an urgent need to assess how climate-driven epidemics are expected to impact on amphibian species across the wider region.


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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.

1. 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. 2. We designed a large scale ‘natural experiment’ that included 21 paired thinned and un-thinned maquis stands in Central Spain. Every stand was sampled by means of 5 point counts, each consisting of a 50-m radius plot, in two consecutive years and in winter and spring. The vegetation structure was characterized after bird censuses in 10-m radius plots that coincided with the centers of the bird point counts. Data analyses were based on repeated-measures ANOVAs. 3. 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. Density of ground searchers was undistinguishable in thinned and in un-thinned stands, whereas density of foliage gleaners was higher in un-thinned stands. Winter density of granivorous species was marginally higher in thinned stands, whereas insectivorous and frugivorous species were marginally more abundant in un-thinned stands. 4. 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. 5. Synthesis and application. 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. Thinning of dense Mediterranean woodland enhances habitat heterogeneity and suitability for several bird species and increased species richness. This practice was also beneficial for species of conservation concern and the hunting of non-threatened game birds. However, some un-thinned patches should be preserved to provide refuge for the few species that are impacted by thinning.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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. Controlling for the positive effect of prevalence, 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. Our results suggest that the limitations caused by those species-specific traits associated with survey work (e.g., conspicuousness, gregariousness or maximum ecological densities) will be difficult to circumvent by either statistical approaches or increasing sampling effort while recording biodiversity in extensive programs.

 

 

 

 

 

 

 

 

 

 

 

Carrascal, L.M.; Polo, V. (2006). Effects of wing area reduction on body mass and foraging behaviour in the coal tit (Parus ater) during winter: field and aviary experiments. Animal Behaviour 72: 663-672.

Theoretical and experimental evidence suggests that an increase in flight costs will cause a decrease in flight performance, and that birds should trade-off the benefits of body reserves to minimize these costs. However, an alternative strategy could be to avoid the dangers of 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 (Parus ater), and in captive birds living in a less restrictive environment (large outdoor aviaries). In the field, there was a clear trend towards body mass decrease when wing area was experimentally reduced, although it was not homogeneous: heavier birds lost more weight than lighter birds as a consequence of an allometric increase in flying costs. However, the experimental reduction of wing area had a non-significant, negligible, effect on body mass in the aviaries. Flight and feeding frequency were significantly affected by the experimental reduction of wing area: birds flew less and ate more when wing area was reduced. Birds with higher wing loads decreased more markedly flying frequency when wing area was reduced. We suggest that the goal of small resident birds living in Mediterranean montane climate would be to maintain daily fat reserves within some narrow limits during autumn and winter, even under contrasting ecological conditions. Our results show a trade-off between wing area reduction and body mass (in the field) and a trade-off between wing area and flying frequency (in the aviaries), both mediated by allometric effects of body size.

 

 

 

 

 

 

 

 

 

 

 

Carrascal, L.M.; Alonso, C.L. (2005). 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 distribution of birds within habitat. The work was carried out in a montane mixed forest of Central Spain with four Parus species, the Long-tailed tit (Aegithalos caudatus) and the Nuthatch (Sitta europaea). 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 remained invariable across years and weather conditions. There was a common pattern of selection of foraging locations by the four Parus species: 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. This pattern was also common for the four studied Parus species. Nevertheless, 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, the results of this paper demonstrate that the selection of feeding locations within habitat follows a pattern minimizing predation risk. Interspecific dominance hyerarchies can lead to the exploitation of unfavourable risky patches by subordinate species.

 

 

 

 

 

 

 

 

 

 

 

 

 

BELLIURE, J.; CARRASCAL. L.M. (2002). Influence of heat transmission mode on heating rates and on the selection of patches for heating in a Mediterranean lizard. Phys. & Bioch. Zool. 75(4):369-376.

Heliothermy (heat gain by radiation) has been given a prominent role in basking lizards. However, thigmothermy (heat gain by conduction) could be relevant for heating in small lizards. To ascertain the importance of the different heat transmission modes to the thermoregulatory processes, we conducted an experimental study where we analyzed the role of heat transmission modes on heating rates and on the selection of sites for heating in the Mediterranean lizard Acanthodactylus erythrurus (Lacertidae). The study was conducted under laboratory conditions, where two situations of different operative temperatures (38° and 50°C) were simulated in a terrarium. In a first experiment, individuals were allowed to heat up during 2 min at both temperatures and under both heat transmission modes. In a second experiment, individuals were allowed to select between patches differing in the main transmission mode, at both temperatures, to heat up. Experiences were conducted with live, nontethered lizards with a starting body temperature of 27°C. Temperature had a significant effect on the heating rate, with heat gain per unit of time being faster at the higher operative temperature (50°C). The effect of the mode of heat transmission on the heating rate was also significant: at 50°C, heating rate was greater when the main heat transmission mode was conduction from the substrate (thigmothermy) than when heating was mainly due to heat gain by radiation (heliothermy); at 38°C, heating rates did not significantly differ between transmission modes. At 38°C, selection of the site for heating was not significantly different from that expected by chance. However, at 50°C, the heating site offering the slowest heating rate (heliothermic patch) was selected. These results show that heating rates vary not only with environmental temperature but also with different predominant heat transmission modes. Lizards are able to identify and exploit this heterogeneity, selecting the source of heat gain (radiation) that minimizes the risk of overheating when temperature is high.

 

 

 

 

 

 

 

 

 

 

 

 

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 studied the effect of solar radiation on the winter biology of Short-toed Treecreepers Certhia brachydactyla inhabiting a montane coniferous forest. We hypothesized that, in temperate latitudes of cold winter climate with low cloudiness and under windless conditions, birds should select sunlit sites (i.e., forest sectors or trunk patches with high levels of exposure to sunlight) 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. Alternatively, there could be added costs (e.g. travel costs, predation risk) to the use of sunlit patches. 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.

Treecreepers were selective in their use of sun-shade patches. This result holded at different spatial scales. At the between-plots scale (habitat preferences across different forest tracts), the abundance of treecreepers was positively related to the availability of sunlit trunks when holding for the effects of tree density, prey availability, and altitude. At the within-plot scale (selection of foraging patches on trunks and thick branches), Ivlev’s electivity for sunlit patches decreased linearly as Tshade increased. Birds preferred to forage on sun exposed surfaces (electivity > 0) when Tshade was lower than » 4 ºC, but they tended to forage on shaded surfaces (electivity < 0) when Tshade was higher than » 9 ºC. The selection of sunlit trunk patches at low temperatures was not a byproduct of their higher food availabilty, because numbers of prey were much less predictable than temperature as a function of trunk exposure (sun vs. shade), the negative relationship between electivity for sunlit patches and Tshade significant after removing the effects of prey availability, and the pecking rates of focal birds did not differ between sunlit and shaded patches. Thus, the selection of sunlit patches at low temperatures can be interpreted as a behavioral thermoregulation strategy allowing birds to save energy. However, the results obtained (i.e., Ivlev’s electivity for sunlit patches became negative at temperatures well below Tlc, and no sunlit patches were used when Tshade » Tlc) lead to the rejection of the "only thermal benefits" hypothesis.

Photometric measurements of treecreeper taxidermic mounts realistically positioned on trunk surfaces, and detection times by simulated (human) predators, suggest that treecreepers were more detectable under direct solar radiation than in deep shade. Crypsis diminished in sunlit patches because of a higher image contrast, and an increased difference in perceivable coloration between bird and background, relative to shaded patches. Average detection times were significantly lower for sunlit mounts. Moreover, focal birds scanned more frequently in sunlit than in shaded patches. 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. We interpret the distribution and behavior of treecreepers as 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.

 

 

 

 

 

 

 

 

 

 

 

 

 

POLO, V.; CARRASCAL, L.M. 1999. Shaping the body size distribution of passeriformes: habitat use and body size are evolutionarily and ecologically related. Journal of Animal Ecology 68:324-337.

The effect of habitat structure on the distribution of the number of species by body size classes has been analysed with the Passeriforms of the Western Palearctic.

Evolutionary history of the group accounted for 68% of the interspecific variation in body mass. The phylogenetic effect is highly significant from the most recent evolutive radiations (i.e. genera) towards more ancient radiations (i.e. parvorders). In a more fine-grained study with a subset of 55 passerine species living in Central Spain, phylogeny accounted for significant proportions of the interspecific variation: 62% in body mass, 27% in habitat use (foraging on ground, vs foraging in foliage) and 12% in complexity of preferred habitats.

Throughout the evolutionary history there has been a considerable concentration of species around 10-40 g (increase in kurtosis), and there have appeared species with greater body masses (increase in skewness). The higher skewness and kurtosis of the distribution of the phylogenetic component (mainly a cladogenetic one in this study) supports the role of cladogenetic processes in body size evolution.

Removing the effect of evolutionary history on present-day variation in body mass (specific component of the phylogenetic autoregressive method), the distributions of body mass of open country and woodland species are markedly different: species from woodland habitats are lighter (mainly due to the large frequency of small-sized species) and their body masses are less concentrated than in species from open country habitats. Results for the phylogenetic component are similar to those of the specific component.

Habitat use was strongly correlated with body mass in a subset of 55 species living in Central Spain: species foraging on ground being heavier than those foraging in foliage and tree branches. This result was significant working with the specific and phylogenetic components. Habitat use and complexity of preferred habitats were significantly correlated using both the specific and the phylogenetic components: species that mainly forage on ground are mainly open country species, while species that forage in pliable and slender substrata mainly inhabit woodland habitats. Complexity of preferred habitats was negatively related to body mass, although this correlation was only significant using phylogenetic residuals (specific component).

These results show that the evolutionary history of Western Palearctic Passeriforms has not produced neutral variation in body mass with respect to habitat preferences and habitat use, and supports the view that macro and micro processes have not been decoupled in the evolution of body size.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CARRASCAL, L.M.; SENAR, J.C.; MOZETICH, I.; URIBE, F.; DOMENECH, J. 1998. Interaction between environmental stress, body condition, nutritional status and dominance in mediterranean great tits (Parus major) during winter. Auk 115:727-738.

Body condition and feather growth rate of Great Tits (Parus major) were studied in relation to dominance in two contrasting Mediterranean localites during late autumn and early winter. The two localities differed in altitude, ambient temperatures (100 vs 1500 m a.s.l., and 11.7 oC vs 4.6 oC, respectively) and arthropod availability. The two study areas were similarly food supplemented (husked peanuts) throughout the study period.

Percentage of time spent at feeders was higher at El Ventorrillo (the locality with colder climate and less natural food availability), and was associated with dominance only in this locality. Number of aggressive displacements per hour suffered by each individual was higher (150-fold greater) in the area with less arthropod availability and lower temperatures. Protein reserves measured as pectoralis muscle thickness was higher at El Ventorrillo, and was positively and consistently related to dominance in both localities. Growth rate of induced feathers was slower in the locality that was colder and had less natural food availability (El Ventorrillo), but was not clearly and directly related to dominance in both localities. Only dominant adult males in El Ventorrillo could compensate the higher environmental harshness of this locality attaining a higher feather growth rate than the other sex-age classes. Feather mass asymmetry during autumn was not associated with body condition, did not change between localities, and was inversely and consistently related to dominance in both localities. The covariation pattern among variables describing bird size, access to supplemented food, body condition, feather growth rate and asymmetry was different in both localities. Only in the locality with colder temperatures and lower arthropod food availability (El Ventorrillo) larger, more dominant, Great Tits spent more time foraging on feeders, had a thicker pectoralis muscle (i.e. body condition), and grew the induced feathers at a higher rate.

 

 

 

 

 

 

 

 

 

 

 

 

 

MORENO, E.; BARBOSA, A.; CARRASCAL, L.M. 1997. Should congruence between intra- and interspecific ecomorphological relationships be expected? A case study with the Great Tit Parus major. Proceedings of The Royal Society London: B 264:533-539.

We studied the relationships between leg morphology and feeding posture while feeding in a population of Great Tit (Parus major) under controlled conditions to investigate to what extent morphology and ecology are linked at the individual level. From predictions generated at the interspecific level within the genus Parus (Moreno & Carrascal 1993, Ecology 74:2037-2044), we test whether interspecific and intraspecific ecomorphological relationships are consistent.

The slopes of the regressions of the leg length segments are significantly lower than those expected under isometry (geometric similarity). For IMI distance (distance from the head of the fibula to the insertion point of the iliofibularis muscle) and IMT distance (distance from the head of the tibiotarsus to the insertion point of the tibialis cranialis muscle) the regression slopes are not higher than those predicted by isometry (for IMI distance the slope is even significantly lower than that expected; p<0.001). The regression slopes of the muscular forces of M. iliofibularis and M. tibialis cranialis do not significantly differ from those expected under isometry. Therefore, only for leg length segments deviations from an isometric relationship with body mass are big enough to allow the emergence of ecomorphological patterns. Combining the coefficients of deviation from the geometric similarity there is no sufficient morphological variation between individuals to promote clear associations between morphology and hanging performance (apart from that expected by geometric similarity due to interindividual differences in body size). Thus, we should not expect significant relationships between leg morphology and average time spent hanging.

Within our population, neither leg bone lengths nor leg muscle morphology were related to the feeding posture of individuals. However, differences in body weight were correlated with inter-individual differences in time spent hanging. These results demonstrate that the association between intraspecific and interspecific ecomorphological relationships is not uniform. We argue that at the intraspecific level body weight overrides the significance of other traits that have a functional meaning at interspecific level (i.e., leg segment lengths, muscular morphology), due to isometric variation of morphological traits (muscular and squeletal) with body mass. Thus, the discrepancy between the ecomorphological associations at interspecific and intraspecific levels is the result of a problem of scale (morphological changes in evolutionary time and isometric variation of morphological traits with body mass in ecological time).

 

 

 

 

 

 

 

 

 

 

 

BELLIURE, J.; CARRASCAL, L.M.; DÍAZ, J.A. 1996. Covariation of thermal biology and foraging mode in two mediterranean lacertid lizards. Ecology 77:1163-1173.

Body temperatures, heat exchange rates, behavioral thermoregulation, and movement behavior (as an index of foraging mode) were studied in two widely distributed, medium sized lacertid lizards (Acanthodactylus erythrurus and Psammodromus algirus). Psammodromus algirus mainly inhabits broad-leaved forests, while A. erythrurus prefers open sandy areas with sparsely distributed vegetation. These habitat preferences parallel differences between the areas in which both genera presumably originated: Eurosaharian xeric steppes with high operative temperatures (Te’s) for Acanthodactylus, and Mediterranean open forests with lower Te’s for Psammodromus.

Field observations showed that percentage of time spent basking and basking rate (no. of basks per minute) were negatively related to Te, although average bask duration was not. Percentage of time spent moving, moving rate (no. of moves per minute), and the average duration of individual moves were inversely related to Te, and were higher in P. algirus. The percentage of total locomotion time that was spent moving in the shade was also higher in P. algirus. Behavioral thermoregulation strategies differed between both species in a laboratory thermogradient where P. algirus basked more often and for shorter periods, and selected warmer patches, than A. erythrurus. Selected body temperatures (Tb’s) in a laboratory thermogradient were significantly higher in A. erythrurus than in P. algirus. Shade Seeking Tb was higher in A. erythrurus, while Resume Basking Tb did not differ significantly between the two species. Heating and cooling rates were also different in the two species: A. erythrurus warmed more slowly, and cooled faster, than P. algirus.

Our data support the existence of a complex syndrome which combines aspects of the behavior, physiology, and ecology of both species, so that the thermal consequences of inhabiting a certain type of habitat can be counterbalanced by behavioral and physiological means that, in turn, affect movement (and hence foraging) behavior. Thus, the more active species (P. algirus) heated faster, cooled more slowly, and basked more often but for shorter periods and at warmer patches than the less active one (A. erythrurus).

 

 

 

 

 

 

 

 

 

 

 

 

CARRASCAL, L.M.; MORENO, E.; VALIDO, A. 1994. Morphological evolution and changes in foraging behaviour of island and mainland populations of Blue Tit, Parus caeruleus. A test of convergence and ecomorphological hypoteses. Evolutionary Ecology 7:25-35.

We study the leg morphology and feeding postures of two subspecies of Blue Tit (Parus caeruleus; Tenerife Island and Iberian Peninsula) and Coal Tit (P. ater; Iberian Peninsula). We search for evidence supporting the hypothesis of convergent evolution in morphological and ecological traits, and we discuss the role of ecomorphological hypotheses as predictors of foraging differences at intraspecific level. To overcome the problems introduced by environmental characteristics not related to locomotion and competition, we make observations under controlled situations to manage food quality and food access.

Island Blue Tit has longer tarsometatarsus, larger foot span, and a more proximal insertion of tibialis cranialis muscle (flexor of the tarsometatarsus) than the mainland Blue Tit. These morphological differences are consistent with the more frequent use of hanging and clinging head-up postures by the Iberian Blue Tit. Several ecomorphological hypotheses obtained at interspecific level with other taxa, have proved to be of high predictive value for explaining ecological differences considering morphological evolution. Tenerife Blue Tit and Iberian Coal Tit clearly show close convergence in both feeding postures and leg structure, although some differences in morphology were found between these two species. Convergence in foraging methods between island Blue Tit and mainland Coal Tit can be explained without considering current interspecific competition as a determinant of niche space.

 

 

 

 

 

 

 

 

 

 

 

 

 

TELLERÍA, J.L.; CARRASCAL, L.M. 1994. Weight-density relationships between and within bird communities. Implications of niche space and vegetation structure. American Naturalist 141:1083-1092.

The population density of a species in a given area is limited by the number of individuals that the area can support, equivalent to the amount of energy available to the population divided by the energetic requirements per individual of each species. Some studies have attempted to evaluate this capacity rule by examining the inverse relationship between density (D) and body weight (W) in several animal groups using the equation D=aWb.

We develop two different analyses that compare bird communities on two distinct spatial scales. The first approach incorporates information on foraging behavior to analyze body weight-density relationships within different assemblages (according to substrate use). This is a large scale comparison that emphasizes similarities among forest bird communities in widely different forest habitats across two continents; species from different habitats and continents are assigned to the same set of foraging assemblages. The second analysis compares communities of forest birds in the same geographic region, analyzing the allometric relationship of population density for all species in the same community. The results are compared across a systematically varying environmental gradient (foliage volume).

To analyze the relationship between mean body weight of assemblages and rate of density change with bird size, we reviewed studies on bird use of space during the breeding season in five woodland communities of North America and in two of Europe. The second analysis, focussed at the community level, was performed on data on passerine density and vegetation structure of 17 habitats in northern Spain differing in foliage height diversity and volume. For each of the 17 bird communities we calculated the slope (b) of the log-log regression model of species density on bird weight. In both within- and between-community level analyses, species heavier than 350 g were excluded as they are usually censused inaccurately by methods employed to record small passerine abundance.

Mean body weight of assemblages decreased as thinness and pliability of foraging substrates increased. The relationship between density and body mass within each assemblage, as shown by slopes from allometric equations (b), gave an inverse association with thinness of foraging substrates (log-log correlation: r=0.51, n=28). Slope b was positively correlated with mean weight (weighted by density) of birds in each assemblage; i.e., the lower the body weight of birds in assemblages, the more negative the slope of the allometric regression of D on W. These results support the view that bird assemblages show varying relationships between density and species' body weight within the niche space of communities.

Analysis at the community level provided similar results. Average weight (weighted by density of each species) of bird communities decreased with increasing foliage-volume index (log-log regression: r=-0.704, p=0.002, n=17). Slopes of the allometric regressions of D on W (b) were inversely and significantly correlated with the foliage-volume index (log-log model: r=-0.761, p=0.0004, n=17), and directly associated with average weight of bird communities (log-log model: r=0.613, n=17; significance not provided due to partial dependence between b and W).

Correlation coefficients between body weight and maximum ecological density was -0.457 in the 17 habitats of northern Spain using phylogenetic independent contrasts (p=0.011; one-tailed test). This result points out that phylogenetic relatedness alone cannot explain the consistent patterns of change of b within and between communities.

The W-D relationships, as measured by b, suggest that larger species are able to gain resources in proportion to their size, whereas smaller species have more equitable resource allocations, and so show the expected D-W associations. The results provided by this paper illuminate the previously contrasting patterns obtained about resource extraction by species within communities. The confusing patterns of the D-W relationships that are so frequently observed in birds could be at least partly due to the use of bird densities obtained from habitats that, because of their different structure, provide different niche opportunities to species of different sizes. Therefore, a more autecological approach ought to be employed in the analysis of allometric relationships linking body weight to density.

 

 

 

 

 

 

 

 

 

 

 

MORENO, E.; CARRASCAL, L.M. 1993. Leg morphology and feeding postures in four Parus species: an experimental ecomorphological approach. Ecology 74:2037-2044.

We investigate the ecomorphology of four phylogenetically closely related species of Parus (P. major, P. caeruleus, P. cristatus, and P. ater) that cooccur in a mixed Mediterranean woodland of Central Spain. We investigate the relation of foraging modes (hanging vs. standing back up) to leg morphology (osteology and myology). To partially control for food quality, food access and escape distance to the nearest refuge, we provided wild birds with special feeders. We also include a tentative phylogenetic analysis of the morphological and ecological (feeding postures) evolution within the genus Parus.

The relative length of the leg (femur + tibiotarsus + tarsometatarsus lengths) differed significantly among tit species, Blue and Great Tits having shorter legs than Crested and Coal Tits. Significant differences were also found in tarsometatarsus length with Great and Blue Tits having shorter tarsometatarsus than that of Coal and Crested Tits. The insertion of the M. tibialis cranialis onto the cranial surface of the tarsometatarsus is proportionally more distal in the Blue Tit than in the other three Tits.

Our results demonstrate that all tit species studied are able to use hanging and standing postures. However, there exist differences in the "preferred" foraging postures among the four Parus species. The Blue Tit used hanging in a higher proportion than the other three Parus species; the Crested Tit spent the lowest proportion of time hanging. The Blue Tit and the Crested Tit also showed the most contrasting hindlimb morphological designs. The ranking of the four tit species according to hanging frequency is consistent with the predicted order derived from morphofunctional hypotheses (including muscles iliotibialis cranialis, gastrocnemius, fibularis brevis, and tibialis cranialis, relative length of legs, and body mass).

Blue Tit is the species with shortest legs. It has the main flexor muscles of the hip and intratarsal joints (M. iliotibialis cranialis and M. tibialis cranialis respectively) modified in the direction that increases the force of their action (i.e., closing the joints). M. fibularis brevis is also modified to strengthen its action maintaining the tarsometatarsus at its position once it is flexed. Pars interna of M. gastrocnemius, the main extensor of the ankle, is, on the contrary, partially atrophied in the Blue Tit. This morphological pattern fits the mechanical requirements for hanging; i.e., morphological design should tend to counteract the force of gravity (the main force acting upon the bird while hanging) which pulls the body downwards and tends to open the leg joints. Conversely, the Crested Tit has the longest legs. The main extensor muscle of the ankle, M. gastrocnemius, is modified by the addition of extra fibers to its pars interna, increasing ankle extension, as the force exerted by a muscle is related to its number of fibres. Leg flexor muscles are not as well developed as in the Blue Tit (decreased leg flexion power). This hind limb morphology better fits the mechanical requirements for standing; i.e., morphological design should tend to counteract the force of gravity, which, while standing, tend to close the leg joints. It is plausible to hypothesize an unspecialized postural selection as the primitive behavioural character state for Parus.