(ISI Web of Science 10-05-2011)
AU Carrascal, LM
TI Coal tits, Parus ater, lose weight in response to chases by predators
SO ANIMAL BEHAVIOUR (1999) 58:281-285.
AB Theoretical models predict that birds should decrease their body mass in response to increased predation risk because lighter birds take off faster and are more manoeuvrable. We studied the effect of predation risk by chasing coal tits in large outdoor aviaries thus simulating an attempt to capture them. With this increase in predation risk, both perceived and actual, coal tits lost significantly more weight than in a control situation when they were not pursued. This pattern was attributable to a smaller gain in weight only during the day; nocturnal weight did not change in relation to diurnal predation risk. The lower daily weight gain was not consistent with predictions from models of interrupted foraging, but war consistent with predictions from risk adjustment models. Moreover, there was no difference in weight gain over 2-h periods that included a 1-h fast and those in which feeding was ad libitum, suggesting that coal tits could easily regain their body mass after a predator had interrupted their feeding. Our results therefore suggest that pursuit by predators leads to a decrease in the body mass of small birds. (C) 1999 The Association for the Study of Animal Behaviour.
TC 20 citas
AU Polo, V
TI Shaping the body mass distribution of Passeriformes: habitat use and body mass are evolutionarily and ecologically related
SO JOURNAL OF ANIMAL ECOLOGY (1999) 68:324-337.
AB 1. The effect of habitat structure on the distribution of the number
of species by body size classes was analysed for 277 Passeriformes of the
2. The evolutionary history of the group accounted for 68 % of the interspecific variation in body mass (estimated with the phylogenetic autoregressive method). The phylogenetic effect decreased from the most recent taxonomic level towards the earlier phases of evolutionary history. In a more fine-grained study with a subset of 55 passerine species living in central Spain, phylogeny explained significant proportions of the interspecific variation in body mass (62%), habitat use (foraging on the ground vs. foraging in the foliage of scrub/trees; 27%) and structural complexity of preferred habitats (12% ).
3. Throughout the evolutionary history there has been a considerable concentration of species around a body mass of 10-40 g (increase in kurtosis). and species with greater body masses have also appeal-ed (increase in skewness).
4. When the effect of evolutionary history on present-day variation in body mass was removed (specific component of the phylogenetic autoregressive method), the distributions of body masses changed with the structural complexity of preferred, habitats: species from woodland habitats were lighter (mainly because of the large frequency of small-sized species) and their body masses were less concentrated around the modal class than in species from open-country habitats. Results for the phylogenetic component (attributable to the phylogenetic relatedness of the species) were similar to those of the specific component.
5. Habitat use (i.e. the use of foraging substrata) was strongly correlated with body mass in a subset of 55 species living in central Spain: species foraging on the ground were heavier than those foraging in foliage and small branches of scrub/trees. This result was significant with both specific and phylogenetic components. Habitat use and structural complexity of preferred habitats were significantly correlated using both the specific and the phylogenetic components: species that mainly forage on the ground are mainly open-country species, while species that forage in pliable and slender substrata have mainly woodland habitats. Structural complexity of preferred habitats was negatively related to body mass, although this correlation was only significant using phylogenetic residuals (specific component).
6. These results show that the evolutionary history of Western Palearctic Passeriformes has not produced neutral variation in body mass with respect to habitat preferences and habitat use.
TC 21 citas
AU Carrascal, LM
TI Interactions among environmental stress, body condition, nutritional status, and dominance in great tits
SO AUK (1998) 115:727-738.
AB We studied body condition and feather growth rate in Great Tits (Parus major) in relation to dominance in two localities during late autumn and early winter. The two localities differed in elevation, ambient temperature, and arthropod availability. We supplemented the two study areas with food (husked peanuts) throughout the study period. The percentage of time tits spent at feeders was higher at El Ventorrillo (the locality that was colder and had lower natural food availability) and was associated with dominance only at this locality. The number of aggressive displacements per hour experienced by each individual was 150 times higher in the area with lower arthropod availability and lower temperatures. Protein reserves (measured as pectoralis muscle thickness) were higher at El Ventorrillo and were positively and consistently related to dominance at both localities. Growth rate of induced feathers was slower at Fl Ventorrillo but was not directly related to dominance in either locality. Only dominant adult males at El Ventorrillo compensated for the environmental harshness at this locality by attaining a higher feather growth rate than the other sex/age classes. Feather-mass asymmetry of induced feathers during autumn was not associated with body condition, did not change between localities, and was inversely and consistently related to dominance at both localities. The covariation among variables describing bird size, access to supplemental food, body condition, feather growth rate, and asymmetry was different at the two localities. Larger, dominant Great Tits spent more time foraging at feeders, had a thicker pectoralis muscle (i.e. body condition), and grew induced feathers at a higher rate only at the locality with colder temperatures and lower food availability.
TC 45 citas
AU Belliure, J
TI Covariation of thermal biology and foraging mode in two Mediterranean lacertid lizards
SO ECOLOGY (1996) 77:1163-1173.
AB 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). P. algirus mainly inhabits broad-leaved forests, whereas
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 (T-e) for Acanthodactylus, and Mediterranean open forests with
lower T-e for Psammodromus.
Field observations showed that percentage of time spent basking and basking rate (number of basks per minute) were negatively related to T-e, although average bask duration was not. Percentage of time spent moving, moving rate (number of moves per minute), and the average duration of individual moves were inversely related to T-e 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 in a laboratory thermogradient, where P. algirus basked more often and for shorter periods and selected warmer patches than did A. erythrurus. Selected body temperatures (T-b) in a laboratory thermogradient were significantly higher in A. erythrurus than in P. algirus. Shade Seeking T-b was higher in A. erythrurus, but Resume Basking T-b did not differ significantly between the two species. Heating and cooling rates also differed in the two species: A. erythrurus warmed more slowly and cooled faster than did P. algirus.
Our data support the existence of a complex syndrome that combines aspects of the behavior, physiology, and ecology of both species. 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 species (A. erythrurus).
TC 36 citas
AU CARRASCAL, LM
TI MORPHOLOGICAL EVOLUTION AND CHANGES IN FORAGING BEHAVIOR OF ISLAND AND MAINLAND POPULATIONS OF BLUE TIT (PARUS-CAERULEUS) - A TEST OF CONVERGENCE AND ECOMORPHOLOGICAL HYPOTHESES
SO EVOLUTIONARY ECOLOGY (1994) 8:25-35.
AB We study the leg morphology and feeding postures of two subspecies of the Blue Tit (Parus caeruleus; Tenerife island and the Iberian Peninsula) and the Coal Tit (Parus 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 the 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. We determine that the island Blue Tit has a longer tarsometatarsus, larger foot span and a more proximal insertion of the 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 the interspecific level with other taxa, have proved to be of high predictive value for explaining ecological differences considering morphological evolution. The Tenerife Blue Tit and the 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 the island Blue Tit and the mainland Coal Tit can be explained without considering current interspecific competition as a determinant of niche space.
TC 14 citas