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
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
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
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
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
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,
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,
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]
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.;
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.;
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.;
Carrascal, L.M.; Seoane,
J.; Palomino, D.; Polo, V. 2008. Explanations for bird species range size: ecological correlates and phylogenetic effects in the
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
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
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
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
De
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
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 (
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
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
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 »
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
Throughout
the evolutionary history there has been a considerable concentration of species
around 10-
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
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,
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
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
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
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;
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
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
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
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.