Jorge M. Palmeirim

Trophic structure of a neotropical frugivore community: is there competition between birds and bats?

SummaryDietary overlap and competition between frugivorous birds and bats in the Neotropics have been presumed to be low, but comparative data have been lacking. We determined the diets of volant frugivores in an early successional patch of Costa Rican wet forest over a one month period. Ordination of the diet matrix by Reciprocal Averaging revealed that birds and bats tend to feed on different sets of fruits and that diets differed more among bat species than among bird species. However, there was overlap between Scarlet-rumped Tanagers and three Carollia bat species on fruits of several Piper species which comprised most of the diet of these bats. Day/night exclosure experiments on P. friedrichsthalli treetlets provided evidence that birds deplete the amount of ripe fruit available to bats. These results indicate that distantly related taxa may overlap in diet and compete for fruit, despite the apparent adaptation of animal-dispersed plant species for dispersal by particular animal taxa.

The Importance of Distance to Resources in the Spatial Modelling of Bat Foraging Habitat

Many bats are threatened by habitat loss, but opportunities to manage their habitats are now increasing. Success of management depends greatly on the capacity to determine where and how interventions should take place, so models predicting how animals use landscapes are important to plan them. Bats are quite distinctive in the way they use space for foraging because (i) most are colonial central-place foragers and (ii) exploit scattered and distant resources, although this increases flying costs. To evaluate how important distances to resources are in modelling foraging bat habitat suitability, we radio-tracked two cave-dwelling species of conservation concern (Rhinolophus mehelyi and Miniopterus schreibersii) in a Mediterranean landscape. Habitat and distance variables were evaluated using logistic regression modelling. Distance variables greatly increased the performance of models, and distance to roost and to drinking water could alone explain 86 and 73% of the use of space by M. schreibersii and R. mehelyi, respectively. Land-cover and soil productivity also provided a significant contribution to the final models. Habitat suitability maps generated by models with and without distance variables differed substantially, confirming the shortcomings of maps generated without distance variables. Indeed, areas shown as highly suitable in maps generated without distance variables proved poorly suitable when distance variables were also considered. We concluded that distances to resources are determinant in the way bats forage across the landscape, and that using distance variables substantially improves the accuracy of suitability maps generated with spatially explicit models. Consequently, modelling with these variables is important to guide habitat management in bats and similarly mobile animals, particularly if they are central-place foragers or depend on spatially scarce resources.

Mapping Mediterranean scrub with satellite imagery: biomass estimation and spectral behaviour

Millennia of intensive use have led to severe land degradation in the Mediterranean basin, much of which is now under serious risk of desertification. Very large extents are presently covered with scrub dominated by plants of the genus Cistus. The level of soil protection provided by these shrubs is proportional to their biomass, so it is important to be able to quantify this variable. The potential for mapping Cistus scrub biomass using optical satellite imagery was investigated in this study. It was found that the peculiar adaptations of the Cistus to summer drought strongly influence its spectral behaviour, which, during this season, is similar to that of vegetation of arid and semi-arid regions. During the rainy winter this pattern changes and becomes very similar to that of active green vegetation. In summer images, individual Landsat Thematic Mapper (TM) bands, including the near-infrared band, presented negative correlations with biomass. However, in spite of these inverse relationships, the Normalized Difference Vegetation Index (NDVI) had a high positive correlation with biomass, so this variable can be adequately mapped using satellite images. Seventy-four per cent of the biomass values estimated with linear regression models, using the NDVI as predictor, were within 50% of the ground measurements.

Which factors regulate the reproduction of ectoparasites of temperate-zone cave-dwelling bats?

We studied the factors which regulate the reproduction of ectoparasites of temperate-zone cave-dwelling bats, using the Schreiber’s bat (Miniopterus schreibersii) and its ectoparasites as a model. For this, we searched 969 bats during 2003 and 2004 at important stages of the bat yearly cycle and found four ectoparasite species regularly occurring on them: two nycteribiids (Nycteribia schmidlii and Penicillidia conspicua), one wing mite (Spinturnix psi), and one hard tick (Ixodes simplex simplex). These parasites were present throughout the yearly cycle, but their reproductive activity greatly fluctuated seasonally. Also, we found that sex, age, and reproductive status of the host strongly influenced the reproductive activity of parasites. Overall, the four parasite species had a similar reproductive pattern, reproducing more intensively during the pregnancy and nursing seasons of M. schreibersii, mainly on pregnant and juvenile bats. Moreover, parasites greatly reduced reproductive activity during winter, while bats were in deep torpor or hibernating. We conclude that reproduction in ectoparasites of M. schreibersii and of many other temperate cave-dwelling bats is mostly regulated by the reproductive cycle of their bat hosts, but also limited by roost temperatures during winter. The fact that the reproductive cycle of parasite species of such distinct taxonomic groups are similarly adjusted to that of their bat host suggests that this adjustment is a highly adaptive trait.

Automatic Mapping of Avian Species Habitat Using Satellite Imagery

The Thematic Mapper is a remote sensing instrument aboard the most recent Landsat satellites that generates digital imagery of the earth with a ground resolution of 30 m. This imagery was digitally processed to produce a habitat classification in a study area located in NE Kansas, USA. In addition, bird counts were done throughout this study area. The two data bases were then combined and processed to obtain habitat suitability estimates and produce maps reflecting the habitat needs of individual species. This processing considered not only the types of habitat present (e.g., rangeland, mesic forest, xeric forest) but also the spatial characteristics of the habitat of a species (e.g. minimum habitat patch size, distance to edge). Using this approach it was possible to automatically generate distribution, suitability and density maps, and make rough estimates of population size.

Trait-related responses to habitat fragmentation in Amazonian bats

Summary: Understanding how interspecific variation in functional traits influences species’ capacity to persist in fragments and use patches in fragmented landscapes is fundamental for the creation of effective conservation plans. This study uses phylogenetic comparative methods to investigate which functional traits of bat species are correlated with their vulnerability to fragmentation in a tropical landscape with low fragment–matrix contrast. Bats were captured over two years in eight forest fragments, nine control sites in continuous forest, and in the secondary forest matrix at the Biological Dynamics of Forest Fragments Project, Central Amazon, Brazil. We tested the hypothesis that there is a significant relationship between species functional traits, environmental gradients (continuous forest and fragment interiors, edges and matrix) and patterns of species distribution using phylogenetic generalized least squares (PGLS) models, as well as a combination of RLQ and fourth-corner analyses. Mobility, body mass, wing morphology, and trophic level were the most important traits linked to fragmentation sensitivity based on the PGLS analysis, while body mass and trophic level emerged as the best predictors in the fourth-corner analysis. These last two traits were correlated with the loss of continuous forest characteristics, such as high-stature trees and forest cover. Many animalivorous bat species rarely persist in small fragments ( Synthesis and applications. Functional traits of species and environmental variables jointly predict local variation in patterns of bat occupancy and abundance in fragmented tropical landscapes. To minimize local extinctions, we recommend increasing habitat availability and enhancing structural and functional connectivity at the landscape scale through the creation, restoration and maintenance of corridors and stepping stones. These measures should be coupled with improving matrix quality by promoting secondary forest regeneration and persistence to effectively reduce fragment–matrix contrast.

Foraging behaviour and habitat use by the European free-tailed bat Tadarida teniotis

Autumnal foraging behaviour and habitat use by Tadarida teniotis were studied in Southern Portugal, using seventeen radio-marked individuals, followed over multiple nights from fixed and mobile stations. Tadarida teniotis proved to be a late emerger, leaving the roost about one hour after sunset and, in contrast to most insectivorous bat species, only had one foraging bout. These bouts were very long, lasting an average of 6 hours and 39 minutes. Bout duration was unrelated to climatic conditions and so probably determined by foraging success. In the early evening almost all bats were foraging, but this activity declined steadily through the night. They kept flying even during fairly cold nights, but did not leave the roost on the coldest nights, in which they probably remained in torpor. As predicted by its body mass and wing morphology, T. teniotis was found to be a strong flyer, reaching speeds of over 50 km/h, and flying for up to 10 hours without resting periods. The observed speeds were 2.5 times higher than the predicted maximum range speed, which may be possible due to peculiar adaptations to high-speed flight. On most nights bats flew straight to a previously identified feeding site, but on a few they made slower indirect flights, suggesting a search for profitable foraging areas. Upon arriving to a feeding site most bats remained there for the rest of the foraging trip. The median size of these sites was just over 100 ha. Several tracked bats used the same feeding area simultaneously. The range of the colony had a radius of over 30 km, but most feeding sites were concentrated in a mountainous region located about 5 km north of the roost. The studied bats foraged preferentially over forested areas, particularly pine and cork oak woodlands. They used both alluvial plains and the valleys of a mountainous area, but not its ridges. Our observations support the hypothesis that T. teniotis is an opportunistic forager, depending on temporary concentrations of prey, such as insect swarms.

Mitochondrial DNA variation and population structure of the island endemic Azorean bat ( Nyctalus azoreum)

The Azorean bat Nyctalus azoreum is the only endemic mammal native to the remote archipelago of the Azores. It evolved from a continental ancestor related to the Leislers bat Nyctalus leisleri and is considered threatened because of its restricted and highly fragmented distribution. We studied the genetic variability in 159 individuals from 14 colonies sampled throughout the archipelago. Sequences of the D‐loop region revealed moderate but highly structured genetic variability. Half of the 15 distinct haplotypes were restricted to a single island, but the most common was found throughout the archipelago, suggesting a single colonization event followed by limited interisland female gene flow. All N. azoreum haplotypes were closely related and formed a star‐like structure typical of expanded populations. The inferred age of demographic expansions was consistent with the arrival of founder animals during the Holocene, well before the first humans inhabited the Azores. Comparisons with a population of N. leisleri from continental Portugal confirmed not only that all N. azoreum lineages were unique to the archipelago, but also that the current levels of genetic diversity were surprisingly high for an insular species. Our data imply that the Azorean bat has a high conservation value. We argue that geographical patterns of genetic structuring indicate the existence of two management units.

Environmental factors drive habitat partitioning in birds feeding in intertidal flats: implications for conservation

We present data on the low-tide distribution of shorebirds in the Tagus estuary, Portugal, and relate the distribution of the bird assemblage with environmental factors. The study was based on an extensive survey of the majority of the intertidal flats, carried out with a high spatial resolution. The environmental factors that mostly affected the distribution of shorebirds were the exposure period, the type of sediment and the extent of the shell banks. The feeding bird assemblage could be divided into four main groups of species, and these occupied distinct areas of the estuary. These findings imply that maintaining the overall value of the estuaries for foraging shorebirds requires relatively extensive intertidal areas, encompassing sediment flats with the large diversity of ecological characteristics required by different species.

Seasonal patterns of spatial variation in understory bird assemblages across a mosaic of flooded and unflooded Amazonian forests.

We examined seasonal patterns of spatial variation in understory bird assemblages across a mosaic of upland and floodplain forests in central Amazonia, where variation in flooding patterns and floodwater nutrient load shapes a marked spatial heterogeneity in forest structure and composition. Despite great differences in productivity due to flooding by either nutrient-rich “white waters” (várzea) or nutrient-poor “black waters” (igapó), bird assemblages in the two floodplain forest types were relatively similar, showing lower abundances than adjacent upland forests (terra firme) and sharing a set of species that were absent or scarce elsewhere. Species that breed in pensile nests overhanging water were abundant in floodplain forests, whereas species that feed on the ground were generally scarce. Flooding affected assemblage dynamics in floodplain forests, with some influx of ground-dwelling species such as ant-following birds from adjacent upland during the low-water season, and the occupation by riverine and aquatic species such as kingfishers during floods. Spatial configuration influenced the seasonal pattern of assemblage structuring, with movements from terra firme occurring primarily to adjacent igapó forests. No such influx was detected in várzea forests that were farther from terra firme and isolated by wide river channels. Results support the view that habitat heterogeneity created by flooding strongly contributes to maintain diverse vertebrate assemblages in Amazonia forest landscapes, even in the case of largely sedentary species such as understory forest birds. Including both upland and floodplain forests in Amazonia reserves may thus be essential to preserve bird diversity at the landscape scale.