Spatial versus spatio-temporal approaches for studying metacommunities: a multi-taxon analysis in Mediterranean and tropical temporary ponds.

Prior research on metacommunities has largely focused on snapshot surveys, often overlooking temporal dynamics. In this study, our aim was to compare the insights obtained from metacommunity analyses based on a spatial approach repeated over time, with a spatio-temporal approach that consolidates all data into a single model. We empirically assessed the influence of temporal variation in the environment and spatial connectivity on the structure of metacommunities in tropical and Mediterranean temporary ponds. Employing a standardized methodology across both regions, we surveyed multiple freshwater taxa in three time periods within the same hydrological year from multiple temporary ponds in each region. To evaluate how environmental, spatial and temporal influences vary between the two approaches, we used nonlinear variation partitioning analyses based on generalized additive models. Overall, this study underscores the importance of adopting spatio-temporal analytics to better understand the processes shaping metacommunities. While the spatial approach suggested that environmental factors had a greater influence, our spatio-temporal analysis revealed that spatial connectivity was the primary driver influencing metacommunity structure in both regions. Temporal effects were equally important as environmental effects, suggesting a significant role of ecological succession in metacommunity structure.

Host space, not energy or symbiont size, constrains feather mite abundance across passerine bird species.

Comprehending symbiont abundance among host species is a major ecological endeavour, and the metabolic theory of ecology has been proposed to understand what constrains symbiont populations. We parameterized metabolic theory equations to investigate how bird species' body size and the body size of their feather mites relate to mite abundance according to four potential energy (uropygial gland size) and space constraints (wing area, total length of barbs and number of feather barbs). Predictions were compared with the empirical scaling of feather mite abundance across 106 passerine bird species (26,604 individual birds sampled), using phylogenetic modelling and quantile regression. Feather mite abundance was strongly constrained by host space (number of feather barbs) but not by energy. Moreover, feather mite species' body size was unrelated to the body size of their host species. We discuss the implications of our results for our understanding of the bird-feather mite system and for symbiont abundance in general.

Evaluating Different Factors That Affect the Nesting Patterns of European and Algerian Hedgehogs in Urban and Suburban Environments.

Small undisturbed patches in urban environments serve as important refuges for wildlife, e.g., hedgehogs. However, the effects of urbanization on certain biological aspects, like nesting behavior, remain unknown. We captured and tracked the movement of 30 male hedgehogs of two co-existing species: Algerian and European hedgehogs. The study was carried out in Valencia (eastern Spain). We distinguished six macrohabitats and five subhabitats. We analyzed the proportions of the macro and subhabitats where nests were found to calculate a resource selection function and fit GLMs. Hedgehog nests tended to concentrate in areas with little human disturbance and were built in hedges or under bush-like vegetation. We did not find any significant differences between species or other considered groups. We noted that nests were distributed around hard-to-find suitable habitat patches. We even recorded a case of two males from both species simultaneously using one nest. Our results suggest that hedgehog conservation in urban environments can be improved by the correct management of forest patches by conserving bush-like vegetation and improving the connectivity between suitable patches with ecological corridors.

Inconsistent response of taxonomic groups to space and environment in mediterranean and tropical pond metacommunities.

The metacommunity concept provides a theoretical framework that aims at explaining organism distributions by a combination of environmental filtering, dispersal, and drift. However, few works have attempted a multitaxon approach and even fewer have compared two distant biogeographical regions using the same methodology. We tested the expectation that temperate (mediterranean-climate) pond metacommunities would be more influenced by environmental and spatial processes than tropical ones, because of stronger environmental gradients and a greater isolation of waterbodies. However, the pattern should be different among groups of organisms depending on their dispersal abilities. We surveyed 30 tropical and 32 mediterranean temporary ponds from Costa Rica and Spain, respectively, and obtained data on 49 environmental variables. We characterized the biological communities of bacteria and archaea (from the water column and the sediments), phytoplankton, zooplankton, benthic invertebrates, amphibians and birds, and estimated the relative role of space and environment on metacommunity organization for each group and region, by means of variation partitioning using generalized additive models. Purely environmental effects were important in both tropical and mediterranean ponds, but stronger in the latter, probably due to their larger limnological heterogeneity. Spatially correlated environment and pure spatial effects were greater in the tropics, related to higher climatic heterogeneity and dispersal processes (e.g., restriction, surplus) acting at different scales. The variability between taxonomic groups in the contribution of spatial and environmental factors to metacommunity variation was very wide, but higher in active, compared with passive, dispersers. Higher environmental effects were observed in mediterranean passive dispersers, and higher spatial effects in tropical passive dispersers. The unexplained variation was larger in the tropical setting, suggesting a higher role for stochastic processes, unmeasured environmental factors, or biotic interactions in the tropics, although this difference affected some actively dispersing groups (insects and birds) more than passive dispersers. These results, despite our limitations in comparing only two regions, provide support, for a wide variety of aquatic organisms, for the classic view of stronger abiotic niche constraints in temperate areas compared with the tropics. The heterogeneous response of taxonomic groups between regions also points to a stronger influence of regional context than organism adaptations on metacommunity organization.

Bases conceptuales para la compensación ambiental bajo el enfoque ecológico

Introducción: La generación de impactos negativos producto de proyectos de infraestructura o actividades de desarrollo generan pérdida de biodiversidad y reducción de la calidad de los servicios que el ambiente provee a sociedades humanas. Afortunadamente, muchos de esos impactos pueden ser reducidos, controlados o resarcidos por medio de medidas de mitigación, rehabilitación y compensación, que suelen sustentarse en el marco jurídico ambiental de los países o estados donde son implementados. Esta revisión provee una visión teórica del uso de compensación ambiental como instrumento jurídico/técnico integrado al manejo del entorno natural. Metodología: Realizamos una revisión de la literatura global sobre el tema mediante los buscadores de referencias GoogleScholar y SciELO empleando varios indicadores en inglés y español. Resultados: Un total de 244 referencias sobre compensación ambiental fueron encontradas, catalogadas y evaluadas, mostrándose un claro patrón de incremento del número de ellas en la última década. La compensación ambiental constituye un instrumento jurídico/técnico que permite resarcir por pérdidas ambientales y suele ser un componente de los Estudios de Impacto Ambiental regulado por el estado. Varias estrategias metodológicas son empleadas para establecer acciones compensatorias, cada una de ellas sustentada en alguno de cuatro enfoques posibles: económico, ecológico, político y cultural/social. Dentro del enfoque ecológico, se busca la equivalencia ecológica entre los elementos ambientales impactados y la compensación, procurando que no exista pérdida neta. Así, este enfoque tiene la ventaja de posibilitar la incorporación de múltiples criterios para la evaluación del daño y de las acciones de indemnización, por lo que es posible de aplicar en situaciones diversas. A pesar de su uso, la aplicación de medidas compensatorias no está exenta de crítica y hay situaciones en que la singularidad de los elementos impactados imposibilita un resarcimiento efectivo de las pérdidas. Conclusiones: La compensación tiene gran relevancia actualmente en la gestión ambiental y debe favorecer el derecho universal a un ambiente sano. Sin embargo, su aplicación efectiva requiere claridad en los procedimientos seguidos y una muy estrecha vigilancia prevenir pérdidas o incluso una ganancia neta ambiental.

Introduction: Infrastructure projects or development activities often generate a loss of biodiversity and reduce the quality of the environment's services to human societies. Fortunately, many of these impacts can be reduced, controlled, or compensated through mitigation, rehabilitation, and compensation measures, which usually rely on the environmental legal framework of the countries or states where they are implemented. This review provides a theoretical vision of using environmental compensation as a legal/technical instrument integrated into natural environment management. Methodology: We reviewed the global literature on the subject using the GoogleScholar and SciELO reference search engines using various indicators in English and Spanish. Results: We found 244 references on environmental compensation, showing a clear increasing pattern in the last decade. Environmental compensation constitutes a legal/technical instrument that allows offsets for environmental losses and often is part of the Environmental Impact Studies regulated by the state. Several methodological strategies are used to establish compensatory actions, each of them based on one of four possible approaches: economic, ecological, political, and cultural. The ecological equivalence between the impacted environmental elements and compensation is sought within the ecological approach, ensuring no net loss. Thus, this approach allows the incorporation of multiple criteria for the evaluation of damage and compensation actions: it can be applied in different situations. Nevertheless, compensatory measures are not exempt from criticism. There are situations in which the singularity of the impacted elements makes an adequate compensation for losses impossible. Conclusions: Compensation is highly relevant in environmental management and must favor the universal right to a healthy environment. However, its practical application requires clear procedures and close vigilance to prevent losses or even a net environmental gain.

Compensación Ambiental en Costa Rica: Legislación y alcances

Introducción: La compensación ambiental es un instrumento técnico-jurídico de gestión ambiental utilizado para compensar el daño ambiental debido a los impactos irreversibles e inevitables de proyectos de desarrollo. Por lo general, las regulaciones de compensación se incluyen en la legislación ambiental nacional. Este artículo resume la legislación de compensación ambiental en Costa Rica, un país con una reconocida tradición de conservación y conciencia ambiental. Nuestro objetivo es describir cómo se formula la compensación en ese país e identificar posibles vacíos regulatorios. Métodos: Realizamos una revisión sistemática de la legislación ambiental a través del Sistema Costarricense de Información Jurídica (http://www.pgrweb.go.cr/scij/avanzada_pgr.aspx), considerando tanto normativa como pronunciamientos sobre medidas de compensación y mitigación. Resultados: La Constitución Política de Costa Rica reconoce el medio ambiente sano como un derecho fundamental de todos los ciudadanos. Actualmente se encuentran en vigencia al menos siete leyes que tratan de temas ambientales y sus respectivos reglamentos. Esta voluminosa legislación tiene como objetivo proteger los recursos naturales regulando su uso y creando un conjunto de áreas silvestres protegidas. Sin embargo, la legislación es algo repetitiva y abierta a interpretación, lo que facilita la confusión. Las acciones que requieren compensación están reguladas de manera general, lo que dificulta establecer cuándo y cómo aplicarlas. Además, la compensación se considera en función de cuándo se identifica el daño y no debido a su nivel de impacto ambiental. Asimismo, la normativa no hace explícitos los principios y objetivos que sustentan las medidas compensatorias ni cómo deben llevarse a cabo, mencionando brevemente algunas acciones que no aseguran que la pérdida ambiental neta sea cero. Conclusiones: Esta revisión revela la necesidad de estandarizar los mecanismos para determinar las medidas compensatorias a nivel regulatorio, analizando además las estrategias que se seguirán para asegurar la proporcionalidad y la equivalencia ecológica. La legislación debe enfatizar la importancia de la compensación como práctica positiva, la cual debe ser incorporada dentro de los lineamientos del Estudio de Impacto Ambiental.

Introduction: Environmental compensation is a technical-legal instrument of environmental management used to offset damage due to non-reversible and unavoidable impacts. Usually, offset regulations are included in national environmental legislations. This paper summarizes environmental compensation legislation in Costa Rica, a country with a recognized conservation tradition and environmental awareness. Our goal is to describe how compensation is formulated in that country and identify possible regulations gaps. Methods: We carried out a systematic review of environmental legislation through the Costa Rican Legal Information System (http://www.pgrweb.go.cr/scij/avanzada_pgr.aspx), considering both regulations and pronouncements on compensation measures and mitigation. Results: The Political Constitution of Costa Rica recognizes a healthy environment as a fundamental right for all citizens. At least seven laws dealing with environmental issues and their respective regulations are currently enforced. This bulky legislation aims to protect natural resources by regulating their use and creating an assemblage of protected wild areas. However, the legislation is somewhat repetitive and open to interpretation, facilitating confusion. Actions requiring compensation are regulated in a general way, making it difficult to establish when and how to apply them. In addition, compensation is considered based on when the damage is identified and not on its level of environmental impact. Furthermore, the regulations do not make explicit the principles and goals that support the compensatory measures or how they should be carried out, briefly mentioning some actions that do not ensure that the net environmental loss is zero. Conclusions: This review reveals the need to standardize the mechanisms to determine compensatory measures at the regulatory level, also analyzing the strategies that will be followed to ensure proportionality and ecological equivalence. The legislation must emphasize the importance of compensation as a positive practice, which must be incorporated within the guidelines of the Environmental Impact Study.

Uso de la diversidad biológica de grupos indicadores para evaluar la compensación ecológica: el caso del Embalse Río Piedras, Costa Rica

Introducción: Cerca de 113 hectáreas dentro de la Reserva Biológica Lomas de Barbudal (RBLB) se inundarían si se llegara a establecer el embalse de riego Río Piedras en el noroeste de Costa Rica. Ante ese impacto inevitable, la legislación costarricense requiere evaluar la pérdida de diversidad en el sitio y compensarla siguiendo el principio de equivalencia ecológica. Objetivo: Nuestro objetivo fue evaluar la pérdida de diversidad en el sitio y, valorar esta condición en una propiedad privada adyacente considerada como sitio potencial para compensar por esas pérdidas. Metodología: La diversidad, composición y prioridad de conservación de plantas vasculares, fauna vertebrada y artrópodos del sotobosque fueron evaluadas en el sitio de inundación en RBLB y en una propiedad privada adyacente identificada como sitio potencial de compensación. La equivalencia en diversidad entre ambos sitios se valoró mediante un procedimiento que asigna puntajes a los diferentes indicadores del sitio de compensación respecto a los observados en RBLB. La suma de esos puntajes representa la condición de diversidad del sitio de compensación y puede utilizarse como criterio para fundamentar acciones resarcitorias. Resultados: Todos los grupos sustitutos registraron un alto número de especies, aunque la información aportada por las plantas herbáceas, los mamíferos no voladores y los reptiles fue limitada. En contraste, los otros grupos indican una mayor diversidad en el sitio potencial de inundación, atribuida a sutiles diferencias ambientales y a su mejor conservación. En consecuencia, se valoró sustituir el área afectada por un área mayor del sitio de compensación para resarcir las perdidas en diversidad estimadas. Conclusión: Nuestro análisis muestra que grupos sustitutos pueden ser empleados en estudios ambientales a corto plazo. Sin embargo, los grupos a utilizar deben seleccionarse cuidadosamente, considerando los objetivos y el alcance del proyecto. Cuantificar la condición de diversidad del sitio de compensación respecto a la que se encuentra en un sitio de referencia parece ser un procedimiento válido, repetible y evaluable que permite establecer criterios sobre los cuales basar medidas resarcitorias.

Introduction: About 113 hectares within the Lomas de Barbudal Biological Reserve (RBLB) would be flooded if the Río Piedras irrigation reservoir were established in northwestern Costa Rica. Given this inevitable impact, Costa Rican legislation requires evaluating the loss of diversity in the site and compensating for it following the principle of ecological equivalence. Objetive: Our goal was to assess the loss of diversity at that site and evaluate the condition of an adjacent private property as a potential site to compensate for those losses. Methodology: The diversity, composition, and conservation priority of vascular plants, vertebrate fauna, and understory arthropods were assessed at the RBLB flood site and on an adjacent private property identified as a potential offset site. The equivalence in diversity between both sites was evaluated by assigning scores to the different indicators at the compensation site concerning those observed in RBLB. The sum of these scores represents the diversity condition of the compensation site and can be used as a criterion to support compensatory actions. Results: All surrogate groups recorded a high number of species, although the information provided by herbaceous plants, non-flying mammals, and reptiles was limited. In contrast, the other groups indicate a greater diversity in the potential flood site, attributed to subtle environmental differences and the better conservation at this site. Consequently, it was assessed to replace the affected area with a larger offset site area to compensate for the estimated losses in diversity. Conclusion: Our analysis shows that surrogate groups can be used in short-term environmental studies. However, the groups to be used must be carefully selected, considering the objectives and scope of the project. Quantifying the diversity condition of the compensation site concerning that found in a reference site seems to be a valid, repeatable, and evaluable procedure that allows establishing criteria on which to base compensatory measures.

Patterns of adult tick parasitization of coexisting European (Erinaceus europaeus) and Algerian (Atelerix algirus) hedgehog populations in eastern Iberia.

The availability of data regarding population abundance and dynamics of ticks in wild vertebrate populations is crucial to understand the host-tick relationship and to assess the risk for domestic animals and humans from possible zoonotic diseases. In this study we analyse several host-intrinsic and environmental factors affecting the tick population of two sympatric hedgehog species (the European and the Algerian hedgehog) in two differently anthropized habitats in eastern Spain. We captured 215 hedgehogs and sampled 356 adult ticks of four different species (Rhipicephalus sanguineus, R. turanicus, R. bursa and R. pusillus). We analysed by General Linear Mixed Models how the hosts' species, sex, capture month and site and their interactions affected tick presence and tick load. Further, we carried out Spearman correlation tests to analyse how environmental temperature and precipitation affect tick presence and load on hedgehogs. We found that, in general, male hedgehogs were more infested than females. However, the effects of the different factors depended on the tick species, especially related to their endophilic or exophilic character. High values of general tick infestation can be explained by the coincidence of tick activity peaks and higher male host activity levels, especially within areas with higher habitat diversity and species richness. We also discuss how the potential immunosuppressive effect of testosterone could be affecting our results. Our results show that in highly anthropized environments hedgehogs potentially act as important mixing vessels for tick-borne zoonotic pathogens and that monitoring ticks in periurban wildlife is important to assess potential health risks for pets and humans.

Prevalence of Infection of Canine Distemper Virus, Feline Immunodeficiency Virus, and Feline Leukemia Virus in Wild Ecuadorian Ocelots; Efficacy of Their Diagnosis, and Recovery from Infection.

This retrospective study provides an analysis of the prevalence and detectability of canine distemper virus (CDV), feline leukemia virus (FeLV), and feline immunodeficiency virus (FIV) in ocelots (Leopardus pardalis) sheltered in a wild animal recovery center in Guayaquil, Ecuador. Blood samples of 19 rescued ocelots from 2019-20 were analyzed using FeLV p27 antigen enzyme-linked immunosorbent assays (ELISA) and commercial insulated isothermal reverse transcriptase PCR (iiRT-PCR) kits. Using this PCR we detected positive results for CDV (4/ 17; 23.5%) and FeLV (14/16; 87.5%), but not for FIV (0/8). Three previously positive cases of CDV and two of FeLV showed negative results on retesting 6 mo later. Moreover, a third analysis was conducted and was negative for CDV. Our results suggest that ocelots can recover from the local CDV and FeLV strains. An ELISA for the FeLV p27 antigen showed no capability to detect FeLV in ocelots that were confirmed positive by iiRT-PCR. Regional lineages, viral virulence, and host immune response capabilities should be addressed in further research to inform management and decision making for wildlife conservation.

Within-season movements of Alpine songbird distributions are driven by fine-scale environmental characteristics.

Information about distribution and habitat use of organisms is crucial for conservation. Bird distribution within the breeding season has been usually considered static, but this assumption has been questioned. Within-season movements may allow birds to track changes in habitat quality or to adjust site choice between subsequent breeding attempts. Such movements are especially likely in temperate mountains, given the substantial environmental heterogeneity and changes occurring during bird breeding season. We investigated the within-season movements of breeding songbirds in the European Alps in spring-summer 2018, using repeated point counts and dynamic occupancy models. For all the four species for which we obtained sufficient data, changes in occupancy during the season strongly indicated the occurrence of within-season movements. Species occupancy changed during the season according to fine-scale vegetation/land-cover types, while microclimate (mean temperature) affected initial occupancy in two species. The overall occupancy rate increased throughout the season, suggesting the settlement of new individuals coming from outside the area. A static distribution cannot be assumed during the breeding season for songbirds breeding in temperate mountains. This needs to be considered when planning monitoring and conservation of Alpine birds, as within-season movements may affect the proportion of population/distribution interested by monitoring or conservation programs.

Weak effects of geolocators on small birds: A meta-analysis controlled for phylogeny and publication bias.

Currently, the deployment of tracking devices is one of the most frequently used approaches to study movement ecology of birds. Recent miniaturization of light-level geolocators enabled studying small bird species whose migratory patterns were widely unknown. However, geolocators may reduce vital rates in tagged birds and may bias obtained movement data. There is a need for a thorough assessment of the potential tag effects on small birds, as previous meta-analyses did not evaluate unpublished data and impact of multiple life-history traits, focused mainly on large species and the number of published studies tagging small birds has increased substantially. We quantitatively reviewed 549 records extracted from 74 published and 48 unpublished studies on over 7,800 tagged and 17,800 control individuals to examine the effects of geolocator tagging on small bird species (body mass <100 g). We calculated the effect of tagging on apparent survival, condition, phenology and breeding performance and identified the most important predictors of the magnitude of effect sizes. Even though the effects were not statistically significant in phylogenetically controlled models, we found a weak negative impact of geolocators on apparent survival. The negative effect on apparent survival was stronger with increasing relative load of the device and with geolocators attached using elastic harnesses. Moreover, tagging effects were stronger in smaller species. In conclusion, we found a weak effect on apparent survival of tagged birds and managed to pinpoint key aspects and drivers of tagging effects. We provide recommendations for establishing matched control group for proper effect size assessment in future studies and outline various aspects of tagging that need further investigation. Finally, our results encourage further use of geolocators on small bird species but the ethical aspects and scientific benefits should always be considered.

Hydrology Affects Environmental and Spatial Structuring of Microalgal Metacommunities in Tropical Pacific Coast Wetlands.

The alternating climate between wet and dry periods has important effects on the hydrology and therefore on niche-based processes of water bodies in tropical areas. Additionally, assemblages of microorganism can show spatial patterns, in the form of a distance decay relationship due to their size or life form. We aimed to test spatial and environmental effects, modulated by a seasonal flooding climatic pattern, on the distribution of microalgae in 30 wetlands of a tropical dry forest region: the Pacific coast of Costa Rica and Nicaragua. Three surveys were conducted corresponding to the beginning, the highest peak, and the end of the hydrological year during the wet season, and species abundance and composition of planktonic and benthic microalgae was determined. Variation partitioning analysis (as explained by spatial distance or environmental factors) was applied to each seasonal dataset by means of partial redundancy analysis. Our results show that microalgal assemblages were structured by spatial and environmental factors depending on the hydrological period of the year. At the onset of hydroperiod and during flooding, neutral effects dominated community dynamics, but niche-based local effects resulted in more structured algal communities at the final periods of desiccating water bodies. Results suggest that climate-mediated effects on hydrology can influence the relative role of spatial and environmental factors on metacommunities of microalgae. Such variability needs to be accounted in order to describe accurately community dynamics in tropical coastal wetlands.

Repeatability of feather mite prevalence and intensity in passerine birds.

Understanding why host species differ so much in symbiont loads and how this depends on ecological host and symbiont traits is a major issue in the ecology of symbiosis. A first step in this inquiry is to know whether observed differences among host species are species-specific traits or more related with host-symbiont environmental conditions. Here we analysed the repeatability (R) of the intensity and the prevalence of feather mites to partition within- and among-host species variance components. We compiled the largest dataset so far available: 119 Paleartic passerine bird species, 75,944 individual birds, ca. 1.8 million mites, seven countries, 23 study years. Several analyses and approaches were made to estimate R and adjusted repeatability (R(adj)) after controlling for potential confounding factors (breeding period, weather, habitat, spatial autocorrelation and researcher identity). The prevalence of feather mites was moderately repeatable (R = 0.26-0.53; R(adj) = 0.32-0.57); smaller values were found for intensity (R = 0.19-0.30; R(adj )= 0.18-0.30). These moderate repeatabilities show that prevalence and intensity of feather mites differ among species, but also that the high variation within species leads to considerable overlap among bird species. Differences in the prevalence and intensity of feather mites within bird species were small among habitats, suggesting that local factors are playing a secondary role. However, effects of local climatic conditions were partially observed for intensity.

Phenotypic divergence among west European populations of Reed Bunting Emberiza schoeniclus: the effects of migratory and foraging behaviours.

Divergent selection and local adaptation are responsible for many phenotypic differences between populations, potentially leading to speciation through the evolution of reproductive barriers. Here we evaluated the morphometric divergence among west European populations of Reed Bunting in order to determine the extent of local adaptation relative to two important selection pressures often associated with speciation in birds: migration and diet. We show that, as expected by theory, migratory E. s. schoeniclus had longer and more pointed wings and a slightly smaller body mass than the resident subspecies, with the exception of E. s. lusitanica, which despite having rounder wings was the smallest of all subspecies. Tail length, however, did not vary according to the expectation (shorter tails in migrants) probably because it is strongly correlated with wing length and might take longer to evolve. E. s. witherbyi, which feed on insects hiding inside reed stems during the winter, had a very thick, stubby bill. In contrast, northern populations, which feed on seeds, had thinner bills. Despite being much smaller, the southern E. s. lusitanica had a significantly thicker, longer bill than migratory E. s. schoeniclus, whereas birds from the UK population had significantly shorter, thinner bills. Geometric morphometric analyses revealed that the southern subspecies have a more convex culmen than E. s. schoeniclus, and E. s. lusitanica differs from the nominate subspecies in bill shape to a greater extent than in linear bill measurements, especially in males. Birds with a more convex culmen are thought to exert a greater strength at the bill tip, which is in agreement with their feeding technique. Overall, the three subspecies occurring in Western Europe differ in a variety of traits following the patterns predicted from their migratory and foraging behaviours, strongly suggesting that these birds have became locally adapted through natural selection.

[The Raffia-swamps as sources or sinks of avifauna: a first approach to the problem]. / Los yolillales como fuentes o sumideros de ornitofauna: una primera aproximación al problema.

In the Tortuguero region, northeastern Costa Rica, tropical forests are home to over 300 species of birds. Within this ecosystem, wetlands dominated by the raffia palm Raphia taedigera and the royal palm Manicaria saccifera extend in large monospecific swamps locally known as yolillales. These wetlands are characterized by low plant diversity, simple structure, waterlogged soils, and extended hydroperiod. There is hardly any information on the bird communities that inhabit or uses yolillales. We describe this omitofauna, comparing the species that inhabit the palm-swams and in the adjacent forest in terms of species richness and diversity. During October-November 2008, we used transects and hearing stations in both habitats in four locations in the region. We located a total of 11 bird species in the palm-swamps and 31 in the adjacent forests. Our observations suggest that palm-swamps have lower species richness than adjacent forests and that these environments also differ in species composition. Despite their low diversity, yolillales are employed by species with different degrees of vulnerability, so that they may be important for bird conservation in the region. Sampling in yolillales is very hard, so our data should be considered preliminary. Further efforts in these environments are needed to improve our knowledge on the bird community that uses them.

Phylogeography of a habitat specialist with high dispersal capability: the Savi's Warbler Locustella luscinioides.

In order to describe the influence of Pleistocene glaciations on the genetic structure and demography of a highly mobile, but specialized, passerine, the Savi's Warbler (Locustella luscinioides), mitochondrial DNA sequences (ND2) and microsatellites were analysed in c.330 individuals of 17 breeding and two wintering populations. Phylogenetic, population genetics and coalescent methods were used to describe the genetic structure, determine the timing of the major splits and model the demography of populations. Savi's Warblers split from its sister species c.8 million years ago and have two major haplotype groups that diverged in the early/middle Pleistocene. One of these clades originated in the Balkans and is currently widespread, showing strong evidence for population expansion; whereas the other is restricted to Iberia and remained stable. Microsatellites agreed with a genetic break around the Pyrenees, but showed considerable introgression and a weaker genetic structure. Both genetic markers showed an isolation-by-distance pattern associated with the population expansion of the eastern clade. Breeding populations seem to be segregated at the wintering sites, but results on migratory connectivity are preliminary. Savi's Warbler is the only known migratory bird species in which Iberian birds did not expand beyond the Pyrenees after the last glaciation. Despite the long period of independent evolution of western and eastern populations, complete introgression occurred when these groups met in Iberia. Mitochondrial sequences indicated the existence of refugia-within-refugia in the Iberian Peninsula during the last glacial period, which is surprising given the high dispersal capacity of this species. Plumage differences of eastern subspecies seemed to have evolved recently through natural selection, in agreement with the glacial expansion hypothesis. This study supports the great importance of the Iberian Peninsula and its role for the conservation of genetic variation.

Different scales of spatial segregation of two species of feather mites on the wings of a passerine bird.

The "condition-specific competition hypothesis" proposes that coexistence of 2 species is possible when spatial or temporal variations in environmental conditions exist and each species responds differently to those conditions. The distribution of different species of feather mites on their hosts is known to be affected by intrinsic host factors such as structure of feathers and friction among feathers during flight, but there is also evidence that external factors such as humidity and temperature can affect mite distribution. Some feather mites have the capacity to move through the plumage rather rapidly, and within-host variation in intensity of sunlight could be one of the cues involved in these active displacements. We analyzed both the within- and between-feather spatial distribution of 2 mite species, Trouessartia bifurcata and Dolichodectes edwardsi , that coexist in flight feathers of the moustached warbler Acrocephalus melanopogon. A complex spatial segregation between the 2 species was observed at 3 spatial levels, i.e., "feather surfaces," "between feathers," and "within feathers." Despite certain overlapping distribution among feathers, T. bifurcata dominated proximal and medial regions on dorsal faces, while D. edwardsi preferred disto-ventral feather areas. An experiment to check the behavioral response of T. bifurcata to sunlight showed that mites responded to light exposure by approaching the feather bases and even leaving its dorsal face. Spatial heterogeneity across the 3 analyzed levels, together with response to light and other particular species adaptations, may have played a role in the coexistence and segregation of feather mites competing for space and food in passerine birds.

Breeding success of a colony of Boat-billed Herons Cochlearius cochlearius (Ciconiiformes: Ardeidae) in pasturelands of Costa Rica

The breeding success of a double-brooding colony of Boat-billed Herons Cochlearius cochlearius was studied in pasturelands of Costa Rica. Mean clutch size in the first clutches (2.9 eggs/nest) was higher than in second and repeat clutches (2.3 eggs/nest). Breeding success was similar in the first attempt and second attempts (20.7% and 21.7%, respectively). In both attempts earlier nests enjoyed a higher breeding success. Starvation of the youngest chicks within the nest and destruction of nests by bad weather conditions were the main factors related to nestling death. No effects of human activity on the reproduction of the breeding colony were observed.

Estudiamos el éxito reproductivo de una colonia del ave Cochlearius cochlearius en una zona ganadera de Costa Rica. El promedio de huevos por nido fue mayor durante el periodo de primeras puestas (2.9 huevos/nido) que durante el periodo de segundas puestas y reposiciones (2.3 huevos/nido). El éxito reproductor de los dos periodos fue similar (20.7 % y 21.7 %, respectivamente). En ambos tuvieron más éxito las parejas que comenzaron la puesta antes. Las principales causas de mortandad fueron inanición de los pollos más jóvenes del nido y la destrucción de los nidos debido a condiciones climáticas adversas. No notamos efectos adversos por la actividad humana.