Precipitation explains Wood Thrush (Hylocichla mustelina) occupancy patterns in Northern Costa Rica / Patrones de ocurrencia del Zorzal del Bosque (Hylocichla mustelina) explicados por la precipitación en el Norte de Costa Rica

Abstract Introduction: The Wood Thrush is a migratory bird that has experienced dramatic declines in its populations in recent decades. This species overwinters in forest fragments with intermediate levels of habitat modification in Central America. However, more studies detailing the use of remnant forests through time are needed to elucidate the threats this species faces in the wintering grounds. Objective: To understand the effects of environmental and forest structure variables on the occupancy of Wood Thrush in Northern Costa Rica. Methods: The study area was the Área de Conservación Guanacaste (ACG), located in Northern Costa Rica, in December 2016, and during the 2018-2019 migration season. We estimated Wood Thrush occupancy and detection probability in four locations of ACG (dry forest, cloud forest, and two locations in the wet forest) using single-season occupancy models. We also estimated Wood Thrush occupancy and probability of persistence in different months in three vegetation types (open area, secondary forest, and old-growth forest) in the wet forest of ACG using a multi-season occupancy model approach. Results: Wood Thrush occupancy was best described by precipitation in the four locations of the ACG; the probability of occupancy increased with precipitation. The average occupancy of Wood Thrushes varied with vegetation type: open area with shrubs and forest edge (0.69 ± 0.09), secondary forest (0.46 ± 0.1), and old-growth forest (0.61 ± 0.1). Wood Thrush probability of persistence responded partially to changes in precipitation, with an unexpected increase in persistence when the rainfall continued decreasing in the season. Conclusion: Wood Thrush occupancy was best predicted by changes in precipitation considering a larger spatial scale. Its probability of persistence partially varied with precipitation. An increase in persistence closer to Spring migration might be explained by the start of the breeding season of resident birds, potentially reducing territorial conflicts and conserving energy before migration. The long-term protection of wet forests in Northern Costa Rica is of paramount importance for the conservation of Wood Thrushes in their wintering grounds.

Resumen Introducción: El Zorzal del Bosque es un ave migratoria que ha experimentado caídas dramáticas en sus poblaciones en las últimas décadas. Esta especie pasa el invierno en fragmentos de bosque con niveles intermedios de modificación de hábitat en Centroamérica. Sin embargo, se necesitan más estudios que detallen el uso de los bosques remanentes a lo largo del tiempo para dilucidar las amenazas que enfrenta esta especie en las zonas de invernada. Objetivo: Comprender los efectos de variables ambientales y de estructura del bosque en la ocurrencia del Zorzal del Bosque en el Norte de Costa Rica. Métodos: El área de estudio fue el Área de Conservación Guanacaste (ACG), ubicada en el Norte de Costa Rica, en diciembre de 2016, y en la temporada migratoria 2018-2019. Estimamos la ocurrencia y la probabilidad de detección del Zorzal del Bosque en cuatro ubicaciones de ACG (bosque seco, bosque nuboso y dos ubicaciones en el bosque húmedo) utilizando modelos de ocurrencia de una sola temporada. También estimamos la ocurrencia del Zorzal del Bosque y la probabilidad de persistencia en diferentes meses en tres tipos de vegetación (área abierta, bosque secundario y bosque primario) en el bosque húmedo de ACG utilizando un enfoque de modelo de ocurrencia multi-estacional. Resultados: La ocurrencia del Zorzal del Bosque estuvo mejor descrita por la precipitación en las cuatro localidades del ACG; la probabilidad de ocurrencia aumentó con las precipitaciones. La ocurrencia media de zorzales varió con el tipo de vegetación: área abierta con arbustos y borde de bosque (0.69 ± 0.09), bosque secundario (0.46 ± 0.1) y bosque primario (0.61 ± 0.1). La probabilidad de persistencia del zorzal respondió parcialmente a cambios en la precipitación, con un aumento inesperado en la persistencia cuando las precipitaciones continuaron disminuyendo en la temporada. Conclusión: La ocurrecia del Zorzal del Bosque varió con la precipitación considerando una escala espacial mayor. Su probabilidad de persistencia varió parcialmente con la precipitación. Un aumento en la persistencia más cerca de la migración de primavera podría explicarse por el inicio de la temporada de reproducción de las aves residentes, lo que podría reducir los conflictos territoriales y conservar energía antes de la migración. La protección a largo plazo de los bosques húmedos en el norte de Costa Rica es de suma importancia para la conservación de los Zorzales del Bosque en sus zonas de invernada.

Developing Oak Buds Produce Volatile Emissions in Response to Herbivory by Freshly Hatched Caterpillars.

Plant responses to damage by insectivorous herbivores are well-documented in mature leaves. The resulting herbivore-induced plant volatiles (HIPVs) protect the plant by attracting carnivorous arthropods and even some insectivorous vertebrates, to parasitize or consume the plant invaders. However, very little is known about plant production of HIPVs in developing buds, particularly when herbivorous insects are too small to be considered a prey item. It is additionally unclear whether plants respond differently to generalist and specialist chewing insects that overlap in distribution. Therefore, we compared HIPV production of Downy oak (Quercus pubescens Willd.) buds infested with freshly hatched caterpillars of Tortrix viridana (specialist) and Operophtera brumata (generalist), against uninfested buds. Of the compounds identified in both years of the experiment, we found that (Z)-hex-3-enyl acetate, (E)-ß-ocimene, acetophenone, linalool, (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT), methyl salicylate, α-copaene, α-humulene, (E)-caryophyllene, and (E,E)-α-farnesene appeared to be higher in infested buds compared to controls. We found no difference in HIPV production between the specialist and the generalist herbivores. Production of HIPVs was also associated with leaf damage, with higher HIPV production in more severely attacked buds. Thus, our study shows that oak trees already start responding to insect herbivory before leaves are developed, by producing compounds similar to those found in damaged mature leaves. Future work should focus on how Downy oak may benefit from initiating alarm cues at a time when carnivorous arthropods and insectivorous vertebrates are unable to use herbivorous insects as host or food.

Effect of feathers on drag in plunge-diving birds.

This study explores the impact of feathers on the hydrodynamic drag experienced by diving birds, which is critical to their foraging efficiency and survival. Employing a novel experimental approach, we analyzed the kinematics of both feathered and nonfeathered projectiles during their transition from air to water using high-speed imaging and an onboard accelerometer. The drag coefficients were determined through two methods: a direct calculation from the acceleration data and a theoretical approach fitted to the observed velocity profiles. Our results indicate that feathers significantly increase the drag force during water entry, with feathered projectiles exhibiting approximately double the drag coefficient of their smooth counterparts. These findings provide new insights into the role of avian feather morphology in diving mechanics and have potential implications for the design of bioinspired aquatic vehicles in engineering. The study also discusses the biological implications of increased drag due to feathers and suggests that factors such as body shape might play a more critical role in the diving capabilities of birds than previously understood.

Causes of admissions and mortality in patients of a wildlife rehabilitation centre in Bulgaria.

Wildlife rescue centres are specialised units with ecological, conservational and veterinary medical activities, which include treatment, rehabilitation, breeding and releasing rare and endangered wild animals into their natural habitat, as well as environmental education. These centres provide an opportunity to monitor ongoing ecological changes in wildlife, environmental pollution and emerging diseases. With the present study, we aimed to analyse the causes and conservation status of the largest wildlife rehabilitation centre in Bulgaria. A total of 18,720 patients, from 26 orders with various conservation statuses and different etiology, have been admitted to the rehabilitation centre for over 25 years. The summarised results showed that 40% of the patients were admitted with an unknown etiology and the proportion of anthropogenic causes was 18%. Natural factors related to incidents with wild animals were 32%, while a share of 10% of the wildlife which resided at the WRBC referred to a part of re-introduction programmes. This type of analysis of wildlife rehabilitation centres could provide useful information about the status of populations and ecosystems, as well as support conservation practices.

Strong and consistent effects of waterbird composition on HPAI H5 occurrences across Europe.

Since 2014, highly pathogenic avian influenza (HPAI) H5 viruses of clade 2.3.4.4 have been dominating the outbreaks across Europe, causing massive deaths among poultry and wild birds. However, the factors shaping these broad-scale outbreak patterns, especially those related to waterbird community composition, remain unclear. In particular, we do not know whether these risk factors differ from those of other H5 clades. Addressing this knowledge gap is important for predicting and preventing future HPAI outbreaks. Using extensive waterbird survey datasets from about 6883 sites, we here explored the effect of waterbird community composition on HPAI H5Nx (clade 2.3.4.4) spatial patterns in the 2016/2017 and 2020/2021 epidemics in Europe, and compared it with the 2005/2006 HPAI H5N1 (clade 2.2) epidemic. We showed that HPAI H5 occurrences in wild birds in the three epidemics were strongly associated with very similar waterbird community attributes, which suggested that, in nature, similar interspecific transmission processes operate between the HPAI H5 subtypes or clades. Importantly, community phylogenetic diversity consistently showed a negative association with H5 occurrence in all three epidemics, suggesting a dilution effect of phylogenetic diversity. In contrast, waterbird community variables showed much weaker associations with HPAI H5Nx occurrence in poultry. Our results demonstrate that models based on previous epidemics can predict future HPAI H5 patterns in wild birds, implying that it is important to include waterbird community factors in future HPAI studies to predict outbreaks and improve surveillance activities.

Who cares? Elucidating parental care evolution in extant birds.

Extant birds stand out among vertebrates in the diversity of parental care types they present, spanning absence of care to uniparental care by either sex, biparental or even cooperative care. Despite years of research, key questions remain regarding parental care evolution in birds. Firstly, the parental care type in the most recent ancestor of extant birds is a matter of controversy, with proposed ancestral states including no care, uniparental male or female care, and biparental care. Another unsolved question is the direction, order, and frequency of transitions between parental care types. We address these key questions using a database of 5,438 bird species (~50% of extant diversity) and modern phylogenetic comparative methods controlling simultaneously for model and phylogenetic uncertainty as well as potential confounding effects of state-dependent diversification. Our results indicate that the most likely ancestral state for extant birds is male-only care, with a posterior probability of 0.8. Transition rates across parental care types were generally low and heterogenous; loss of parental care virtually never occurs and transitions away from female only or cooperative care most often lead to biparental care. Given the low transition rates, future research should analyze the factors favoring the maintenance of care types.

Evolutionary variation in gene conversion at the avian MHC is explained by fluctuating selection, gene copy numbers and life history.

The major histocompatibility complex (MHC) multigene family encodes key pathogen-recognition molecules of the vertebrate adaptive immune system. Hyper-polymorphism of MHC genes is de novo generated by point mutations, but new haplotypes may also arise by re-shuffling of existing variation through intra- and inter-locus gene conversion. Although the occurrence of gene conversion at the MHC has been known for decades, we still have limited understanding of its functional importance. Here, I took advantage of extensive genetic resources (~9000 sequences) to investigate broad scale macroevolutionary patterns in gene conversion processes at the MHC across nearly 200 avian species. Gene conversion was found to constitute a universal mechanism in birds, as 83% of species showed footprints of gene conversion at either MHC class and 25% of all allelic variants were attributed to gene conversion. Gene conversion processes were stronger at MHC-II than MHC-I, but inter-specific variation at both MHC classes was explained by similar evolutionary scenarios, reflecting fluctuating selection towards different optima and drift. Gene conversion showed uneven phylogenetic distribution across birds and was driven by gene copy number variation, supporting significant role of inter-locus gene conversion processes in the evolution of the avian MHC. Finally, MHC gene conversion was stronger in species with fast life histories (high fecundity) and in long-distance migrants, likely reflecting variation in population sizes and host-pathogen coevolutionary dynamics. The results provide a robust comparative framework for understanding macroevolutionary variation in gene conversion at the avian MHC and reinforce important contribution of this mechanism to functional MHC diversity.

Movement of juvenile migratory birds from settlement to adulthood across the non-breeding range.

Among migratory vertebrates, high levels of fidelity to non-breeding sites during adulthood are common. If occupied sites vary in quality, strong site fidelity can have profound consequences for individual fitness and population demography. Given the prevalence of adult site fidelity, the regions of the non-breeding range to which juveniles first migrate, and the scale of any subsequent movements, are likely to be pivotal in shaping distributions and demographic processes across population ranges. However, inherent difficulties in tracking migratory individuals through early life mean that opportunities to quantify juvenile settlement and movements across non-breeding ranges, and the mechanisms involved, are extremely rare. Through long-term, range-wide resightings of hundreds of colour-marked individuals from their first migration to adulthood and the application of state-space models, we quantify levels of juvenile and adult regional-scale movements and distances at different life stages across the whole non-breeding distribution range in a migratory shorebird, the Black-tailed Godwit (Limosa limosa islandica). We show that the probability of individuals changing non-breeding regions (seven historical wintering regions spanning the Western Europe range) at all ages is very low (mean movement probability = 10.9% from first to subsequent winter, and 8.3% from first adult winter to later winters). Movement between regions was also low between autumn and winter of the same year for both juveniles (mean movement probability = 17.0%) and adults (10.4%). The great majority of non-breeding movements from the first autumn to adulthood were within regions and less than 100 km. The scarcity of regional-scale non-breeding movements from the first autumn to adulthood means that the factors influencing where juveniles settle will be key determinants of non-breeding distributions and of the rate and direction of changes in distributions.

Oxidative stress across multiple tissues in house sparrows (Passer domesticus) acclimated to warm, stable cold, and unpredictable cold thermal treatments.

With climate change increasing not just mean temperatures but the frequency of cold snaps and heat waves, animals occupying thermally variable areas may be faced with thermal conditions for which they are not prepared. Studies of physiological adaptations of temperate resident birds to such thermal variability are largely lacking in the literature. To address this gap, we acclimated winter-phenotype house sparrows (Passer domesticus) to stable warm, stable cold, and fluctuating cold temperatures. We then measured several metrics of the oxidative stress (OS) system, including enzymatic and non-enzymatic antioxidants and lipid oxidative damage, in brain (post-mitotic), kidney (mitotic), liver (mitotic) and pectoralis muscle (post-mitotic). We predicted that high metabolic flexibility could be linked to increases in reactive oxygen damage. Alternatively, if variation in ROS production is not associated with metabolic flexibility, then we predict no antioxidant compensation with thermal variation. Our data suggest that ROS production is not associated with metabolic flexibility, as we found no differences across thermal treatment groups. However, we did find differences across tissues. Brain catalase activity demonstrated the lowest values compared with kidney, liver and muscle. In contrast, brain glutathione peroxidase (GPx) activities were higher than those in kidney and liver. Muscle GPx activities were intermediate to brain and kidney/liver. Lipid peroxidation damage was lowest in the kidney and highest in muscle tissue.

Trophic plasticity of a tropical seabird revealed through DNA metabarcoding and stable isotope analyses.

DNA metabarcoding and stable isotope analysis have significantly advanced our understanding of marine trophic ecology, aiding systematic research on foraging habits and species conservation. In this study, we employed these methods to analyse faecal and blood samples, respectively, to compare the trophic ecology of two Red-billed Tropicbird (Phaethonaethereus; Linnaeus, 1758) colonies on Mexican islands in the Pacific. Trophic patterns among different breeding stages were also examined at both colonies. Dietary analysis reveals a preference for epipelagic fish, cephalopods, and small crustaceans, with variations between colonies and breeding stages. Isotopic values (δ15N and δ13C) align with DNA metabarcoding results, with wider niches during incubation stages. Differences in diet are linked to environmental conditions and trophic plasticity among breeding stages, influenced by changing physiological requirements and prey availability. Variations in dietary profiles reflect contrasting environmental conditions affecting local prey availability.

Pharmaceuticals in avian scavengers and other birds of prey: A toxicological perspective to improve risk assessments.

Pharmaceuticals are emerging contaminants given their increasing use worldwide due to intensive food production and population growth. These compounds reach the environment through different pathways with potential negative consequences for wildlife. One dramatic example occurred in Asia, where three native vulture populations collapsed almost to extinction due to acute intoxication with diclofenac, a veterinary use non-steroidal anti-inflammatory drug (NSAID). As seen with diclofenac, avian scavengers are useful sentinels to monitor for the presence of pharmaceuticals in the environment given their position at the top of the trophic chain, and in the case of obligate avian scavengers (vultures), their intimate link to domestic animal carcasses. Unfortunately, little is known about the wider exposure and potential health and population risks of pharmaceuticals to birds of prey. Here we compile literature data regarding relevant toxicological aspects of the most important pharmaceutical groups for birds of prey in terms of toxicity: NSAIDs, antibiotics, external antiparasitics and barbiturates. This work also includes critical information for future risk assessments, including concentrations of drug residues that can remain in animal tissues after treatment, or specific pharmaceutical features that might influence their toxicity in avian scavengers and other birds of prey. We also consider future research needs in this field and provide management recommendations to prevent potential intoxication events with pharmaceuticals in these species. This review highlights the need to consider specific risk assessments regarding exposure to pharmaceuticals, especially those used in veterinary medicine, for birds of prey.

Correlated evolution of oxidative physiology and MHC-based immunosurveillance in birds.

Maintenance and activation of the immune system incur costs, not only in terms of substrates and energy but also via collateral oxidative damage to host cells or tissues during immune response. So far, associations between immune function and oxidative damage have been primarily investigated at intra-specific scales. Here, we hypothesized that pathogen-driven selection should favour the evolution of effective immunosurveillance mechanisms (e.g. major histocompatibility complex, MHC) and antioxidant defences to mitigate oxidative damage resulting from immune function. Using phylogenetically informed comparative approaches, we provided evidence for the correlated evolution of host oxidative physiology and MHC-based immunosurveillance in birds. Species selected for more robust MHC-based immunosurveillance (higher gene copy numbers and allele diversity) showed stronger antioxidant defences, although selection for MHC diversity still showed a positive evolutionary association with oxidative damage to lipids. Our results indicate that historical pathogen-driven selection for highly duplicated and diverse MHC could have promoted the evolution of efficient antioxidant mechanisms, but these evolutionary solutions may be insufficient to keep oxidative stress at bounds. Although the precise nature of mechanistic links between the MHC and oxidative stress remains unclear, our study suggests that a general evolutionary investment in immune function may require co-adaptations at the level of host oxidative metabolism.

Short Communication: The effect of in ovo creatine monohydrate on early pen use activity in chicks.

First-week survival and egg hatchability are lower in chicks from younger broiler breeder hen flocks. Creatine is a naturally occurring compound synthesised from the amino acid arginine or obtained from the diet and is important in the storage and transport of energy. Previous research found an improvement in the hatch rate but no posthatch performance improvements when fertile eggs from young breeder hens were injected with creatine monohydrate (CrM) on embryonic day 14. This pilot study aimed to further investigate the possibility of early posthatch improvements by examining the activity of chicks during the 1st week posthatch. Behaviours were broadly classified as active or inactive, the pen was split into three areas, and the amount of time spent in the heat lamp, feed hopper, or drinker line areas was recorded. Chicks given in ovo CrM spent less time in the heat lamp area over the whole 7 days compared to saline (t = 2.352, P = 0.021) and control groups (t = 3.336, P = 0.003) and more time in the feed hopper area during the first 4 days compared to the control group (t = 2.174, P = 0.033). This finding suggests that creatine may improve energy reserves in young chicks allowing them to spend more time away from the heat lamp.

Specialized diving traits in the generalist morphology of Fulica (Aves, Rallidae).

Foot-propelled diving comprises the primary locomotion-based feeding strategy for many birds, including families such as Phalacrocoracidae, Anhingidae, Podicipedidae, Gaviidae, and the diving ducks within Anatidae. While the morphology of specialized divers is well known, the corresponding morphology is less known for birds not as specialized but capable of diving, such as the coots (Rallidae, Fulica spp.). To compare the osteology of Fulica with other (non-diving) Rallidae, and with foot-propelled diving birds that are distantly related, we considered osteological characters, as well as the proportion of the hind limb bones and the femoral splay angle to construct a phylomorphospace, and to perform a comparative disparity analysis considering ecomorphologically relevant characters related to swimming and diving. Coots resulted to be significantly disparate from other Rallidae showing many traits of specialized foot-propelled divers, but only noticeable when compared with other rallids, as the degree of development of these traits is markedly less than in loons, grebes, or cormorants. This may correspond to a stabilizing selection of characteristics associated with a generalist morphology in Fulica. Studying adaptation in generalist taxa broadens our understanding of ecomorphologically significant features, thereby enabling us to generalize their evolutionary patterns.

Quantifying the effects of landscape and habitat characteristics on structuring bird assemblages in urban habitat patches.

Understanding the determinants of biodiversity in fragmented habitats is fundamental for informing sustainable landscape development, especially in urban landscapes that substantially fragment natural habitat. However, the relative roles of landscape and habitat characteristics, as emphasized by two competing frameworks (the island biogeography theory and the habitat diversity hypothesis), in structuring species assemblages in fragmented habitats have not been fully explored. This study investigated bird assemblages at 26 habitat patches (ranging in size from 0.3 to 290.4 ha) in an urban landscape, southwest China, among which habitat type composition and woody plant species composition varied significantly. Through 14 bird surveys conducted over six breeding seasons from 2017 to 2022, we recorded 70 breeding bird species (excluding birds recorded only once and fly-overs, such as raptors, swallows and swifts), with an average of 26 ± 10 (SD) species per patch. We found that patch area had significant direct and indirect effects on bird richness, with the indirect effects mediated by habitat richness (i.e., the number of habitat types). Isolation (measured as the distance to the nearest patch), perimeter to area ratio (PAR), and woody plant richness did not significantly predict variation in bird richness. Furthermore, none of these factors significantly sorted bird species based on their functional traits. However, the overall makeup of bird assemblages was significantly associated with the specific habitat types and woody plant species present in the patches. The results suggest that neither the island biogeography theory nor the habitat diversity hypothesis can fully explain the impacts of habitat fragmentation on bird richness in our study system, with their roles primarily being linked to patch area. The findings that habitat and plant compositions were the major drivers of variation in bird assemblage composition offer valuable insights into urban planning and green initiatives. Conservation efforts should focus not only on preserving large areas, but also on preventing urban monocultures by promoting diverse habitats within those areas, contributing to the persistence of meta-communities.

Assessing avian influenza surveillance intensity in wild birds using a One Health lens.

Wildlife disease surveillance, particularly for pathogens with zoonotic potential such as Highly Pathogenic Avian Influenza Virus (HPAIV), is critical to facilitate situational awareness, inform risk, and guide communication and response efforts within a One Health framework. This study evaluates the intensity of avian influenza virus (AIV) surveillance in Ontario's wild bird population following the 2021 H5N1 incursion into Canada. Analyzing 2562 samples collected between November 1, 2021, and October 31, 2022, in Ontario, Canada, we identify spatial variations in surveillance intensity relative to human population density, poultry facility density, and wild mallard abundance. Using the spatial scan statistic, we pinpoint areas where public engagement, collaborations with Indigenous and non-Indigenous hunter/harvesters, and working with poultry producers, could augment Ontario's AIV wild bird surveillance program. Enhanced surveillance at these human-domestic animal-wildlife interfaces is a crucial element of a One Health approach to AIV surveillance. Ongoing assessment of our wild bird surveillance programs is essential for strategic planning and will allow us to refine approaches and generate results that continue to support the program's overarching objective of safeguarding the health of people, animals, and ecosystems.

Targeted risk assessment of maximum residue levels for lambda-cyhalothrin in commodities from poultry and birds' eggs.

In accordance with Article 43 of Regulation (EC) No 396/2005, EFSA received a mandate from the European Commission to perform a targeted risk assessment for residues of lambda-cyhalothrin in poultry products (meat/muscle, fat, liver, kidney, edible offal) and bird's eggs. EFSA performed the acute (short-term) and chronic (long-term) dietary risk assessment considering the lambda-cyhalothrin exposure via residues in food commodities from poultry and birds' eggs at the levels of the proposed temporary maximum residue level (MRL) of 0.03 mg/kg and 0.02 mg/kg, respectively. These temporary MRLs were derived by the European Commission from monitoring data provided by EU member States and compiled by EFSA in a central database. Based on the risk assessment results, EFSA concluded that the proposed temporary MRL is unlikely to pose a risk to consumer health.

Patterns and processes underlying understory songbird communities in southern China.

Understory bird communities, especially those comprising insectivores, are highly sensitive to forest loss and fragmentation. Currently, there is little knowledge regarding the large-scale diversity patterns of understory bird communities, particularly in Eastern Asia. Consequently, we aimed to identify the distribution patterns of understory birds in southern China and the factors underlying these patterns. We analysed the diversity distribution patterns of taxonomic and functional α and ß diversity for understory Passeriformes birds in southern China utilising cluster and ordination analyses. Subsequently, we analysed the effects of geographic distance, annual mean temperature, annual temperature range, annual mean precipitation, and annual precipitation range on diversity distribution patterns. In total, 9282 individuals belonging to 11 orders, 48 families, and 297 species were captured over 98,544 net hours, with Alcippeidae being the most abundant family in southern China. The understory bird communities of the 25 sites were categorised into six sub-regions of the Oriental Realm (Indo-Malayan Realm). The pattern in the distribution of taxonomic and functional ß-diversity of understory birds in southern China was consistent with zoogeographical regionalisation. Three distinct geographical groups were identified: Group 1 was located in the Min-Guang Coast and Hainan sub-regions; Group 2 was located in the East Hilly Plain, Southwest Mountains, and Western Mountains and Plateaus sub-regions; and Group 3 was located in the Southern Yunnan Mountain subregion. The most critical factors related to the distribution patterns of ß-diversity were geographical distance, annual mean temperature, and annual temperature range. Our results showed that the understory bird communities of the Southwest Mountain, East Hilly Plain, and Western Mountains, and Plateaus sub-regions were similar, as were those of the Min-Guang Coast and Hainan sub-regions. Our results underscore the joint roles of distance, temperature, and historical evolution in understory bird communities.

West Nile Virus Seroprevalence in Wild Birds and Equines in Madrid Province, Spain.

West Nile virus (WNV) is a re-emerging flavivirus, primarily circulating among avian hosts and mosquito vectors, causing periodic outbreaks in humans and horses, often leading to neuroinvasive disease and mortality. Spain has reported several outbreaks, most notably in 2020 with seventy-seven human cases and eight fatalities. WNV has been serologically detected in horses in the Community of Madrid, but to our knowledge, it has never been reported from wild birds in this region. To estimate the seroprevalence of WNV in wild birds and horses in the Community of Madrid, 159 wild birds at a wildlife rescue center and 25 privately owned equines were sampled. Serum from thirteen birds (8.2%) and one equine (4.0%) tested positive with a WNV competitive enzyme-linked immunosorbent assay (cELISA) designed for WNV antibody detection but sensitive to cross-reacting antibodies to other flaviviruses. Virus-neutralization test (VNT) confirmed WNV antibodies in four bird samples (2.5%), and antibodies to undetermined flavivirus in four additional samples. One equine sample (4.0%) tested positive for WNV by VNT, although this horse previously resided in a WN-endemic area. ELISA-positive birds included both migratory and resident species, juveniles and adults. Two seropositive juvenile birds suggest local flavivirus transmission within the Community of Madrid, while WNV seropositive adult birds may have been infected outside Madrid. The potential circulation of flaviviruses, including WNV, in birds in the Madrid Community raises concerns, although further surveillance of mosquitoes, wild birds, and horses in Madrid is necessary to establish the extent of transmission and the principal species involved.

From islands to infectomes: host-specific viral diversity among birds across remote islands.

BACKGROUND: Accelerating biodiversity loss necessitates monitoring the potential pathogens of vulnerable species. With a third of New Zealand's avifauna considered at risk of extinction, a greater understanding of the factors that influence microbial transmission in this island ecosystem is needed. We used metatranscriptomics to determine the viruses, as well as other microbial organisms (i.e. the infectomes), of seven bird species, including the once critically endangered black robin (Petroica traversi), on two islands in the remote Chatham Islands archipelago, New Zealand. RESULTS: We identified 19 likely novel avian viruses across nine viral families. Black robins harboured viruses from the Flaviviridae, Herpesviridae, and Picornaviridae, while introduced starlings (Sturnus vulgaris) and migratory seabirds (Procellariiformes) carried viruses from six additional viral families. Potential cross-species virus transmission of a novel passerivirus (family: Picornaviridae) between native (black robins and grey-backed storm petrels) and introduced (starlings) birds was also observed. Additionally, we identified bacterial genera, apicomplexan parasites, as well as a novel megrivirus linked to disease outbreaks in other native New Zealand birds. Notably, island effects were outweighed by host taxonomy as a significant driver of viral composition, even among sedentary birds. CONCLUSIONS: These findings underscore the value of surveillance of avian populations to identify and minimise escalating threats of disease emergence and spread in these island ecosystems. Importantly, they contribute to our understanding of the potential role of introduced and migratory birds in the transmission of microbes and associated diseases, which could impact vulnerable island-endemic species.