AVONET: morphological, ecological and geographical data for all birds

Fundamental Interaction Niches: Towards a Functional Understanding of Ecological Networks' Resilience

Global change will create new species interactions and alter or eliminate existing ones, a process known as interaction rewiring. This rewiring can significantly affect how ecosystems function. To better predict the future structure of ecological networks, assessing their ability to adapt to changes is crucial. Here, we introduce two concepts: 'rewiring capacity' of a single species (the multidimensional trait space of all its potential interaction partners within a region) and 'rewiring potential' of a local community (the total trait space covered by interaction partners of the species at the target trophic level locally). To quantify the rewiring capacity and potential, we apply existing methods for determining species' functional interaction niches in a novel way to assess species' and communities' ability to form new interactions and the functional resilience of interaction networks to global change. To illustrate the applicability of these concepts, we quantified the rewiring capacity and potential of interactions between 1002 flowering plant species and 318 hummingbird species across the Americas. The rewiring capacity and potential metrics offer a new way to understand and quantify network resilience, allowing us to map how ecological networks respond to global change.

Seed-dispersing vertebrates and the abiotic environment shape functional diversity of the pantropical Annonaceae

Mutualistic interactions between fruiting plants and frugivorous animals are shaped by interaction-relevant functional traits. However, it is unclear whether 'trait matching' underlies broad-scale relationships in plant and frugivore species and their functional diversity. We integrated novel trait data and global occurrences for c. 1900 species in a major tropical plant family (Annonaceae) with data for 7607 bird and mammal species, including 1418 frugivores, alongside data on the abiotic environment. We applied structural equation models to evaluate the direct and indirect drivers of global and continental variation in frugivory-related functional diversity in Annonaceae, and assessed frugivory-exclusive drivers through comparisons with non-frugivores. We show that global variation in Annonaceae frugivory-related functional diversity is influenced by species richness (SRic) and trait matching with co-occurring frugivorous mammals. Frugivorous birds and mammals indirectly influenced Annonaceae functional diversity at continental scales by affecting Annonaceae SRic. We found that climate, elevation, and seed dispersers jointly shaped Annonaceae diversity globally. Our results suggest that seed dispersal interactions with mammals are particularly important for shaping global variation in Annonaceae diversity, possibly through mutualistic co-evolutionary dynamics. However, distinct effects of frugivores on Annonaceae diversity across biogeographical realms suggest that biogeography modulates how mutualistic interactions promote diversity.

Skeletal trait measurements for thousands of bird species

Large comparative datasets of avian functional traits have been used to address a wide range of questions in ecology and evolution. To date, this work has been constrained by the limited availability of skeletal trait datasets that include extensive inter- and intra-specific sampling. We use computer vision to identify and measure bones from photographs of museum skeletal specimens to assemble an extensive dataset of functionally important skeletal elements in birds. The dataset spans 2,057 species of birds (Aves: Passeriformes) and includes measurements of 12 skeletal elements from 14,419 individuals. In addition to the trait values directly measured from photographs, we leverage the multi-dimensional nature of our dataset and known phylogenetic relationships of the species to impute missing data under an evolutionary model. To facilitate use of the dataset, the taxonomy has been reconciled with an existing comprehensive avian phylogeny and an additional dataset of external functional traits for all birds.

Functional safeguards for conservation: Identifying climate change refugia for frugivorous and nectarivorous birds in a degraded area of Colombia

Habitat loss and climate change are major drivers of biodiversity loss, but their synergistic effects and functional perspectives have to be better understood. We employed species distribution models under future contrasting socioeconomic scenarios to assess the impacts of climate change and human footprint on avian frugivore and nectarivore functional groups in the Magdalena Valley, a highly transformed and biodiverse region in Colombia. We constructed the functional groups based on a dissimilarity matrix with 16 anatomical and ecological traits. Two types of future climatic refugia (type 1: areas that will maintain the current climatic conditions and type 2: regions outside the current distribution area that will have the current climatic conditions) were identified to guide conservation efforts for these groups and associated ecosystem services. Of the 27 functional groups identified, 19 are projected to undergo range reductions of 1-75%, with an average upward shift of their climatic niches along the altitudinal gradient of 690 m. Large frugivores from intermediate elevations, such as toucans and cracids, as well as nectarivores with extreme adaptations and specializations, are expected to experience the most severe range reductions. Distributional and altitudinal shifts will lead to spatial reorganization of communities and a reduction or complete loss of functional group richness, particularly in lowland areas. This could impact ecosystem services relevant for degraded area restoration, such as seed dispersal, fruit availability, and pollination of specialized plant species with economic importance. The low representation of future climatic refugia within protected areas highlights the need to incorporate climate change trends into future conservation strategies for these landscapes.

Variation in albumin glycation rates in birds suggests resistance to relative hyperglycaemia rather than conformity to the pace of life syndrome hypothesis

The pace of life syndrome (POLS) hypothesis suggests that organisms' life history and physiological and behavioural traits should co-evolve. In this framework, how glycaemia (i.e. blood glucose levels) and its reaction with proteins and other compounds (i.e. glycation) covary with life history traits remain relatively under-investigated, despite the well-documented consequences of glucose and glycation on ageing, and therefore potentially on life history evolution. Birds are particularly relevant in this context given that they have the highest blood glucose levels within vertebrates and still higher mass-adjusted longevity compared to organisms with similar physiology as mammals. We thus performed a comparative analysis on glucose and albumin glycation rates of 88 bird species from 22 orders in relation to life history traits (body mass, clutch mass, maximum lifespan, and developmental time) and diet. Glucose levels correlated positively with albumin glycation rates in a non-linear fashion, suggesting resistance to glycation in species with higher glucose levels. Plasma glucose levels decreased with increasing body mass, but, contrary to what is predicted in the POLS hypothesis, glucose levels increased with maximum lifespan before reaching a plateau. Finally, terrestrial carnivores showed higher albumin glycation compared to omnivores despite not showing higher glucose, which we discuss may be related to additional factors as differential antioxidant levels or dietary composition in terms of fibres or polyunsaturated fatty acids. These results increase our knowledge about the diversity of glycaemia and glycation patterns across birds, pointing towards the existence of glycation resistance mechanisms within comparatively high glycaemic birds.

Syntopy promotes song divergence in a Neotropical avian radiation

Theory predicts that selection against maladaptive hybridization leads to divergence of sexual characters in co-occurring closely related species. Consequently, signal disparity should be greater between sympatric vs. allopatric lineage pairs. However, this pattern may also result from species sorting or the greater evolutionary age of sympatric pairs. We used species pairs comparisons to examine the existence of acoustic divergence in a Neotropical montane radiation, the Rhinocryptidae, whose members tend to occupy different elevational ranges. Most rhinocryptids exhibit conservative morphology and are only differentiated by song attributes. Our results show that sympatric species pairs that overlap in elevation exhibited overall greater song divergence compared to allopatric species pairs after controlling for morphological differences, age and phylogenetic effects. Song divergence decreased when excluding sympatric pairs that do not overlap in elevation, suggesting that selection for improved species identification between co-occurring (syntopic) species accentuates signal differentiation. Comparative evolutionary models of signal differentiation over time revealed a similar pattern, which suggests that sexual selection in syntopy might have driven reproductive character displacement in this radiation. We conclude that selection against the production of unfit hybrids could favor acoustic traits that reliably signal species identity in tropical environments where many taxa are poorly differentiated by visual attributes.

Different traits shape winners and losers in urban bird assemblages across seasons

Urbanisation is a major driver of global biodiversity decline, profoundly affecting animal communities. While most studies on bird communities have primarily focused on the breeding season, we aimed to identify species responses and their associated traits by adopting a stratified design and using a multi-season approach considering a gradient from highly urbanised city centres to the urban-rural fringe across six Italian cities. We found that bird assemblages exhibited different responses to urbanisation according to season. Winners (i.e. species positively affected by urbanisation) were characterised by traits such as colonial nesting, high productivity and longevity. In winter, these species displayed generalist foraging strategies and solitary behaviour. Losers (i.e. species negatively affected by urbanisation) tended to be insectivorous, ground-nesting and short-distance migratory species. Interestingly, intra-specific variations emerged, with wintering populations of some species exploiting highly urbanised areas despite not breeding there. Urban adapters, although not strictly winners, displayed resilience by navigating a range of urban conditions, effectively exploiting intermediate levels of urbanisation. This study provides novel insights into the complex ecological dynamics occurring within the urban matrix in different seasons. Our findings emphasise the importance of adopting a multi-season approach in research and urban planning to better understand species responses and develop more effective, sustainable strategies for biodiversity conservation in urban environments.

Adaptations to marine environments and the evolution of slow-paced life histories in endotherms

All organisms face a certain risk of dying before reproducing, putting strong pressure on individuals to reproduce as early as possible. Despite this, some organisms delay maturity, defer reproduction, and age slowly. The evolution of such slow-paced life is classically attributed to allometric effects and reduced extrinsic mortality, but might also result from the invasion of challenging environments requiring adaptations that boost adult survival yet impose substantial energetic and developmental costs. Here, we reveal that the invasion of marine environments by endotherms may have triggered adaptive shifts towards slow life histories, particularly in pelagic lineages. Such life history convergences may have been facilitated by the slow-paced nature of their non-marine ancestors, and were associated with adaptations for enhanced energy acquisition and storage, enabling a long reproductive lifespan at the expense of extended development. Ancestral traits and lifestyle changes might thus have been important in shaping the evolution of slow life histories.

Using a large citizen science dataset to uncover diverse patterns of elevational migration in Himalayan birds

Among montane birds, elevational migration is a well-described phenomenon. Yet, apart from mountain ranges in the Americas, there is little information on the large-scale patterns and extent of elevational migration. Using a large citizen science dataset (eBird), we determine the elevational ranges of 377 Himalayan bird species in their breeding and non-breeding periods. Based on the position of species' seasonal elevation ranges, we describe five elevational migration patterns that broadly include post-breeding upslope and downslope migration. Most high-elevation breeders (65-75%) were downslope migrants, which were further subdivided into four distinct patterns: 'displace' (complete downslope), 'shift' (partial downslope), 'expand' (lower limit expansion) and 'contract' (upper limit contraction). We find significant intraspecific variation in migration patterns across the Himalayas, possibly determined by local biotic and abiotic conditions. Specialized dietary guilds like invertivores were more likely to show shift or displace migration, potentially tracking seasonally fluctuating food resources, while generalists like omnivores and human commensals were more likely to be resident. Territorial birds were largely non-migratory, most likely to retain high-quality breeding territories. As mountains are a bounded domain with limited combinations of species' seasonal elevation ranges, the patterns we describe here are useful for understanding elevational migration globally.

Drivers of avian genomic change revealed by evolutionary rate decomposition

Modern birds have diversified into a striking array of forms, behaviours and ecological roles. Analyses of molecular evolutionary rates can reveal the links between genomic and phenotypic change1-4, but disentangling the drivers of rate variation at the whole-genome scale has been difficult. Using comprehensive estimates of traits and evolutionary rates across a family-level phylogeny of birds5,6, we find that genome-wide mutation rates across lineages are predominantly explained by clutch size and generation length, whereas rate variation across genes is driven by the content of guanine and cytosine. Here, to find the subsets of genes and lineages that dominate evolutionary rate variation in birds, we estimated the influence of individual lineages on decomposed axes of gene-specific evolutionary rates. We find that most of the rate variation occurs along recent branches of the tree, associated with present-day families of birds. Additional tests on axes of rate variation show rapid changes in microchromosomes immediately after the Cretaceous-Palaeogene transition. These apparent pulses of evolution are consistent with major changes in the genetic machineries for meiosis, heart performance, and RNA splicing, surveillance and translation, and correlate with the ecological diversity reflected in increased tarsus length. Collectively, our analyses paint a nuanced picture of avian evolution, revealing that the ancestors of the most diverse lineages of birds underwent major genomic changes related to mutation, gene usage and niche expansion in the early Palaeogene period.

Nest location and architecture as primary drivers of variation in UV reflectance in avian eggs

Two main hypotheses have been proposed to explain the function of ultraviolet (UV) reflection in avian eggs. The UV resistance hypothesis suggests that high UV reflectance protects embryos against solar exposure in open nests, whereas the egg detectability hypothesis posits that higher UV reflectance helps eggs stand out against the dark background of the nest, making them easier for parents to locate in enclosed nests. Therefore, eggshell reflection in the UV spectrum may serve multiple (possibly even opposing) forces, including UV protection and visual signalling. We tested these two hypotheses using large-scale comparative analyses of eggshell UV reflection for over 500 avian species while considering the influence of various ecological, life history and environmental traits associated with light exposure. We did not find strong support for either of the two hypotheses across all birds. However, in two clades exhibiting notably high levels of UV reflectance (Passeriformes and Charadriiformes), species with higher UV reflectance values predominantly nest in open nests, suggesting a stronger effect of the UV resistance hypothesis. This research contributes to a deeper understanding of the mechanisms driving UV coloration in avian eggs and unravels the interplay between life history traits potentially associated with UV reflectance in specific clades under variable nesting conditions.

Diverse relationships between amplitude and frequency in bird vocalizations

Animals use sounds to communicate in contexts that are crucial for survival and reproduction. One compelling feature of acoustic signals is that two main domains of variation-frequency and amplitude-can interact with each other for reasons both evolutionary and mechanistic, in ways that are framed by conflicting predictions. To explore this issue, we obtained amplitude-calibrated field recordings and assessed relationships between vocal frequency and amplitude in 53 species of birds. Our main findings are twofold. First, we identify considerable variation across species in their amplitude-frequency relationships, emerging as positive in 27 species, negative in 12 species and not discernible in 14 species. This variation, as well as results from phylogenetic models, suggests that amplitude-frequency relationships in birds are not governed by any universal rule. Second, throughout our sample-and particularly in oscines (songbirds)-we find that ranges of frequency variation are, by and large, amplitude-dependent, with 28 of our 35 most intensively sampled species producing broad ranges of frequencies at low amplitudes yet narrower ranges at high amplitudes. This finding is consistent with the idea that birds are constrained to produce high-amplitude songs only within the narrow ranges of frequencies that resonate most constructively within their vocal tracts-which, if upheld, could lead to intensity-complexity trade-offs at the song level.

Elevational constraints on flight efficiency shape global gradients in avian wing morphology

Wings with an elongated shape or larger surface area are associated with increased flight efficiency in a wide range of animals from insects to birds.1,2,3,4 Inter- and intra-specific variation in these attributes of wing shape is determined by a range of factors-including foraging ecology, migration, and climatic seasonality5,6,7,8-all of which may drive latitudinal gradients in wing morphology.9,10 A separate hypothesis predicts that wing shape should also follow an elevational gradient5,11 because air density declines with altitude,12 altering the aerodynamics of flight and driving the evolution of more efficient wings in high-elevation species to compensate for reduced lift.13,14,15 Although previous analyses have shown a tendency for longer or larger wings at higher elevations, at least locally,16,17,18,19,20 it is difficult to rule out a range of alternative explanations since we currently lack a global synthesis of elevational gradients in wing shape for any taxonomic group. In this study, we use phylogenetic models to explore elevational effects on metrics of wing morphology linked to aerodynamic function in 9,982 bird species while simultaneously controlling for multiple climatic factors and ecological attributes of species. We found that relative wing elongation (hand-wing index) and wing area increase with elevation, even when accounting for latitude, temperature seasonality, body mass, habitat, aerial lifestyle, and altitudinal migration. These results confirm a pervasive elevational gradient in avian wing morphology and suggest that aerodynamic constraints linked to air density, perhaps coupled with oxygen deficiency, contribute to global patterns of trait evolution in flying animals.

Phylogenetic and ecological drivers of the avian lung mycobiome and its potentially pathogenic component

Vertebrate lungs contain diverse microbial communities, but little is known about the drivers of community composition or consequences for health. Microbiome assembly by processes such as dispersal, coevolution, and host-switching can be probed with comparative surveys; however, few studies exist for lung microbiomes, particularly for the fungal component, the mycobiome. Distinguishing among fungal taxa that are generalist or specialist symbionts, potential pathogens, or incidentally inhaled spores is urgent because of potential for emerging diseases. Here, we characterize the avian lung mycobiome and test the relative influences of environment, phylogeny, and functional traits. We used metabarcoding and culturing from 195 lung samples representing 32 bird species across 20 families. We identified 526 fungal taxa as estimated by distinct sequence types (zOTUs) including many opportunistic pathogens. These were predominantly from the phylum Ascomycota (79%) followed by Basidiomycota (16%) and Mucoromycota (5%). Yeast and yeast-like taxa (Malassezia, Filobasidium, Saccharomyces, Meyerozyma, and Aureobasidium) and filamentous fungi (Cladosporium, Alternaria, Neurospora, Fusarium, and Aspergillus) were abundant. Lung mycobiomes were strongly shaped by environmental exposure, and further modulated by host identity, traits, and phylogenetic affinities. Our results implicate migratory bird species as potential vectors for long-distance dispersal of opportunistically pathogenic fungi.

Common developmental origins of beak shapes and evolution in theropods

Vertebrate beaks show a remarkable diversity of forms, epitomized by birds and non-avian theropods. Few studies have investigated how underlying developmental processes influence beak shape. The power cascade is a model of growth describing the log-log linear relationship of the beak radius with distance from the tip. We measured beak and toothed snout shapes in 127 species across 120 families of extant birds and extinct non-avian theropods and found that 95% followed the power cascade model. Ancestral state estimation suggests that the power cascade constitutes a fundamental growth pattern of the theropod rostrum, and perhaps all vertebrate rostra. The morphospace defined by the power cascade shows how bird beak shape explores the geometries associated with ecological specializations while adhering to the growth model. We show that the power cascade influences the macroevolutionary exploration of rostrum morphospace, enabling extant birds to inhabit all components of Earth's biosphere.

NDVI and vegetation volume as predictors of urban bird diversity

Urban expansion and densification pose a challenge to urban biodiversity. Rapid estimation of biodiversity could help urban planners balance development and conservation goals. While the Normalised Difference Vegetation Index (NDVI) has proven useful for predicting urban bird diversity, new products derived from remote sensing, such as vegetation volume, could provide more detailed descriptions of available habitat, potentially improving biodiversity predictions. We evaluated the effectiveness of NDVI and vegetation volume as predictors of urban bird diversity and local community composition for different buffers around 86 sampling points in Munich, Germany. Using linear models, we showed that a 100 m buffer best described bird diversity (highest R2) for both NDVI and vegetation volume compared to the other buffers. Contrary to expectations, NDVI was better than vegetation volume in predicting bird diversity (mean R2 NDVI = 0.47, mean R2 vegetation volume 0.37). We found a shift in community composition from species associated with human-modified landscapes to those associated with forests along an urban greenness gradient. In contrast to diversity, we found that vegetation volume was slightly better at predicting community composition. Using NDVI to predict bird diversity across Munich, we demonstrated its potential for predicting city-wide bird diversity. We discuss how such predictive maps can be used for urban planning and conservation. As urbanisation continues to impact global biodiversity, refining ecological models for urban planning will be crucial to developing more biodiverse urban environments.

Assessing microplastic and nanoplastic contamination in bird lungs: evidence of ecological risks and bioindicator potential

Microplastics (MPs, 1 µm-5 mm) and nanoplastics (NPs, < 1 µm), collectively termed micro(nano)plastics (MNPs), are pervasive airborne pollutants with significant ecological risks. Birds, recognized as bioindicators, are particularly vulnerable to MNP exposure, yet the extent and risks of MNP pollution in bird lungs remain largely unexplored. This study assessed MP exposure in bird lungs of 51 species and NP exposure in the lungs of five representative species using laser direct infrared (LDIR) and pyrolysis gas chromatography-mass spectrometry (Py-GC-MS) techniques, respectively. The LDIR analysis revealed different degrees of MP contamination in bird lungs, with an average abundance of 221.20 items per species and 416.22 MP particles per gram of lung. Among 32 identified MP types, chlorinated polyethylene (CPE) and butadiene rubber (BR) predominated, with particles primarily in film and pellet forms, concentrated in the 20-50 μm size range. The polymer hazard index (PHI) indicated elevated ecological risks (levels Ⅲ or Ⅳ) in most bird lungs. Py-GC-MS detected nylon 66 (PA66), polyvinyl chloride (PVC), and polypropylene (PP) NPs at varying concentrations. Terrestrial, carnivorous, and larger-bodied birds exhibited higher MNP burdens. This study provides the first evidence of MNP contamination in bird lungs, highlighting their potential as bioindicators of airborne MNP pollution.

Three-Dimensional Habitat Structure Drives Avian Functional and Trait Diversity Across North America

Understanding how three-dimensional (3D) habitat structure drives biodiversity patterns is key to predicting how habitat alteration and loss will affect species and community-level patterns in the future. To date, few studies have contrasted the effects of 3D habitat composition with those of 3D habitat configuration on biodiversity, with existing investigations often limited to measures of taxonomic diversity (i.e., species richness). Here, we examined the influence of Light Detecting and Ranging (LiDAR)-derived 3D habitat structure-both its composition and configuration-on multiple facets of bird diversity. Specifically, we used data from the National Ecological Observatory Network (NEON) to test the associations between 11 measures of 3D habitat structure and avian species richness, functional and trait diversity, and phylogenetic diversity. We found that 3D habitat structure was the most consistent predictor of avian functional and trait diversity, with little to no effect on species richness or phylogenetic diversity. Functional diversity and individual trait characteristics were strongly associated with both 3D habitat composition and configuration, but the magnitude and the direction of the effects varied across the canopy, subcanopy, midstory, and understory vertical strata. Our findings suggest that 3D habitat structure influences avian diversity through its effects on traits. By examining the effects of multiple aspects of habitat structure on multiple facets of avian diversity, we provide a broader framework for future investigations on habitat structure.

Latitudinal variations in incubation behaviour among uniparental incubating birds

Uniparental incubating birds must resolve the trade-off between self-maintenance and incubation. This balance manifests through diverse incubation behaviours that vary significantly among species and geographic regions. However, limited research has examined the variability of incubation behaviours across species and regions. Using Bayesian phylogenetic mixed models, we investigated how three incubation behaviours (off-bout frequency, off-bout duration and incubation constancy) vary with latitude across 201 uniparental incubating bird species. Our findings reveal distinct incubation strategies adopted by uniparental birds across latitudes. Species at lower latitudes exhibit fewer off-bouts and, meanwhile, have longer off-bout durations. Conversely, those at higher latitudes exhibit more frequent but shorter off-bouts. Notably, a clear latitude-dependent pattern emerges in incubation constancy, with higher latitudes showing greater incubation constancy. Additionally, smaller-bodied birds tend to take more frequent off-bouts. Significant variations in off-bout frequency were observed across different habitats. Herbivorous species, in particular, show higher incubation constancy compared to omnivorous and carnivorous birds. These findings offer valuable insights into the association of latitudinal variation with the evolutionary dynamics of life histories in uniparental incubating birds.

Viewing conditions predict evolutionary diversity in avian plumage colour

Animals communicate using multiple sensory channels, including via vision. The colourful plumage of birds is a model system to study visual communication, having evolved through a complex interplay of processes, acting not only on the ability of a plumage patch to convey information, but also in response to physiological and environmental factors. Although much research on inter-specific variation in bird plumage has concentrated on sexual selection, much less has considered the role of non-sexual selection and how it is affected by the joint effects of avian viewing conditions and receiver vision. Here, we combined a taxonomically diverse database of avian plumage reflectance measurements with bird vision models, habitat and behavioural data to test the effect of three factors that affect viewing conditions-habitat openness, migratory preference and diel activity-on avian plumage contrast, accounting for shared evolutionary history and variation in avian visual systems. We find that habitat structure and migratory preference predicted plumage visual contrast, especially for females. Our study therefore demonstrates the important role of non-sexually selected traits, viewing conditions and bird vision, in shaping avian plumage contrast.

Reassessing niche partitioning in MacArthur's warblers: foraging behaviour, morphology and diet differentiation in a phylogenetic context

Owing in large part to Robert MacArthur's classic research, wood warblers in the family Parulidae are textbook exemplars of species competition and niche partitioning. Conventional wisdom suggests that subtle differences in foraging behaviour are the principal means by which these nearly morphologically indistinguishable species are able to co-occur and avoid extinction. Yet, MacArthur's study was in fact quite limited in scale, and he said little about the relevance of evolution to the study system. Here, we reassess MacArthur's conclusions across an expanded set of syntopic warbler species in a forest in northern New York. We combine morphometrics, quantitative foraging data and faecal metabarcoding-a direct measure of warbler diet-to study competition and niche partitioning in an evolutionary framework. We find close relationships between morphology and foraging behaviour, but little connection between warbler ecomorphology and the 2237 invertebrate taxa detected in their diets. Instead, diet remains phylogenetically conserved-closely related warblers eat similar suites of invertebrates, regardless of where they forage. Finally, we present evidence that these species not only partition niche space in the present day but also that competition has shaped their behaviours over evolutionary time.

Migration, Habitat and Hunting Style Do Not Affect the Malar Stripe of Different Falcon Species

The solar glare hypothesis suggests that the malar stripe of a falcon decreases the sun's glare in the eye, possibly increasing their hunting success. The amount of sunlight an individual experiences could be affected by its migratory strategy, hunting style or main habitat. However, it is not known if these environmental variables impact the size and intensity of the malar stripe. Therefore, this study aimed to analyse differences in size and intensity of malar stripes between individuals of 12 falcon species with different migratory strategies, habitats, and hunting styles distributed worldwide. The malar stripes of 12 falcon species were measured and scored using more than 6000 photos from citizen science repositories. The measurements of the malar stripes were first reduced with a principal component analysis (PCA) and then analysed using a linear mixed model that included migratory strategy, habitat and hunting style as fixed factors and several posture variables as random factors. The relationships between the measurements of the malar stripe and solar radiation of the individual's location were also analyzed using linear mixed models. Overall, we found no differences in malar stripe size and intensity between species with differing migratory strategies, habitats, and hunting styles. The relationships between various characteristics of the malar stripe and solar radiation did depend on the species and the habitat the individual occupied. Therefore, migratory strategy, habitat and hunting style do not markedly influence the size and intensity of malar stripes across falcon species, suggesting that other mechanisms, such as thermoregulation or camouflage, also play a role.

Distribution-wide morphometric data of Jungle Crows (Corvus macrorhynchos)

Understudied, widespread species may harbour underappreciated variation in morphology. Museum specimens represent a rich source of morphometric data, and for many species this information is untapped. Here we present a dataset derived from standardised photography of museum specimens of Jungle Crows (Corvus macrorhynchos), a widespread Asian Corvid. We photographed 1105 crows, for which 1069 we managed to collect measurements of hard tissue (i.e., bill characteristics and tarsus length). We combined these measurements with museum-curated data on the locality of the specimens, resulting in a geotagged dataset of Jungle Crow morphology. The measured crows originated from across their distribution, representing the most comprehensive morphometric dataset for Corvus macrorhynchos to date. The dataset is a valuable resource for exploring the driving forces behind morphological variation in Corvus macrorhynchos, as well as a foundation for intraspecific comparison of proposed subspecies and interspecific comparisons of other bird species.

Understanding and counteracting the denial of insect biodiversity loss

Biodiversity loss is occurring globally with negative impacts on ecosystem function and human well-being. There is a scientific consensus that diverse environmental and anthropogenic factors are altering different components of insect biodiversity, with changes occurring at all levels of biological organisation. Here, we describe how uncertainty around specific trends and the semantics of 'decline' in relation to insect biodiversity have been leveraged by denialist campaigns to manufacture doubt around the insect biodiversity crisis. Disinformation is one of the biggest threats to social cohesion and environmental integrity globally. We argue that scientists, academic institutions, policymakers, and journalists must combat denialism by relying on robust research, supporting efforts to communicate scientific uncertainty more effectively, and build consensus on the global impacts of insect biodiversity loss.

Mapping bird and bat assemblage vulnerability for predicting wind energy impact

The drive towards decarbonization has led countries to seek renewable energy sources to mitigate global warming. Wind energy is an attractive option due to its low cost and sustainability, but it poses significant risks to birds and bats through collisions and barotrauma with wind turbines. We examined the main ecological traits linked to wind turbine mortality in 214 bird and 19 bat species in peninsular Spain. We assessed the vulnerability of bird and bat assemblages to help understand the potential impact of wind energy development on the most vulnerable assemblages. Our findings indicate that bird and bat casualties were driven by morphological and ecological traits. For birds, scavenger species, those with partial migratory patterns, and aerial lifestyles were most affected by turbine collisions. We also found that vulnerability was positively correlated with observed mortality rates at the province level, but the effect was weaker for birds. Sensitive areas for birds and bats are located in southern, south-eastern, and central Spain, with birds showing additional vulnerability in western and northern regions, while future wind energy development affects bats more in eastern Spain. Our research highlights the importance of mitigating impacts on vulnerable bird and bat species, as well as abundant species. The study highlights the potential risk of ecosystem function loss for bird and bat assemblages due to wind energy projects. We provide spatial tools to identify high-vulnerability areas, guiding energy development to minimize ecological impacts. This work calls on authorities to implement measures to protect species and preserve essential ecosystem functions.

Global Avian Frugivore-Fruit Trait Matching Decreases Toward the Tropics

Trait matching, the phenomenon where ecological interactions are mediated by compatibility, constitutes a cornerstone of frugivore-fruit interaction network dynamics. Given that biotic interactions have long been hypothesized to be more intense or specialized in the tropics, the intensity of trait matching patterns might likewise exhibit a latitudinal gradient in frugivory networks, yet this remains unverified. Here, we established a dataset encompassing 200 avian frugivorous networks to explore the relationships between the body mass and gape size of frugivore birds and fruit traits (size and color) on a global scale. Our results indicated that frugivore traits were closely associated with fruit traits regardless of the climate, demonstrating a biotic match between the two counterparts. We detected a significant decrease in frugivore-fruit trait matching toward the tropics, which challenges prevailing concepts considering the high biodiversity therein. Our structural equation modeling clarified that latitude and temperature exert an indirect influence on trait matching by affecting gape size and fruit traits. These discoveries emphasize the impact of the latitudinal gradient of temperature in driving the observed patterns of trait matching. The weaker trait matching in tropical regions may suggest more complex interactions therein and also highlights the potential for altered network structures amid global climate change.

Birds With Distinct Ecological Traits Show Varied Haemoglobin Adaptations Along Elevation Gradients

Ecological systems are highly dynamic, with organisms continually adapting to various environmental stressors along natural gradients. Birds along elevation gradients serve as excellent models for examining physiological adaptations, such as elevated haemoglobin concentrations at high altitudes due to lower oxygen availability. This study aimed to examine how various ecological traits influence the haemoglobin concentration responses of multiple bird taxa to an elevation gradient. We measured haemoglobin concentration in 920 birds of 133 species at six sites representing an elevation gradient spanning from 60 to 1,600 m above sea level. Using MCMC Bayesian mixed models, we identified important ecological determinants of haemoglobin concentration and further ran separate models to test whether haemoglobin concentration responses to elevation differ between various functional groups of birds. Our results showed that haemoglobin concentration increased significantly with elevation and was strongly influenced by wing morphology, body mass, season, and primary lifestyle. The rate of increase with elevation varied by lifestyle: terrestrial and perching birds exhibited a steeper increase in haemoglobin concentration with elevation, while aerial birds also increased haemoglobin but at a more gradual rate. However, the remaining traits did not alter how species respond to hypoxia; for example, birds increased haemoglobin at the same rate in both the dry and wet seasons, meaning seasonal changes did not strongly impact elevation-driven haemoglobin adjustments. Elevation is the primary driver of variation, while lifestyle influences baseline levels rather than the rate of change. Despite differences in lifestyle-driven oxygen demands, birds exhibit a similar haemoglobin response to hypoxia at moderate elevations, where adjustments remain within physiological limits, indicating that hypoxia-driven haemoglobin adjustments occur independently of baseline oxygen demands. These findings demonstrate how birds regulate oxygen transport relative to ecological constraints, providing insights into their physiological flexibility across environmental gradients.

Ecophysical constraints on avian adaptation and diversification

The evolution of morphological diversity is ultimately governed by physical laws and ecological contexts, which together impose a range of ecophysical constraints. Substantial progress has been made in identifying how these constraints shape the form and function of producers (plants), but similar knowledge is lacking for consumers, in part because the requisite data have not been available at sufficient scale for animals. Using morphometric measurements for all birds, we demonstrate that observed variation is restricted-both for beak shape and body shape-to triangular regions of morphospace with clearly defined boundaries and vertices (corners). By combining morphometric data with information on ecological and behavioral functions, we provide evidence that the extent of avian morphospace reflects a trade-off between three fundamental physical tasks for feeding (crush, engulf, and reach) that characterize resource acquisition and processing by the beak and three physical tasks (fly, swim, and walk) that characterize avian lifestyles or locomotion. Phylogenetic analyses suggest that trajectories of morphological evolution trend toward the vertices, with lineages evolving from a core of functional generalists toward more specialized physical tasks. We further propose that expansion beyond the current boundaries of morphospace is constrained by the shorter evolutionary lifespan of functional specialists, although patterns of speciation rate and current extinction risk provide only weak support for this hypothesis. Overall, we show that the structure of avian morphospace follows relatively simple rules defined by ecophysical constraints and trade-offs, shedding light on the processes shaping modern animal diversity and responses to environmental change.

Adaptive cross-country optimization strategies in thermal soaring birds

Thermal soaring enables birds to perform cost-efficient flights. Although aerodynamic rules dictate the costs of flight, soaring species vary strongly in their morphologies and behavioral strategies. To quantify morphology-related differences in behavioral cross-country strategies, we analyzed a large dataset consisting of over a hundred individuals from 12 soaring species recorded with high-frequency tracking devices. We quantified their performance during thermalling and gliding flights and their overall cross-country behavior. Our results confirmed aerodynamic theory across the species; species with higher wing loading typically flew faster and consequently turned on a larger radius than lighter ones. Furthermore, the combination of circling radius and minimum sink speed determines the maximum benefits soaring birds obtain from thermals. Notably, we observed a spectrum of strategies regarding the adaptivity to thermal strength and uncovered a universal rule for cross-country strategies for all analyzed species which can provide inspiration for technical applications, like autopilot for robotic gliders.

Landscape scale effects of primary productivity on forest bird species occurrence and abundance in Argentina

Context

Approaches estimating landscape effects on biodiversity frequently focus on a single extent, finding one 'optimal' extent, or use narrow extents. However, species perceive the environment in different ways, select habitat hierarchically, and respond to multiple selection pressures at extents that best predict each pressure.

Objective

We aimed to assess multi-scale relationships between primary productivity and species occurrences and abundances.

Methods

We used a multi-scale approach, called 'scalograms', to assess landscape level effects of primary productivity, in the form of Dynamic Habitat Indices (DHIs) on the occurrences and abundances of 100 Argentinian forest bird species. We used average DHI values within multiple extents (3 × 3 to 101 × 101 pixels; 30 m resolution), and 11 'scalogram' metrics as environmental inputs in occurrence and abundance models.

Results

Average cumulative DHI values in extents 81 × 81 to 101 × 101 pixels (5.9 - 9.2 km2) and maximum cumulative DHI across extents were in the top three predictors of species occurrences (included in models for 41% and 18% of species, respectively). Average cumulative DHI values in various extents contributed ~ 1.6 times more predictive power to occurrence models than expected. For species abundances, average DHI values and scalogram measures were in the top three predictors for < 2% of species and contributed less model predictive power than expected, regardless of DHI type (cumulative, minimum, variation).

Conclusions

Argentinian forest bird occurrences, but not abundances, respond to high levels of primary productivity at multiple, broad extents rather than a single 'optimal' extent. Factors other than primary productivity appear to be more important for predicting abundance.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10980-025-02081-5.

Flight style and time-activity budgets of the smallest petrels

Procellariforms are the most oceanic among birds, regularly embarking on the longest journeys in the animal kingdom to find food over an apparently featureless sea surface. To minimize energy expenditure, many species harness wind energy through dynamic soaring, extracting kinetic energy from the wind shear. The smallest members of this order, storm petrels, have functional traits that prevent this type of locomotion, and are predicted to rely on flapping flight despite their high motility. However, theoretical predictions have never been validated and their flight strategy and activity budgets are unclear. We hypothesized that, as the benefits of dynamic soaring are out of reach, these birds should rely on gliding to some extent to sustain their long-ranging movements and save energy. To test our hypothesis we used, for the first time, miniaturized inertial measurement units on one of the world's smallest seabirds, the Mediterranean storm petrel (Hydrobates pelagicus melitensis). We demonstrate that these small seafarers spend 78% of the time flying during their foraging trips, with wingbeat frequencies up to 15 Hz. During transiting flight, they flap their wings at high frequency (mean±s.d.: 8.8±0.8 Hz) for 91% of the time, gliding sporadically and only for an instant (mean±s.d.: 0.11±0.17 s). Flight activity was high during the night and early morning, while they rested on the sea in the central hours of the day. Overall, our results reveal a peculiar locomotory strategy among procellariforms and raise questions about how they can energetically sustain foraging trips spanning hundreds of kilometres.

CaecilianTraits, an individual level trait database of Caecilians worldwide

Functional traits differ among species, which determine the ecological niche a species occupies and its ability to adapt to environment. However, differences in traits also exist at intraspecific level. Such variations shape differences in individual survival capabilities. Investigating intraspecific differences of functional traits is important for ecology, evolutionary biology and biodiversity conservation. Individual trait-based approaches have been applied in plant ecology. But for animals, most databases only provide data at the species level. In this study, we presented a global database of morphological traits for caecilians (Amphibia, Gymnophiona) at both species and individual level. Caecilians are a unique group of amphibians characterized by their secretive habits, which have limited our understanding of this taxon. We compiled the most comprehensive database covering 218 out of 222 known species, with 215 of them have individual level data. This database will facilitate research in the ecology, evolutionary biology, conservation biology, and taxonomy of caecilians. Furthermore, this dataset can be utilized to test ecological and evolutionary hypotheses at the individual level.

Functional connectivity of animal-dispersed plant communities depends on the interacting effects of network specialization and resource diversity

Plant functional connectivity-the dispersal of plant propagules between habitat patches-is often ensured through animal movement. Yet, there is no quantitative framework to analyse how plant-animal interactions and the movement of seed dispersers influence community-level plant functional connectivity. We propose a trait-based framework to quantify plant connectivity with a model integrating plant-frugivore networks, animal-mediated seed-dispersal distances and the selection of target patches by seed dispersers. Using this framework, we estimated how network specialization, between-patch distance and resource diversity in a target patch affect the number and diversity of seeds dispersed to that patch. Specialized networks with a high degree of niche partitioning in plant-frugivore interactions reduced functional connectivity by limiting the diversity of seeds dispersed over long distances. Resource diversity in the target patch increased both seed number and diversity, especially in specialized networks and within short and intermediate distances between patches. Notably, resource diversity was particularly important at intermediate distances, where the number and diversity of seeds reaching a patch increased more strongly with resource diversity than at longer distances. Using a trait-based framework, we show that resource diversity in the target patch is a major driver of connectivity in animal-dispersed plant communities.

Pesticides and veterinary pharmaceuticals in neotropical avian carnivores: A scoping review

Organic contaminants have long been known to have negative consequences for wildlife health. For avian carnivores, particular concern surrounds the use of compounds such as pesticides and pharmaceutical drugs, derived from global agricultural and veterinary practices. Previous cases of avian poisoning in North America, Europe and Asia have received great attention, owing to significant declines in avian populations and wider consequences. By contrast, the Neotropics, comprised of Latin America and the Caribbean, has received relatively little attention, despite an extensive agricultural sector and uniquely high avian biodiversity. To evaluate the available evidence on this topic, a scoping review on the effects of agriculturally derived organic contaminants on Neotropical avian carnivores was conducted. Articles from seven databases were screened using exclusion criteria. Of these, 206 primary research articles published since 1965 were identified, investigating 144 compounds in 83 species. Findings indicate substantial knowledge gaps, particularly in observational studies conducted within the Neotropics. Whilst cross-sectional studies were fairly well-represented, with transitions towards less-invasive sampling methods, there were few longitudinal studies, raising concerns of undetected chronic exposure in Neotropical populations. Multiple avian taxonomic families were underrepresented, including globally recognized sentinel species - the osprey and barn owl, as were pharmaceutical drugs in comparison to pesticides. There was a large geographical bias in observational study location, with no research outputs identified from most Neotropical countries. Further research in the Neotropics is required to better understand the pervasiveness of contaminants in native populations, along with improving our understanding of their precise consequences on avian carnivore health.

Deciduous forests hold conservation value for birds within South Andaman Island, India

Greater diversity of habitats on islands is often correlated with higher species richness (including endemic and threatened taxa), implying the need to understand species-habitat associations. Such habitat associations could also point toward the role of abiotic filtering and competition in structuring species communities, necessitating the examination of the role of species traits and phylogenetic relationships in intra-island community organization, an aspect poorly examined in the literature. We investigated the composition and structuring of forest bird communities in closely co-occurring evergreen and deciduous forests within South Andaman Island (Indian Ocean), wherein the importance of deciduous forests for birds is undervalued. We sampled 27 transects over 2 years and compared bird species composition and diversity across the two habitats. We examined species-specific associations with habitat (forest) type, basal area, and distance from human settlements, and tested whether these associations were explained by species functional traits and tested for phylogenetic signal after factoring in the effects of environmental predictors. Bird species compositions were markedly distinct across the two habitat types, with deciduous forests having greater taxonomic and functional, but not greater phylogenetic, diversity of forest birds. The distribution of forest birds, including several endemic and threatened species within the island, was largely explained by habitat type (with 39% of the bird species analyzed showing higher occurrence probabilities in deciduous forests), followed by distance from human settlements and basal area. We did not find evidence of species traits or phylogenetic relationships mediating these habitat preferences, perhaps due to a relatively impoverished species pool, as is typical on islands. Nevertheless, our results underscore the value of deciduous forests in harboring high islandic species diversity and being the preferred habitat of several endemic and threatened bird species. Given the historic focus on evergreen forests and the increasing anthropogenic pressure on the forests of the Andamans, we highlight the critical need to include rapidly diminishing deciduous forests in existing conservation plans.

Predicting the global economic costs of biological invasions by tetrapods

Globalisation has accelerated rates of biological invasions worldwide, leading to widespread environmental perturbations that often translate into rapidly expanding socio-economic costs. Although such monetary costs can be estimated from the observed effects of invasions, the pathways that lead invasive species to become economically impactful remain poorly understood. Here, we implement the first global-scale test of the hypothesis that adaptive traits that influence demographic resilience predict economic costs, using invasive terrestrial vertebrates as models given their well-catalogued impacts and characteristics. Our results reveal that total global costs of invasive tetrapods are conservatively in the tens of billions of dollars, with the vast majority due to damage costs from invasive mammals. These monetary impacts are predicted by longevity, female maturation age, diet and invasion pathway traits, although the directionality in the association between impacts and these drivers varied across classes. Alarmingly, costs remain unknown for >90 % of recorded established alien tetrapods worldwide, and across the majority of invaded countries. These huge socio-economic costs demonstrate the necessity of mitigating tetrapod invasions and filling knowledge gaps. Effective identification of traits predictive of costs among and within these groups can facilitate the prioritisation of resources to efficiently target the most damaging existing and emerging invasive tetrapod species.

Generative AI extracts ecological meaning from the complex three dimensional shapes of bird bills

Data on the three dimensional shape of organismal morphology is becoming increasingly available, and forms part of a new revolution in high-throughput phenomics that promises to help understand ecological and evolutionary processes that influence phenotypes at unprecedented scales. However, in order to meet the potential of this revolution we need new data analysis tools to deal with the complexity and heterogeneity of large-scale phenotypic data such as 3D shapes. In this study we explore the potential of generative Artificial Intelligence to help organize and extract meaning from complex 3D data. Specifically, we train a deep representational learning method known as DeepSDF on a dataset of 3D scans of the bills of 2,020 bird species. The model is designed to learn a continuous vector representation of 3D shapes, along with a 'decoder' function, that allows the transformation from this vector space to the original 3D morphological space. We find that approach successfully learns coherent representations: particular directions in latent space are associated with discernible morphological meaning (such as elongation, flattening, etc.). More importantly, learned latent vectors have ecological meaning as shown by their ability to predict the trophic niche of the bird each bill belongs to with a high degree of accuracy. Unlike existing 3D morphometric techniques, this method has very little requirements for human supervised tasks such as landmark placement, increasing it accessibility to labs with fewer labour resources. It has fewer strong assumptions than alternative dimension reduction techniques such as PCA. Once trained, 3D morphology predictions can be made from latent vectors very computationally cheaply. The trained model has been made publicly available and can be used by the community, including for finetuning on new data, representing an early step toward developing shared, reusable AI models for analyzing organismal morphology.

Social associations across species during nocturnal bird migration

An emerging frontier in ecology explores how organisms integrate social information into movement behavior and the extent to which information exchange occurs across species boundaries.1,2,3 Most migratory landbirds are thought to undertake nocturnal migratory flights independently, guided by endogenous programs and individual experience.4,5 Little research has addressed the potential for social information exchange aloft during nocturnal migration, but social influences that aid navigation, orientation, or survival could be valuable during high-risk migration periods.1,2,6,7,8 We captured audio of >18,000 h of nocturnal bird migration and used deep learning to extract >175,000 in-flight vocalizations of 27 species of North American landbirds.9,10,11,12 We used vocalizations to test whether migrating birds distribute non-randomly relative to other species in flight, accounting for migration phenology, geography, and other non-social factors. We found that migrants engaged in distinct associations with an average of 2.7 ± 1.9 SD other species. Social associations were stronger among species with similar wing morphologies and vocalizations. These results suggest that vocal signals maintain in-flight associations that are structured by flight speed and behavior.11,13,14 For small-bodied and short-lived bird species, transient social associations could play an important role in migratory decision-making by supplementing endogenous or experiential information sources.15,16,17 This research provides the first quantitative evidence of interspecific social associations during nocturnal bird migration, supporting recent calls to rethink songbird migration with a social lens.2 Substantial recent declines in bird populations18,19 may diminish the frequency and strength of social associations during migration, with currently unknown consequences for populations.

Evolutionary drivers of caching behaviour in corvids

Caching has recurrently evolved across a range of animal taxa to withstand fluctuations in food availability and in the context of intraspecific competition. It is widespread in the corvid family, which exhibit considerable interspecific variation in their behavioural and morphological adaptations to caching. However, the evolutionary drivers responsible for this diversity have seldom been explored. The present study systematically reviews the literature on caching behaviour in corvids globally to determine (1) which food caching strategies species have adopted (specialist, generalist or non-cacher) and (2) whether ecological factors affect the occurrence of different strategies, namely (a) climate breadth, (b) trophic niche, (c) habitat breadth, (d) centroid latitude, (e) centroid longitude, (f) breeding system, and (g) body mass. In addition, the ancestral states of caching are reconstructed to assess the evolutionary trajectory of each strategy. Caching strategies were identified in 63 species from 16 genera (out of 128 corvid species and 22 genera). Ancestral state analysis suggested specialist caching as the ancestral state in corvids. Type of caching is associated with distance from equator and by average body mass, with generalist caching concentrated around the equatorial zone and among heavier corvids, while specialist caching occurring more commonly in smaller species found farther from the equator. Although specialist caching most likely was the ancestral state in corvids, both specialist and generalist caching evolved several times independently in the family of corvids. Our results show caching to be widespread in corvids and affected by body size and latitude but ecological factors such as topic niche and habitat breadth and breeding system, not to be strong drivers shaping caching behaviour.

Convergent evolution of noncoding elements associated with short tarsus length in birds

BACKGROUND

Convergent evolution is the independent evolution of similar traits in unrelated lineages across the Tree of Life. Various genomic signatures can help identify cases of convergent evolution at the molecular level, including changes in substitution rate in the same genes or gene networks. In this study, utilizing tarsus measurements of ~ 5400 species of birds, we identify independent shifts in tarsus length and use both comparative genomic and population genetic data to identify convergent evolutionary changes among focal clades with shifts to shorter optimal tarsus length.

RESULTS

Using a newly generated, comprehensive and broadly accessible set of 932,467 avian conserved non-exonic elements (CNEEs) and a whole-genome alignment of 79 birds, we find strong evidence for convergent acceleration in short-tarsus clades among 14,422 elements. Analysis of 9854 protein-coding genes, however, yielded no evidence of convergent patterns of positive selection. Accelerated elements in short-tarsus clades are concentrated near genes with functions in development, with the strongest enrichment associated with skeletal system development. Analysis of gene networks supports convergent changes in regulation of broadly homologous limb developmental genes and pathways.

CONCLUSIONS

Our results highlight the important role of regulatory elements undergoing convergent acceleration in convergent skeletal traits and are consistent with previous studies showing the roles of regulatory elements and skeletal phenotypes.

Interconnecting fragmented forests: Small and mobile birds are cornerstones in the plant-frugivore meta-network

Habitat fragmentation is causing the collapse of seed dispersal interactions and ecosystem functioning. When management and conservation strategies aim to sustain ecosystem functioning of fragmented forests, species' traits and functional performance are critical in guiding decisions. However, to date, we lack a quantitative understanding of the role of frugivores' body size and dispersal ability in ecosystem sustainability among fragmented forests. Focusing on avian frugivory and seed dispersal in a multi-island setting, we address the data gap by recording more than 20,000 frugivory events in an artificial insular fragmented landscape constructed in 1959 and nearby unfragmented forests on the mainland. We show that large-bodied and dispersal-limited frugivorous birds are largely confined to large islands and the unfragmented mainland, whereas on small islands, small-bodied and highly mobile birds predominantly engage in frugivory interactions. The plant-frugivore meta-network exhibits a distinct compartmentalization, driven by island area and bird mobility. Birds with smaller size and greater mobility have higher topological importance, and the presence of small-bodied birds significantly enhances meta-network robustness. These results suggest that among insular fragmented forests where frugivory interactions are degraded, small-bodied and highly mobile birds disproportionately contribute to meta-community cohesion and ecosystem functioning because of the lack of large-bodied and dispersal-limited birds. We thus advocate for the restoration of landscapes to facilitate seed dispersal and functional connectivity, ensuring the presence of large patches along with small patches as stepping-stones. Meanwhile, we recommend prioritizing conservation on small-bodied and highly mobile birds in fragmented landscapes, a subset of underappreciated species that yet play crucial roles in ecosystem functioning.

Uptake of metals, metalloids, and radiocesium varies with habitat use among passerine communities at coal combustion and nuclear fission legacy waste sites

Releases of coal combustion and nuclear fission wastes create contaminated landscapes that pose long-term management challenges. Efforts to facilitate the natural attenuation of legacy wastes in the environment can provide attractive habitat for passerine birds. Passerines have diverse foraging and nesting behaviors that lead to heterogenous contaminant exposure, yet few studies investigate contaminant uptake in passerines on a community scale. This study evaluated whether variation in habitat use strategies among passerines predicted the ongoing uptake of waste-derived elements by birds inhabiting coal combustion and nuclear fission legacy waste areas on the Savannah River Site in South Carolina. Blood concentrations of selenium, arsenic, mercury, zinc, copper, and lead were measured in 362 birds from 35 species. Whole-body radioactivity concentrations due to cesium-137 were measured in vivo in 143 birds from 31 species using a novel, field-based gamma spectrometry system. Generalized linear mixed effects models were used to evaluate whether trophic category and degree of terrestriality predicted contaminant burdens among passerine communities. Selenium, mercury, arsenic, and cesium-137 were elevated in passerines inhabiting legacy waste sites compared to those at reference sites. Blood concentrations of selenium and mercury varied by trophic category, whereas arsenic and cesium-137 increased with degree of terrestriality. The behavioral correlates of contaminant uptake among passerines provide insight into the mobility of waste-derived elements in ecosystems and inform species-level risk assessments. Future studies should use in vivo gamma spectrometry to conduct long-term field studies that evaluate the effects of internal radiation in small-bodied wildlife.

Integrating animal tracking and trait data to facilitate global ecological discoveries

Understanding animal movement is at the core of ecology, evolution and conservation science. Big data approaches for animal tracking have facilitated impactful synthesis research on spatial biology and behavior in ecologically important and human-impacted regions. Similarly, databases of animal traits (e.g. body size, limb length, locomotion method, lifespan) have been used for a wide range of comparative questions, with emerging data being shared at the level of individuals and populations. Here, we argue that the proliferation of both types of publicly available data creates exciting opportunities to unlock new avenues of research, such as spatial planning and ecological forecasting. We assessed the feasibility of combining animal tracking and trait databases to develop and test hypotheses across geographic, temporal and biological allometric scales. We identified multiple research questions addressing performance and distribution constraints that could be answered by integrating trait and tracking data. For example, how do physiological (e.g. metabolic rates) and biomechanical traits (e.g. limb length, locomotion form) influence migration distances? We illustrate the potential of our framework with three case studies that effectively integrate trait and tracking data for comparative research. An important challenge ahead is the lack of taxonomic and spatial overlap in trait and tracking databases. We identify critical next steps for future integration of tracking and trait databases, with the most impactful being open and interlinked individual-level data. Coordinated efforts to combine trait and tracking databases will accelerate global ecological and evolutionary insights and inform conservation and management decisions in our changing world.

Two-Step Loss of GLUTs in the High-Metabolism Passerines

Glucose transporters (GLUTs) play vital roles in cellular metabolism. Understanding their evolutionary dynamics in birds is essential for elucidating avian physiology and adaptation. However, the choice of gene detection method in gene family analysis may affect the conclusion. Here, we present a comprehensive investigation of methodologies and GLUT gene loss events in avian lineages, focusing on the loss of GLUT4 and GLUT8. To illustrate the effects of these methods, we first employed BUSCO-based homolog identification, calculated pairwise evolutionary distances between different species, and performed separate blastn and blastp searches to identify homologs in two groups of animals. Our analyses revealed a significant decline in blastn accuracy with increasing evolutionary distance, represented by relative divergence times. Through a more robust blastp-based gene detection pipeline, we provide evidence for the loss of GLUT genes in birds based on 58 vertebrate genomes, including 47 bird species. Our results support the reported early loss of GLUT4 in Aves. We also newly emphasize the absence of GLUT8 in passerines, potentially due to adaptation to high-sugar diets in their ancestors. These findings enhance our knowledge of avian metabolism and the evolution of GLUT genes.

Social context and the evolution of delayed reproduction in birds

One puzzling feature of avian life histories is that individuals in many different lineages delay reproduction for several years after they finish growing. Intraspecific field studies suggest that various complex social contexts-such as cooperative breeding groups, nesting colonies, and display leks-result in delayed reproduction because they require forms of sociosexual development that extend beyond physical maturation. Here, we explicitly propose this hypothesis and use a full suite of phylogenetic comparative methods to test it, analyzing the evolution of age at first reproduction (AFR) in females and males across 963 species of birds. Phylogenetic regressions support increased AFR in colonial females and males, cooperatively breeding males, and lekking males. Continuous Ornstein-Uhlenbeck models support distinct evolutionary regimes with increased AFR for all of cooperative, colonial, and lekking lineages. Discrete hidden state Markov models suggest a net increase in delayed reproduction for social lineages, even when accounting for hidden state heterogeneity and the potential reverse influence of AFR on sociality. Our results support the hypothesis that the evolution of social contexts reshapes the dynamics of life history evolution in birds. Comparative analyses of even the most broadly generalizable characters, such as AFR, must reckon with unique, heterogeneous, historical events in the evolution of individual lineages.

Integrating Functional and Phylogenetic Diversity to Assess Bird Community Assembly Along the Major Rivers of Hainan Island, South China

Understanding the mechanisms associated with community assembly can contribute to explaining the formation and maintenance of biodiversity patterns. In this study, we used the line transect method to survey breeding birds along the three major rivers of the Nandu River, Changhua River and Wanquan River on Hainan Island, south China. The patterns of community assembly were subsequently assessed by integrating functional and phylogenetic diversity, whereas environmental factors and interspecific competition intensity were incorporated to determine whether community assembly in these rivers is driven by environmental filtering or interspecific competition. Our findings revealed that bird communities within rivers were characterized by an overall slight clustering (i.e., more similar species), with the upper reaches of the Changhua River and the lower reaches of the Nandu River showing over-dispersion, whereas the lower, middle, and upper reaches of the Wanquan River all showed clustering. Altitude and the human influence index were identified as the main factors driving bird community assembly within the three major rivers. Notably, for bird communities along different river reaches, the integration of functional and phylogenetic diversity prevented the mis-classification of over-dispersion or clustering in community structure caused by traits with weak phylogenetic signals, or the observation of traits unrelated to community assembly patterns. This empirical study demonstrates the importance of integrating functional and phylogenetic diversity, which not only contributes to gaining an understanding of the mechanisms underlying the development of community assemblies but also facilitates a determination of the extents to which function and phylogeny contribute to shaping the patterns of communities.

Assessing the effects of anthropogenic pressures on biodiversity: a multi-taxonomic approach in Basilicata, Italy

The combined pressures of anthropogenic activities require rapid assessments of environmental impacts on ecosystems to develop strategies for sustainable management and biodiversity conservation. This study investigates the consequences of the anthropogenic effects in the upper Val d'Agri (Basilicata, Italy) by employing a multi-taxonomic analysis to investigate spatial dynamics and species responses to these pressures. By cataloguing 151 diverse species of small mammals, reptiles, birds, ground beetles, and lichens, we established a valuable baseline for analysing the local biodiversity. We assessed the relationship between anthropic impacts (industrial areas, roads, agriculture, forestry, etc.), vegetation cover, and species diversity. Our findings revealed a negative relationship between the number of species and proximity to industrial areas, emphasising the impact of these activities. Moreover, we observed a predominance of generalist biological traits across taxa in all the study sites rather than an increase in species specialisation with increased distance. This may suggest a homogenising effect caused by various anthropogenic activities that cause habitat fragmentation and species mortality, underlining the lasting influence of these activities on the biodiversity of the upper Agri Valley. Additionally, our study identifies numerous protected species, highlighting their vulnerability and emphasising the necessity for targeted conservation efforts to safeguard their existence.

Continent-Wide Patterns of Climate and Mast Seeding Entrain Boreal Bird Irruptions

Avian irruptions are facultative, often periodic, migrations of thousands of birds outside of their resident range. Irruptive movements produce regional anomalies of abundance that oscillate over time, forming ecological dipoles (geographically disjunct regions of low and high abundance) at continental scales. Potential drivers of irruptions include climate and food variability, but these relationships are rarely tested over broad geographic scales. We used community science data on winter bird abundance (1989-2021) to identify spatiotemporal patterns of irruption for nine boreal birds across the United States and Canada and compared them to time series of winter climate and annual tree seed production. We hypothesized that, during irruption, bird abundance would decrease in regions experiencing colder winter climates (climate variability hypothesis) or low seed production resulting from the boom-and-bust of widespread mast-seeding patterns (resource variability hypothesis). Across all species, we detected latitudinal or longitudinal irruption modes, or both, demonstrating north-south and east-west migration dynamics across the northern United States and southern Canada. Seven of nine species displayed associations consistent with the climate variability hypothesis and six with the resource variability hypothesis. While irruption dynamics are likely entrained by multiple environmental drivers, future climate change could alter the spatial and temporal characteristics of avian irruption.

Global Trends of Trait Matching in Avian Frugivory and Its Consequences for the Complementarity and Irreplaceability of Birds

It is generally accepted that small birds cannot eat large fruits and that highly frugivorous species prefer lipid-poor ones (morphological and nutritional trait-matching). Yet, it is unclear if these rules operate globally and if their strength varies with latitude and on islands. This could have important functional implications for the degree of complementarity and irreplaceability of birds. We analyse avian frugivory in 59 communities across the globe and show that trait-matching is widespread. The strength of morphological trait-matching increased with latitude, and especially on islands, leading to high complementarity between large and small birds. However, whether this resulted in irreplaceability depended on the range of fruit sizes available in the community. Nutritional trait-matching was also common, but did not lead to complementarity or irreplaceability because birds with contrasting diets did not show opposite responses to lipid-poor fruits. We show that trait-matching is pervasive, but its functional consequences are complex.