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opencc-by-4.0Jun 2024View details →

Data & codes for "Changes in abundance and distribution of European forest bird populations depend on biome, ecological specialisation and traits"

<h1>1.    Selection of European forest bird species and classification of their biome preferences</h1> We selected all species that are related to forest and woodland based on two data sources: Storchová & Hořák (2018) and Tobias et al. (2022), resulting in 107 bird species studied (Data S1). We defined forest bird species as those using environments ranging from closed-canopy forests to more open-canopy woodlands (A. Lehikoinen & Virkkala, 2018; Storchová & Hořák, 2018; Tobias et al., 2022). We determined their biome specialisation using breeding distribution centroids and the overall breeding distribution of each of the species, using the global map of terrestrial ecoregions from Olson et al. (2001) and range data from European Breeding Bird Atlas 1 and 2 (Hagemeijer & Blair, 1997; Keller et al., 2020). We categorised species as Mediterranean, temperate, or boreal based on their predominant biogeographic region. We considered species commonly occurring over several biomes as “generalists”. For instance, we reclassified the two typically boreal species Glaucidium passerinum Linnaeus and Strix uralensis Pallas as “generalists” due to significant range expansions into central and southern Europe in recent decades, therefore no longer restricted to the boreal region. For the complete list of species, biome specialisation, traits, and specialisation indices, refer to Data S1. <h1>2.    Changes in abundance and distribution of European forest bird species</h1> We assessed long-term changes in European forest bird populations through two approaches: (i) changes in estimated total European-level species abundance over a 40-year timeframe; and (ii) changes in species spatial distribution over a 30-year timeframe (Fig. 1). We utilized the estimated trends in European-level population size (i.e., the total number of individuals) for each common native European bird species from 1980 to 2017, as reported by Burns et al. (2021). Three species out of the 107 studied forest species were missing in the original manuscript and we used data generated with the same method from 1980 to 2018 from the European assessment, Article 12 (https://nature-art12.eionet.europa.eu/article12/). These abundance trends were calculated by Burns et al. (2021) using multi-sourced annual times series. For each species, they gathered population estimates and trends from each European country as well as European Union (EU)-level population trends. They analysed these data with a Bayesian hierarchical model to reconstruct EU-level smoothed species population time series. The model outputs include an average annual rate of abundance change and an associated 95% credible interval (Burns et al., 2021). Therefore, we did not directly use the average annual rate of abundance change, as this would have led us to consider species with low uncertainty as similar to those with high uncertainty. To account for the uncertainty, we categorised species as (i) declining, i.e., annual rates below one, (ii) increasing, i.e., annual rates above one and (iii) stable, i.e., annual rate whose 95% CI overlap one, i.e., no significant change. To better acknowledge the magnitude of the abundance change, significant changes with rates below 0.98 were labelled as “strongly declining” (i.e., 6.5% of the 107 species), while those above 1.02 were labelled as “strongly increasing” (i.e., 11% of the 107 species). To evaluate the sensitivity of the decision to categorised abundance change data, we also analysed abundance trend as continuous variable (see Supporting Information Fig. S8). To determine changes in species distributions, we used a comparison of species distributions between two periods (i.e., 1985-1988 and 2013-2017) using the European Breeding Bird Atlas 1 and 2 (EBBA 1 & 2; Hagemeijer & Blair, 1997; Howard et al., 2023; Keller et al., 2020). Howard et al. (2023) provided calculations of observed colonisation and extinction areas at a 50 x 50 km resolution across Europe. We measured changes in range as the difference between colonisations and extinctions of each species, with negative values indicating contracting ranges and positive values indicating expanding ranges. Additionally, we calculated the shift in the centre of gravity of the distribution range between the two periods, as a distance (km) along the south-north gradient for each species (Howard et al., 2023). <h1>3.    Trait and specialisation data for European forest bird species</h1> We extracted data for six functional traits from several sources (Table 1). (i) The species temperature index (STI)represents the long-term average temperature within the species’ breeding range (A. Lehikoinen et al., 2021). (ii) Diet data during the breeding season were obtained from Storchová & Hořák (2018), classifying species into binary variables as vertebrate carnivorous, invertebrate carnivorous, and herbivores (combining the leaf and seed eaters). Storchová & Hořák (2018) classified species into a diet category when the corresponding food resource represented at least 10% of the species diet throughout the breeding season. Therefore, one species can be in several categories (i.e., omnivores). (iii) We obtained nesting site data from Pearman et al. (2014), classifying species into binary variables as ground nesters, tree hole nesters, or elevated nesters (> 1 m in a tree or shrub). We also included data on (iv) species dependence on old-growth forests (Data S1; mostly from Fraixedas et al. (2015) and Mönkkönen et al. (2014), if present on both references, we classified them as “1” and if only in one reference as “0.5”), (v) migration distance (Howard et al., 2023), and (vi) body mass (Tobias et al., 2022). Finally, we extracted and developed seven species specialisation indices. (i) We used an overall specialisation index based on multiple traits (i.e., temperature, diet, foraging behaviour and substrate, habitat, and nesting site), and (ii) a nesting specialisation index, both obtained from Morelli et al. (2019). Both indices represent species specialization based on the dispersion of trait preferences for each species: e.g., nesting specialism equal 0 for species that nest in all habitat type and equal 1 for species that nest in only one habitat type). They are both calculated using the Gini index of inequality, which measures overall dispersion across, e.g., all traits for the overall specialization, based on data from Pearman et al. (2014) and Storchová & Hořák (2018). For additional information, see Morelli et al. (2019). We also used (iii) the diet specialisation index, (iv) the species distribution range during the breeding season (hereafter “breeding range area”) and (v) the climatic niche breadth from Reif et al. (2016). The diet specialisation index was calculated as the coefficient of variation for diet preferences for each species, where high values denotes specialized species (Reif et al., 2016). The breeding range area was evaluated as the number of 50-km squares in the distribution maps in Europe occupied by each species during the reproduction period, and is based on EBBA 1 (Hagemeijer & Blair, 1997). The climatic niche breadth was calculated as the difference between the 5% hottest and the 5% coldest mean temperature between April and June in which each species occurs, using EBBA 1 (Hagemeijer & Blair, 1997; Reif et al., 2016). Additionally, (vi) we calculated a broadleaf forest specialisation index based on binary forest habitat preferences (Storchová & Hořák, 2018), assigning values of one for species found only in broadleaf forests; zero for those in coniferous forests, and 0.5 for those found in both. Lastly, (vii) we created a forest specialisation index based on the species habitat preferences (Storchová & Hořák, 2018). The forest specialisation index was calculated as the mean of species affinity across habitats. We used increasing habitat weights along a gradient of tree dominance: open habitats as 1, shrubland as 1.5, woodland as 2 (i.e., species associated with habitats structured by trees in lower density than in forest), forest generalist (found in both coniferous and broadleaf dense forests) as 3, and forest specialist (found only either in coniferous or broadleaf dense forests) as 4. For instance, the index value for species occurring either in shrubland, woodland or both broadleaf and coniferous forests is 2.167. <h1>4.    Data analysis</h1> Data analyses were conducted with R software version 4.4.1. (R Core Team, 2024). Given the non-independence of species due to their genetic relatedness, we accounted for interspecific phylogenetic distance in all models. We constructed the phylogenetic tree for the 107 European forest bird species using ‘rotl’ and ‘ape’ R-packages (Michonneau et al., 2022; Paradis et al., 2023). We used rotl as an interface with the "Open Tree of Life", employing tol_induced_subtree R-function to generate the phylogenetic tree and compute.brlen R-function to set branch lengths using Grafen’s computation. We generated separate phylogenetic trees for boreal (17), temperate (15), Mediterranean (16) and “generalist” (59) species to perform biome-specific analysis (see Supplementary Information, Figs. S1 & S2). To investigate the effects of functional traits and specialisation indices on abundance, range changes, and distribution shift, we used two regression methods. All methods were based on the relationships between a measure of change and a functional trait or specialisation index. Our sample unit is an individual forest bird species (i.e., one value for each species, either abundance or range change, or distribution shift). Abundance change was a categorical variable (i.e., strong decline – decline – stable – increase – strong increase), while range change (i.e., difference between colonisation and extinction) and distribution shift (i.e., south-north shift) were continuous variables. Therefore, to study abundance changes, we used proportional-odds linear mixed effects model using (Phylo)clmm R-function from the ‘ordinal’ R-package (Christensen, 2022). Interspecific phylogenetic relatedness was included as a random effect, reflecting the correlation between species based on phylogenetic distances (see also Hagge et al. (2021) and Seibold et al. (2015)). For distribution changes, we employed phylogenetic generalised least squares regression (PGLS) using the gls R-function from the ‘nlme’ R-package (Pinheiro et al., 2023). The phylogenetic correlation structure was integrated into PGLS using Pagel’s lambda parameter (λ; Pagel (1999)) a widely used measured of phylogenetic signal strength (see, e.g., Hagge et al., 2021; Triviño et al., 2013). Furthermore, we included latitude, a key driver of bird communities at broad scales (Luoto et al., 2007), as a fixed covariable (centroid latitude of the species’ breeding distribution) in all global models (i.e., species from all biomes together), except for the STI model due to strong correlation. For biome-specific analysis, we included latitude only in boreal species models for range change and distribution shift, as it significantly improved model fit (ΔAIC < -2). We did not add latitude for models specific to temperate, Mediterranean, and generalist species since it did not improve model fits (ΔAIC > -2). Additionally, we included breeding range area in range change and distribution shift models, assuming that species with larger ranges would exhibit larger shifts. We scaled predictors to a mean of 0 and standard deviation of 1 to facilitate effect size comparisons. We adjusted p-values using the Holm method (for n=3) to account for multiple testing of traits and specialisation indices on three response variables.

opencc-zeroOct 2021View details →

Major population splits coincide with episodes of rapid climate change in a forest-dependent bird

Climate change influences population demography by altering patterns of gene flow and reproductive isolation. Direct mutation rates offer the possibility for accurate dating on the within-species level but are currently only available for a handful of vertebrate species. Here, we use the first directly estimated mutation rate in birds to study the evolutionary history of pied flycatchers (Ficedula hypoleuca). Using a combination of demographic inference and environmental niche modelling, we show that all major population splits in this forest-dependent system occurred during periods of increased climate instability and rapid global temperature change. We show that the divergent Spanish subspecies originated during the Eemian-Weichselian transition 115 – 104 thousand years ago (kya), and not during the last glacial maximum (26.5 - 19 kya), as previously suggested. The magnitude and rates of climate change during the glacial-interglacial transitions that preceded population splits in pied flycatchers were similar to, or exceeded, those predicted to occur in the course of the current, human-induced climate crisis. As such, our results provide a timely reminder of the strong impact that episodes of climate instability and rapid temperature changes can have on species' evolutionary trajectories, with important implications for the natural world in the Anthropocene.

opencc-zeroNov 2021View details →

Landscape genetics Afromontane forest birds - microsatellite data

<a name="_Hlk61564128"></a>Species confined to naturally fragmented habitats may exhibit intrinsic population complexity which may challenge interpretations of species response to anthropogenic landscape transformation. In South Africa, where native forests are naturally fragmented, forest‐dependent birds have undergone range declines since 1992, most notably among insectivores. These insectivores appear sensitive to the quality of natural matrix habitats, and it is unknown whether transformation of the landscape matrix has disrupted gene flow in these species. We undertook a landscape genetics study of four forest‐dependent insectivorous songbirds across southeast South Africa. Microsatellite data were used to conduct a priori optimization of landscape resistance surfaces (land cover, rivers and dams, and elevation) using cost‐distances along least‐cost pathway (LCP), and resistance distances (IBR). We detected pronounced declines in effective population sizes over the past two centuries for the endemic forest specialist Cossypha dichroa and Batis capensis, alongside recent gene flow disruption in B. capensis, C. dichroa and Pogonocichla stellata. Landscape resistance modelling showed both native forest and dense thicket configuration facilitates gene flow in P. stellata, B. capensis and C. dichroa. Facultative dispersal of P. stellata through dense thicket likely aided resilience against historic landscape transformation, whereas combined forest‐thicket degradation adversely affected the forest generalist B. capensis. By contrast, Phylloscopus ruficapilla appears least reliant upon landscape features to maintain gene flow and was least impacted by anthropogenic landscape transformation. Collectively, gene flow in all four species is improved at lower elevations, along river valleys, and riparian corridors— where native forest and dense thicket better persist. Consistent outperformance of LCP over IBR land‐cover models for P. stellata, B. capensis and C. dichroa demonstrates the benefits of wildlife corridors for South African forest‐dependent bird conservation, to ameliorate the extinction debts from past and present anthropogenic forest exploitation.

opencc-zeroFeb 2022View details →

Weak effects of birds, bats and ants on their arthropod prey on pioneering tropical forest gap vegetation

The relative roles of plants competing for resources versus top-down control of vegetation by herbivores, in turn impacted by predators, during early stages of tropical forest succession remain poorly understood. Here we examine the impact of insectivorous birds, bats and ants exclusion on arthropods communities on replicated 5x5 m of pioneering early successional vegetation plots in lowland tropical forest gaps in Papua New Guinea. In plots from which focal taxa of predators were excluded we observed increased biomass of herbivorous and predatory arthropods, and increased density, and decreased diversity of herbivorous insects. However, changes in the biomass of plants, herbivores and arthropod predators were positively correlated or uncorrelated between these three trophic levels and also between individual arthropod orders. Arthropod abundance and biomass correlated strongly with the plant biomass irrespective of the arthropods' trophic position – a signal of bottom-up control. Patterns in herbivore specialization confirm lack of a strong top-down control and were largely unaffected by the exclusion of insectivorous birds, bats and ants. No changes of plant-herbivore interaction networks were detected except for decrease in modularity of the exclosure plots. Our results suggest weak top-down control of herbivores, limited compensation between arthropod and vertebrate predators, and limited intra-guild predation by birds, bats and ants. Possible explanations are strong bottom-up control, a low activity of the higher order predators, especially birds, possibly also bats, in gaps, and continuous influx of herbivores from surrounding mature forest matrix.

opencc-zeroMay 2022View details →

Territory-level temperature influences breeding phenology and reproductive output in three forest passerine birds

Temperature plays an important role in determining the breeding phenology of birds in temperate climates, with higher spring temperatures associated with earlier breeding. However, the effect of localised territory-scale temperature variations is poorly understood, with relationships between temperature and breeding phenology mostly studied using coarse-grained climatic indices. Here, we interpolate spring temperatures recorded at 150 m2 grid intersections encompassing 417 ha of forest to examine the influence of territory-scale temperature, and its interaction with mean annual temperature, on territory selection, breeding phenology, clutch size and fledging success for three co-occurring single-brooded passerine birds using data from 672 nests over four years. All species exhibited significant trends in reproductive traits associated with territory-scale temperature. Pied flycatchers Ficedula hypoleuca settled in cooler territories first, where they raised more fledglings. Blue tits Cyanistes caeruleus laid larger clutches in warmer territories in warm years and always laid earlier at warmer territories irrespective of annual temperature variation. Contrastingly, pied flycatcher and wood warbler Phylloscopus sibilatrix breeding phenology was earlier at warmer territories in cool years and cooler territories in warm years, with wood warbler clutch size responding similarly to this interaction. Greater previous breeding experience and increased higher rates of historical territory occupancy (territory quality) also predicted earlier breeding phenology and higher fledging success for pied flycatchers. We suggest that the migratory pied flycatcher and wood warbler are best synchronised with their prey availability in cooler years at a local population level. However resident blue tits match local phenology across all years, which is potentially advantageous under warmer predicted climate change scenarios. We conclude that temperature at the territory scale can be an important driver of settlement and breeding phenology and influence reproductive traits.

opencc-zeroMay 2022View details →

Subarctic afforestation: effects of forest plantations on ground-nesting birds in lowland Iceland

Planting forests is a commonly suggested measure to mitigate climate change. The resulting changes in habitat structure can greatly influence the diversity and abundance of pre-existing wildlife. Understanding these consequences is key for avoiding unintended impacts of afforestation on habitats and populations of conservation concern. Afforestation in lowland Iceland has been gaining momentum in recent years and further increases are planned. Iceland supports internationally important breeding populations of several ground-nesting, migratory bird species that mostly breed in open habitats. If afforestation impacts the distribution and abundance of these species, the consequences may be apparent throughout their non-breeding ranges across Europe and Africa. To quantify the effects of plantation forests on the abundance and distribution of ground-nesting birds (in particular waders, Charadriiformes), surveys were conducted on 161 transects (surrounding 118 plantations) perpendicular to forest edges throughout Iceland. The resulting variation in density with distance from plantation was used to estimate the likely changes in bird numbers resulting from future afforestation plans, and to explore the potential effects of different planting configuration (size and number of forest patches) scenarios. Of seven wader species, densities of five (golden plover (Pluvialis apricaria), whimbrel (Numenius phaeopus), oystercatcher (Haematopus ostralegus), dunlin (Calidris alpina) and black-tailed godwit (Limosa limosa)) in the 200 m surrounding plantations were just over half of those further away (up to 700 m). Redshank (Tringa totanus) densities were lowest <150 m from the plantation edge while snipe (Gallinago gallinago) densities were 50% higher close to plantations (0-50 m) than further away (51-700 m), and no consistent effects of plantation height, diameter, density or type were identified. Plantations are typically small and widespread, and simulated scenarios indicated that total declines in bird abundance resulting from planting trees in one large block (1000 ha) could result in only ~11% of the declines predicted from planting multiple small blocks (1 ha) in similar habitats. Synthesis and application: The severe impact that planting forests in open landscapes can have on populations of ground-nesting birds emphasises the need for strategic planning of tree-planting schemes. Given Iceland's statutory commitments to species protection and the huge contribution of Iceland to global migratory bird flyways, these are challenges that must be addressed quickly, before population-level impacts are observed across migratory ranges.

opencc-zeroJun 2022View details →

Ecological and geographical marginality in rear edge populations of Palaearctic forest birds (data)

The centre–periphery hypothesis predicts that habitat suitability will decrease at the edge of a species' range, a pattern often questioned by empirical data. Here we explore if habitat suitability decreases southwards and shapes the abundance distribution of rear edge populations of forest birds within the restricted geographical setting of the south-western Palaearctic. We also test if birds endemic to the area fit more poorly to the latitudinal decrease of habitat suitability due to the putative effect of adaptations to regional conditions. Location: North-western Africa (Morocco) Time period: Present day Major taxa studied: Passerines (11 species) Methods: Bird occurrences were used to model species distribution and line transects were used to estimate bird abundance. Occurrence probabilities provided by species distribution models were used to display the spatial patterning of habitat suitability. Habitat suitability was employed to predict abundance after controlling for the effect of the distance to some regional source areas of forest birds (tree covered large areas). The species were classified as North African endemic according to an updated review of their taxonomic status. Results: Habitat suitability decreased southwards, supporting the predicted relationship between ecological and geographical marginality in most species. Abundance was positively correlated to habitat suitability and negatively correlated to distance to source areas. The taxonomic status of birds did not affect the patterns. Main conclusions: The southward decrease of habitat suitability predicted by the centre–periphery hypothesis shapes the distribution of rear edge populations of forest birds within the south-western Palaearctic. As most of these populations are endemic, the results suggest that they track the gradients in isolation within the geographical setting of north-western Africa. These results support the vulnerability of these isolated, peripheral populations of forest birds to large-scale environmental changes in a region under the effect of increasing drought and temperature.

opencc-zeroJul 2022View details →

Trait shifts in bird communities from primary forest to human settlements in Mexican seasonal forests: Are there ruderal birds?

Agriculture, cattle grazing, and human settlements negatively affect bird biodiversity, driving the loss of ecologically specialized species and favoring the dominance of generalists. Because ecological pressures define organisms' success by acting on their intrinsic traits, biodiversity loss due to anthropization might cause directional trait shifts. Here, we use a trait-based approach to find empirical evidence of trait-shifts in bird communities across an anthropization gradient in seasonal forests in central Mexico. We performed point-count bird surveys within a region of tropical deciduous and seasonal oak forests considering three degrees of anthropization: primary forest, secondary growth, and human settlements. A multivariate analysis (PCA) showed similar trait-covariation patterns for both forest types; in the anthropized habitat the bird communities exhibited shorter life-cycles, higher fecundity, and broader ecological niches (diet, foraging habitat, and nesting resources) than those in the primary forests. Our finding of directional trait shifts resembles Evolutionary Ecological Strategies Theory (EES) predictions for successful organisms within highly disturbed anthropized habitats, which are known as a "ruderal adaptative strategy" in the EES framework. The use of trait-based approaches could improve ecological generalizations in bird communities, leading to a better understanding of avian biodiversity's responses to anthropization.

Figure 3 in Composition and dynamics of mixed flocks of birds in a remnant of Submontane Atlantic Rain Forest in southern Brazil

Figure 3. Distribution of the three sampling sectors (I, II, and III) in the study area, in Parque Nacional Aparados da Serra, municipality of Praia Grande, southern Santa Catarina state, Brazil.

Figure 1 in Composition and dynamics of mixed flocks of birds in a remnant of Submontane Atlantic Rain Forest in southern Brazil

Figure 1. Location of the study area in Parque Nacional Aparados da Serra, municipality of Praia Grande, southern Santa Catarina state, Brazil.

Figure 7 in Composition and dynamics of mixed flocks of birds in a remnant of Submontane Atlantic Rain Forest in southern Brazil

Figure 7. Monthly variation of the average size (in the number of individuals) of the mixed flocks of birds, in Parque Nacional Aparados da Serra, municipality of Praia Grande, southern Santa Catarina, Brazil, between October 2016 and September 2017.

Figure 4 in Composition and dynamics of mixed flocks of birds in a remnant of Submontane Atlantic Rain Forest in southern Brazil

Figure 4. Simple linear regression of the relationship between species richness and the number of individuals from mixed flocks of birds, in Parque Nacional Aparados da Serra, municipality of Praia Grande, southern Santa Catarina state, Brazil, between October 2016 and September 2017.

opencc-by-nc-4.0Oct 2021View details →

Figure 3 in Bird-plant interaction networks in native forests and eucalyptus plantations within a protected area

Figure 3. Comparison of the number of interactions between frugivorous birds and plants between native forest and eucalyptus plantation in the PEIT. (a): Fecal samples interactions (P-value = 0.83, W = 3.5); (b): Focal observation interactions (P-value = 0.99, W = 4.0).

opencc-by-nc-4.0Oct 2021View details →

Figure 2 in Bird-plant interaction networks in native forests and eucalyptus plantations within a protected area

Figure 2. Interaction networks between frugivorous birds and zoochoric plants, according to the focal observations of birds in both sampled habitats. The circles represent the plant species, and the species of birds are represented by triangles. The acronyms in the center of the figures are the scientific names of the species (Supplementary material 1). The thickness of the links (lines) is related to the connectivity between each species (the thicker the line, the more records this interaction had). Each color represents a cluster of species that are more connected within each other than with between species from other clusters due to its modularity (Q). (a): Fragments of native forest; (b): Fragments of eucalyptus plantation.

opencc-by-nc-4.0Oct 2021View details →

Figure 1 in Bird-plant interaction networks in native forests and eucalyptus plantations within a protected area

Figure 1. Interaction networks between frugivorous birds and zoochoric plants, according to the fecal samples of birds in the understory of the two sampled habitats. The circles represent the plant species, and the triangles are representing the species of birds. The acronyms in the center of the figures are the scientific names of the species (Supplementary material 1). The thickness of the links (lines) is related to the connectivity between each species (the thicker the line, the more records this interaction had). Each color represents a cluster of species that are more connected within each other than with species from other clusters due to its modularity (Q). (a): F fragments of native forest; (b): Fragments of eucalyptus plantation.

opencc-zeroMay 2024View details →

Data from: Amazonian rivers are leaky barriers to gene flow in forest understory birds

Ever since Alfred Russel Wallace's nineteenth-century observation that related terrestrial species are often separated on opposing riverbanks, major Amazonian rivers have been recognized as key drivers of speciation. However, rivers are dynamic entities whose widths and courses may vary through time. It thus remains unknown how effective rivers are at reducing gene flow and promoting speciation over long timescales. We fit demographic models to genomic sequence to reconstruct the history of gene flow in three pairs of avian taxa fully separated by different Amazonian rivers, and whose geographic ranges do not make contact in headwater regions. Models with gene flow were best fit, but still supported an initial period without any gene flow which ranged from 187,000 to over 959,000 years, suggesting that rivers are capable of initiating speciation through long stretches of allopatric divergence. Allopatry was followed by either bursts or prolonged episodes of gene flow that retarded genomic differentiation but did not homogenize populations. Our results support Amazonian rivers as key barriers that promoted speciation and the buildup of species richness, but they also suggest that river barriers are often leaky, with genomic divergence accumulating slowly due to episodes of substantial gene flow.

opencc-zeroJun 2024View details →

Acoustic phenology of tropical resident birds differs between native forest species and parkland colonizer species

Most birds are characterized by a seasonal phenology closely adapted to local climatic conditions, even in tropical habitats where climatic seasonality is slight. In order to better understand the phenologies of resident tropical birds, and how phenology may differ among species at the same site, we used ~70,000 hours of audio recordings collected continuously for two years at four recording stations in Singapore and nine custom-made machine learning classifiers to determine the vocal phenology of a panel of nine resident bird species. We detected distinct seasonality in vocal activity in some species but not others. Native forest species sang seasonally. In contrast, species which have had breeding populations in Singapore only for the last few decades exhibited seemingly aseasonal or unpredictable song activity throughout the year. Urbanization and habitat modification over the last 100 years have altered the composition of species in Singapore, which appears to have influenced phenological dynamics in the avian community. It is unclear what is driving the differences in phenology between these two groups of species, but it may be due to either differences in seasonal availability of preferred foods, or newly established populations may require decades to adjust to local environmental conditions. Our results highlight the ways that anthropogenic habitat modification may disrupt phenological cycles in tropical regions in addition to altering the species community.

opencc-zeroJun 2024View details →

Data from: Insectivorous birds and bats outperform ants in the top-down regulation of arthropods across strata of a Japanese temperate forest

Birds, bats, and ants are recognized as significant arthropod predators. However, empirical studies reveal inconsistent trends in their relative roles in top-down control across strata. Here, we describe the differences between forest strata in the separate effects of birds, bats, and ants on arthropod densities and their cascading effects on plant damage. We implemented a factorial design to exclude vertebrates and ants in both the canopy and understory. Additionally, we separately excluded birds and bats from the understory using diurnal and nocturnal exclosures. At the end of the experiments, we collected all arthropods and assessed herbivory damage. Arthropods responded similarly to predator exclusion across forest strata, with a density increase of 81% on trees without vertebrates and 53% without both vertebrates and ants. Additionally, bird exclusion alone led to an 89% increase in arthropod density, while bat exclusion resulted in a 63% increase. Herbivory increased by 42% when vertebrates were excluded and by 35% when both vertebrates and ants were excluded. Bird exclusion alone increased herbivory damage by 28%, while the exclusion of bats showed a detectable but non-significant increase (by 22%). In contrast, ant exclusion had no significant effect on arthropod density or herbivory damage across strata. Our results reveal that the effects of birds and bats on arthropod density and herbivory damage are similar between the forest canopy and understory in this temperate forest. In addition, ants were not found to be significant predators in our system. Furthermore, birds, bats, and ants appeared to exhibit antagonistic relationships in influencing arthropod density. These findings highlight, unprecedentedly, the equal importance of birds and bats in maintaining ecological balance across different strata of a temperate forest.

opencc-zeroJun 2024View details →

Occupancy of two Colombian endemic birds (Habia gutturalis) and White-Mantled Barbet (Capito hypoleucus) in fragmented forests of the Central Andes in Colombia

The Sooty Ant-Tanager (Habia gutturalis) and White-mantled Barbet (Capito hypoleucus) are endangered and endemic birds of Colombia. Both species have small geographic ranges and presumably low population sizes possibly due to habitat destruction and fragmentation. In order to estimate the effects of landscape features on the occupancy of both species, we sampled a variety of landscape configurations within the buffer zones of two hydroelectric impoundments in the Central Andes of Colombia and applied occupancy models to estimate the proportion of area occupied as a function of these covariates. We surveyed 35 point-counts in each hydroelectric impoundment, between June and July of 2014 and 2015. We used single-season models to estimate occupancy while recognizing imperfect detection. Mean occupancy estimates in the study area were similar for both species (0.61 SD=0.33 for the Sooty Ant-Tanager and 0.63 SD=0.25 for the White-mantled). Nonetheless, occupancy probability within the study area was very different between them. The best model for the Sooty Ant-Tanager indicated a decrease in occupancy with elevation, whereas the top model for the White-mantled Barbet indicated an increase in occupancy with distance from streams. Detection probabilities were similar for both species (>0.4) and declined significantly during the second year. Our results provide quantitative guidelines that can be used to evaluate and monitor the state of these populations on the short and long term.