Forest Birds Research Articles

Protected Areas Do Not Outweigh the Species Richness or Functional Diversity and Traits of Birds in Brazil

Protected areas (PAs) are widely recognized as being essential for maintaining global biodiversity. In this study, I aimed to determine whether PAs support a greater richness of forest bird species than unprotected habitats and whether they exhibit functional diversity indices and traits comparable to those found in protected forests in the eastern Brazilian Semideciduous Atlantic Forest. I conducted bird surveys across 20 forest fragments of varying sizes (43 to 37,000 ha), 12 of which were legally designated as PAs. The results indicated that species richness was not significantly higher in PAs and that there were no significant differences in functional diversity indices and traits between unprotected and protected forests. In eastern Brazil, some forest remnants were designated as PAs merely because they were among the last remaining patches within a heavily fragmented landscape. Therefore, protected areas do not necessarily serve as accurate proxies for well-preserved habitats.

Changes in breeding activity of Southeast Asian songbirds in response to the severity of the dry season

Droughts are expected to become more frequent and severe as the climate changes. Tropical songbirds likely reduce reproductive output during extreme droughts such as El Niño events in Southeast Asia as a tradeoff for reducing mortality risks. However, the timing of these rainfall responses and the extent of these reproductive costs are largely unknown in this region. Here we quantified how the amount and frequency of rainfall impacted nest initiation (first egg dates), and how the amount of rainfall may impact the duration of nesting in a given season (last expected fledging date). We tested these hypotheses on seven species of understory passerines in a secondary dry evergreen forest in northeastern Thailand. Using ten years of data (2014–2023) we examined the relationship between rainfall examining both total amounts occurring at key parts of the year (such as just prior to the breeding season) as well the number of “no-rain” days (rainfall gap) on (1) first egg dates and the (2) last expected fledging date of a given season. More severe dry seasons (longer time gaps in rainfall) caused longer delays in the start of egg laying and gap days tended to have a stronger effect than total rainfall. Lower breeding season rainfall resulted in later fledge dates for four species; lower rainfall amounts during the dry season resulted in later fledge dates for three species. There was no relationship between first egg dates and last expected fledging dates for any target species. Overall, it appears that droughts are likely shortening the breeding seasons of many tropical forest birds, but the reproductive costs are still difficult to estimate precisely. Further investigation is also recommended as to how rainfall is affecting nesting success particularly whether greater rainfall is regularly associated with earlier end of season fledging dates.

Comparing Historical and Contemporary Observations of Avian Fauna on the Yáláƛi (Goose Island) Archipelago, British Columbia, Canada.

In an era of global change, historical natural history data can improve our understanding of ecological phenomena, particularly when evaluated with contemporary Indigenous and place-based knowledge. The Yáláƛi (Goose Island) Archipelago is a group of islands in Heiltsuk (Haíɫzaqv) territory on the Central Coast of British Columbia, Canada. Not only has this region been important to the Heiltsuk for millennia but also it is both a federally and internationally recognized important bird area. In this study, we compare data collected by Charles J. Guiguet, a biologist who documented bird communities at Yáláƛi in the summer of 1948, to three different contemporary surveys and to citizen-science data. We find that the relative abundances of forest bird species (i.e., birds that use the terrestrial island ecosystems) in 1948 differed to those observed in systematic surveys in 2011. While Orange-crowned Warblers, Dark-eyed Juncos, and Red Crossbills comprised 55% of detections by Guiguet in 1948, the three most abundant species in 2011 were Bald Eagles, Varied Thrushes, and Pacific Wrens, and these accounted for only 25% of detections. Although we could not make a quantitative comparison, we provide summaries of each species observed in surveys or reported on eBird. We also incorporate Heiltsuk place-based knowledge to enrich our discussion of the variability in bird communities over time, from how changes in mammal communities and human use may have shaped vegetation dynamics to how large-scale natural phenomena impacted topography. To understand which birds are present and how their communities are changing over time, we recommend continued monitoring of the bird communities at Yáláƛi.

Oropouche Virus: An Emerging Neuroinvasive Arbovirus.

Oropouche virus (OROV) is an arthropod-borne virus (arbovirus) in the Orthobunyavirus genus and Peribunyaviridae viral family that is endemic to parts of South America, Central America, and the Caribbean. It has recently emerged in Cuba, and travel-imported cases are recently being reported in the United States and Europe. Typically maintained in a sylvatic cycle between certain forest sloths, non-human primates, birds, and mosquitoes, OROV disease outbreaks can occur in an urban cycle between certain biting midges and/or mosquitoes and humans. Clinically, approximately 60% of infections are symptomatic with an abrupt fever and non-specific influenza-like illness within 3 to 10 days. Many initial OROV infections can present similarly to chikungunya, dengue, and Zika virus infections. Interestingly, OROV infections can follow a biphasic course with recurrence of symptoms approximately 1 week after initial symptom onset. Concerningly, similar to Zika virus, it appears that vertical transmission of OROV may occur with potentially adverse effects on fetal development including miscarriages. Neuroinvasion of OROV occurs in animal models, and human cases of meningitis, encephalitis, and peri-infectious Guillain-Barré syndrome have all been reported. Diagnosis is either through detection of OROV nucleic acid, OROV immunoglobulin M, or OROV neutralizing antibodies in the serum and/or cerebrospinal fluid. No antiviral treatments are available, and there are no current vaccines. Preventing mosquito and biting midge bites is key. Neurologists should be aware of and report any potential neuroinvasive OROV disease cases to local/state/territorial health departments. ANN NEUROL 2024.

Formation of the spatial structure of the bird population in High-mountainous Dagestan and the concept of preserving its avifauna

The presented work is the concluding part of a previously published article (Vilkov 2023) and based on a mathematical analysis of the empirical material collected during route bird surveys in 1998–2021 in the High­mountainous Province of Dagestan. Based on the long­term average population density data for 96 birds nesting and likely nesting, a cluster analysis was carried out, during which the identified avifaunal communities were grouped according to the similarity of their abundance. Using correlation analysis, environmental factors were identified that determine the territorial variability of bird population abundance. Based on the estimates of the strengths of connections determined from the Jaccard­Naumov coefficients similarity data matrix, a graph was constructed that reflects the spatial structure of the bird population at the level of selected key areas. When interpreting the spatial structure of the bird population using cluster and correlation analysis data, as well as faunal and ecological ranking data, similarities between the compared avifaunal communities were revealed, and 4 main trends in bird population changes in factor space were identified. Based on the results of assessing the strength and generality of the relationships between structure­forming factors and the territorial variability of the bird population (taking into account the areas of landscapes), the most significant was the impact of afforestation, the area of open spaces and the area of residential landscapes. When interpreting spatial differences taking into account natural and anthropogenic changes, it is possible to create a predictive model of the transformation of avifaunal communities within the study area. Analysis of existing threats that have a negative impact on the number and species diversity of birds allowed developing a population management concept based on 4 strategic directions. 1. Gasification of High­Mountain Dagestan to prevent deforestation and restore the species diversity of forest birds. 2. To preserve the species diversity of meadow birds, redirect cattle grazing to areas of meadows with increased overgrowth of grassy vegetation. 3. Increase the area of fields for sowing grain crops to preserve the species diversity of granivorous birds. 4. To preserve the species diversity of birds of prey, install perches in a mosaic pattern in the fields of grain crops.

Essential steps for establishing a large‐scale passive acoustic monitoring for an elusive forest bird species: the Eurasian Woodcock (Scolopax rusticola)

In light of global biodiversity loss, comprehensive monitoring of species and biodiversity is fundamental for effective conservation management. Technology‐driven approaches, particularly in the field of bioacoustics, have gained importance, with autonomous recording units (ARUs) such as the AudioMoth being a notable example. However, a systematic application of this technology in large‐scale passive acoustic monitoring (PAM) schemes is challenging because of a lack of species‐specific calibration techniques and information on survey design. Using Eurasian Woodcock Scolopax rusticola as our focal species, we present application‐oriented guidelines for testing and implementing a terrestrial, single‐species PAM scheme. In this process, we assessed the species‐specific detection space of AudioMoths, considering the influence of recording setup and location. ARUs had similar detection rates as a human observer when set up in locations with low vegetation. A further comparative analysis of bioacoustic and traditional roding surveys confirmed the comparability of the two methods. The last step comprised an evaluation of BirdNET as a means of automated species detection. Although BirdNET reliably detected Woodcock occurrence, our results underline the need for rigorous testing of computer‐aided data analysis as well as recording hardware before establishing PAM. We demonstrate that low‐cost open source ARUs and open access analysis tools can yield results on a par with traditional survey methods, and we provide specific recommendations for PAM for Eurasian Woodcock.

Limited evidence for the influence of the physical structure and floristics of habitat on a boreal forest bird community

Studies conducted at regional and continental scales show that avian richness, community composition, and abundance are associated with variation in the vegetation physical structure and community composition (floristics) within broad habitat types. The relative contributions of physical structure and floristics are contested, and relationships are often taxon-specific. We used 110 microphone arrays deployed across 90 sampling locations and two breeding seasons to survey an avian community in the boreal forest in Labrador, Canada. Our objectives were (1) to describe the avian community of an underrepresented portion of the boreal forest, (2) to estimate the relationships between avian species richness and habitat characteristics, (3) to estimate if species detection at a given location was related to local habitat characteristics, and (4) to investigate the spatial and temporal patterns of the avian community composition. We detected 32 species at our sampling locations; physical structure and floristics were not related to avian species richness, although estimates of richness were higher on warmer days and lower on windier days. Habitat characteristics were associated with the detection of Boreal Chickadee (Poecile hudsonicus), Yellow-rumped Warbler (Setophaga coronata), American Robin (Turdus migratorius), and Black-throated Green Warbler (Setophaga virens). Finally, avian community composition was only moderately consistent among three categorical forest types and between audio sampling periods in two consecutive breeding seasons. Overall, we show that the structural and floristic traits measured at our study site are not related to the detection of most avian species or to species richness.

Climatic drought and trophic disruption in an endemic subalpine Hawaiian forest bird

Overexploitation, habitat conversion, and introduced species have caused unprecedented extinctions and heavily degraded native bird populations in island ecosystems. In the Hawaiian Islands, stemming these losses has proven difficult as the highly specialized avifauna are often impacted – among other things – by poorly understood trophic disruptions as well as persistent climatic shifts. Here we investigate these dynamics by examining the trophic positions of 7 different taxa of producers and consumers across the last century in the subalpine māmane (Sophora chrysophylla) forest ecosystem on the island of Hawaiʻi. From museum collections and contemporary sampling, we analyzed the stable nitrogen (δ15N) values of producers and consumers to identify trophic and source amino acids and derive trophic enrichment constants specific to this food web. This enables us to reconstruct the diet of the palila (Loxioides bailleui), a critically endangered finch whose population recently declined 90 %. Our results show that from 1890 to 2006, the palila trophic position declined from 2.6 to 2.2, with cascading implications for its diet. Bayesian mixing model reconstructions indicate that palila trophic position changes likely arose from a 76 % decline (69.3 % to 16.6 % of diet) in the consumption of native moth caterpillars, and a 172 % increase (30.7 % to 83.4 %) in native plants. From the available ecosystem variables, exploratory Bayesian multiple regressions selected surface temperature changes, and the interactions of surface temperatures with drought and caterpillar parasitism as the primary drivers of these trophic changes. Despite the predicted increases of warming and drought, management interventions may build resiliency in this unique island ecosystem.

Improving bird abundance estimates in harvested forests with retention by limiting detection radius through sound truncation

ABSTRACT An inherent challenge with acoustically surveying birds is that the distance at which they can be detected depends on how far their song can be heard. We developed a distance-based sound detection space truncation method to correct for variable sampling radii due to surveying in forested or open conditions. The method was pivotal in evaluating bird responses to retention patches; without this methodological advancement, the impact of retention patches on songbird abundance was vastly underestimated. In the boreal forest, these patches of live trees are retained in regenerating harvested forests to provide ecological services for species adapted to natural disturbances. Although we did not verify our a priori assumption with ground observations, our findings suggest that limited-distance sampling better captures the effects of retention patches on bird use of harvested forests. When evaluated using unlimited distance surveys, retained trees had a negligible effect on bird abundance, whereas applying detection distance truncation highlighted the importance of retention on forest birds. We found that early to mid-seral forest songbirds benefited from retention patches, with notable increases in abundance after 10 years of regeneration. The size of retention patches, ranging from 0.1 to 1.2 ha, did not have a linear relationship with bird abundance. Instead, edge effects stemming from the configuration of these patches emerged as key determinants of abundance for the majority of the species studied. Retention patches that were nearest to unharvested forests were used the most, compared to further into harvest areas. Our research not only highlights the underestimated impact of small-scale live tree retention on forest songbirds but also introduces a significant methodological innovation in the field of acoustic monitoring.

Ptačí diverzita v historickém zámeckém parku – implikace pro ochranu biodiverzity v hospodářských lesích

Long-term trends of abundance and diversity of forest birds have been very stable over past decades in European managed forests. It can be caused by high heterogeneity on habitat scale. In European cultural landscapes, there is another habitat very similar to managed forests, and that is a historic manor park. The parks can even show higher bird diversity than managed forests. However, there is an evident knowledge gap related to long-term changes of bird abundance and diversity in the habitats of manor parks. In this study we observed long-term changes of bird community in the historic manor park Čechy pod Kosířem (Czech Republic) using comparison of bird territory mapping in 2022–2023 with older bird studies in this locality. We gained an overview of bird community changes in the manor park for the period of 1997–2023. Results show that the bird community in historic manor park was remarkably unvarying in abundance and diversity. Historic manor parks can be considered as important refuges for forest bird diversity in cultural landscapes. We discuss the research implications for conserving bird diversity in managed forests especially in connection with large old trees preservation providing heterogeneity of nest habitats.

The disruption of birds' double mutualistic interactions in novel ecosystems.

Non-native trees disrupt ecological processes vital to native plant communities. We studied how forests dominated by Acacia dealbata and Eucalyptus globulus affect the role of birds as dual pollinators and seed dispersers in a region heavily impacted by these two non-native species. We compared bird-plant interactions in the native and in the two non-native forest types. We constructed a multilayer regional network for each forest type and evaluated differences in network dissimilarity between networks. We also calculated the bird's importance in connecting processes and variables associated with module diversity. To determine how the networks react to changes in species richness, we did a simulation of species richness gradient and link percentage for each forest type. The number of birds acting both as pollinators and seed dispersers was higher in native than in non-native forests. However, birds in non-native forests still play a crucial role in maintaining the ecological services provided to native plant communities. However, the eucalyptus network exhibited a concerning simplification, forcing bird species to fully exploit the few remaining resources, leaving little room for structural adjustments and limiting the ecosystem's ability to withstand further species loss. These findings highlight how non-native trees may trigger cascading effects across trophic levels.

Temporal dynamics of acoustic diversity in managed forests

IntroductionIn production forests, management can have cascading effects on biodiversity and ecosystem services. Acoustic diversity reflects the diversity of vocalizing animals and has also considerable recreational value for human well-being, but the relationship between acoustic diversity and forest management remains largely unexploredMethodWe recorded acoustic diversity on forest plots along a gradient of silvicultural management intensity (SMI) in three regions of Germany. We explored the diurnal and seasonal temporal dynamics in acoustic diversity index (ADI) from March to July using generalized additive mixed models (GAMMs). We further investigated the interrelation between acoustic diversity and silvicultural management intensity, forest structural diversity, as well as tree diversity, bird species richness and abundance using structural equation modeling (SEM).ResultsSilvicultural management intensity had significant effects on the temporal dynamics of ADI in May and June from dawn till dusk, but variance explained by SMI was low. We confirmed our hypothesis that ADI was reduced by SMI due to its cascading effects on forest structural diversity and bird species richness and abundance.DiscussionAcoustic diversity indices can provide valuable insights into how forest management affects the acoustic activity of soniferous communities. We discuss how this can indicate both changes in species diversity as well as their vocal activity. We further address potential implications for forest management.

Taxonomic, Functional and Phylogenetic Beta Diversity of Upland Forest Birds in the Amazon: The Relative Importance of Biogeographic Regions, Climate and Geographic Distance

Taxonomic, Functional and Phylogenetic Beta Diversity of Upland Forest Birds in the Amazon: The Relative Importance of Biogeographic Regions, Climate and Geographic Distance

Environmental constraints can explain clutch size differences between urban and forest blue tits: Insights from an egg removal experiment.

Urban environments present novel ecological challenges to wild species. In birds, urban populations generally exhibit reduced clutch sizes compared to forest populations. However, whether smaller urban clutches are adaptive or a result of environmental constraints is unclear. To investigate these two hypotheses, we quantified the ability of urban and non-urban blue tits (Cyanistes caeruleus) to lay new eggs after an experimental manipulation aimed to increase egg production. We removed the first four eggs laid by urban and forest birds to test their ability to produce new eggs. If the urban environment imposes constraints on egg production, we predicted that urban birds would not lay new eggs. If the small clutches of urban birds are an adaptive response, we predicted they would lay new eggs to reach the optimal clutch size for the environment. Consistent with the environmental constraint hypothesis, our results suggest that urban females do not lay new eggs to the same extent as forest birds following egg removal. Forest birds laid approximately two new eggs after our experimental manipulation, while urban birds laid approximately 0.36 new eggs following egg removal. Our manipulation resulted in a brood reduction in the urban experimental nests, yet there was no difference in the number of fledged offspring between urban control and experimental nests. This suggests that females might be misjudging urban habitat quality and produce a clutch with more eggs than nestlings they can rear. Overall, our results suggest that environmental constraints could limit the number of eggs that urban females lay, generating urban versus non-urban differences in this trait.

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 sequences 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 where rivers may cease to be barriers. 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 fully homogenize populations. Our results support Amazonian rivers as key barriers that promoted speciation and the build-up of species richness, but they also suggest that river barriers are often leaky, with genomic divergence accumulating slowly owing to episodes of substantial gene flow.

Does presence of top predator improve forest birds' survival and diversity? An ecological case study assessing umbrella conservational impact of tiger using carrion

After hunting, predators tend to leave a large amount of carrion behind. It is widely reported that this resource is commonly used by various species in the ecosystem and is essential for the survival of scavengers, particularly in winter. Although recent studies are focused on mammals, little is known about how this works with facultative scavenger birds, which may lead to a serious underestimation of the key role that top predators such as the Amur tiger (Panthera tigris altaica) play in ecosystems. Here, we conducted a field feeding experiment to quantitatively evaluate the effects of Amur tiger on avian scavengers by simulating their predation residue. The results show that the Corvidae is the main bird species that consumes carrion, while woodpeckers and some insectivorous songbirds also benefit from the remains that Amur tiger leaves behind. We assumed that in winter, if the daily energy demand for the six main scavenger birds completely relied on the predation residues of Amur tiger separately, the prey remains of one Amur tiger could feed about 28 crows, 49 Azure-winged magpies, 61 Eurasian jays, 235 Eurasian nuthatches, 96 Great spotted woodpeckers, or 385 Willow tits. It means that the prey remains of top predators like Amur tiger may be an extremely important resource to avian scavengers and carrion could be a potential ecological indicator of Amur tiger keystone effect. This study provides experimental evidence from the field for the first time, and reveals the ecological mechanism of the role of keystone species of the Amur tiger, i.e., how to indirectly protect other animal groups in the forest ecosystem that have important ecological value for the biodiversity and the health of local forest vegetation through the protection of the Amur tiger.

Attributing spatially stratified heterogeneity in biodiversity of urban–rural interlaced zones based on the OPGD model

Urban–rural interlaced zones are characterized by the interpenetration of urban and rural elements, drastic changes in construction, relatively weak planning and management, and anthropogenic activities that constantly impact the ecological background. However, the ecological barriers and hinterland spaces of the city center provide important ecological functions. In this study, we selected forest birds as indicator species of the urban ecological environment and explored the spatial stratification and heterogeneity effects of environmental substrates and anthropogenic activities on bird diversity (species richness, abundance, Shannon–Wiener index, and Simpson index) in urban–rural interlaced zones using the optimal parameter geographic detector model to characterize the changes in ecological functions in these zones. The results of this study are as follows:(1) The bird diversity index in Minhang District, Shanghai, showed an obvious urban-rural gradient divergence with the transition of urban zone- rural-urban interface - rural zone.An agglomerative spatial differentiation pattern was observed more in the southeast but less in the northwest, with a high degree of spatial distribution concentrations and evident imbalance characteristics.(2) The spatially stratified heterogeneity in bird diversity in urban–rural interlaced zones was because of the combined action of multiple driving factors under the three dimensions of habitat environment, degree of urbanization, and anthropogenic interference. Most of the interactions between any two factors showed non-linear or bifactorial enhancement effects. Furthermore, the one-factor explanatory power of urbanization and anthropogenic interference factors on bird diversity was significantly higher than that of the habitat environment factor.(3) Population heat distribution (PD), distance to the center of Shanghai (DC), and nighttime lighting index(NTL) were the main drivers of spatially stratified heterogeneity in bird diversity and the key indicators of urban–rural gradient changes. The interaction between PD and DC had the strongest explanatory power for the spatial differentiation of bird diversity.

Forest structural heterogeneity positively affects bird richness and acoustic diversity in a temperate, central European forest

IntroductionForests managed for timber production can also be managed for biodiversity conservation by retaining structures typical of old-growth forests, which provide heterogenous structures for forest-dwelling species, including birds. Ecoacoustic monitoring of forest birds is now a well-studied field, however the extent to which acoustic indices can reflect bird assemblage responses to stands of lower or higher structural heterogeneity is disputed. MethodIn this study, we acoustically surveyed 75 plots over two years in mature, previously managed forests and computed acoustic indices from the recordings. We first identified an acoustic index that significantly correlated with bird richness over more than one spring season. Next, we tested the response of bird richness to individual forest structural elements using linear regressions. We then repeated this analysis but combined the individual structural elements into one structural composition variable using an NMDS and gam smooth overlay, to compare the effect of individual forest structures versus overall forest heterogeneity on bird richness. We then repeated this analysis using our selected acoustic index, the Normalized Difference Soundscape Index (NDSI), to see if it followed the same patterns as bird richness in response to individual and collective forest structural elements.ResultsOur results showed that plots with high bird richness were also associated with high NDSI values, and high values of both variables occurred in plots with high structural heterogeneity (tree species richness, tree size variability, and snag height variability) and low amounts of standing and lying deadwood. DiscussionOur findings suggest that once an acoustic index can be identified as a robust correlate of bird richness, it can serve as a proxy for the response of birds to differences in forest structural heterogeneity within a managed forest context. It is therefore possible for forest managers interested in conserving or increasing bird richness in their production forests to identify a robust acoustic index to track the response of bird richness to management decisions over time.

Delayed responses and extinction debt: an opportunity for the conservation of Chaco Serrano forest birds

Delayed responses and extinction debt: an opportunity for the conservation of Chaco Serrano forest birds

The Genetic Response of Forest Birds to Urbanization: Variability in the Populations of Great and Blue Tits

The Genetic Response of Forest Birds to Urbanization: Variability in the Populations of Great and Blue Tits