Spatial patterns of woody plant and bird diversity: functional relationships or environmental effects?

Aim To understand cross‐taxon spatial congruence patterns of bird and woody plant species richness. In particular, to test the relative roles of functional relationships between birds and woody plants, and the direct and indirect environmental effects on broad‐scale species richness of both groups. Location Kenya. Methods Based on comprehensive range maps of all birds and woody plants (native species > 2.5 m in height) in Kenya, we mapped species richness of both groups. We distinguished species richness of four different avian frugivore guilds (obligate, partial, opportunistic and non‐frugivores) and fleshy‐fruited and non‐fleshy‐fruited woody plants. We used structural equation modelling and spatial regressions to test for effects of functional relationships (resource–consumer interactions and vegetation structural complexity) and environment (climate and habitat heterogeneity) on the richness patterns. Results Path analyses suggested that bird and woody plant species richness are linked via functional relationships, probably driven by vegetation structural complexity rather than trophic interactions. Bird species richness was determined in our models by both environmental variables and the functional relationships with woody plants. Direct environmental effects on woody plant richness differed from those on bird richness, and different avian consumer guilds showed distinct responses to climatic factors when woody plant species richness was included in path models. Main conclusions Our results imply that bird and woody plant diversity are linked at this scale via vegetation structural complexity, and that environmental factors differ in their direct effects on plants and avian trophic guilds. We conclude that climatic factors influence broad‐scale tropical bird species richness in large part indirectly, via effects on plants, rather than only directly as often assumed. This could have important implications for future predictions of animal species richness in response to climate change.     

Effect of Urbanization and Seasonality in Bird Communities of Kathmandu Valley,Nepal

Kathmandu Valley, Nepal is undergoing rapid urbanization but its effects on the bird communities have not been reported till date. Kathmandu Valley was categorized into urban, sub-urban and rural to study the impact of urbanization in bird communities. By mobilizing volunteers, we monitored 24 transects each with one km long in summer and winter seasons of 2016. A total of 13,749 individuals of birds belonging to 102 species were recorded. Species richness and diversity of all birds declined from rural to urban areas and showed significant variation along urban–rural gradients. Insectivore was the most species-rich guild while nectarivore the least. The richness of insectivore, frugivore and carnivore guilds showed significant variations along the urban–rural gradients and higher preference towards the rural areas. Similarly, species richness of all birds and richness of insectivore and carnivore guilds showed significant seasonal variation and were higher in the winter season. Our results indicate that richness, diversity and feeding guilds of birds show different response towards the urbanization gradients and seasons. Sub-urban areas can function as bird refugia, however, habitat enrichments (like increasing green spaces, setting up new parks and gardens, plantation of native fruiting trees etc.) are utmost necessary to support the bird communities in urban areas of Kathmandu Valley.     

Avian Use of Wetlands in Reclaimed Minelands in Southwestern Indiana

We studied the use of mineland wetlands by birds and the relationship between avian communities and wetland characteristics. Data were collected from 20 wetlands in Pike County, Indiana, and included wetland size, depth, water conductivity and salinity, aquatic macroinvertebrate abundance, vegetation, and bird use. Principal component analysis showed that physical variables could be explained by two principal component scores and that wetlands could be grouped on the basis of size and conductivity. Principal component analysis could not reduce vegetation variables to fewer principal component scores, meaning that wetland vegetation characteristics were independent of one another and did not show any trend. Most wetlands had low invertebrate density, and wetlands with higher invertebrate density had low invertebrate diversity. Wetlands with similar habitat characteristics (physical, vegetative, and invertebrate) did not necessarily show similarities in bird assemblages. Bird similarity index values ranged from 0 to 59%, implying that each wetland has its own bird community. Stepwise multiple regression analysis (α= 0.05) relating bird use and habitat characteristics showed that bird species richness increased with the species richness of submergent vegetation and was correlated negatively with the species richness of emergent vegetation. There was no significant relationship between bird species richness or bird species diversity and wetland size. The number of species within different avian guilds correlated with different habitat characteristics. The species richness of submergent plants was a factor that correlated positively with the number of species of several guilds (dabblers, wading birds, and plunge divers). Wetland age was not a factor that determined bird use.     

千岛湖陆桥岛屿鸟类集团对栖息地片段化的敏感性及其季节变化

为探究千岛湖陆桥岛屿不同鸟类集团对栖息地片段化敏感性的差异和季节变化,于2009年4月—2012年1月鸟类繁殖季(4、5、6月)和冬季(11、12、1月)对千岛湖41个陆桥岛屿鸟类集团进行了研究。结果表明,冬季杂食鸟对片段化敏感性高于食虫鸟,繁殖季时二者无显著差异,繁殖季和冬季时下层鸟对片段化敏感性均高于林冠鸟,冬季留鸟对片段化敏感性高于候鸟,繁殖季则无显著差异。杂食鸟和留鸟对片段化敏感性存在季节差异,而食虫鸟、林冠鸟、下层鸟和候鸟对片段化敏感性均无季节差异。不同鸟类集团对栖息地片段化敏感性的差异和季节变化规律,有助于人们在栖息地管理和保护区设计时采取更有针对性的鸟类保护措施。     

Associations between avian functional guild response and regional landscape properties for conservation planning

This project facilitates a regional approach to conservation planning in Pennsylvania based on avian breeding habitat selection. The objectives were to: (1) determine the sensitivity of spatial pattern in avian diversity to changing thresholds of intra-guild species richness and (2) relate change of spatial pattern in avian diversity with landscape characteristics of bird Atlas blocks. Two state-wide spatial data layers, based on Landsat satellite data were constructed for this study. These regional landscape data were compared to Breeding Bird Atlas data from 1983 to 1989 using a geographic information system. Breeding bird data were recorded from 4928 blocks that form a grid covering Pennsylvania. Correlation analysis reduced landscape variables to 12 originally derived from forest, urban, roads, streams, and topographic data.Avian functional response guilds were used to analyze associations between breeding bird data and landscape variables. Functional response guilds were created by grouping organisms based on shared habitat preferences or behavioral characteristics. Most of the 18 avian guilds identified for this study were based on shared structural resource characteristics of preferred breeding habitat. Preferred structural resources frequently included the amount and type of forest. For this study, guilds separate resource characteristics by: (1) primary habitat (i.e. forest interior, forest edge), (2) area sensitivity (i.e. forest and grassland), (3) migratory status (i.e. resident, temperate, and tropical), and (4) nest placement (i.e. canopy nester, forest ground nester). Wetland obligate species were treated as a separate guild. Breeding Bird Atlas blocks were tabulated with respect to the number of species present from each guild. For a given guild, the number of its species in a block is termed guild-specific species richness. Sample blocks having high species richness for a given guild often occur adjacent or in close proximity forming spatial clusters in the landscape. Spatial coherence (adjacency/proximity) among the blocks forming these islands is shared guild-specific richness. Spatial clustered blocks of each guild represent areas that presumably possess required resources for members of that guild. Blocks having high intra-guild richness were evaluated with a group of block-level continuous variables using multiple logistic regressions. Logistic regression results indicate that a convincing connection exists between landscape properties of Breeding Bird Atlas blocks and habitat selection characteristics of guild members. Percent of forest cover and mean elevation were the most important habitat characteristics influencing intra-guild richness for most of the guilds tested. Concordance values from logistic regression were used to determine the strength of each guild model. Concordance, the proportion that represents the percent of correct guild richness predictions versus incorrect predictions, suggests a relationship between guild-rich clusters and habitat resources required by each guild. The highest concordance was for the exotics guild at 76.3% and the next highest was 74.8% for the grassland area sensitive guild. This signifies a 75% certainty that landscape variables could predict occurrence of a guild-rich block. Eight more guilds had concordance values greater than 65%.By using a guild approach, this study goes beyond total diversity to the more informative structural and functional diversity of guilds. Spatially clustered blocks of high species richness for a particular guild are more indicative of habitat availability and quality than would be the case for overall species richness. Clusters of blocks having high intra-guild species richness become candidate areas for conservation efforts.     

Bird assemblages in fragmented agricultural landscapes: the role of small brigalow remnants and adjoining land uses

Agricultural intensification typically leads to changes in bird diversity and community composition, with fewer species and foraging guilds present in more intensively managed parts of the landscape. In this study, we compare bird communities in small (2–32 ha) brigalow (Acacia harpophylla) remnants with those in adjacent uncultivated grassland, previously cultivated grassland and current cropland, to determine the contribution of different land uses to bird diversity in the agricultural landscape. Twenty remnant brigalow patches and adjacent agricultural (‘matrix’) areas in southern inland Queensland, Australia were sampled for bird composition and habitat characteristics. The richness, abundance and diversity of birds were all significantly higher in brigalow remnants than in the adjacent matrix of cropping and grassland. Within the matrix, species richness and diversity were higher in uncultivated grasslands than in current cultivation or previously cultivated grasslands. Forty-four percent of bird species were recorded only in brigalow remnants and 78% of species were recorded in brigalow and at least one other land management category. Despite high levels of landscape fragmentation and modification, small patches of remnant brigalow vegetation provide important habitat for a unique and diverse assemblage of native birds. The less intensively managed components of the agricultural matrix also support diverse bird assemblages and thus, may be important for local and regional biodiversity conservation.     

Birds,Cattle, and Bracken Ferns: Bird Community Responses to a Neotropical Landscape Shaped by Cattle Grazing Activities

Large areas of tropical moist forests have been converted to cattle pastures, generating complex landscapes where different habitats are represented by small patches with an uneven spatial distribution. Here, we describe how bird communities respond to the different elements present in a livestock landscape that was originally dominated by tropical moist forest. We surveyed six habitats: open pastures, pastures with shrubs, early‐ and middle‐secondary forests, mature forest, and pastures invaded by bracken ferns (Pteridium aquilinum). Bird diversity was high in secondary and mature forests, and low in fern‐invaded sites and open pastures. Fern‐dominated sites had the lowest bird species richness, and trophic guild diversity of all habitats. Habitat structure affected both bird species richness and densities in similar ways. Tree species richness was the habitat attribute that had a bigger positive effect on bird species richness. Bird community structure varied among sampled habitats, separating habitats in two major groups (forests and pastures). Our data indicate that bracken fern‐invaded pastures were the worst habitat condition for avian communities. To increase bird diversity, we recommend to eliminate or manage bracken fern and to increase shrub and tree cover in open pastures to provide food resources and shelter for birds. Finally, we encourage the maintenance of secondary and mature forest remnants as a strategy to conserve resident birds within a landscape dominated by livestock activities.     

Rapid redistribution of agricultural land alters avian richness,abundance, and functional diversity

The conversion of natural, or seminatural, habitats to agricultural land and changes in agricultural land use are significant drivers of biodiversity loss. Within the context of land‐sharing versus land‐sparing debates, large‐scale commercial agriculture is known to be detrimental to biodiversity, but the effects of small‐scale subsistence farming on biodiversity are disputed. This poses a problem for sustainable land‐use management in the Global South, where approximately 30% of farmland is small‐scale. Following a rapid land redistribution program in Zimbabwe, we evaluated changes in avian biodiversity by examining richness, abundance, and functional diversity. Rapid land redistribution has, in the near term, resulted in increased avian abundance in newly farmed areas containing miombo woodland and open habitat. Conversion of seminatural ranched land to small‐scale farms had a negative impact on larger‐bodied birds, but species richness increased, and birds in some feeding guilds maintained or increased abundance. We found evidence that land‐use change caused a shift in the functional traits of the communities present. However, functional analyses may not have adequately reflected the trait filtering effect of land redistribution on large species. Whether newly farmed landscapes in Zimbabwe can deliver multiple benefits in terms of food production and habitat for biodiversity in the longer term is an open question. When managing agricultural land transitions, relying on taxonomic measures of diversity, or abundance‐weighted measures of function diversity, may obscure important information. If the value of smallholder‐farmed land for birds is to be maintained or improved, it will be essential to ensure that a wide array of habitat types is retained alongside efforts to reduce hunting and persecution of large bird species.     

Heterogeneous Landscapes on Steep Slopes at Low Altitudes as Hotspots of Bird Diversity in a Hilly Region of Nepal in the Central Himalayas

Understanding factors determining the distribution of species is a key requirement for protecting diversity in a specific area. The aim of this study was to explore the factors affecting diversity and distribution of species of birds on different forested hills in central Nepal. The area is rich in species of birds. Because the area is characterized by steep gradients, we were also interested in the importance of altitude in determining the diversity and species composition of the bird communities. We assessed bird diversity and species composition based on point observations along a gradient of increasing altitude in two valleys (Kathmandu and Palung) in central Nepal. Data on environmental variables were also collected in order to identify the main determinants of bird diversity and species composition of the bird communities. We recorded 6522 individual birds belonging to 146 species, 77 genera and 23 families. Resident birds made up 80% (117 species) of the total dataset. The study supported the original expectation that altitude is a major determinant of species richness and composition of bird communities in the area. More diverse bird communities were found also in areas with steeper slopes. This together with the positive effect of greater heterogeneity suggests that forests on steep slopes intermixed with patches of open habitats on shallow soil at large spatial scales are more important for diverse bird communities than more disturbed habitats on shallow slopes. In addition, we demonstrated that while different habitat characteristics such as presence of forests edges and shrubs play an important role in driving species composition, but they do not affect species richness. This indicates that while habitat conditions are important determinants of the distribution of specific species, the number of niches is determined by large scale characteristics, such as landscape level habitat heterogeneity and altitude. Thus, to protect bird diversity in the mid-hills of central Nepal, we should maintain diverse local habitats (viz. forest, shrubs, open land, etc.) but also make sure the natural habitats on steeper slopes with large scale heterogeneity are maintained.     

Guild-specific responses of avian species richness to LiDAR-derived habitat heterogeneity

Ecological niche theory implies that more heterogeneous habitats have the potential to support greater biodiversity. Positive heterogeneity-diversity relationships have been found for most studies investigating animal taxa, although negative relationships also occur and the scale dependence of heterogeneity-diversity relationships is little known. We investigated multi-scale, heterogeneity-diversity relationships for bird communities in a semi-arid riparian landscape, using airborne LiDAR data to derive key measures of structural habitat complexity. Habitat heterogeneity-diversity relationships were generally positive, although the overall strength of relationships varied across avian life history guilds (R² range: 0.03–0.41). Best predicted were the species richness indices of cavity nesters, habitat generalists, woodland specialists, and foliage foragers. Heterogeneity-diversity relationships were also strongly scale-dependent, with strongest associations at the 200-m scale (4 ha) and weakest associations at the 50-m scale (0.25 ha). Our results underscore the value of LiDAR data for fine-grained quantification of habitat structure, as well as the need for biodiversity studies to incorporate variation among life-history guilds and to simultaneously consider multiple guild functional types (e.g. nesting, foraging, habitat). Results suggest that certain life-history guilds (foliage foragers, cavity nesters, woodland specialists) are more susceptible than others (ground foragers, ground nesters, low nesters) to experiencing declines in local species richness if functional elements of habitat heterogeneity are lost. Positive heterogeneity-diversity relationships imply that riparian conservation efforts need to not only provide high-quality riparian habitat locally, but also to provide habitat heterogeneity across multiple scales.     

Effects of habitat fragmentation and black-tailed prairie dogs on urban avian diversity

Urbanization and habitat fragmentation have the potential to influence bird communities. In addition, these phenomena, as well as ongoing lethal control measures, have also greatly reduced the range of the black-tailed prairie dog (Cynomys ludovicianus) since the beginning of the 20th century. Although prairie dogs are highly interactive species that can influence avian communities, few studies have investigated whether these interactions persist in urban settings. Our goal was to investigate the relative impacts of habitat fragmentation and prairie dogs on bird communities within an urban matrix. We performed bird surveys on 20 habitat fragments (10 colonized by prairie dogs, 10 uncolonized by prairie dogs) distributed throughout the Denver metropolitan area, and calculated Shannon–Weiner diversity and richness of all birds and native species, as well as total counts of grassland birds and raptors. Diversity, richness, and counts of many species increased with increasing fragment connectivity, and decreased on fragments isolated for longer periods of time. Avian diversity and richness did not differ between fragments with and without prairie dogs, suggesting that this element of the ecological role of prairie dogs is not fully retained in urban habitat. Future studies of the role of prairie dogs as keystone species in urban systems should include other taxa as well as consider the influence of the urban matrix surrounding prairie dog habitat. Our results emphasize that conservation of urban avian diversity should focus on landscape connectivity as well as local habitat features.     

Forest edges have high conservation value for bird communities in mosaic landscapes

A major conservation challenge in mosaic landscapes is to understand how trait‐specific responses to habitat edges affect bird communities, including potential cascading effects on bird functions providing ecosystem services to forests, such as pest control. Here, we examined how bird species richness, abundance and community composition varied from interior forest habitats and their edges into adjacent open habitats, within a multi‐regional sampling scheme. We further analyzed variations in Conservation Value Index (CVI), Community Specialization Index (CSI) and functional traits across the forest‐edge‐open habitat gradient. Bird species richness, total abundance and CVI were significantly higher at forest edges while CSI peaked at interior open habitats, i.e., furthest from forest edge. In addition, there were important variations in trait‐ and species‐specific responses to forest edges among bird communities. Positive responses to forest edges were found for several forest bird species with unfavorable conservation status. These species were in general insectivores, understorey gleaners, cavity nesters and long‐distance migrants, all traits that displayed higher abundance at forest edges than in forest interiors or adjacent open habitats. Furthermore, consistently with predictions, negative edge effects were recorded in some forest specialist birds and in most open‐habitat birds, showing increasing densities from edges to interior habitats. We thus suggest that increasing landscape‐scale habitat complexity would be beneficial to declining species living in mosaic landscapes combining small woodlands and open habitats. Edge effects between forests and adjacent open habitats may also favor bird functional guilds providing valuable ecosystem services to forests in longstanding fragmented landscapes.     

Impacts of an invasive willow (Salix × rubens) on riparian bird assemblages in south‐eastern Australia

We explored how a woody plant invader affected riparian bird assemblages. We surveyed 15 200‐m‐long transects in riparian zones in a much‐changed landscape of eastern Victoria, Australia. Abundance, species‐richness, foraging‐guild richness and composition of birds were compared in transects in three habitat types: (i) riparian zones dominated by the invasive willow Salix × rubens; (ii) riparian zones lined with native woody species; and (iii) riparian zones cleared of almost all woody vegetation. We also measured abundance and richness of arthropods and habitat structure to explore further the effects of food resources and habitat on the avifauna. We observed 67 bird species from 14 foraging guilds. Native riparian transects had more birds, bird species and foraging guilds than willow‐invaded or cleared transects. Habitat complexity increased from cleared to willow‐invaded to native riparian transects, as did abundance of native and woodland‐dependent birds. Native shrub and trees species had more foliage and branch‐associated arthropods than did willows, consistent with a greater abundance and variety of foraging guilds of birds dependent on this resource. Willow spread into cleared areas is unlikely to facilitate greatly native bird abundance and diversity even though habitat complexity is increased. Willow invasion into the native riparian zone, by decreasing food resources and altering habitat, is likely to reduce native bird biodiversity and further disrupt connectivity of the riparian zone.     

Influence of habitat complexity and landscape configuration on pollination and seed-dispersal interactions of wild cherry trees

Land-use intensification is a major cause for the decline in species diversity in human-modified landscapes. The loss of functionally important species can reduce a variety of ecosystem functions, such as pollination and seed dispersal, but the intricate relationships between land-use intensity, biodiversity and ecosystem functioning are still contentious. Along a gradient from forest to intensively used farmland, we quantified bee species richness, visitation rates of bees and pollination success of wild cherry trees (Prunus avium). We analysed the effects of structural habitat diversity at a local scale and of the proportion of suitable habitat around each tree at a landscape scale. We compared these findings with those from previous studies of seed-dispersing birds and mammals in the same model system and along the same land-use gradient. Bee species richness and visitation rates were found to be highest in structurally simple habitats, whereas bird species richness—but not their visitation rates—were highest in structurally complex habitats. Mammal visitation rates were only influenced at the landscape scale. These results show that different functional groups of animals respond idiosyncratically to gradients in habitat and landscape structure. Despite strong effects on bees and birds, pollination success and bird seed removal did not differ along the land-use gradient at both spatial scales. These results suggest that mobile organisms, such as bees and birds, move over long distances in intensively used landscapes and thereby buffer pollination and seed-dispersal interactions. We conclude that measures of species richness and interaction frequencies are not sufficient on their own to understand the ultimate consequences of land-use intensification on ecosystem functioning.     

Does bird community structure vary with landscape patchiness? A Chihuahuan Desert perspective

During the springs of 1995–1997, we studied birds and landscapes at 70 sites in the Chihuahuan Desert to assess relations between bird community structure and landscape patchiness. Within each of two spatial extents (1‐km and 2‐km‐radius areas centered on each site), we measured the number of patches of individual land‐cover types and the total number of patches of all land‐cover types. Mean bird richness, and the mean abundance and probability of occurrence of most bird species were significantly correlated with one or more of these variables. Contrary to evidence from other systems, positive association with landscape patchiness did not increase with the degree to which species were habitat generalists, was not negatively related to body size, and did not differ between neotropical migrants and nonmigrants. For the communities’ primary constituent species as a group, the strength of positive and negative associations with patchiness did not differ between landscape extents. Within the 1‐km but not the 2‐km extent, habitat specialists were more positively and negatively associated with patchiness than were habitat generalists. In general, however, neither habitat breadth, body size, nor migratory status seemed to be responsible for associations with landscape patchiness. Mean richness, and the mean abundance and probability of occurrence of most species were significantly correlated with patchiness within one or both extents, and patchiness of all of the most extensive land‐cover types was influential. The simplest explanation for most of the bird‐patchiness relations we found is that the associations reflected species‐specific habitat needs. Through effects on avian richness, abundance, and occurrence, landscape patchiness affected bird community structure. A more complete understanding of the effects of landscape patchiness on bird community structure is likely to emerge when ecologists study the patchiness of major land‐cover types at various spatial extents.     

Avian diversity and function across the world's most populous cities

Understanding the composition of urban wildlife communities is crucial to promote biodiversity, ecosystem function and links between nature and people. Using crowdsourced data from over five million eBird checklists, we examined the influence of urban characteristics on avian richness and function at 8443 sites within and across 137 global cities. Under half of the species from regional pools were recorded in cities, and we found a significant phylogenetic signal for urban tolerance. Site-level avian richness was positively influenced by the extent of open forest, cultivation and wetlands and avian functional diversity by wetlands. Functional diversity co-declined with richness, but groups including granivores and aquatic birds occurred even at species-poor sites. Cities in arid areas held a higher percentage of regional species richness. Our results indicate commonalities in the influence of habitat on richness and function, as well as lower niche availability, and phylogenetic diversity across the world's cities.     

Bats are Not Birds – Different Responses to Human Land‐use on a Tropical Mountain

Land‐use intensification has consequences for biodiversity and ecosystem functioning, with various taxonomic groups differing widely in their sensitivity. As land‐use intensification alters habitat structure and resource availability, both factors may contribute to explaining differences in animal species diversity. Within the local animal assemblages the flying vertebrates, bats and birds, provide important and partly complementary ecosystem functions. We tested how bats and birds respond to land‐use intensification and compared abundance, species richness, and community composition across a land‐use gradient including forest, traditional agroforests (home garden), coffee plantations and grasslands on Mount Kilimanjaro, Tanzania. Furthermore, we asked how sensitive different habitat and feeding guilds of bats and birds react to land‐use intensification and the associated alterations in vegetation structure and food resource availability. In contrast to our expectations, land‐use intensification had no negative effect on species richness and abundance of all birds and bats. However, some habitat and feeding guilds, in particular forest specialist and frugivorous birds, were highly sensitive to land‐use intensification. Although the habitat guilds of both, birds and bats, depended on a certain degree of vegetation structure, total bat and bird abundance was mediated primarily by the availability of the respective food resources. Even though the highly structured southern slopes of Mount Kilimanjaro are able to maintain diverse bat and bird assemblages, the sensitivity of avian forest specialists against land‐use intensification and the dependence of the bat and bird habitat guilds on a certain vegetation structure demonstrate that conservation plans should place special emphasis on these guilds.     

Assessing the role of invasive weeds in the impact of successional habitats on the bird assemblage in overgrowing agriculture

Agricultural habitats are assumed to be biodiversity refuges. However, some studies treat agricultural land management as a cause of the biodiversity decline, to which habitat loss and heterogeneity may contribute. Between the crops, the successional habitats appear – ruderal plant communities and bush areas. Their influence on farmland biodiversity is unknown. This research assessed the impact of spatial relationships between agricultural areas, semi-natural meadows and successional habitats on the bird species richness, Shannon diversity index, and Faith’s phylogenetic diversity index. An additional habitat variable was the presence of weeds, i.e., invasive Caucasian hogweeds Heracleum sp., treated as crops in the past. The birds and habitats research was on 74 sites set in pairs (invaded vs control) in south-eastern Poland. Results showed that birds assembling in agricultural and semi-natural areas were more diverse and contained protected farmland species, while birds appearing in overgrown habitats (i.e., successional and invaded) were clumped with their habitat requirements. In the presence of plant invaders, ruderal habitats negatively affected the bird phylogenetic diversity index. In invaded sites, bush areas had no positive effects on the Shannon diversity index and species richness of birds, in contrast with control sites. The presented research suggests the need to re-evaluate the importance of successional non-crop habitats considered positive in agricultural landscapes if those habitats develop in areas with plant invasion.     

Modeling Spatial Trends in Estimated Species Richness using Breeding Bird Survey Data: A Valuable Tool in Biodiversity Assessment

We used data from the French breeding bird survey to estimate local bird species richness within sampled sites, using capture–recapture models. We investigated the possible effects of habitat structure and composition (landscape fragmentation, habitat cover and diversity) on estimated species richness at a local scale, and used the identified trends to help with modeling species richness at a large spatial scale. We performed geostatistical analyses based on spatial autocorrelation – cokriging models – to interpolate estimated species richness over the entire country, providing an opportunity to predict species-rich areas. We further compared species richness obtained with this method to species and rarity richness obtained using a national atlas of breeding birds. Estimated species richness was higher in species richness hotspots identified by the atlas. Combining informations on rare species from Atlas and species richness estimates from sound sampling based schemes should help with identifying species-rich areas for various taxa and locating biodiversity hotspots to be protected as high conservation value areas, especially in temperate zones where diversity hotspots are likely to match centers of high species richness because of very few centers of true endemicity.     

Fine-scale habitat structure complexity determines insectivorous bird diversity in a tropical forest

Habitat complexity in reforested stands has been acknowledged as a key factor that influences habitat use by birds, being especially critical for habitat disturbance-sensitive species such as tropical understory insectivorous birds. Most studies regarding the relationship between forest structure and species diversity were conducted at the landscape scale, but different diversity patterns may emerge at a finer scale (i.e., within a habitat patch). We examined a tropical reforested area (State of Caldas, Colombia), hypothesizing that insectivorous bird richness, abundance, and foraging guild abundance would increase as intra-habitat complexity increases. We established 40 monitoring plots within a reforested area, measured their structural features, and determined their relationships with species richness, total abundance, and foraging guild abundance, using Generalized Additive Models. We found that the increasing variation in basal area, stem diameter, and number of stems was positively correlated with species richness, total abundance, and foraging guild abundance. Relationships between richness or abundance and structural features were not lineal, but showing curvilinear responses and thresholds. Our results show that heterogeneity on basal area, stem diameter, and the number of stems was more correlated to insectivorous bird richness and abundance than the average of those structural features. Promoting structural variation on reforested areas by planting species with different growth rates may contribute to increase the richness and abundance of a tropical vulnerable group of species such as the understory insectivorous birds.