Change In Avian Communities Research Articles

Small-scale forest restoration in peri-urban areas provides immediate benefits for birds

Summary Forests of urban/suburban areas are being increasingly restored, but before/after-control/impact studies addressing effects on biodiversity in peri-urban forest restorations are virtually lacking. Using a before/after-control/impact (BACI) design, we explored the effects on birds (commonly used as indicators for restoration impacts) of small-scale restoration interventions in 2019 targeting residual forests north of Milan, in the largest Italian conurbation, with trees and shrub planting around existing patches or in formerly cultivated areas. Birds were surveyed in 2018, 2019, and 2021, at 20 intervention and 20 control sites. We evaluated the short-term effects of restoration by analysing changes in avian communities (i.e. richness, richness and abundance of forest specialists, single species’ abundance), considering the effect of year and intervention (i.e. before/during/after intervention). Species richness of breeding birds was largely unaffected by on-going interventions, while it was positively related to concluded restoration. The abundance of five individual species varied according to restoration: on-going interventions had positive effects on two species, Common Blackbird Turdus merula and Hooded Crow Corvus corone cornix, and negative effects on Barn Swallow Hirundo rustica, while concluded restoration positively affected two species, Common Blackbird Turdus merula again, and the forest specialist Marsh Tit Poecile palustris. Even small-scale interventions in peri-urban areas may provide tangible benefits to breeding birds in the short term: peri-urban forest restoration could contribute to biodiversity conservation.

Assessing protected area network effectiveness through the temporal change in avian communities’ composition

Current rates of land use are driving temporal changes in avian communities. Thus, it is essential to properly designate and manage protected areas since they mitigate the adverse effects of temporal changes on species populations. By using common bird monitoring data in Czechia from two periods (2005/2006 and 2014/2015), we calculated two indices of temporal change per each site, the Jaccard dissimilarity index (temporal dissimilarity between the community composition) and the difference in bird species richness between both periods (delta bird species richness). We tested three main predictions on temporal change in bird communities between protected and unprotected areas: (i) bird species richness will be higher inside protected areas, (ii) temporal changes in avian communities will be lower inside protected areas, (iii) the effect of protected areas will interact with land-use types, land-use richness, and altitudinal zones. Bird species richness was higher inside protected areas in 2014/2015, ten years after the implementation of Natura 2000 in Czechia. Both indices of temporal change were lower inside protected areas. The interactions of protected areas and land-use types on the indices of temporal change were not significant. However, interactions with altitudinal zones had a significant positive effect on the indices, i.e., in higher altitudes, delta bird species richness and higher dissimilarity levels. Our study underlines the importance of protected areas for conservation by buffering the consequences of factors driving temporal community changes. Together, our results indicate a positive ‘umbrella’ effect of protected areas on avian communities that was likely facilitated by the implementation of Natura 2000.

Combining historical accounts with contemporary bird survey data identifies changes in an avian community over a period of anthropogenic change

Declines in bird abundance and diversity are well documented over regional‐to‐global extents. Identifying long‐term change in bird communities over smaller extents, particularly during periods of rapid anthropogenic change, is vital to understanding how such change affects species, though such local‐level declines are less well documented. Although datasets exist to support such analyses over large extents, their late twentieth and early twenty‐first century focus and broadly dispersed sampling locations limit their usefulness in local‐level analyses. Local‐level studies may therefore lack data at appropriate spatio‐temporal scales; however, descriptive, historical accounts could inform such analyses. We integrated historical accounts with contemporary data to identify local changes in songbird abundance. We focused on Johnson County, Iowa, USA, during a period of agricultural expansion and intensification and urbanization. We used Kruskal–Wallis and Dunn’s multiple‐comparison tests to identify changes in songbird functional‐group abundance using an early twentieth century account and contemporary field‐collected data, both classified to ordinal scales to facilitate analyses. Species richness increased overall, largely due to colonization by exotic species. The relative abundance of most groups remained similar (e.g. exotics, non‐migratory, urban‐tolerant, granivores) and species that use anthropogenic resources increased in abundance, but many groups decreased (e.g. grassland species and insectivores). These findings shed light on ways in which avian communities change over relatively small extents during periods of rapid anthropogenic land‐cover change. Additionally, by demonstrating a systematic approach for integrating qualitative historical accounts with contemporary abundance data, this work will facilitate additional studies that build understanding of long‐term, local‐level change in bird communities. Identifying local‐level changes in avian communities in urbanizing agricultural regions such as this one could additionally identify species likely to require conservation interventions to survive periods of intense land‐cover change.

Influence of sugarcane growth stages on bird diversity and community structure in an agricultural-savanna environment

Agricultural intensification is a threat to terrestrial ecosystems around the world. Agricultural areas, especially monocultures, create homogenous landscapes for wildlife. However, certain crops, such as sugarcane, are harvested in phases, creating a mosaic of fields in different stages of growth. We investigated changes in avian communities across four different sugarcane growth stages: emerging, short, medium and tall sugarcane, as well as control sites that represented native savanna habitat in northeast Eswatini prior to conversion to agriculture. In total, we sampled nine sites in sugarcane fields (at different growth stages) and three in native savanna. We conducted bird counts at 5-week intervals along 200m line transects over both the breeding and non-breeding seasons. We recorded a total of 124 bird species belonging to 58 families. Bird species richness and diversity were higher in savannas compared to any stages of growth in sugarcane. In contrast, functional beta diversity and uniqueness were higher in sugarcane than in savanna. Community composition was also different between the two land-uses. While there was overlap in bird species composition between different sugarcane growth stages, there was high beta diversity and high turnover between sites, indicative of the high temporal and spatial variability in bird communities in sugarcane fields. We demonstrated that the spatial and temporal variability created by the different growth stages of sugarcane promotes the occurrence of species with different traits, which may contribute to ecosystem functioning and promote the conservation of bird species as sugarcane fields can provide resource complementation for species with different needs.

Forest structure determines spatial changes in avian communities along an elevational gradient in tropical Africa

AbstractAimTo test if tree species richness and forest structure drive spatial variation in avian communities along a tropical elevation gradient and to present information about the role of detailed forest parameters.LocationA 2,000‐m long elevational gradient of tropical forest on Mt. Cameroon, west‐central Africa.TaxonBirds and trees.MethodsWe performed bird censuses and vegetation mapping at the same plots across six forested sites at elevations of 350, 650, 1,100, 1,500, 1,850, and 2,200 m a.s.l., with 16 plots per elevation. We tested the effects of elevation, forest structure and tree diversity on the species richness, functional diversity and β‐diversity of birds (Bray–Curtis dissimilarity). We used conditional inference trees based on random forests (RF) to investigate these relationships across all elevation sites as well as within elevations.ResultsBoth tree and bird species richness declined monotonically with elevation. Vegetation structure correlated with elevation, and all vegetation attributes significantly differed among elevations. The RF explained 70% of the variance in avian species richness, with the most important predictors being elevation, proportion of dead trees, tree species richness and herb layer coverage. We found that elevation (and shrub layer) was a particularly important predictor of avian functional diversity. We identified no important predictor of bird species richness after standardization within elevations, and the proportion of dead trees was the sole important predictor of functional diversity. Within‐elevation β‐diversity in avian community composition was determined by the dissimilarity of the tree community and differences in leaf area index, solar radiation and spatial distance. The functional dissimilarity was best explained by leaf area index.Main conclusionsApart from elevation itself, spatial distance even within elevations correlated with compositional and functional variation among avian assemblages. Forest structural traits can have a significant influence on distribution of birds. Thus, gaps in the spatial distribution of species such as along elevations might be caused by fine‐scale recognition of suitable habitats.

Large-Scale Removal of Invasive Honeysuckle Decreases Mosquito and Avian Host Abundance.

Invasive species rank second only to habitat destruction as a threat to native biodiversity. One consequence of biological invasions is altered risk of exposure to infectious diseases in human and animal populations. The distribution and prevalence of mosquito-borne diseases depend on the complex interactions between the vector, the pathogen, and the human or wildlife reservoir host. These interactions are highly susceptible to disturbance by invasive species, including terrestrial plants. We conducted a 2-year field experiment using a Before-After/Control-Impact design to examine how removal of invasive Amur honeysuckle (Lonicera maackii) in a forest fragment embedded within a residential neighborhood affects the abundance of mosquitoes, including two of the most important vectors of West Nile virus, Culex pipiens and Cx. restuans. We also assessed any potential changes in avian communities and local microclimate associated with Amur honeysuckle removal. We found that (1) removal of Amur honeysuckle reduces the abundance of both vector and non-vector mosquito species that commonly feed on human hosts, (2) the abundance and composition of avian hosts is altered by honeysuckle removal, and (3) areas invaded with honeysuckle support local microclimates that are favorable to mosquito survival. Collectively, our investigations demonstrate the role of a highly invasive understory shrub in determining the abundance and distribution of mosquitoes and suggest potential mechanisms underlying this pattern. Our results also give rise to additional questions regarding the general impact of invasive plants on vector-borne diseases and the spatial scale at which removal of invasive plants may be utilized to effect disease control.

Long-term monitoring reveals an avian species credit in secondary forest patches of Costa Rica.

Degraded and secondary forests comprise approximately 50% of remaining tropical forest. Bird community characteristics and population trends in secondary forests are infrequently studied, but secondary forest may serve as a “safety net” for tropical biodiversity. Less understood is the occurrence of time-delayed, community-level dynamics such as an extinction debt of specialist species or a species credit resulting from the recolonization of forest patches by extirpated species. We sought to elucidate patterns and magnitudes of temporal change in avian communities in secondary forest patches in Southern Costa Rica biannually over a 10 year period during the late breeding season and mid-winter. We classified birds caught in mist nets or recorded in point counts by residency status, and further grouped them based on preferred habitat, sensitivity to disturbance, conservation priority, foraging guild, and foraging strata. Using hierarchical, mixed-effects models we tested for trends among species that share traits. We found that permanent-resident species increased over time relative to migrants. In both seasons, primary forest species generally increased while species typical of secondary forest, scrub, or edge declined. Species relatively sensitive to habitat disturbance increased significantly over time, whereas birds less sensitive to disturbance decreased. Similarly, generalists with higher habitat breadth scores declined. Because, we found very few changes in vegetation characteristics in secondary forest patches, shifts in the avian community toward primary forest species represent a species credit and are likely related to vegetation changes in the broader landscape. We suggest that natural regeneration and maturation of secondary forests should be recognized as a positive conservation development of potential benefit even to species typical of primary forest.

Seasonal changes in avian communities living in an extensively used farmland of Western Poland

Abstract To study the seasonal changes in avian communities, we collected data in an extensively used farmland in Western Poland during 2006-2013. Generalized additive mixed models were used in order to study the effects of seasonality and protected areas on the overall bird species richness. A similarity percentage analysis was also conducted in order to identify the species that contribute most strongly to dissimilarity among each bird according to the phenological season. Furthermore, the differences in bird communities were investigated applying the decomposition of the species richness in season, trend, and remainder components. Each season showed significant differences in bird species richness (seasonality effect). The effect of the protected areas was slightly positive on the overall species richness for all seasons. However, an overall negative trend was detected for the entire period of eight years. The bird community composition was different among seasons, showing differences in terms of dominant species. Greater differences were found between breeding and wintering seasons, in particular, the spatial pattern of sites with higher bird richness (hotspots) were different between breeding and wintering seasons. Our findings showed a negative trend in bird species richness verified in the Polish farmlands from 2006. This result mirrors the same negative trend already highlighted for Western Europe. The role of protected areas, even if slightly positive, was not enough to mitigate this decline process. Therefore, to effectively protect farmland birds, it is necessary to also consider inter-seasons variation, and for this, we suggest the use of medium-term temporal studies on bird communities’ trends.

Time trumps habitat in the dynamics of an avian community

AbstractPredictions of change in avian biodiversity often fail to account for the natural dynamism of species assemblages. Information from historical datasets can be useful indicators of how avian communities may change in the future. However, simple comparisons of diversity and abundances over time may overlook additional changes in bird–habitat associations. In 2013, we revisited sites from a unique, highly detailed avian survey from the Willamette Valley, Oregon, conducted in 1952. Our objectives were to quantify and describe the extent of avian community change; relate observed species assemblages to changes in vegetation type and land‐use class; and identify species with specific associations to either survey era. Using nonparametric ordination, we assessed whether the distribution of the avian community within the environmental space varied temporally. We used blocked indicator species analysis to identify species with specific association to historical or modern survey eras. Nonparametric permutation procedures identified both plot, each representing a different major habitat type, and year as significant factors defining communities. Year was more strongly related to the second ordination axis than the other environmental variables examined. Ordination of survey sites in species space confirmed modern avian communities were significantly different from their historical counterparts. Bird species richness increased and community composition changed by at least 50% despite the physiognomic characteristics of each plot's habitat and the surrounding landscape remaining comparatively stable. Because of this, we conclude time trumped, or was more strongly associated with community change, than alterations in physiognomic habitat. These results suggest avian communities are naturally dynamic even in areas with relatively stable habitat conditions. Predictions that only address changes in climate, land use, or vegetation cover type may fail to predict changes in avian community composition. Historical datasets are a valuable means of understanding real‐world changes in avian communities. We suggest additional factors, such as vegetation structure and microhabitat, may predict fine‐scale shifts in avian species assemblages. Nevertheless, major changes in community composition occurred with apparently minor shifts in physiognomic habitat characteristics in our study area.

Spatial scaling of temporal changes in avian communities

AbstractAimBiodiversity patterns and the mechanisms driving these patterns are inherently scale dependent. Studies investigating biodiversity scaling have focused mostly on evaluating community turnover without taking into consideration its underlying processes of local extinction (hereafter, extinction) and colonization. Our goal was to evaluate the spatial scaling of change in avian assemblages through time and identify environmental drivers of community‐wide dynamics across a range of spatial scales, with a focus on extinction and colonization.LocationNew York State.MethodsWe analysed community dissimilarity, temporal turnover, extinction and colonization as measures of temporal change in avian communities at five spatial resolutions (5 × 5, 10 × 10, 20 × 20, 40 × 40 and 80 km × 80 km). We evaluated the relationships between community change and change in climatic conditions, landscape fragmentation and elevation at each spatial grain using Bayesian spatially varying intercept models.ResultsWe found that the decline in colonization with increasing spatial scale was less steep than the decline in community dissimilarity, temporal turnover or extinction. We also found that the importance of environmental drivers to community change was dependent on both scale and metric, though we did not find optimal spatial scales at which either landscape or climatic processes consistently drove patterns of community change. Landscape characteristics were the most important correlate of extinction at all spatial scales, while colonization was not predicted well by any of the environmental factors.Main conclusionsThe slower decline in colonization across spatial grains is probably a consequence of the high mobility and dispersal abilities of birds. We further conclude that the two processes underlying community change – extinction and colonization – are driven by different factors. Landscape characteristics strongly affect the rates of extinctions in avian communities. On the contrary, patterns of colonization are likely to be a result of intrinsic characteristics of birds – specifically, high dispersal ability – that allow them to colonize new sites, regardless of the environmental context.

Sixty years of change in avian communities of the Pacific Northwest.

Bird communities are influenced by local and regional processes. The degree to which communities are dynamic has implications for projecting responses in community composition as birds track geographic shifts of their habitats. Historic datasets offer a legacy of information that can be used to quantify changes over time in avian community composition. A rare, highly-detailed avian survey of multiple habitat types in the Willamette Valley, Oregon, was conducted in 1952. We resurveyed the same sites in 2013 and evaluated whether observed results agreed with theoretical patterns of community change. We compared alpha, beta, and gamma diversity between survey periods and evaluated shifts in categorical abundances of species. Most patterns of change were consistent with community turnover. Nearly 50% of species were replaced over six decades, with increased species richness and decreased evenness at local and regional spatial extents. Patterns of regional species turnover reflected local turnover. Evidence that local shifts in habitat type drove bird community change were not strongly supported, although historic data on habitats within study plots were limited to macro-level aerial photographs. Thus, regional factors and structural changes likely played important roles determining species composition and abundance.

Patterns and Magnitude of Temporal Change in Avian Communities in the Ecuadorian Andes

Abstract. The tropical Andes rank first among the world's 25 “hotspots” of biodiversity and endemism yet are threatened and little studied. We contrast population trends in avian diversity in montane cloud forest (bosque altoandino) and similar forest degraded by the planting of introduced tree species (bosque introducido) in the Mazan Reserve, Ecuador. We describe changes in bird diversity and abundance in these habitats over 12 years and evaluate the nature of change within these avian communities. On the basis of 2976 count detections and 419 net captures of 76 species of landbirds, indices of similarity between the habitats were low, with only 47.6% of species occurring in both forest types. From 1994–95 to 2006–07, species richness decreased from 54 to 31 in bosque introducido and from 67 to 30 in bosque altoandino. Capture rates also declined from 56.0 to 28.5 birds per 100 mist-net hr in bosque introducido and from 38.0 to 22.4 birds per 100 mist-net hr in bosque altoandino. We explore various pote...

Changes in avian communities of Budongo Forest Reserve after 70 years of selective logging

Owiunji, I. 2000. Changes in avian communities of Budongo Forest Reserve after 70 years of selective logging. Ostrich 71 (1 & 2): 216–219. Budongo Forest Reserve, located in the west of Uganda, has been selectively logged for timber for over 70 years, and has a well documented management history. Changes in the avian community, species diversity and relative densities were assessed in two unlogged and three logged and arboricidally treated compartments. Tree-species diversity was highest in the disturbed forest. Over 100 forest bird species were recorded (including a new record for East Africa, Puvel's Illadopsis Illadopsis puveli. Both point counts and mist-netting showed that bird species diversity was higher in the logged and treated than in the unlogged forest. Five species had significantly higher densities in logged forest, three species had significantly higher densities in unlogged forest and 14 species showed no significant change in densities. The response of Budongo Forest birds to disturbance was species-specific.

Within‐ and Between‐Habitat Avian Diversity in African and Neotropical Lowland Habitats

The general pattern of changes in avian communities along latitudinal, successional, or moisture gradients have been clarified in recent years. However, few studies have compared avifaunas of similar vegetation types and climates in two tropical regions. In this study I asked two questions. How similar ecologically are the avian communities in two tropical areas (Panama and Liberia) with similar climate? To what extent might differences be due to historical factors? In general, there is convergence in the structural and functional characteristics of species and communities in the two tropical regions. However, because historical factors have been different in detail, avifaunas of varying faunal complexity have developed. The forest fauna of Panama is richer than that of Africa but the situation is reversed in grassland and savanna. This seems to be due to the geographic extent of these habitats and their degree of fragmentation during the Pleistocene. Food and habitat specializations are more striking in the neotropics than in Africa. In addition, several feeding guilds, especially bark—gleaners, hover—gleaners, and salliers, are less well represented in Africa. A lower number of bird species feeding on fruit and flower resources in Africa parallels a similar trend in bat communities. The reasons for these differences are complex and outweigh the trends toward convergent evolution in areas of similar climate. Differences of historical geography in the two regions are correlated with the differences in the two avifaunas. These include long— and short—term effects of weather and climate, differences in distribution and abundance of dispersal barriers, trophic role replacements, variation in coevolutionary interactions among groups, and varying histories of human influence. In brief, it appears that the avifaunas of Central America and Africa would be more similar if (1) there were fewer isolating barriers (especially mountains and rivers) in South America, (2) Central America were more isolated from the barriers and consequent high speciation rates of South America, (3) man's influence had been of longer duration in Central America, and (4) the Central American dry season was longer and/or less predictable. These factors and their interactions have produced faunas that are clearly tropical but which are different in a number of respects.