Predictors Of Bird Species Richness Research Articles

The influence of urban park characteristics on bird diversity in Nanjing, China

BackgroundHabitat loss, fragmentation and decrease of habitat quality caused by urbanization have led to a dramatic decline in biodiversity worldwide. For highly urbanized areas, parks have become “islands” or habitat fragments for wildlife. As an important indicator group of urban ecosystem health, the response of birds to urbanization has attracted the global attention of ecologists. Understanding the key factors affecting bird diversity in urbanized environment is crucial to the protection of biodiversity in urban ecosystems.MethodsWe used the line-transect method to survey birds in 37 urban parks in Nanjing, China. We also measured a number of park characteristics (area, isolation, shape index, environmental noise, distance to city center, and habitat diversity) that are commonly assumed to influence bird diversity. We then used the information-theoretic multi-model inference approach to determine which park characteristics had significant impacts on bird species richness.ResultsWe found that park area, habitat diversity and the distance to city center were the best positive predictors of bird species richness in Nanjing urban parks. By contrast, park isolation, park shape and environmental noise had little or no influence on bird diversity.ConclusionsOur study highlights the importance of park area, habitat diversity and the distance to city center in determining bird diversity in Nanjing city parks. Therefore, from a conservation viewpoint, we recommend that large parks with complex and diverse habitats far away from the city center should be retained or constructed to increase bird diversity in urban design and planning.

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.

Metrics of Lidar-Derived 3D Vegetation Structure Reveal Contrasting Effects of Horizontal and Vertical Forest Heterogeneity on Bird Species Richness

The structural heterogeneity of vegetation is a key factor for explaining animal diversity patterns at a local scale. Improvements in airborne light detection and ranging (lidar) technologies have enabled researchers to study forest 3D structure with increasing accuracy. Most structure–animal diversity work has focused on structural metrics derived from lidar returns from canopy and terrain features. Here, we built new lidar structural metrics based on the Leaf Area Density (LAD) at each vegetation height layer, and used these metrics to study how different aspects of forest structural heterogeneity explain variation in bird species richness. Our goals were to test: (1) whether LAD-based metrics better explained bird species richness compared to metrics based on the top of the canopy; and (2) if different aspects of structural heterogeneity had diverse effects on bird richness. We used discrete lidar data together with 61 breeding landbird points provided by the National Ecological Observatory Network at five forest sites of the eastern US. We used the lidar metrics as predictors of bird species richness and analyzed the shape of the response curves against each predictor. Metrics based on LAD measurements had better explanatory power (43% of variance explained) than those based on the variation of canopy heights (32% of variance explained). Dividing the forest plots into smaller grids allowed us to study the within-plot horizontal variation of the vertical heterogeneity, as well as to analyze how the vegetation density is horizontally distributed at each height layer. Bird species richness increased with horizontal heterogeneity, while vertical heterogeneity had negative effects, contrary to previous research. The increasing capabilities of lidar will allow researchers to characterize forest structure with higher detail. Our findings highlight the need for structure–animal diversity studies to incorporate metrics that are able to capture different aspects of forest 3D heterogeneity.

Riparian reserves help protect forest bird communities in oil palm dominated landscapes

Abstract Conversion of forest to oil palm agriculture is a significant and ongoing threat to tropical biodiversity. Despite this, little is known about the value of riparian reserves in oil palm and how these conservation set‐asides might best be managed to maintain biodiversity. We characterized bird communities of 28 sites in an oil palm‐forest mosaic in Sabah, Malaysia using 6,104 encounters from 840 point counts. Sites included oil palm riparian reserves of various vegetation quality and reserve widths, which were compared to oil palm streams without a riparian reserve as well as riparian and nonriparian control areas in continuous logged forest. Riparian reserves, oil palm waterways, and control sites in riparian and nonriparian forest supported distinct avifaunal communities. Riparian reserve width, forest quality, and amount of forest cover were the strongest predictors of bird species richness. For forest‐dependent species, each of these predictors had a stronger effect size when compared with all species. On average, reserves held 31% of all species and 30% of forest specialists, whereas riparian forest controls averaged 32% of all species, but 38% of forest species. Riparian reserves with >40 m of natural vegetation on each bank supported similar bird diversity to riparian forest control habitats found in continuous forest. However, to support equivalent numbers of forest‐dependent species and species of conservation concern, reserves would need to be at least 100‐m wide on each bank. The largest numbers of species were found in riparian reserves with above‐ground carbon densities exceeding 75 tC/ha, highlighting the importance of forest quality, as well as width, in supporting riparian bird communities. Synthesis and applications. If designed and protected appropriately, riparian reserves in oil palm estates support diverse bird communities, including many species of conservation concern. This can be achieved by designating large reserves (80–200 m total width). But, to maximize species numbers, forest disturbance should also be minimized prior to conversion as well as during plantation operations.

Multiple species of cuckoos are superior predictors of bird species richness in Asia

AbstractThe abundance and the presence of common cuckoos Cuculus canorus have been shown to predict species richness of birds across Europe, while there are no such analyses available for other continents where species richness of parasitic cuckoos is larger. Here, we tested whether species richness of birds increased with the number of cuckoo species in two study areas in China and one in Japan. We also tested whether species richness of birds can be predicted by the number of cuckoo individuals. Furthermore, we compared the strength of association between overall bird species richness and species richness of cuckoos, Paridae, Corvidae, and birds of prey. This is the first study demonstrating that cuckoo species richness is more strongly associated with overall bird species richness than richness of species belonging to other families, and rather than occurrence of a single cuckoo species, as already demonstrated for the common cuckoo in Europe. The number of cuckoo species was positively associated with both non‐host and host species richness. We found evidence of the number of cuckoo species being associated with species richness of birds independently of country and year, while abundance of individual cuckoos was not a statistically significant predictor. Furthermore, we showed that richness of host species is strongly positively correlated with overall bird species richness in both countries. This implies that the high species richness of cuckoos in South‐East Asia is a reliable predictor of overall bird species richness.

The influence of small urban parks characteristics on bird diversity: A case study of Petaling Jaya, Malaysia

The capacity of small urban park to serve as urban habitats are rarely explored. This study analyses the characteristics of small urban parks and their potential to support urban biodiversity and ecological functions. Nine small urban parks were studied in Malaysia in August and September 2014 using the combined field survey method of structured observation and field measurements. The measured variables were divided into three broad categories of physical characteristics, species richness and human factors. Bird species richness and abundance were used as the indicators for assessing biodiversity. Pearson correlations and multiple regressions were conducted to analyse the relationships between variables and to identify which variables had a significant effect on bird species richness and abundance. The results demonstrated that park area and vegetation variables ( e.g. the percentage of tree canopy cover, open grass/ground, native-exotic plants) are the important predictors of bird species richness and abundance. The percentage of canopy covers (negative relation) and park area (positive relation) are the best predictors of bird species richness in small urban parks. Meanwhile, the best predictors for bird abundance are the percentage of canopy covers (negative relation) and native vegetation species (positive relation). Human activities and park surroundings have a marginal effect on the presence of bird species in small parks. Based on the findings, we provide two general recommendations that could probably increase bird diversity in small urban parks: (1) the park development and management plan should incorporate a social-ecological approach that can benefit both city-dwellers and bird species, and (2) findings from the study should be used to rethink the planting design and composition of especially newly established small urban parks.

Farmland conservation in West Africa: how do hedgerow characteristics affect bird species richness?

Capsule The value of farmland for birds at a site in Nigeria, West Africa, was highly dependent upon the habitat structure, with wider and more continuous hedges supporting more bird species. Aim To understand the value of hedges in Nigerian farmland to bird species richness. Methods We used line transects to survey birds and vegetation on 166 systematically selected hedgerows on fallow, cultivated and harvested fields in Jos East, Nigeria. Results Wider hedges supported higher species richness. Plant species composition was a weak predictor of bird species richness compared to hedge width. There was no observed difference in distribution of bird richness across field types, suggesting that the value of hedgerows for biodiversity is comparable, regardless of farming method. Continuous hedgerows (hedgerows with vegetation gap < 1.5 m) held higher species richness compared with discontinuous (hedgerows with vegetation gap > 1.5 m) hedges. Conclusion This result suggests that hedge size and structure, rather than plant species composition, is an important predictor of avian species richness in hedgerows surrounding farmland. Therefore, the value of farmland for birds in this part of Africa is highly dependent upon the habitat structure, with wider and more continuous hedges supporting more bird species.

Direct and indirect effects of area, energy and habitat heterogeneity on breeding bird communities

Aim To compare the ability of island biogeography theory, niche theory and species–energy theory to explain patterns of species richness and density for breeding bird communities across islands with contrasting characteristics. Location Thirty forested islands in two freshwater lakes in the boreal forest zone of northern Sweden (65°55′ N to 66°09′ N; 17°43′ E to 17°55′ E). Methods We performed bird censuses on 30 lake islands that have each previously been well characterized in terms of size, isolation, habitat heterogeneity (plant diversity and forest age), net primary productivity (NPP), and invertebrate prey abundance. To test the relative abilities of island biogeography theory, niche theory and species–energy theory to describe bird community patterns, we used both traditional statistical approaches (linear and multiple regressions) and structural equation modelling (SEM; in which both direct and indirect influences can be quantified). Results Using regression-based approaches, area and bird abundance were the two most important predictors of bird species richness. However, when the data were analysed by SEM, area was not found to exert a direct effect on bird species richness. Instead, terrestrial prey abundance was the strongest predictor of bird abundance, and bird abundance in combination with NPP was the best predictor of bird species richness. Area was only of indirect importance through its positive effect on terrestrial prey abundance, but habitat heterogeneity and spatial subsidies (emerging aquatic insects) also showed important indirect influences. Thus, our results provided the strongest support for species–energy theory. Main conclusions Our results suggest that, by using statistical approaches that allow for analyses of both direct and indirect influences, a seemingly direct influence of area on species richness can be explained by greater energy availability on larger islands. As such, animal community patterns that seem to be in line with island biogeography theory may be primarily driven by energy availability. Our results also point to the need to consider several aspects of habitat quality (e.g. heterogeneity, NPP, prey availability and spatial subsidies) for successful management of breeding bird diversity at local spatial scales and in fragmented or insular habitats.

THE INFLUENCE OF HABITAT HETEROGENEITY ON BIRD DIVERSITY IN IRISH FARMLAND

ABSTRACTThe intensification and specialisation of agricultural practices have led to a widespread decline offarmland bird diversity across much of Europe. Increasing habitat heterogeneity at multiple spatialscales has been suggested as one possible strategy to reverse these declines. This study examined therelationship between habitat heterogeneity, as measured by a number of indices, and bird diversity atfarm scale using study sites in the east and south-east of Ireland. Generalised Linear Models indicatedthat there was a positive relationship between the documented heterogeneity of farmland habitatsand the numbers of bird species observed during standardised farm surveys. However, thisrelationship was not evident when bird diversity was quantified using both the Shannon and theSimpson’s diversity indices. It is concluded that agri-environmental policy that aims to influence theheterogeneity of habitats at the farm level can provide a useful means to maintain farmlandbiodiversity. Future research should aim to develop an improved system of habitat classification and adeeper understanding of the ecological value of different habitat types in Irish farmland.INTRODUCTIONMany authors have stressed the importance oflandscape structure in understanding the causes ofdecline in farmland bird populations (McGarigalet al. 2002; Sua´rez-Seoane et al. 2002; Benton et al.2003; Verhulst et al. 2004). Landscape ecology islargely based on the presumption that changes in therange and diversity of landscape elements have astrong influence on ecological characteristics,including bird populations, over time (McGarigalet al. 2002). One of the first to note that wildlifediversity was greater in more diverse landscapes wasLeopold (1933). In Sweden, the structure of thesurrounding landscape explained at least some of thevariation documented in both the species richness(number of species)and the diversity of a wide rangeof taxa (vascular plants, butterflies, bumblebees,ground beetles, dung beetles and birds) found insemi-natural grasslands (So ¨derstrom et al. 2001).Different landscape features have been found toinfluence the species richness and diversityof different taxa. For example, landscapeheterogeneity has been highlighted as an importantdeterminant of carabid beetle species diversity(Weibull and O¨ stman 2003). Bird species richnessand abundance are influenced by local resourceavailability and vegetation composition, in additionto the size of habitat patches (MacArthur andMacArthur 1961; Cody 1985). It has been arguedthat agricultural intensification has resulted in a lossof ecological heterogeneity at multiple spatial andtemporal scales and that biodiversity policy shouldaim to reverse this trend in Europeanagroecosystems (Benton et al. 2003).The Common Agricultural Policy (CAP)substantially influenced the intensification ofagriculture within the European Union (Donaldet al. 2001). The CAP has also resulted in theabandonment of agricultural practices withinproductively marginal parts of Western Europe(Pain and Pienkowski 1997), which is alsobelieved to have had a negative effect onbiodiversity (Sua´rez-Seoane et al. 2002). Studieshave shown that extensively used farmland can holdthe highest diversity and abundance of farmlandbirds (Verhulst et al. 2004). This view is reinforcedby the work of Sua´rez-Seoane et al. (2002), whofound that agricultural mosaics of low-intensitycultivation maintain the highest diversity ofendangered bird species.Different elements of landscape structure,including the density of hedgerows and woodlands,have been highlighted as likely predictors of overallbird species abundance. For example, cereal cropsare positively associated with open-land and arablespecialists, such as skylark (Alauda arvensis) andyellowhammer (Emberiza citronella), respectively(Fuller et al. 1997). An index of the ecologicalcharacteristics of field boundaries*the fieldboundary evaluation and grading system (FBEGS)developed by Collier and Feehan (2003)*has beenshown to be a useful predictor of bird speciesrichness and diversity within field boundary habitats

Relation between habitat attributes and bird richness in a western Mexico suburb

As an area becomes urbanized, the replacement of original habitats with human-made structures can reduce biodiversity. Urban ecology studies demonstrate that bird species richness is negatively related to increased urbanization. Nevertheless, our understanding of the processes that determine how bird communities respond to urbanization is still rudimentary. In particular, there is lack of studies investigating the dynamics of urban bird communities in tropical areas. I explored the effects of human-influenced attributes on bird richness at eight plots within a suburb in tropical Guadalajara, Mexico. Results of this study suggest that tree foliar cover and maximum tree height are predictors of bird species richness at this site. Additionally, tree foliar cover was related to which trophic guilds dominated the avian community. In order to assist in the maintenance and promotion of native bird species within tropical urbanized areas, I suggest three urban planning and management activities: (1) the evaluation of fast growing, tall, wide-ranging foliar cover tree species native to the study area, (2) the increase of green area extension with the selected tree species along the urbanized area, and (3) the use of urban ecology research recommendations into managing and developmental plans.

Laser remote sensing of canopy habitat heterogeneity as a predictor of bird species richness in an eastern temperate forest, USA

Habitat heterogeneity has long been recognized as a fundamental variable indicative of species diversity, in terms of both richness and abundance. Satellite remote sensing data sets can be useful for quantifying habitat heterogeneity across a range of spatial scales. Past remote sensing analyses of species diversity have largely been limited to correlative studies based on the use of vegetation indices or derived land cover maps. A relatively new form of laser remote sensing (lidar) provides another means to acquire information on habitat heterogeneity. Here we examine the efficacy of lidar metrics of canopy structural diversity as predictors of bird species richness in the temperate forests of Maryland, USA. Canopy height, topography and the vertical distribution of canopy elements were derived from lidar imagery of the Patuxent National Wildlife Refuge and compared to bird survey data collected at referenced grid locations. The canopy vertical distribution information was consistently found to be the strongest predictor of species richness, and this was predicted best when stratified into guilds dominated by forest, scrub, suburban and wetland species. Similar lidar variables were selected as primary predictors across guilds. Generalized linear and additive models, as well as binary hierarchical regression trees produced similar results. The lidar metrics were also consistently better predictors than traditional remotely sensed variables such as canopy cover, indicating that lidar provides a valuable resource for biodiversity research applications.

High-resolution image texture as a predictor of bird species richness

We tested image texture as a predictor of bird species richness in a semi-arid landscape of New Mexico. Bird species richness was summarized from 10-min point counts conducted at 12 points within 42 plots (108 ha each) from 1996 to 1998. We calculated 14 first- and second-order texture measures in eight different window sizes on a set of digital orthophotos acquired in 1996. For each of the 42 plots, we summarized mean and standard deviation of each texture value within multiple window sizes. The relationship between image texture and average bird species richness was assessed using linear regression models. Single image texture measures such as the standard deviation described up to 57% of the variability in species richness. Coupling multiple measures of texture or coupling elevation with a single texture measure described up to 63% of the variability in bird species richness. Models incorporating two measures of texture and coarse habitat type described 76% of the variability in bird species richness. These results show that image texture analysis is a very promising tool for characterizing habitat structure and predicting patterns of species richness in semi-arid ecosystems. This method has several advantages over methods that rely on classified imagery, including cost-effectiveness, incorporation of within-habitat vegetation variability, and elimination of errors associated with boundary delineation.