Bird Community Composition Research Articles

Looking beyond rare species as umbrella species: Northern Bobwhites (Colinus virginianus) and conservation of grassland and shrubland birds

Changes in land use and land cover throughout the eastern half of North America have caused substantial declines in populations of birds that rely on grassland and shrubland vegetation types, including socially and economically important game birds such as the Northern Bobwhite (Colinus virginianus; hereafter bobwhites). As much attention is focused on habitat management and restoration for bobwhites, they may act as an umbrella species for other bird species with similar habitat requirements. We quantified the relationship of bobwhites to the overall bird community and evaluated the potential for bobwhites to act as an umbrella species for grassland and shrubland birds. We monitored bobwhite presence and bird community composition within 31 sample units on selected private lands in the south-central United States from 2009 to 2011. Bobwhites were strongly associated with other grassland and shrubland birds and were a significant positive predictor for 9 species. Seven of these, including Bell’s Vireo (Vireo bellii), Dicksissel (Spiza americana), and Grasshopper Sparrow (Ammodramus savannarum), are listed as species of conservation concern. Species richness and occupancy probability of grassland and shrubland birds were higher relative to the overall bird community in sample units occupied by bobwhites. Our results show that bobwhites can act as an umbrella species for grassland and shrubland birds, although the specific species in any given situation will depend on region and management objectives. These results suggest that efficiency in conservation funding can be increased by using public interest in popular game species to leverage resources to meet multiple conservation objectives.

Bird communities in tropical agroforestry ecosystems: an underappreciated conservation resource

Tropical conservation and research focus primarily on protected areas and often ignore conservation values of surrounding agricultural lands. Understanding how species utilize agricultural land will maximize conservation efforts. We compared bird community composition in four habitats in northeastern Costa Rica: shade-grown cacao, live fences, riparian forest buffers, and preserved late-successional rainforest. Point counts over 2 months found 167 species from 36 families. Rainforest contained the most species unique to a habitat although richness per point was lower than in agricultural habitats. Half, 31, of the rainforest species did not occur in other habitats, while 106 species, mostly those preferring open areas, occurred in agroforest habitats but not rainforest. While agricultural habitats had fairly similar species composition to each other as determined by distance in an ordination, each also contained significant numbers, 9–30, of unique species. While intact rainforest remains central to conservation of tropical birds, agricultural lands with substantial trees, e.g., live fences, riparian buffers, and plantations with shade trees, can support a high richness of birds. These avian communities are not simply subsets of the rainforest species but include substantial numbers of unique species. Conservation contributions of these lands to species richness and complexity should be considered in conservation, and trees in these habitats preserved.

Use of restored habitat by rainforest birds is limited by spatial context and species’ functional traits but not by their predicted climate sensitivity

Active restoration of biodiverse forest uses significant resource investment to produce rapid partial recovery of biodiversity, but with unknown longer term outcomes. Here we test the capacity of intensive high diversity rainforest restoration plantings to develop forest-like bird communities beyond their first decade of growth. Across a network comprising 16 such plantings aged 10–24years and eight old growth rainforest reference sites, spread across about 700km2 in the Australian Wet Tropics, we measured bird community composition and 18 attributes related to the sites’ local and landscape vegetation cover and other spatial properties. We compiled additional information on the bird species’ habitat use, movement patterns, responses to edges between forest and cleared land, and expected climate sensitivities. Data analyses showed that bird communities in restoration plantings did not become more similar to those of reference rainforest during their second decade of development. Across replanted sites, occupancy by bird species was significantly predicted by their functional traits, being least among rainforest-dependent species that were also either endemic or sedentary edge-avoiders. Occupancy by rainforest-dependent species was least when nearby remnant rainforest cover (within 200m) was lowest. Species predicted to be climate-sensitive occupied restored habitat at similar rates to other species. These findings provide a foundation for better spatial planning for both habitat-focused and species-focused restoration, and show that expectations based on promising early outcomes of intensive forest restoration projects must be tempered with awareness of likely longer term limitations, highlighting the need to set realistic restoration goals.

Agricultural landscape composition as a driver of farmland bird diversity in Brittany (NW France)

In agriculture-dominated landscapes, agricultural intensification and associated landscape homogenization have caused large declines in farmland biodiversity. This study was aimed at determining how agricultural landscape composition drives community diversity and composition of farmland birds in the characteristic bocage landscape in Brittany (NW France) on a broad scale. Using bird atlas data from the region (2004–2008; 10×10km), we analyzed the importance of different components of agricultural landscape composition (types of crops, amount of semi-natural covers and elements, and artificial lands) on the alpha diversity and beta diversity of farmland birds of different functional groups, defined depending on the degree of farmland specialization and ecological requirements.Agricultural landscape composition features explained a small amount of variation in alpha and beta diversity, particularly for specialists and residents. Cereal crops were negatively correlated with alpha diversity of all the functional groups considered whereas rotational grasslands were negatively associated with migrant and insectivorous alpha diversity. Although shrublands are not common in Brittany, they were positively associated with the occurrence of some species and particularly with alpha diversity of all the functional groups but specialists and residents. At the spatial grain of analysis, community composition was mainly driven by a gradient of alteration of the bocage.To conclude, we claim for the consideration of regional idiosyncrasies in far-reaching planning schemes to prevent future biodiversity loss in agriculture-dominated landscapes due to agricultural intensification. In view of the observed large-scale trends gathered from atlas data analysis and the small amount of explained variation, we also advocate for subsequent finer scale bespoke surveys to determine the biodiversity status associated with the valuable bocage agricultural landscape.

Influence of vegetation on montane riparian bird communities in the Sky Islands of Arizona, USA

Abstract Montane riparian areas across the Sky Island region of the southwestern United States and northwestern Mexico contribute disproportionally to biodiversity at local and regional scales. We explored how composition and structure of vegetation influenced species richness and community composition of songbirds breeding in riparian areas of southern Arizona. We surveyed birds and vegetation during two breeding seasons at 45 stations established across three riparian canyons in two mountain ranges. Species richness of songbirds increased as volume of understory vegetation, density of Arizona sycamore (Platanus wrightii), and density of alligator juniper (Juniperus deppeana) increased; species richness decreased as density of Acacia and Mimosa species increased and oak (Quercus) trees increased. Composition of breeding bird communities was structured along an elevation and vegetation gradient, from open-canopy desert scrub to closed-canopy oak woodlands. Richness and composition of breeding bird communi...

Relative influence of local and landscape factors on bird communities vary by species and functional group

Introduction Both fine scale patterns of vegetation and coarser scale landscape patterns affect bird community composition, but the relative importance of these two sets of patterns tends to be context dependent, varying by location and taxonomic group. Here, we explore the relative roles of landscape pattern and stand structure and composition in defining bird communities in 44 remnant oak stands in the Willamette Valley, Oregon. We focused on: (1) whether bird communities are influenced more by landscape (matrix and patch) patterns or stand composition and structure, and (2) in what contexts each of these spatial scales are more important. Specifically, we focused on how different groups of bird species (functional groups, synanthropic and non-synanthropic species, and individual species) were differentially influenced by landscape and more local patterns.

Comparison of animal biodiversity in three livestock systems of open environments of the semi-arid Chaco of Argentina

Increasing global food demand requires the exploration of agricultural production systems that minimise the conflict between food production and biodiversity conservation. Cattle ranching is a main land-use in tropical and sub-tropical South American semi-arid ecosystems, such as the Chaco eco-region of sub-tropical Argentina, one of the most active frontiers of land-use change. Despite open habits being a key component of the Chaco landscape, conservation studies and policies have focussed on forests. In this study, bird and mammal communities of three different open-canopy livestock-producing systems in the semi-arid Argentinian Chaco: natural grasslands, sown non-native pastures and silvopastoral systems are discussed. Diversity (Inverse Simpson index) and species composition (multivariate ordinations) were measured and species identified that characterise each system (indicator species). The three livestock systems did not significantly differ in terms of diversity but showed differences in the composition of bird communities. Natural grasslands had the highest number of bird and mammal indicator species (including Myrmecophaga tridactyla, a high conservation-value species). These results highlight natural grasslands as a landscape unit with a high conservation value and indicate that they should be explicitly targeted by conservation and land-use policies, particularly because they represent a small and rapidly decreasing proportion of the semi-arid Argentinian Chaco.

Evaluation of microhabitats for wild birds in a Shanghai urban area park

Shanghai is the most crowded city in China and the conservation of biodiversity is essential for the health of its urban ecosystem. The best methods for quantifying and enhancing the function of urban green spaces as wild bird habitats are major concerns. This type of study may explain how the wildlife community responds to different vegetation compositions and provide important insights into urban re-vegetation with respect to biodiversity conservation in a city experiencing rapid urbanization. Thus, we studied the interactions between bird communities and the microhabitat vegetation composition in Binjiang Forest Park. Birds were surveyed at 40 sampling sites and in interconnecting habitat line transects. The bird species richness, abundance, and behavior were quantified, and these indices were related to plant species richness, density, and a vegetation structure. Among the 60 bird species observed in the three habitat types, significantly more species, i.e., 55 species, were observed in woodland with shrubs, 36 species in woodland without shrubs, but only 29 species we recorded on lawns. Multiple linear regression models confirmed that the vegetation complexity and the structure had significant positive effects on the bird community compositions. Regression tree analysis also demonstrated that the woody plant species richness and diversity were significant microhabitat variables for all of the three bird community indices (i.e., bird species richness, abundance, and diversity). Moreover, we confirmed that the vegetation horizontal coverage, particularly the horizontal shrub coverage, was essential for birds living in heavily human-disturbed areas. In addition, our data suggested that well-designed water systems may be beneficial for bird conservation in urban areas. This study highlights the importance of the microhabitat vegetation composition and structure for bird conservation in heavily urbanized areas. However, we also suggest that studies of the relationships between bird communities and urban green vegetation in Shanghai City should be performed in more urban parks in the near future based on considerations of the urban landscape context.

Effects of environmental variation on the composition and dynamics of an arid-adapted Australian bird community

Environmental variables influence the dynamics of bird communities. Australian arid-adapted bird communities must cope with particularly high levels of spatial and temporal variability, including inevitable but unpredictable periods of drought. Over four years, which included a severe drought and a period of above-average rainfall, I quantified the responses of a bird community in arid north-western New South Wales to regular seasonal and irregular climatic variation, especially rainfall, as well as spatial variation. I found pronounced changes in the abundance and composition of the avifauna that related to drought and, to a lesser extent, seasonal variability. Overall bird abundance and species richness declined during the drought but the magnitude and direction of population fluctuations of resident, nomadic and migratory species, different feeding groups, and individual species were not consistent. Avian densities and species richness in the study area were higher in mesic habitats associated with drainage lines than in run-off areas. The study demonstrated the importance of local habitat heterogeneity. The asynchronous species responses to a fluctuating environment indicated that drought is likely to have a differential effect on resources and that individual species respond differently to environmental variability. Effective land management and conservation of Australian arid-adapted bird communities requires an understanding of their spatial and temporal variability and dynamics at both local and regional level. A proper understanding of the variability and dynamics of the avifauna is especially important as climate change is predicted to exacerbate the climatic variability and unpredictability of the arid zone in future years.

Forest development phases as an integrating tool to describe habitat preferences of breeding birds in lowland beech forests

Land management causes changes in forest structure and thus influences the composition and abundance of communities of forest-inhabiting bird species. However, it is unclear how these changes translate into local habitat suitability for certain bird species given that detailed knowledge on habitat use by forest bird species is still scarce. We have analyzed the habitat preferences of 37 breeding bird species in 19 lowland beech forests, each with an average size of 40 ha. We used Jacobs habitat selection index to quantify preference or avoidance of certain forest developmental phases (fdp). Fdp divide the forest life cycle into different periods, each characterized by a certain combination of habitat parameters (canopy cover, tree dimension, deadwood amount, regeneration cover), thereby integrating several age-specific structural properties. We found that fdp representing the last third of the forest life cycle were significantly preferred by most of the bird species. Of the 37 bird species analyzed, 19 showed the highest preference for the terminal phase or the disintegration phase; this was especially true for hole breeders, semi-hole breeders, ground breeders and beech forest indicator species. Moreover, each bird species showed a characteristic profile of preferred and avoided fdp. Some bird species, such as several free breeders, also preferred younger fdp, such as gaps or regeneration phases. Further, mean fdp patch size turned out to be a strong predictor of bird community composition. Our study confirms that most bird species show a strong preference for later fdp, such as the terminal phase and disintegration phase. However, the simultaneous availability of a mixture of different fdp on local scales meets the habitat preferences of most species and promotes biodiversity of breeding bird communities in lowland beech forests.

Migratory bird species benefit from traditional agricultural gardens in arid South Sinai

In temperate and tropical regions agricultural conversion of natural habitat typically has negative impacts upon the diversity and functional complexity of bird communities. In arid environments however, the irrigation associated with agricultural can lead to an increase in local abundances of plant and insect resources, so has the potential to benefit bird communities. South Sinai is a key migratory corridor for many birds making the annual journey from wintering sites in Africa to breeding sites in Europe. We assess the importance of traditional Bedouin agricultural gardens for both resident and migratory species by comparing the density and functional composition of birds within the irrigated gardens to those in the unmanaged desert habitat. Estimated bird densities were significantly higher within the gardens than the unmanaged habitat, with a higher estimated species richness within the gardens. Functional composition of bird communities differed between the two habitats, with gardens supporting a higher proportion of insectivorous and migratory birds in addition to the resident desert species that were associated with the unmanaged habitat. Migratory species were almost entirely absent from the unmanaged habitat, suggesting that this region may not be used as a migratory stop-off if not for the presence of traditional agricultural gardens.

Energy use by migrants and residents in North American breeding bird communities

AbstractAimOf the order of 5 billion birds comprising more than 700,000 tonnes of biomass migrate across North America every year to exploit seasonal resource pulses at high latitudes during breeding. Despite this impressive scale, little is known about the metabolic role of these migrants in their breeding grounds across temperate ecosystems. I estimate the energy use of short‐ and long‐distance migrant passerines as well as residents in over 2000 breeding bird communities covering the geographic scope of North America. My aim was to characterize the geographic patterns of energy use by each migratory group and test the hypothesis that seasonal patterns of resource availability structure temperate breeding bird communities.LocationNorth America from 25 to 69° N.MethodsI estimated the energy use of migrant and resident passerines using abundance data from the North American Breeding Bird Survey and scaling relationships for field metabolic rate as a function of body size. Linear regression was used to test the relationship between energy use by each migratory group and latitude as well as indirect measures of environmental productivity during different seasons.ResultsEnergy use by all groups showed a strong relationship with latitude except for long‐distance migrants, which were surprisingly invariant across geography. Energy use by migrants was highest in environments with low winter productivity and high seasonality, while resident energy use was highest where annual productivity was the highest.Main conclusionsMigrant passerines contribute significantly to temperate breeding bird communities, especially in high latitudes. They account for 78% of consumption in habitats north of 50° N compared with 1.7% in the subtropics south of 35° N. Short‐distance migrants are especially important to community energy use in the habitats where migrants consume the most. Future shifts in breeding bird community composition are likely to occur as climate change alters seasonal cycles of resource availability.

The importance of riparian habitats for avian communities in a highly human-modified Neotropical landscape

Intensification of agriculture and urban development are the main forces degrading natural ecosystems, particularly within species-rich countries. In this study, we determined the variation in bird communities between anthropogenic (i. e., cattle grazing lands, crop fields, urban areas) and riparian habitats within a highly humanmodified landscape in northwestern Colombia. For this purpose, we assessed differences in bird community diversity, structure, and composition among studied habitats. We also investigated similarities of surveyed habitats according to the habitat preferences of species. Results showed that riparian habitats play a fundamental role in human-dominated landscapes, as they maintain diverse and complex bird communities, support interior forest bird species, and might promote heterogeneous bird communities in nearby habitats. Cattle grazing lands also exhibited heterogeneous bird communities, which might be a result of the presence of tall trees, abundant shrub cover, and proximity of riparian habitats. Few species were over dominant within crop fields and urban areas due to a simple vegetation structure, leading to homogeneous avian communities where disturbed-site species thrive. Given that increasing human population depends on agricultural and urban ecosystems worldwide, there is an urgent need to foster management and conservation activities within such ecosystems to support wildlife and enhance human welfare.

Road networks predict human influence on Amazonian bird communities

Road building can lead to significant deleterious impacts on biodiversity, varying from direct road-kill mortality and direct habitat loss associated with road construction, to more subtle indirect impacts from edge effects and fragmentation. However, little work has been done to evaluate the specific effects of road networks and biodiversity loss beyond the more generalized effects of habitat loss. Here, we compared forest bird species richness and composition in the municipalities of Santarém and Belterra in Pará state, eastern Brazilian Amazon, with a road network metric called 'roadless volume (RV)' at the scale of small hydrological catchments (averaging 3721 ha). We found a significant positive relationship between RV and both forest bird richness and the average number of unique species (species represented by a single record) recorded at each site. Forest bird community composition was also significantly affected by RV. Moreover, there was no significant correlation between RV and forest cover, suggesting that road networks may impact biodiversity independently of changes in forest cover. However, variance partitioning analysis indicated that RV has partially independent and therefore additive effects, suggesting that RV and forest cover are best used in a complementary manner to investigate changes in biodiversity. Road impacts on avian species richness and composition independent of habitat loss may result from road-dependent habitat disturbance and fragmentation effects that are not captured by total percentage habitat cover, such as selective logging, fire, hunting, traffic disturbance, edge effects and road-induced fragmentation.

Temporal changes in randomness of bird communities across Central Europe.

Many studies have examined whether communities are structured by random or deterministic processes, and both are likely to play a role, but relatively few studies have attempted to quantify the degree of randomness in species composition. We quantified, for the first time, the degree of randomness in forest bird communities based on an analysis of spatial autocorrelation in three regions of Germany. The compositional dissimilarity between pairs of forest patches was regressed against the distance between them. We then calculated the y-intercept of the curve, i.e. the ‘nugget’, which represents the compositional dissimilarity at zero spatial distance. We therefore assume, following similar work on plant communities, that this represents the degree of randomness in species composition. We then analysed how the degree of randomness in community composition varied over time and with forest management intensity, which we expected to reduce the importance of random processes by increasing the strength of environmental drivers. We found that a high portion of the bird community composition could be explained by chance (overall mean of 0.63), implying that most of the variation in local bird community composition is driven by stochastic processes. Forest management intensity did not consistently affect the mean degree of randomness in community composition, perhaps because the bird communities were relatively insensitive to management intensity. We found a high temporal variation in the degree of randomness, which may indicate temporal variation in assembly processes and in the importance of key environmental drivers. We conclude that the degree of randomness in community composition should be considered in bird community studies, and the high values we find may indicate that bird community composition is relatively hard to predict at the regional scale.

Measuring habitat heterogeneity reveals new insights into bird community composition.

Fine-scale vegetation cover is a common variable used to explain animal occurrence, but we know less about the effects of fine-scale vegetation heterogeneity. Theoretically, fine-scale vegetation heterogeneity is an important driver of biodiversity because it captures the range of resources available in a given area. In this study we investigated how bird species richness and birds grouped by various ecological traits responded to vegetation cover and heterogeneity. We found that both fine-scale vegetation cover (of tall trees, medium-sized trees and shrubs) and heterogeneity (of tall trees, and shrubs) were important predictors of bird richness, but the direction of the response of bird richness to shrub heterogeneity differed between sites with different proportions of tall tree cover. For example, bird richness increased with shrub heterogeneity in sites with high levels of tall tree cover, but declined in sites with low levels of tall tree cover. Our findings indicated that an increase in vegetation heterogeneity will not always result in an increase in resources and niches, and associated higher species richness. We also found birds grouped by traits responded in a predictable way to vegetation heterogeneity. For example, we found small birds benefited from increased shrub heterogeneity supporting the textual discontinuity hypothesis and non-arboreal (ground or shrub) nesting species were associated with high vegetation cover (low heterogeneity). Our results indicated that focusing solely on increasing vegetation cover (e.g. through restoration) may be detrimental to particular animal groups. Findings from this investigation can help guide habitat management for different functional groups of birds.

Dispatches

Dispatches

Isolation, patch size and matrix effects on bird assemblages in forest reserves

Habitat fragmentation is one of the most studied topics in ecology but our knowledge is still limited particularly concerning matrix effects on species distribution in a human-dominated landscape. We tested the ability of random sampling hypothesis, colonization–extinction dynamics and matrix-related concepts to explain the variation in species richness, total bird density and community composition in old-forest bird assemblages in two contrasting landscapes. We collected data on breeding bird abundances from 66 old-growth forest reserves in NE Finland and six larger areas in adjacent Russian Karelia using the line transect method. In Finland, protected old-forest patches are embedded in a matrix dominated by young regeneration stands. In Russia, study areas were situated in continuous, old forest dominated landscapes. Bird assemblages in old-forest patches embedded in human-modified matrix in Finland were not random samples from Russian bird assemblages. In the Finnish assemblages, species richness was lower and total bird density higher. Species richness declined with increasing distance (isolation) to Russia. Bird assemblages in large forest reserves in Finland close to Russia were structurally more similar to assemblages in the continuous reference landscape than those in small and more distant reserves. The results support the idea that several mechanisms related to colonisation–extinction dynamics and to matrix resource availability influence species distribution in fragmented landscapes but in species-specific ways. We conclude that even though small and isolated protected areas may foster high relative bird species density their ecological integrity is compromised, and therefore, improving matrix quality around reserves may lead to considerable conservation benefits.

Land tenure and biological communities in dry Chaco forests of northern Argentina

Environmental factors and land use control habitat quality and resources availability, thus regulating species distribution. Land tenure in general, and particularly traditional indigenous properties, strongly influence land use in forest ecosystems, but their association with biodiversity is poorly explored. We surveyed 43 forests in the Northern Argentina Gran Chaco, to (1) compare species diversity and composition of birds, mammals and trees between land tenures across a 17 million-hectares region; and to (2) compare diversity between Wichí indigenous properties and non-indigenous properties, within a more restricted geographic range to control for climatic and soil factors (n = 19). Contrary to our expectations, protected areas did not include higher biodiversity, although they showed higher densities of species specifically targeted for human harvest. Wichí properties were the most original regime in terms of community composition of birds and trees. Every land tenure had particular indicator bird and tree species; thus a territorial conservation strategy could include a combination of all them, with a special focus on indigenous properties. Land tenure differences in biodiversity could be the complex result of different habitat quality derived from land use practices and of different geographic location.

Bird communities in traditional wood-pastures with changing management in Eastern Europe

Wood-pastures are fragile ecosystems because they were formed by, and depend on specific, low-intensity multifunctional management. Although their ecological and cultural significance is high, wood-pastures are rapidly deteriorating all over Europe, mainly due to changing land use. We still lack a basic understanding of the ecological value of wood-pastures, and in which features they differ from other landscape elements. In this paper we investigated the ecological value of wood-pastures for passerine birds by (i) comparing bird assemblages of wood-pastures with those of closed forests and open pastures and (ii) exploring the relationships between variables describing wood-pastures and species traits of the bird assemblages. Our study region (Southern Transylvania, Romania) provides a unique opportunity to understand the importance of a traditional cultural and ecological environment for many different organisms. Wood-pastures had a higher overall number of bird species, and a higher spatial turnover in bird community composition than closed forests and open pastures. We found significant associations between bird species traits and habitat structural elements in wood-pastures such as large trees, oak- and pear trees and shrubs. Our findings suggest that traditional wood-pastures in Southern Transylvania have distinct and rich passerine bird communities. This richness is inextricably linked to the multifunctional, low-intensity land use traditionally applied in the wood-pastures that promotes high niche diversity. For effective conservation of the biodiversity of wood-pastures, a detailed understanding is needed of how different management regimes may influence the key structural elements of wood-pastures relevant for biodiversity and these should be protected.