Avian Assemblages Research Articles

Foraging in the tropics: relationships among species’ abundances, niche asymmetries and body condition in an urban avian assemblage

Two main theories attempt to explain species coexistence: the neutral theory considers all the species as equivalents so biodiversity is mainly regarded as a function of total available resources (i.e. niche expansion), while the niche theory stresses the relevance of differences in niche use between species (i.e. niche packing). The relative importance of these forces is under discussion and has been largely tested in natural ecosystems. However, few studies have addressed this issue in tropical-urban environments. In this work we studied niche overlap asymmetries among the most common urban resident birds, and the effect of habitat type on this pattern, in a subtropical location of South China (Nanning, Guangxi). We found differences in abundances and niche use among species and urban habitats (parks, streets and orchards). We also recorded strong asymmetries in niche use between species, which we divided into three categories: species with positive asymmetries, which showed highly specific niches and were able to exploit other species’ niches; species with neutral asymmetries, which showed high levels of niche overlap with the rest of species; and species with negative asymmetries, which showed low specificity in their niches and were unable to exploit other species’ niches. These differences in niche use correlated with differences in fat scores. Species from the first group showed higher fat scores than other two groups. Ultimately, niche asymmetries correlated with species’ body condition and mediated their differences in abundance, which supports the view that in this urban context niche theory is more appropriate than neutral theory.

Avian guild assemblages in forest fragments around Budongo Forest Reserve, western Uganda

Remnant forest fragments provide an opportunity for conservation in fragmented landscapes but some patches are more useful than others. Forest fragments around Budongo Forest Reserve, an Important Bird Area in western Uganda, were surveyed to explore the effects of different aspects of habitat fragmentation on bird guild composition. We recorded 1 128 individuals of 75 bird species over 7 056 net hours. The greatest number of birds and species were recorded in the forest fragments that were large, near to the continuous forest and surrounded by subsistence farmland. However, rarefied species richness was not affected by distance, size or matrix type; instead, forest specialist species were replaced by generalists and visitors with increasing fragmentation. The proportion of forest specialists and of terrestrial insectivores decreased with distance from the main forest, canopy openness and matrix intensity but not with fragment area. The findings show that bird assemblages vary in their response to habitat fragmentation but within guilds the response to fragmentation can be consistent, and can make ecological sense. Forest bird conservation can therefore benefit from information on species ecology when deciding which bird species and which parts of the landscape are to be prioritised for conservation or monitoring purposes.

Geographical variation in reproductive investment across avian assemblages in Europe: effects of environmental drivers differ between altricial and precocial species

Reproductive traits provide information about the ways by which available resources are allocated during breeding. We tested for environmental drivers of large scale geographical patterns in assemblage mean clutch size, number of broods and overall reproductive investment per breeding season in European birds. We combined data about geographical distribution with published information about reproductive traits, and calculated mean trait values for avian assemblages occurring in 50 × 50 km grid cells. In total, we employed data from 499 species and 2059 assemblages. As the time available for breeding and the amount of food limit the reproductive effort, we related the geographical variation in reproductive traits to the length of breeding season, normalized difference vegetation index (NDVI) as a surrogate of resource availability, and its seasonality. Geographical patterns in traits may differ between reproductive modes, thus we performed the analyses separately for altricial Passerines (n = 203) and precocial non‐passerine species (n = 164) and controlled for the effect of taxonomy. Large clutches dominated in areas with high NDVI and, in precocial birds, also in areas with high annual seasonality and a long breeding season. High number of broods and high overall reproductive investment dominated in areas with a long breeding season, and high number of broods was found also in areas with low annual seasonality, but only in precocial species. High overall reproductive investment dominated in highly productive areas and also in areas with low annual seasonality in both groups. The increase in reproductive investment is caused mostly by an increase in the number of broods related to the length of season and partly by increase in clutch size related to NDVI. We found a negative correlation between clutch size and the number of broods in Passerines, which might suggest a trade‐off between these traits. Processes behind trait patterns differ between altricial and precocial species.

Taxonomic, phylogenetic and functional diversity of an urban Amazonian avifauna

Amazonia is undergoing rapid urbanisation, but nothing has been published on the structure and function of urban Amazonian avifaunas. Here we present the results of a year-long survey of the avifauna of an Amazonian city, exploring temporal variation in its taxonomic, phylogenetic and functional diversity. We found urban bird communities to be taxonomically depauperate and dominated by a small subset of common species typical of second growth and river-edge habitats. Broad patterns of phylogenetic community similarity typically resembled those found in other studies on urban Neotropical bird assemblages, with insectivores the dominant guild. There was significant temporal variation in taxonomic and phylogenetic structure owing to the seasonal arrival and departure of a regionally over-represented minority of migratory species. Although the urban avian assemblage is of limited regional conservation value, it may still offer significant biodiversity services and represent one of few points of contact for local people with biodiversity.

Revision of non-passeriform birds from Polgárdi (Hungary, Upper Miocene): 3. Neoaves

A taxonomic revision of Upper Miocene Neoaves from Polgardi locality is summarized. Rallicrex polgardiensis is transferred to the genus Rallus. The taxonomic position of R. kolozsvarensis is discussed. Porzana estramosi veterior and P. kretzoii are transferred to the genus Zapornia former is ranked as species. It is shown that the material referred to Egretta polgardiensis, Surnia robusta, and Otis kalmani actually belong to the fossil barn owl Tyto campiterrae. The genera Cuculus and Tetrao are identified incorrectly and several other taxa cannot be identified to genus. A fragmentary carpometacarpus originally referred to as Gallinago veterior actually belongs to Glareolidae. A complete list of revised non-passeriform taxa from Polgardi is provided and the composition of the avifauna is discussed. The absence of taxa shared with approximately contemporaneous avian assemblage from the Hyargas-Nuur 2 locality in eastern Mongolia is evidence that at least two separate zoogeographical units of temperate avifaunas existed in the Late Miocene of Eurasia.

A large-scale perspective for managing prairie avifauna assemblages across the western US: influences of habitat, land ownership and latitude.

Future demands for increased food production are expected to have severe impacts on prairie biodiversity and ecosystem integrity. Prairie avifauna of North America have experienced drastic population declines, prompting numerous conservation efforts, which have been informed primarily by small-scale studies. We applied a large-scale perspective that integrates scale dependency in avian responses by analyzing observations of 20 prairie bird species (17 grassland obligates and three sagebrush obligate species) from 2009–2012 in the western prairie region of the United States. We employed a multi-species model approach to examine the relationship of land ownership, habitat, and latitude to landscape-scale species richness. Our findings suggest that patterns and processes influencing avian assemblages at the focal-scale (e.g., inference at the sampling unit) may not function at the landscape-scale (e.g., inference amongst sampling units). Individual species responses to land ownership, habitat and latitude were highly variable. The broad spatial extent of our study demonstrates the need to include lands in private ownership to assess biodiversity and the importance of maintaining habitat diversity to support avian assemblages. Lastly, focal-scale information can document species presence within a study area, but landscape-scale information provides an essential complement to inform conservation actions and policies by placing local biodiversity in the context of an entire region, landscape or ecosystem.

No short‐term change in avian assemblage following removal of Yellow‐throated Miner (Manorina flavigula) colonies

SummaryThe overabundance of Yellow‐throated Miner (Manorina flavigula) has been shown to negatively affect the abundance and richness of small birds in areas they occupy, leading to homogenization of the avifauna across the fragmented landscape. In this study, we took advantage of a planned management cull to ask the question, does the removal of Yellow‐throated Miner colonies cause an immediate change in avian species richness and abundance? This cull was undertaken around the Bronzewing Flora and Fauna Reserve (north‐western Victoria, Australia) in order to protect a resident population of endangered Black‐eared Miner (M. melanotis) from hybridization. We conducted avian surveys along roadsides surrounding the reserve at Yellow‐throated Miner colonies (n = 6), control sites with no miners (n = 7), and where colonies were removed (n = 3). We found that the cull was followed by only a very modest increase in the species richness and abundance of small birds, with no significant effects on avian assemblage overall. This result contrasts with far more dramatic increases following culls of other species of miner. Sites where miners were removed were not depauperate of other species prior to the cull, which could have been due to a combination of proximity to refuge for small birds in a neighbouring reserve or the low numbers of miners that made up each culled colony. This study highlights that assumed effects of a management action may be highly dependent upon spatial and temporal context.

Avian Assemblages at Paya Indah Natural Wetland Reserve, Malaysia

Estimating accurate avian assemblages such as density and diversity are key factors for the conservation and management of birds and their habitats. Avian assemblages based on status in five habitats at Paya Indah Natural Wetland Reserve were determined using the distance sampling, point count method, at 121 count stations. A total of 100 bird species (64 resident, 18 migratory, 16 resident-migratory and 2 vagrant bird species) were detected from November 2012 to January 2014. The highest bird density was recorded for resident birds (72.2 ± 3.8 bird’s ha-1) and the lowest for vagrant birds (0.1 ± 0.1 birds ha-1). In which Resident birds have significantly higher density, species diversity, richness and evenness compared to resident-migrant and migratory birds.

A near half-century of temporal change in different facets of avian diversity.

Assessments of spatial patterns of biodiversity change are essential to detect a signature of anthropogenic impacts, inform monitoring and conservation programs, and evaluate implications of biodiversity loss to humans. While taxonomic diversity (TD) is the most commonly assessed attribute of biodiversity, it misses the potential functional or phylogenetic implications of species losses or gains for ecosystems. Functional diversity (FD) and phylogenetic diversity (PD) are able to capture these important trait-based and phylogenetic attributes of species, but their changes have to date only been evaluated over limited spatial and temporal extents. Employing a novel framework for addressing detectability, we here comprehensively assess a near half-century of changes in local TD, FD, and PD of breeding birds across much of North America to examine levels of congruency in changes among these biodiversity facets and their variation across spatial and environmental gradients. Time-series analysis showed significant and continuous increases in all three biodiversity attributes until ca. 2000, followed by a slow decline since. Comparison of avian diversity at the beginning and end of the temporal series revealed net increase in TD, FD, and PD, but changes in TD were larger than those in FD and PD, suggesting increasing biotic homogenization of avian assemblages throughout the United States. Changes were greatest at high elevations and latitudes - consistent with purported effects of ongoing climate change on biodiversity. Our findings highlight the potential of combining new types of data with novel statistical models to enable a more integrative monitoring and assessment of the multiple facets of biodiversity.

Structure of avian assemblages in Zambezian Baikiaea woodlands, northern Namibia

AbstractThe Zambezian Baikiaea woodlands fall entirely within the Kalahari Woodland biome, a subset of savanna. In 2015, the line transect method was employed to study avian assemblages associated with Zambezian Baikiaea. In total, 10 transects were designed along a straight 12 km long line, so that each transect was 1.2 km long. A total of 88 species represented by 1190 pairs were recorded. On average, there were 42.9 species per transect. The overall density was 35.8 pairs/km, ranging from 29.2 to 44.2 on particular transects. Overall, Streptopelia capicola was the only dominant species. It was also the only species recorded as dominant on all the transects. The following other species were recorded as dominant: Cercotrichas leucophrys, Laniarius aethiopicus, Turtur chalcospilos, Dicrurus adsimilis, Lamprotornis nitens, Upupa africana, Apalis flavida, Ploceus velatus, Tchagra australis and Numida meleagris. The proportion of dominant species (cumulative dominance) varied from 18.9 to 37.7 (x = 28.5; n =...

Low Prevalence of Haemosporidian Parasites in Shorebirds

Although shorebirds (Charadriiformes: suborders Scolopaci and Charadrii) face physiological stress during migration and experience a wide range of vector-suitable habitats across their distributions, haemosporidian parasites (order Haemosporida) have rarely been detected in these species worldwide. We ask whether shorebirds remain infection-free when wintering in areas where parasite transmission occurs among landbird species. Blood samples were collected at three locations in Argentina: Patagonia, with an avian assemblage dominated by shorebird species; Mar Chiquita Lagoon, a high-salinity water basin where shorebird and landbird species co-occur; and inland sites in Chaco and Cordoba provinces, where host assemblages included mostly landbird species. We screened 650 samples for the presence of haemosporidian infections and sequenced a part of the parasite mitochondrial cytochrome b gene to determine parasite lineages. Of 342 landbirds, 91 were infected with haemosporidian parasites, compared to only three of 318 shorebirds. Wintering location had no effect on the prevalence of haemosporidian parasites in shorebirds. Haemosporidian infections are rare in shorebirds even when these co-occur with landbird species in inland areas suitable for parasite transmission. The few infections detected in shorebirds might represent spillover infections from landbirds, as the parasite lineages were also found in common landbird species. We suggest that shorebirds are resistant to haemosporidian parasites, and either do not become infected or quickly clear occasional infections.

Effect of fragmentation on the Costa Rican dry forest avifauna.

Deforestation and changes in land use have reduced the tropical dry forest to isolated forest patches in northwestern Costa Rica. We examined the effect of patch area and length of the dry season on nestedness of the entire avian community, forest fragment assemblages, and species occupancy across fragments for the entire native avifauna, and for a subset of forest dependent species. Species richness was independent of both fragment area and distance between fragments. Similarity in bird community composition between patches was related to habitat structure; fragments with similar forest structure have more similar avian assemblages. Size of forest patches influenced nestedness of the bird community and species occupancy, but not nestedness of assemblages across patches in northwestern Costa Rican avifauna. Forest dependent species (species that require large tracts of mature forest) and assemblages of these species were nested within patches ordered by a gradient of seasonality, and only occupancy of species was nested by area of patches. Thus, forest patches with a shorter dry season include more forest dependent species.

The Significance of Habitat Characteristics to the Spatial Distribution of Local Avian Assemblage at Gannoruwa Mountain Forest Reserve, Kandy, Sri Lanka

Distribution patterns corresponding to habitat characteristics in tropical forests have not been largely studied. Natural forest structure as well as the anthropogenic alterations to the forests equally affects the distribution patterns of wet zone avifauna. The study reveals the importance of % canopy closure, distance from the forest edge, tree density, diversity, and elevation to the community composition of local forest birds inhabiting Gannoruwa Forest Reserve, Sri Lanka. The most important factors resulting in the study for shaping the avian distribution pattern are distance from the edge,elevation, and the % canopy closure. With the increase of favouring resources to the avian fauna at the edges and the juxtaposition of the edge, many forest loving species were observed to move towards the edge. The pattern is proven advantageous, but harmful in the long run. Thus, it is advisable that the conservation plans should focus on habitat destruction and the anthropogenic disturbance along forest edges.

Innovativeness and the effects of urbanization on risk-taking behaviors in wild Barbados birds.

The effects of urbanization on avian cognition remain poorly understood. Risk-taking behaviors like boldness, neophobia and flight distance are thought to affect opportunism and innovativeness, and should also vary with urbanization. Here, we investigate variation in risk-taking behaviors in the field in an avian assemblage of nine species that forage together in Barbados and for which innovation rate is known from previous work. We predicted that birds from highly urbanized areas would show more risk-taking behavior than conspecifics from less urbanized parts of the island and that the differences would be strongest in the most innovative of the species. Overall, we found that urban birds are bolder, less neophobic and have shorter flight distances than their less urbanized conspecifics. Additionally, we detected between-species differences in the effect of urbanization on flight distance, more innovative species showing smaller differences in flight distance between areas. Our results suggest that, within successful urban colonizers, species differences in innovativeness may affect the way species change their risk-taking behaviors in response to the urban environment.

Diversity in the monotony? Habitat traits and management practices shape avian communities in intensive vineyards

Spreading of viticulture may pose serious threats to biodiversity and adequate policies targeted at decreasing its impact are urgently required. Current knowledge of viticulture effects on biodiversity is scarce and studies on bird communities in vineyards are even scarcer.We surveyed avian assemblages in Trentino vineyards (North-East Italy) in both breeding and wintering seasons to evaluate the effect of: i) landscape, ii) management and iii) topographic-climatic characteristics on birds and to derive implications for conservation. We calculated four community indexes (species richness, abundance, evenness and conservation index) and modelled their relative variation according to 18 environmental variables belonging to the three above-mentioned groups.Landscape models performed better than the others, except for winter evenness, for which management models were the most supported ones. Generally, models considering the three groups together explained more variation than models from an individual group.Landscape (and agricultural) heterogeneity, extent of marginal habitats, density of traditional elements (hedgerows, tree rows, isolated trees and rural buildings) all had positive effects, whereas vineyard cover had negative impact on the value of the four community indexes.Organic management had no apparent effect on avian communities. We detected a seasonal difference in the effects of environmental characteristics on bird communities, which suggested that local conservation efforts could be tuned according to the seasonal importance of vineyards in different regions.Key measures to promote biodiversity in vineyards include maintaining patches of residual habitats in the vineyard matrix and enhancing heterogeneity. Marginal features appeared particularly important in the homogeneous landscape of intensive vineyards to favour bird communities.

The evolutionary convergence of avian lifestyles and their constrained coevolution with species' ecological niche.

The fit between life histories and ecological niche is a paradigm of phenotypic evolution, also widely used to explain patterns of species co-occurrence. By analysing the lifestyles of a sympatric avian assemblage, we show that species' solutions to environmental problems are not unbound. We identify a life-history continuum structured on the cost of reproduction along a temperature gradient, as well as habitat-driven parental behaviour. However, environmental fit and trait convergence are limited by niche filling and by within-species variability of niche traits, which is greater than variability of life histories. Phylogeny, allometry and trade-offs are other important constraints: lifetime reproductive investment is tightly bound to body size, and the optimal allocation to reproduction for a given size is not established by niche characteristics but by trade-offs with survival. Life histories thus keep pace with habitat and climate, but under the limitations imposed by metabolism, trade-offs among traits and species' realized niche.

Biotic homogenization: Loss of avian functional richness and habitat specialists in disturbed Andean temperate forests

Habitat loss and degradation have the potential to alter the species richness–functional diversity relationship decreasing both species richness and functional richness, and increasing functional biotic homogenization. These anthropogenic disturbances may have strong impacts on species-poor systems with low functional redundancy. We tested the species richness–functional diversity relationship and the potential effects of deforestation and degradation on functional diversity of avian assemblages in a Biodiversity Hotspot, in southern Chile. For 101 sites established across a disturbance gradient, we conducted 505 point-transect surveys to measure avian community structure, 505 vegetation plots to quantify stand-level structure, and measured deforestation at the landscape-level. We used three functional diversity indices for avian assemblages (functional richness, functional evenness, and community-weighted specialization as a measure of functional biotic homogenization). We found a non-saturating relationship between species richness and both functional richness and community-weighted specialization, suggesting low functional redundancy. We also found a non-significant decline of functional evenness indicating that when adding new species to the initial pool, functional redundancy increases slightly. Deforestation led to a decrease in both functional richness and community-weighted specialization, particularly precluding the persistence of specialized species in disturbed forests. Functional evenness did not vary with deforestation suggesting that the regularity of density distribution in filled niche volume may be relatively resilient to disturbance. However, the fact that community-weighted specialization decreased linearly under deforestation serves as evidence of functional biotic homogenization processes (“loser” specialists being replaced by “winner” generalist species) in a Biodiversity Hotspot.

Dawn chorus variation in East-Asian tropical montane forest birds and its ecological and morphological correlates

Many birds in breeding seasons engage in vigorous dawn singing that often turns to a prominent chorus. We examined dawn chorus variation of avian assemblages in a tropical montane forest in Taiwan and tested the hypothesis that onset sequence is affected by eye sizes, foraging heights, and diet of birds. Chorus onset and duration varied between sampling months, but generally peaked in the prime breeding season. Overall dawn chorus length increased with, but mean duration per species was negatively correlated with, species richness. The inter-correlation among trait variables in phylogenetic independent contrasts was calculated and examined. Both foraging height and relative eye size were selected as positively explanatory factors, but no dietary effects were detected, for chorus onsets. Dawn singing onsets also tended to delay as decreasing log (eye sizes) that, however, was not selected with enough explanatory power. The positive relationship of chorus onsets versus relative eye sizes contradicts our prediction, yet the negative correlation of relative eye sizes with log (eye sizes) indicates an allometric constraint on eye sizes along with increasing body sizes. Lowerlayer species initiated singing earlier than upper-layer species, which complies with the positive correlation of onsets with foraging heights and supports our prediction. This pattern may be condition-specific and more likely occurs in forests lacking a sufficient canopy height and layering and a distinct light difference among forest layers. Foraging heights were additionally found negatively correlated with canopy coverage and slightly positively correlated with ground coverage of perches. Our results concord that foraging height is a relevant factor as eye size in determining the onset and sequence of dawn chorus, yet, suggest that forest settings and vegetation structure may likely complicate the prediction.

Avian assemblages in Afro-mountain and Alti-mountain Grasslands in the endemic Maloti/Drakensberg region of Lesotho

In 2000–2001, comparative studies were conducted on avian assemblages in Afro-mountain and Alti-mountain Grasslands of the Maloti/Drakensberg endemic region. The total number of species in the Afro-mountain Grassland (N = 69) was more than twice the species number in the Alti-mountain Grassland (N = 30). The Sorensen Index for these two vegetation types was, therefore, low (S = 0.53). The dominance structure was also different, while the number of dominant species remained similar in both assemblages within respective grassland types (6 spp. in Afro – vs. 7 spp. in the Alti-mountain Grassland). However, dominance structures of avian assemblages in Alti-mountain and Afro-mountain Grasslands were composed of very different bird species. The opposite was true of subdominant bird species. The proportions of breeding pairs among closely related species of such genera as Cercomela, Emberiza, Monticola and Passer were similar, but among such genera as Anthus, Ploceus, Cisticola and Carithagra, the proportions we...

Avian remains from the Early/Middle Pleistocene of the So'a Basin, central Flores, Indonesia, and their palaeoenvironmental significance

The So'a Basin in central Flores contains the earliest known evidence for hominins on this remote Indonesian island, with stone tools from this region dating back at least 1.0Ma. At least 16 late Early to early Middle Pleistocene terrestrial fossil localities record evidence for highly insular endemic faunas and proxy evidence for hominins. The hominin presence in the So'a Basin raises many questions as to how, when, and from where hominins arrived on the island, and key issues regarding their adaptation to this insular environment remain poorly understood. Here, we provide palaeoenvironmental data based on avian remains recovered during recent, systematic excavations of late Early to early Middle Pleistocene deposits at Mata Menge and Bo'a Leza in the So'a Basin. At least six species of birds in five avian orders were recovered, forming the oldest bird remains recovered from Wallacea. Two species, a swan (Cygnus sp.) and an eagle owl (Bubo sp.), no longer occur on Flores. The avian assemblage from Mata Menge and Bo'a Leza described here is indicative of an open environment with a strong open, freshwater component and nearby grasslands, and with forests at a distance. In that, it differs from the Late Pleistocene limestone cave site of Liang Bua, the find locality of Homo floresiensis, and is more similar to the Early Pleistocene Homo erectus sites of the Sangiran Dome on Java. Although little is known regarding the identity of the So'a Basin toolmakers, the presence of an open, savannah-type environment in the late Early to early Middle Pleistocene of Flores may have facilitated their dispersal from the Asian shelf into Wallacea.