Avian Assemblages Research Articles

The avifauna of Bosque Fray Jorge National Park and Chile's Norte Chico

The avifauna of Chile is relatively depauperate, comprising 469 extant species, of which 213 are terrestrial. However, the Coquimbo Region presents a broad ecological transition from the hyperarid Atacama Desert to the north, and the more mesic Chilean Mediterranean region of central Chile, resulting in relatively high species diversity. Approximately 130 species are found here, 8 of which are endemic to Chile although not to this region. Bosque Fray Jorge National Park is a 9959 ha Biosphere Reserve dominated by matorral habitat and hosting up to 123 bird species. Through avian surveys and banding over nearly a decade we have documented 63 terrestrial species and discerned predictable seasonal and interannual structure to avian assemblages, at least through an extended dry period. Recent studies in the matorral habitats of the park indicate seasonal patterns that fall into 4 patterns: year-round residents, winter visitors, summer breeders, and transients. Short-term banding studies demonstrate co-occurring wintering and breeding cohorts among species of Sierra-finches (Phrygilus) in the park; such assemblages and dynamics are reminiscent of North American Mediterranean avian assemblages and pose interesting ecological comparisons. In this period of surveys there appears to have been a gradual transition of the avifauna that may be a response to anthropogenic influence and/or climate change. Research on the foraging behavior of 2 insectivorous species indicate that one of these is convergent on better-known North American taxa while the other clearly is not; these efforts suggest useful avenues for further comparative research. A remarkable coevolutionary association between the Chilean Mockingbird (Mimus thenca) and endoparasitic mistletoes (Tristerix) provides insight into potential convergent ecologies in desert regions with different evolutionary histories.Less than 1% of the park comprises temperate forest remnants that subsist due to extensive water input from fog. Research in these remnants has emphasized the role of habitat fragmentation on avian assemblage composition and on reproductive ecology by forest-dependent species. The avifauna here comprises a subset of that found in intact Valdivian rainforest to the south, and forest remnant size alone explains over 90% of the variation in species numbers. One species has been particularly well studied; the Thorn-tailed Rayadito (Aphrastura spinicauda) is more abundant and has higher nestling survival in larger fragments. We summarize other work on stress responses and variation in song structure in this species. Finally, the role of birds in tree recruitment here has important implications in the face of a recent history of reduction in sizes of forest remnants; numerous birds consume the fruit of the dominant tree, olivillo (Aextoxicon punctatum), but they fail to promote successful recruitment because they defecate viable seeds in locations that provide poor survival of seedlings.Ornithological research in Chile is undergoing a modest renaissance, and while dryland avifaunas are characterized more by what is not known and has yet to be studied than by actual ecological understanding, they provide a baseline for many exciting studies ranging from natural history to the role of migration to comparative dynamics of independent lineages in North and South America.

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.

Who eats whom? Taphonomic analysis of the avian record from the Middle Paleolithic site of Teixoneres Cave (Moià, Barcelona, Spain)

Small animal bones, such as those of birds, are commonly found at many archaeological sites framed in the early Late Pleistocene. Teixoneres Cave, on the Iberian Peninsula, is one of these, and includes evidence of Neanderthal activities involving large game and, sporadically, smaller prey such as rabbits. Here, we present data from the avian assemblage recovered from this site, which is mainly comprised of specimens from the Corvidae and Phasianidae families. In order to determine which predators (hominins, mammalian carnivores and/or raptors) contributed to this avian accumulation, the general occupational dynamics within the site must first be understood. To this end, the bird remains obtained from the four main subunits excavated to date (IIa, IIb, IIIa, IIIb) have been analyzed from a taphonomic perspective. Our results show that the birds at the site mainly originated from non-hominin input episodes. While the activity of nocturnal raptors was found throughout the sequence, the activity of mammalian carnivores seems to be more intense in specific archaeological units. We compared the data yielded by our study with other data from the site, reinforcing the general position that hominins made use of the cave during short-term occupations, which alternated with predator use.

Avian Diversity Along An Altitudinal Gradient In Highveld/Drakensberg Grasslands

Abstract Temperature and rainfall related to altitudinal gradients influence ecological and evolutionary responses of organisms to physical factors. In this study, the line transect method was used during the years 1996–2001 to compare resident (potentially breeding) bird communities in three altitudinal divisions in Highveld/Drakensberg grasslands in Lesotho: lowlands (< 1700 m a. s. l.), foothills (1700–2200 m a. s. l.) and highlands (> 2200 m a. s. l.). In total, 105 resident species were recorded. The total number of species recorded in lowlands was higher than that in highlands and foothills, but this difference was not statistically significant. The highland and foothill did not differ in numbers of species. A group of five species dominated at all three sites, and the proportion of dominant species in relation to the whole assemblage was very similar. The composition of the dominant group (species with more than 5 % of pairs) and the group of species most often encountered (in more than 80 % of transects) was, however, different. Only two species, Cape Canary Serinuscanicollis and Karoo Prinia Priniamaculosa were dominant in all three study areas, and just one species, the Cape Bunting Emberizacapensis, was dominant in two plots. Similarly, only two species, the Cape Turtle-Dove Streptopelia capicola and Cape Canary had a high frequency of occurrence in all three study areas, and two otherspecies, theKaroo Prinia and Cape Bunting — in two study areas. Simpson’s Diversity Index was strikingly the same (S = 0.96) for all three avian assemblages (lowland, foothill and highland) investigated. However, proportions of breeding pairs of some congeneric species were found to change with the altitude. The granivores were more common (44–45 %) in the foothills and highlands than in lowlands (36%), while insectivores were more common in the highlands (50 %) than in foothills and lowlands (36–37 %). In general, avifauna is relatively diverse and unique in the Highveld/Drakensberg grasslands. Results presented here provide data for further investigation of the effect of the supposed climate warming on the diversity and structure of avian communities.

The effect of kleptoparasite and host numbers on the risk of food‐stealing in an avian assemblage

Kleptoparasitism involves the theft of resources such as food items from one individual by another. Such food‐stealing behaviour can have important consequences for birds, in terms of individual fitness and population sizes. In order to understand avian host–kleptoparasite interactions, studies are needed which identify the factors which modulate the risk of kleptoparasitism. In temperate European intertidal areas, Eurasian oystercatchers Haematopus ostralegus feed primarily on bivalve molluscs, which may be stolen by kleptoparasitic species such as carrion crows Corvus corone and herring gulls Larus argentatus. In this study we combined overwinter foraging observations of oystercatchers and their kleptoparasites on the Exe Estuary, UK, with statistical modelling to identify the factors that influence the likelihood of successful food stealing behaviour occurring. Across the winter, 16.4% of oystercatcher foraging attempts ended in successful kleptoparasitism; the risk of theft was lowest in February (10.8%) and highest in December (36.3%). Using an information theoretic approach to compare multiple logistic regression models we present evidence that the outcome of host foraging attempts varied with the number of kleptoparasites per host within the foraging patch for two out of five individual months, and for all months grouped. Successful, kleptoparasitism was more likely to occur when the total number of all kleptoparasites per host was greater. Across the entire winter study period, oystercatcher foraging attempts that resulted in kleptoparasitism were associated with a mean number of kleptoparasites per host that was more than double that for foraging attempts that ended in the oystercatcher successfully consuming the mussel. Conversely, the stage of the tidal cycle within the estuary did not affect the outcome of oystercatcher foraging attempts. Our study provides evidence that bird numbers influence the risk of kleptoparasitism within avian assemblages.

Can Australian bush birds be used as canaries? Detection of pervasive environmental impacts at an arid Australian mine site

A 13-year spatially-replicated monitoring program was analysed to determine avifauna responses to disturbances associated with proximity to a mine in arid Australia. Crested Bellbirds (Oreoica gutturalis), Grey Butcherbirds (Cracticus torquatus), Red-capped Robins (Petroica goodenovii) and Chestnut-rumped Thornbills (Acanthiza uropygialis)were consistently recorded in lower abundances near the mine compared with more remote sites possibly in part due to acoustic masking of their calls. These species were therefore useful indicators of the degree and extent of pervasive mining disturbance, beyond the direct physical effects of mining. By contrast, a suite of synanthropic bird species, or those species that benefit from association with human-made elements of their habitat, were recorded in higher abundances adjacent to the mine. The gradient effect of distance from impact on the key bioindicators was clear, with a significant factor-change difference in a composite measure of bioindicator variables. Despite considerable temporal variation in individual species abundances, we also show that differences associated with proximity to the mine are relatively stable for species richness and for some bird species. Our data demonstrate that the ability to detect pervasive environmental impacts of mining disturbances on avian assemblages is greater when excluding synanthropic species.

Habitat-specific vegetation and seasonal drivers of bird community structure and function in southern Patagonian forests

Biodiversity conservation requires knowledge about the factors that influence the structure and function of biotic assemblages. In southern Patagonian Nothofagus forests, birds are the most abundant and diverse vertebrates and are known to have different requirements for nesting, breeding and feeding. Therefore, we chose this group to analyze key drivers of avian community dynamics; for conservation purposes, this information is requisite to manage Nothofagus forest landscapes and their associated biota. We first characterized forest structure and understory floristic composition in open and closed canopy broadleaved forests of mixed deciduous (MD) and mixed deciduous-evergreen (MDE) species on the southern coast of Tierra del Fuego National Park, Argentina. For each habitat, bird assemblages were assessed using point counts, checklists and mistnetting. We used ANOVAs and multivariate methods to analyze changes in bird species richness, density, and biomass as a function of habitat and seasonal characteristics. Forest structure and understory plant communities influenced avian assemblage and density; MDE forests had significantly greater species richness, but lower density than MD. Plus, particular species were associated with specific understory conditions, such as Anairetes parulus and Zonotrichia capensis whose presence was related to shrubs. Additionally, variations observed between seasons apparently were related to differential uses of each habitat type during certain times of year. Finally, it was not possible to define a single forest type with greater conservation value for birds; each had a specific bird species assemblage. Consequently, our results suggest the importance of a full representation of habitats to preserve the region’s bird diversity, which also has been described for forest invertebrates and understory plants.

Supplementary feeding restructures urban bird communities

Food availability is a primary driver of avian population regulation. However, few studies have considered the effects of what is essentially a massive supplementary feeding experiment: the practice of wild bird feeding. Bird feeding has been posited as an important factor influencing the structure of bird communities, especially in urban areas, although experimental evidence to support this is almost entirely lacking. We carried out an 18-mo experimental feeding study at 23 residential properties to investigate the effects of bird feeding on local urban avian assemblages. Our feeding regime was based on predominant urban feeding practices in our region. We used monthly bird surveys to compare avian community composition, species richness, and the densities of local species at feeding and nonfeeding properties. Avian community structure diverged at feeding properties and five of the commonest garden bird species were affected by the experimental feeding regime. Introduced birds particularly benefitted, with dramatic increases observed in the abundances of house sparrow (Passer domesticus) and spotted dove (Streptopelia chinensis) in particular. We also found evidence of a negative effect on the abundance of a native insectivore, the grey warbler (Gerygone igata). Almost all of the observed changes did not persist once feeding had ceased. Our study directly demonstrates that the human pastime of bird feeding substantially contributes to the structure of avian community in urban areas, potentially altering the balance between native and introduced species.

Feeding wild birds in gardens: A test of water versus food

SummaryBird feeding in residential gardens is an increasingly popular human–wildlife interaction. In Australia, the practice is discouraged by most government and nongovernment wildlife conservation agencies, although advice varies and the most common recommendation is to provide water and habitat for birds rather than supplementary food. This study compares bird abundance and diversity when residents in a Melbourne municipality provide water for birds versus food. Bird abundance was greater when food was provided compared with water, but avian assemblages did not differ.

The effect of range changes on the functional turnover, structure and diversity of bird assemblages under future climate scenarios.

Animal assemblages fulfill a critical set of ecological functions for ecosystems that may be altered substantially as climate change-induced distribution changes lead to community disaggregation and reassembly. We combine species and community perspectives to assess the consequences of projected geographic range changes for the diverse functional attributes of avian assemblages worldwide. Assemblage functional structure is projected to change highly unevenly across space. These differences arise from both changes in the number of species and changes in species' relative local functional redundancy or distinctness. They sometimes result in substantial losses of functional diversity that could have severe consequences for ecosystem health. Range expansions may counter functional losses in high-latitude regions, but offer little compensation in many tropical and subtropical biomes. Future management of local community function and ecosystem services thus relies on understanding the global dynamics of species distributions and multiscale approaches that include the biogeographic context of species traits.

Avian remains from the Upper Pleistocene (MIS3) site of Aguilón P-7, south of the Ebro River, Spain

Aves are represented by abundant fossil remains in Quaternary sites. Birds are well adapted to the environment they inhabit, so they make very good paleoenvironmental indicators for Quaternary sites. Here we analyse the avian remains from the Late Pleistocene (probably MIS3) site of Aguilón P-7 (AGP-7). The Pleistocene sediments fill up a shallow cave, which is located in the Zaragozan part of the Iberian Range, 55 km south of the city of Zaragoza. We have for the first time provided a taxonomic and taphonomic study of the avian assemblage of AGP-7, as well as a preliminary paleoenvironmental analysis based on these data. Nine avian taxa have been identified: Galliformes indet., Lagopus sp., Aquila chrysaetos, Gyps fulvus, Passeridae indet., Anthus sp., Prunella modularis,Sturnus cf. unicolor and Corvus monedula. The taphonomic analysis did not provide conclusive information. However, it suggests an accumulation of uneaten food remains by diurnal birds of prey. The identified taxa currently inhabit the Iberian Peninsula, populating woodland environments with rocky areas. They are found in areas with an oceanic climate, in contrast to the Mediterranean climate that now prevails in Aguilón.

Avian diversity in an urbanized South African grassland

The most critical gaps for urban wildlife researchers are in rapidly urbanizing areas in South America, Africa and Asia. This article presents quantitative studies on birds carried out in South Africa, in the inner part of the city of Bloemfontein during the years 1993–2002. Three methods were employed to quantify the avian assemblages: atlas, mapping and line transects. Atlas studies were conducted in 1997. The whole study area was divided into 1 × 1 km grid squares (100 ha). A total of 67 squares were achieved with a total surface of 5100 ha. Densities as well as the dominance of resident breeding birds were estimated by means of a simplified version of the mapping method in four plots. For a few selected species, namely Crowned Lapwing, Blacksmith Lapwing, Spotted Thick-knee, Crested Barbet, Bokmakierie, Little Swift and African Hoopoe, the numbers of breeding pairs over the whole study area (5100 ha) were estimated by means of the mapping method in a simplified version. A total of 131 bird species wer...

A bird assemblage mobs an adult pitviper in southeastern Brazil

Birds mostly mob avian or mammalian predators, but harass snakes as well. The mobbed snakes are potential or actual bird predators, but records of birds mobbing vipers are rare. I report herein on an avian assemblage mobbing an adult Jararaca Lancehead (Bothrops jararaca) in the Atlantic Forest of southeastern Brazil. The bird assemblage was composed of 8 species and 11 individuals. The most insistent mobber was a Golden-crowned Warbler. Two bird species dived at close range of the moving pitviper: the Sayaca Tanager and the Short-crested Flycatcher, which dived at the snake 2 and 1 times respectively. The snake seemed undisturbed by the harassing birds, but stopped moving after each of the dives. The Jararaca Lancehead occasionally forage at daytime, climb on vegetation, and prey on birds. Thus, it may actually pose a predation risk to the mobbing birds when they are nesting in the vicinity or when they are much distracted while harassing.

Abundance and variety of birds associated with point sources of water in southwestern New Mexico, U. S. A.

Developed waters may improve arid landscapes for birds, but their efficacy requires further study. I counted birds along five 300-m transects originating at point sources of water in a New Mexico grassland, and compared results with those from transects without water. Total birds were nearly three times more abundant on transects with water, but differences were greater in spring and winter than during the wet summer period. Twenty-two of 25 common species trended toward greater abundance on transects with water, eight of these at statistically significant levels, including Gambel's Quail, Mourning Dove, House Finch, and a variety of wintering sparrows. Sixty-four percent of detections along transects with water occurred <50 m from the water sources, at which birds regularly drank. Results suggest 1) that water attracted birds, especially in dry seasons, and 2) that proximity to water may influence the abundance and composition of avian assemblages in arid landscapes.

Structure of avian assemblages in grasslands associated with cattle ranching and soybean agriculture in the Uruguayan savanna ecoregion of Brazil and Uruguay

Conversion of grasslands into crops is a major factor leading to the decline of grassland birds. Cattle ranching represents another disturbance to natural grasslands, but may be less detrimental to grassland birds. We studied the diversity, density, and composition of bird species in Brazilian and Uruguayan grasslands under two different land use types: cattle ranching on seminatural grasslands, and soybean fields with interspersed patches of grassland. Cattle sites had higher species richness (n = 75 species) than soybean sites (n = 57 species). Most birds showed higher densities in cattle sites, but some common and habitat-generalist species were more abundant in soybean sites. Species composition did not differ significantly with land use. The generalist Eared Dove (Zenaida auriculata), however, was strongly associated with soybean sites. Among species of conservation interest, either regionally or globally, all had higher densities in cattle sites, highlighting the importance of maintaining these ranching areas. The persistence of grassland birds in soybean fields may be related to the presence of seminatural grassland patches within soybean crops.

Bird responses to riparian management of degraded lowland streams in southeastern Australia

We assessed the degree to which fencing, livestock exclusion, and replanting of riparian zones affected avian assemblages in massively cleared landscapes. Measurements were made at three creeks in the southern Murray–Darling Basin in southeastern Australia, each of which had circa 1‐km long treated sections and paired “untreated” circa 1‐km sections, where no fencing, planting, or stock exclusion was done. We measured the change in vegetation characteristics and abundances of native birds for up to 8 years after works were completed. Prior to data collection, we developed expected responses of bird species based on the anticipated time‐courses of change in vegetation structure. We used hierarchical Bayesian models to explore the effects of the management actions, and to account for within‐site variation in vegetation characteristics. There were major changes in vegetation structure (reductions in bare ground and increases in shrubs and tree recruitment) but avian responses generally were small and not as expected. There are at least four possible reasons for the limited avian responses: (1) there has been a long‐term decline in woodland birds across the region; (2) the study was conducted during the longest drought in the instrumental record in the study region; (3) the total amount of replanted vegetation was small in a massively denuded region; and (4) monitoring may have been over too short a term to detect responses to longer‐term changes in structural vegetation.

Differences in bird assemblages between native natural habitats and small-scale tree plantations in the semiarid midwest of Argentina

ABSTRACT We studied the effects on structure of bird assemblages after replacement of native natural habitats by small-scale tree plantations used for recreational purposes. The richness and diversity were similar among habitats; however, the total bird abundance was greater in the tree plantations compared to the natural habitats. Also, we found that small-bodied birds that forage in the foliage had higher abundance in the natural habitats, while larger-bodied species that live in open spaces and forage on the ground occurred in higher abundance in the tree plantations. The comparative evaluation of the seasonal effect on avian assemblages of the contrasting habitats showed that natural habitats had a greater annual fluctuation of abundance values, while the tree plantations were more constant. Our study demonstrates that small-scale tree plantations for recreational purposes exert strong effects on bird assemblages, because they increase the abundance of the generalist and common bird species in the region.

Relative roles of grey squirrels, supplementary feeding, and habitat in shaping urban bird assemblages.

Non-native species are frequently considered to influence urban assemblages. The grey squirrel Sciurus carolinensis is one such species that is widespread in the UK and is starting to spread across Europe; it predates birds’ nests and can compete with birds for supplementary food. Using distance sampling across the urbanisation intensity gradient in Sheffield (UK) we test whether urban grey squirrels influence avian species richness and density through nest predation and competition for supplementary food sources. We also assess how urban bird assemblages respond to supplementary feeding. We find that grey squirrels slightly reduced the abundance of breeding bird species most sensitive to squirrel nest predation by reducing the beneficial impact of woodland cover. There was no evidence that grey squirrel presence altered relationships between supplementary feeding and avian assemblage structure. This may be because, somewhat surprisingly, supplementary feeding was not associated with the richness or density of wintering bird assemblages. These associations were positive during the summer, supporting advocacy to feed birds during the breeding season and not just winter, but explanatory capacity was limited. The amount of green space and its quality, assessed as canopy cover, had a stronger influence on avian species richness and population size than the presence of grey squirrels and supplementary feeding stations. Urban bird populations are thus more likely to benefit from investment in improving the availability of high quality habitats than controlling squirrel populations or increased investment in supplementary feeding.

On the historical biogeography of global Galliformes: ancestral range and diversification patterns

In this study, the ancestral distributional ranges and the tempo of diversification patterns of global Galliformes were investigated. Different diversification models characterizing possible tempo patterns were fitted and compared onto the phylogenetic tree for the 197 Galliforme species, consisting of a constant-speciation and constant-extinction model (CONSTANT), a decreasing-speciation and constant-extinction model (SPVAR), a constant-speciation and increasing-extinction model (EXVAR) and a decreasing-speciation and increasing-extinction model (BOTHVAR). Ancestral range reconstruction was conducted using the dispersal-extinction-cladogenesis model. A constant-diversification-rate (CONSTANT) model best quantified the historical speciation patterns of this avian assemblage through model selection. Clade age and species richness are significantly and positively correlated. The most recent common ancestor for Galliformes species was originally found in the disjunctive regions between Southeast Asia and North America. High-frequency dispersal events were identified across the whole evolutionary time. The constant diversification rate for global Galliforme species implied that there were no diversification rate-shifting trends for Galliformes species. The present study may contribute to the understanding of the ecology and diversity patterns of Galliformes from the perspective of historical biogeography, although some limitations existed.

Accounting for the space‐varying nature of the relationships between temporal community turnover and the environment

Non‐spatial regression models are rarely adequate for exploring ecological phenomena, especially in settings where the processes operate at large spatial scales and when model covariates do not explain all variation present in the outcome variable. Given the complexity of ecological processes, it is often unrealistic to assume a set of stationary regression coefficients can capture space‐varying and scale‐dependent relationships between covariates and an ecological response. Spatially‐varying coefficients (SVC) models fit within a Bayesian inferential framework provide a statistically robust method to explore potential space‐varying and scale‐dependent impacts of covariates. Our study objective was to assess the utility of SVC models for capturing non‐stationary relationships between temporal community dynamics in avian assemblages and variation in environmental factors. We also wanted to compare the inference drawn from SVC models to that obtained from space‐varying intercept models and also models that do not acknowledge any spatial structure beyond what is introduced by the covariates. Our analysis examines the temporal turnover, expressed as a proportion, of avian communities across New York State, USA. Given the expected outcome is non‐Gaussian, we detail a generalized linear model specification of the proposed model structures. Our results show the SVC model outperformed the spatially‐varying intercept and non‐spatial models in terms of model fit and model predictive inference. Further, by fitting these models within a Bayesian inferential framework, we were able to make inferences about the spatial impact of covariates and other process parameters, as well as obtain full posterior predictive inference about the rate of turnover at new, unobserved locations. We conclude that SVC models provide a flexible framework for exploring and accounting for non‐stationary mechanisms driving ecological patterns.