Frugivorous Bird Species Research Articles

Fruit removal from rowanberry (Sorbus aucuparia) trees at urban and rural areas in Finland: A multi-scale study

Urbanization changes landscape, causes destruction of natural habitats, and reduces species diversity. Urbanization can alter the interaction between fruit-bearing plants and frugivorous birds such as the Fieldfare, Turdus pilaris, and Bohemian waxwing, Bombycilla garrulus, which are the most abundant frugivorous bird species in Finland. Rowanberry, Sorbus aucuparia, is an ornamental tree species used commonly in the urban landscaping. It can promote bird diversity and the pleasantness of the urban environment for humans. The study was conducted on three spatial scales ranging from the macro scale (600km latitudinal gradient) to the regional scale (rural vs. urban habitats), and to the micro scale (different tree parts) in three towns and their nearby rural areas in Finland. About 25 trees were photographed on each site three times during the autumn until the rowanberry fruit-crop had been used up. At the beginning of the research the crop size was larger on the urban trees than that of rural ones. The fruit removal rate was not related to the geographical location. However, in urban habitats the fruits were consumed later than in rural habitats. At the tree-level, the rowanberry fruits were removed earlier at the tops of trees. Our results suggest that earlier use of rowanberry fruits from rural habitats and tree tops may be related on human and predator-related disturbances. Our results indicated that urban rowanberry fruit crop is important food resource for frugivorous bird species in urban areas.

Effects of tannins on fruit selection in three southern African frugivorous birds

Tannins are common secondary compounds in plant material and are known for their ability to bind to protein which reduces nitrogen availability in the diet. In fruits, these compounds are responsible for their astringency which is thought to result in reduced food intake. In this study, the repellent effects of tannins were examined in three species of frugivorous birds: red-winged starlings Onychognathus morio, speckled mousebirds Colius striatus and Cape white-eyes Zosterops virens. Birds were fed artificial fruit diets containing varying levels of tannins in paired choice tests with the amount of food eaten by birds used to determine preference. Red-winged starlings were attracted to the control diet, indifferent to the medium tannin diet and deterred by the high tannin diet whereas speckled mousebirds and Cape white-eyes were not deterred at all concentrations. The discrepancy in the results was attributed to differences in taste sensitivity, tolerance levels and detoxification mechanisms of secondary compounds between species. Because fruit selection and ultimately fruit removal rates affect plant community composition, the disparity in the results suggests that frugivorous birds do not contribute equally to plant community dynamics. However, plant secondary compounds in fruits are diverse and their effects are similarly diverse and there is potential that different groups of secondary compounds generate disparate effects. Similar studies on other types of secondary compounds may thus contribute towards a broader understanding of the role of secondary compounds in mediating fruit-frugivore interactions.

Does the role that frugivorous bird species play in seed dispersal networks influence the speed of evolutionary divergence?

Extensive work on plant–animal mutualistic networks has shown that species in such networks vary in their number of connections with other species, from highly connected species (‘super-generalists’) to those connected only to a few other species (‘specialists’). How these species with different degrees of network specialization differ in their speciation rate remains largely unexplored. Here we hypothesize that having many interaction partners lowers the amount of leverage of any one partner, and slows coevolution. We then explored the speciation rate in frugivorous birds in a dataset of published seed dispersal networks, using a recent phylogeny that has a date for the divergence time of all bird species from their most closely related sister taxa. We found that generalist species’ divergence time was longer than specialist species’. While there may be other correlated traits to specialization that could contribute to this result, specialists and generalists did not vary in the size of their global distributions, and thus specialists are not simply rarer, if the size of the distribution reflects the species’ abundance. We discuss whether similar tests can be applied to other kinds of plant–animal interactions, and what level of taxonomy is appropriate to investigate to answer these sorts of questions.

Functional importance of avian seed dispersers changes in response to human-induced forest edges in tropical seed-dispersal networks.

Although seed-dispersal networks are increasingly used to infer the functioning of ecosystems, few studies have investigated the link between the properties of these networks and the ecosystem function of seed dispersal by animals. We investigate how frugivore communities and seed dispersal change with habitat disturbance and test whether relationships between morphological traits and functional roles of seed dispersers change in response to human-induced forest edges. We recorded interaction frequencies between fleshy fruited plants and frugivorous bird species in tropical montane forests in the Bolivian Andes and recorded functional bird traits (body mass, gape width and wing tip length) associated with quantitative (seed-removal rate) and qualitative (seed-deposition pattern) components of seed-dispersal effectiveness. We found that the abundance and richness of frugivorous birds were higher at forest edges. More fruits were removed and dispersed seeds were less clustered at edges than in the interior. Additionally, functional and interaction diversity were higher at edges than in the interior, but functional and interaction evenness did not differ. Interaction strength of bird species increased with body mass, gape width and wing tip length in the forest interior, but was not related to bird morphologies at forest edges. Our study suggests that increases in functional and interaction diversity and an even distribution of interaction strength across bird morphologies lead to enhanced quantity and tentatively enhanced quality of seed dispersal. It also suggests that the effects of species traits on ecosystem functions can vary along small-scale gradients of human disturbance.

Avifauna en sistemas silvopastoriles en el Corredor Biológico Mesoamericano, Tabasco, México

Silvopastoral systems support local ecological and economical features as they enhance conservation of floral and faunal communities. As other animal communities, avifauna may be a good representative of habitat alterations, both as the species and functional levels. In order to attend the initiative of Mesoamerican Biological Corridor initiative (CBM) in the state of Tabasco, we studied the diversity of birds in two silvopastoral systems: scattered trees in pastures (ADP), and trees in boundary-hedgerows (AL). For this, we applied the fixed radius counting point method in three priority sites in Tabasco's CBM during the dry and wet season of 2011, and a total of 56, 60 and 62 points were evaluated in Huimanguillo, Tenosique and Tacotalpa, respectively. We observed 2 084 individuals of 154 species (79-89% of expected diversity) and 36 bird families. We detected 92, 87 and 85 species in Huimanguillo, Tenosique and Tacotalpa, respectively, including 35 protected species, of which 23, 19 and 16 in each locality, respectively. All sites showed high diversity (H' ≥ 3.20), low species dominance (D ≥ 0.08) and high equitability (J ≥ 0.77). Species composition showed differences between sites, being most similar Tacotalpa and Tenosique. Ten species were considered characteristic for sites. Although the silvopastoral system did contain protected species, the low diversity and the early successional character of the arboreal components were not attractive to frugivorous bird species. Diversification with native trees can improve the systems to create a complementary habitat and to increase landscape connectivity. The management of silvopastoral practices on cattle dominated landscapes in Tabasco could improve its ecological quality, and thus achieve the CBM's objectives ofbiodiversity conservation combined with human economic activities.

Bird fruit preferences match the frequency of fruit colours in tropical Asia

While many factors explain the colour of fleshy fruits, it is thought that black and red fruits are common in part because frugivorous birds prefer these colours. We examined this still controversial hypothesis at a tropical Asian field site, using artificial fruits, fresh fruits, four wild-caught resident frugivorous bird species, and hand-raised naïve birds from three of the same species. We demonstrate that all birds favored red artificial fruits more than yellow, blue, black and green, although the artificial black colour was found subsequently to be similar to the artificial blue colour in its spectral reflectance. Wild-caught birds preferred both black and red fleshy natural fruits, whereas hand-raised naïve birds preferred black to red natural fleshy fruits and to those of other colours. All birds avoided artificial and naturally ripe green fruits. The inter-individual variation in colour choice was low and the preferences were constant over time, supporting the hypothesis that bird colour preferences are a contributing factor driving fruit colour evolution in tropical Asia.

Mistletoebirds and xylose: Australian frugivores differ in their handling of dietary sugars.

Carbohydrate-rich mistletoe fruits are consumed by a wide range of avian species. Small birds absorb a large portion of water-soluble nutrients, such as glucose, via the paracellular pathway. d-xylose, a pentose monosaccharide, is abundant in some nectars and mistletoe fruits consumed by birds, and it has been suggested that it is most likely absorbed via the paracellular pathway in birds. We measured apparent assimilation efficiency ([Formula: see text]) and bioavailability (f) for d-xylose and d- and l-glucose in three frugivorous Australian bird species. Mistletoebirds, silvereyes, and singing honeyeaters showed significantly lower [Formula: see text] for d-xylose than for d-glucose. Across two diet sugar concentrations, silvereyes and singing honeyeaters significantly increased f of both l-glucose (a metabolically inert isomer of d-glucose commonly used to quantify paracellular uptake) and d-xylose on the more concentrated diet, probably because of increased gut processing time. By contrast, mistletoebirds (mistletoe fruit specialists) did not vary f of either sugar with diet concentration. Mistletoebirds also showed higher f for d-xylose than l-glucose and eliminated d-xylose more slowly than silvereyes and singing honeyeaters, demonstrating differences in the handling of dietary xylose between these species. Our results suggest that d-xylose may be absorbed by both mediated and nonmediated mechanisms in mistletoebirds.

Functional and phylogenetic diversity and assemblage structure of frugivorous birds along an elevational gradient in the tropical Andes

Tropical mountains are hotspots of biodiversity, but the factors that generate this high diversity remain poorly understood. To identify possible mechanisms that influence avian species assemblages in the tropical Andes, we studied the functional and phylogenetic diversity and the structure of species assemblages of an avian feeding guild. We analysed how functional and phylogenetic diversity, structure and composition of frugivorous bird assemblages changed along a 3300 m elevational transect from the lowlands to the tree line with a novel combination of functional and phylogenetic approaches, and used null models to infer possible drivers of the observed patterns. Species richness, functional richness and phylogenetic diversity decreased almost monotonically with increasing elevation, but assemblage structure and composition changed abruptly in the Andean foothills at around 1200 m. In the lowland assemblages, species were functionally and phylogenetically less similar than expected from null models, whereas species in the highland assemblages were functionally and phylogenetically more similar than expected by chance, suggesting an abrupt reduction in the number of functionally and phylogenetically distinct species in the transition from lowlands to the highlands. Nevertheless, the functional and phylogenetic evenness of the assemblages, i.e. the regularity of the spacing of species in functional trait space and phylogeny, remained constant along the gradient, which suggests that the mechanisms that influence the co‐occurrence of species within the assemblages are similar in lowlands and highlands. The observed differences between lowland and highland assemblages imply sharp distributional limits for frugivorous bird species in the Andean foothills, probably caused by environmental factors other than climate, e.g. changes in habitat types or topography, or independent species radiations in lowlands and highlands. These strong distributional limits may hinder uphill range shifts of frugivorous bird species, and the plant species they disperse, in the tropical Andes as a response to climate change.

斑块生境中食果鸟类对南方红豆杉“(Taxus chinensis var. mairei)”种子的取食和传播

生境斑块化对食果鸟类的移动行为产生影响，进而影响其对植物种子的传播格局和效率。南方红豆杉（<em>Taxus chinensis </em>var. <em>mairei</em>）是我国一级保护植物，在南方山区多因人为干扰而呈斑块状分布。2011年，2012年10月底到12月中，以分布于福建梅花山国家级自然保护区红豆杉生态园中南方红豆杉种群为对象，研究斑块生境中鸟类对南方红豆杉种子的取食和传播行为，并评估专性鸟类和泛性鸟类的传播效率。结果发现：南方红豆杉源斑块共吸引22种食果鸟类取食红豆杉种子，并与13种鸟类形成了种子传播关系。不同年间，黑短脚鹎（<em>Hypsipetes leucocephalus</em>）都是植物的主要传播鸟类，而其他鸟类传播者种类具有一定的年间变化。生境斑块化导致专性鸟类黑短脚鹎和泛性鸟类红嘴蓝鹊（<em>Urocissa</em> <em>erythrorhyncha</em>）种子传播效率差异。与红嘴蓝鹊相比，黑短脚鹎飞行的平均距离较短（（16.3±11.0）m，Mean±SD，<em>n </em>= 125），传播距离相对较近；且它们取食后偏好在源斑块中活动，喜栖息在同种成树、甜楮（<em>Castanopsis eyrei</em>）及其他阔叶树等栖树上。红嘴蓝鹊取食后常在斑块间移动，常停歇在同种成树和毛竹（<em>Phyllostachys heterocycla</em>）上，传播距离相对较远（（24.9±20.0）m，Mean±SD，<em>n </em>= 95）。空间一致性结果表明，黑短脚鹎移动距离对幼苗更新距离的空间一致性程度高；而红嘴蓝鹊偏好生境与幼苗更新生境一致性程度高。结果表明，斑块生境中植物能与专性鸟类、泛性鸟类之间形成种子传播互惠关系，且种子传播效率受到专性鸟类和泛性鸟类传播距离和传播生境的影响。;Human disturbance causes the continual loss of natural habitats, and can result in fragmented habitats consisting only of patchy remnants. This habitat modification can lead to changes in plant-animal interactions. Understanding how the movement behavior of animal dispersers affects the regeneration patterns of plant species in patchy environments has been one of the main objectives of ecologists in recent years. Many previous studies have investigated seed dispersal only in terms of the dispersal distance. However, from the perspective of successful plant growth, it is not only important how far seeds are dispersed, but also where they are finally deposited. The quality of seed dispersal crucially depends on the movement patterns of the dispersing animal vectors; however, few ecological studies have focused on how the patchiness of habitats affects the movement patterns of specialist and generalist bird species, and thus, how habitat patchiness affects plant recruitment. Chinese yew (<em>Taxus chinensis</em> var. <em>mairei</em>) is listed as a Category 1 protected species in China, and it has also been listed as a globally endangered species in the IUCN Red List. A large proportion of the wild population of Chinese yew is distributed in patchy environments, and relies on bird vectors for seed dispersal. Previous studies have shown that Chinese yew seedlings can successfully establish away from mature trees as a result of seed dispersal by birds in the Corvidae and Pycnonotidae. However, it is still unknown how habitat patchiness affects the movement patterns of specialist and generalist bird species, and thus, how it affects the regeneration of Chinese yew and the persistence of its populations. In this study, we studied bird dispersal of Chinese yew seeds in the yew ecological garden of Meihuashan National Reserve. We studied the foraging and dispersing behavior of frugivorous birds in this typical patchy environment, and compared the contributions of a specialist (<em>Hypsipetes leucocephalus</em>) and generalist (<em>Urocissa erythrorhyncha</em>) species to seed dispersal by analyzing their post-foraging movement behaviors. The results showed that the Chinese yew source patch attracted 22 species of frugivorous birds to feed on seeds. A mutualistic seed dispersal relationship was formed between 13 bird species and Chinese yew. The main disperser of Chinese yew seeds was <em>H. leucocephalus. </em>There were annual differences in the other disperser species. The effectiveness of seed dispersal differed between the specialist and generalist bird species. After foraging for Chinese yew seeds, the movement and habitat selection differed between the habitat generalist (<em>U. erythrorhyncha</em>) and habitat specialist (<em>H. leucocephalus</em>) bird species. This may explain the differences in the seed dispersal distance and seed deposition sites between these two species. The habitat specialist bird species dispersed seeds over a short distance (16.3±11.0 m, mean±SD; <em>n </em>= 125) and the seeds were randomly distributed in a bamboo recruitment patch. The generalist species always moved between habitat patches and removed the seeds to the recruitment patch, dispersing seeds over a longer distance (24.9±20.0 m, mean±SD; <em>n</em>= 95). There was a high concordance between the movement distance of the specialist species and the seedling recruitment distance (<em>χ</em>²= 5.844, <em>P </em>= 0.211), and also a high spatial concordance between the habitat of the generalist species and the seedling recruitment habitat (<em>χ</em>²= 4.582, <em>P </em>= 0.205). Our results highlight that seed dispersal mutualistic relationships can form between Chinese yew and both specialist and generalist bird species. The effectiveness of Chinese yew dispersal was affected not only by the dispersal distances of specialist and generalist bird species, but also by the habitat in which the seeds were deposited.

Constant properties of plant–frugivore networks despite fluctuations in fruit and bird communities in space and time

Human-induced changes in anthropogenic landscapes are a predominant threat to biodiversity and have been documented to affect mutualistic interactions between plants and animals, such as avian seed dispersal. Interactions between fleshy-fruited plants and frugivorous birds are highly seasonal in temperate ecosystems. Nevertheless, combined effects of landscape modification and seasonal variation on plant-frugivore interactions have never been assessed from a network perspective. Here, we present the first study that simultaneously investigates effects of landscape modification and seasonal variation on plant-frugivore interactions and on functional and interaction diversity of plant-frugivore networks. We recorded visitation rates of 39 frugivorous bird species to 28 fruiting-plant species in Central Germany from early summer to late autumn in hedgerows within three landscape types arranged along a gradient of decreasing anthropogenic modification and increasing structural diversity (i.e., farmland, orchard, forest edge). We analyzed how species richness, abundance, and community composition, as well as functional and interaction diversity of fruiting plants and frugivorous birds changed with landscape type, fruit availability, and season. We found that visitation rates of frugivorous birds were lower in farmland, but only in summer. In autumn, visitation rates were similar in all landscape types and strongly increased with increasing local fruit availability. The functional diversity of fruits and frugivorous birds and their interaction diversity remained surprisingly constant in all landscape types. Due to seasonal changes in communities of fruiting plants and frugivorous birds, functional dispersion of fruiting plants was lower in autumn than in summer, whereas functional richness and dispersion of frugivorous birds was higher in autumn than in summer. Our results indicate that seasonal changes in fruit availability influence the abundance of frugivorous birds along gradients of structural diversity at the landscape scale. Although seasonal fluctuations influenced the functional diversity of avian frugivore communities, we found constant interaction diversity of plant-frugivore networks in space and time, probably due to the functional redundancy of frugivorous birds. These findings indicate a high robustness of avian frugivory to moderate levels of human-induced landscape modification in temperate ecosystems and call for studies testing the generality of these findings for ultimate avian seed dispersal functions.

Frugivorous birds visit fruits of emerging alien shrub species more frequently than those of native shrub species in the South African Mediterranean climate region

We compared daily visitation frequency indices by 4 large (>150g), 7 medium-size (50–150g), 5 small (30–50g) and 8 and tiny (<30g) frugivorous bird species on fleshy fruits of two native shrubs (Olea europaea subsp. africana and Chrysanthemoides monilifera subsp. monilifera), two established alien shrubs (Solanum mauritianum and Lantana camara) and two emerging alien shrubs (Myoporum tenuifolium and Pittosporum undulatum) at nine different sites in the Cape Floristic Region. Large, medium-size and tiny birds as groups displayed significantly higher visitation frequency indices on fruits of both emerging alien shrub species than the other shrub species. Small birds as a group displayed insignificantly different visitation frequency indices on fruits of both emerging and established alien shrub species but significantly higher visitation frequency indices on fruits of both emerging and established alien shrub species than on fruits of the native shrub species. However, there were significant differences in foraging frequency indices of the bird species included within each of these body size groups on fruits of the different shrub species. Among the large birds, Columba guinea and among the medium size birds Sturnus vulgaris, Streptopelia senegalensis, Turdus olivaceus and Onychognathus morio all exhibited significantly higher visitation frequency indices on fruits of both emerging alien shrub species than on fruits of the other shrub species. These findings indicate that alien plant control measures should be focused on eradicating localised populations of emerging aliens to limit preferential consumption of their fruits by birds and consequent dispersal of their seeds that germinate readily into natural areas.

Do frugivorous birds concentrate their foraging activities on those alien plants with the most abundant and nutritious fruits in the South African Mediterranean-climate region?

Alien plants with abundant and nutritious fruits may compete more effectively for avian dispersal services than native shrubs. This premise was examined by comparing daily foraging activity (visitation frequency, foraging bird number and foraging period) by four frugivorous bird species of different size on fruits of two native and two alien shrub species co-occurring at four different sites. Also, the quantities of seeds consumed daily by each of the four birds species from fruits of the four shrub species were measured and compared with the numbers of fruits and seeds, and the mass of fruits present in the shrub canopies as well as with their fruit monosaccharide concentrations. The quantities of seed consumed daily by four different size bird species (Columba arquatrix, Colius striatus, Pycnonotus capensis, Zosterops pallidus subsp capensis) were positively correlated with the numbers of seeds per m2 of canopy area and with fruit mass and fruit monosaccharide content per m2 of canopy area, as well as with the monosaccharide concentration of individual fruits, except in the C. arquatrix (African olive pigeon). All four bird species displayed the highest daily visitation frequencies on fruits of the alien Solanum mauritianum which were more abundant and nutritious than fruits of the other alien Lantana camara and fruits the natives Olea europaea subsp africana and Chrysanthemoides monilifera. They also all consumed greater quantities of seed daily from fruits of the alien S. mauritianum than from fruits of the other shrub species. These results corroborate proposals that frugivorous birds concentrate their foraging activities on those alien plants with the most abundant and nutritious fruits.

Frugivoria por aves em um mosaico de Floresta Estacional Semidecidual e reflorestamento misto em Rio Claro, São Paulo, Brasil

Visando subsidiar futuros projetos de recuperação florestal com base nas interações animal-planta, foram avaliadas as espécies ornitocóricas e o consumo de frutos por aves em um mosaico de Floresta Estacional Semidecidual e um reflorestamento misto, em Rio Claro, São Paulo. Através do monitoramento da frutificação e avaliação dos eventos de frugivoria em sessões focais e ad libitum, foram registradas 31 espécies ornitocóricas fornecendo frutos para 38 espécies de aves consumidoras. No reflorestamento misto foram observadas 90,3% (n=28) das espécies ornitocóricas frutificando ao longo de todo ano, enquanto no fragmento florestal, somente 51,6% (n=16) delas foram registradas, com maiores variações temporais na oferta de frutos; 65,2% (n=1027) dos frutos foram consumidos no reflorestamento misto e 34,8% (n=547) no fragmento florestal. Tais resultados podem estar relacionados ao menor tamanho do fragmento de vegetação nativa, o que, proporcionalmente, poderia determinar uma menor riqueza de espécies vegetais no mesmo e/ou ao fato de a dispersão abiótica tender a predominar nos locais fragmentados e perturbados. O reflorestamento misto, embora apresente algumas espécies vegetais exóticas, está sendo ecologicamente mais funcional para a avifauna e, devido à proximidade com o fragmento, parece estar contribuindo para a manutenção das comunidades de aves residentes e visitantes deste último através dos recursos alimentares oferecidos.

Native fruit traits may mediate dispersal competition between native and non-native plants

Seed disperser preferences may mediate the impact of invasive, non-native plant species on their new ecological communities. Significant seed disperser preference for invasives over native species could facilitate the spread of the invasives while impeding native plant dispersal. Such competition for dispersers could negatively impact the fitness of some native plants. Here, we review published literature to identify circumstances under which preference for non-native fruits occurs. The importance of fruit attraction is underscored by several studies demonstrating that invasive, fleshy-fruited plant species are particularly attractive to regional frugivores. A small set of studies directly compare frugivore preference for native vs. invasive species, and we find that different designs and goals within such studies frequently yield contrasting results. When similar native and non-native plant species have been compared, frugivores have tended to show preference for the non-natives. This preference appears to stem from enhanced feeding efficiency or accessibility associated with the non-native fruits. On the other hand, studies examining preference within existing suites of co-occurring species, with no attempt to maximize fruit similarity, show mixed results, with frugivores in most cases acting opportunistically or preferring native species. A simple, exploratory meta-analysis finds significant preference for native species when these studies are examined as a group. We illustrate the contrasting findings typical of these two approaches with results from two smallscale aviary experiments we conducted to determine preference by frugivorous bird species in northern California. In these case studies, native birds preferred the native fruit species as long as it was dissimilar from non-native fruits, while non-native European starlings preferred non-native fruit. However, native birds showed slight, non-significant preference for non-native fruit species when such fruits were selected for their physical resemblance to the native fruit species. Based on our review and case studies, we propose that fruit characteristics of native plant communities could dictate how well a non-native, fleshy-fruited

Frugivory by five bird species in agroforest home gardens of Pontal do Paranapanema, Brazil

The inefficiency of conservation efforts based exclusively on natural habitat patches has called the attention of some conservationists to the matrix. Described as the major component of a landscape, the matrix is often agricultural, particularly in the tropics. In this context, agroforestry practices have been recognized for their ability to support a rich fauna and flora. Besides the extensive literature concerning bird communities in agroforestry systems, very few studies analyze how different species respond to the management of such practices. Our study describes the diet and habitat use frequency of five frugivorous bird species in agroforest home gardens, secondary forests, and pastures in the region of Pontal do Paranapanema, Brazil. The focal species were Ramphastos toco (Toco Toucan), Pteroglossus castanotis (Chestnut-eared Aracari), Amazona aestiva (Blue-fronted Amazon), Ara chloroptera (Green-winged Macaw), and Cyanocorax chrysops (Plush-crested Jay). We gathered both habitat use frequency and diet using the “feeding-bout” method. Overall frequency was higher in the secondary forest when compared to pasture and home gardens for all bird species except A. aestiva. The number of feeding bouts was higher in home gardens than in forests for all species with the exception of C. chrysops. Differences in monthly median feeding activity were only statistically significant for C. chrysops and for A. aestiva. The latter was the only species observed feeding in pasture habitats. The total number of food taxa was larger in home gardens than in the forest. Our results reinforce the importance of agroforestry systems as a resource-rich habitat for frugivorous birds.

A univariate analysis of variance design for multiple-choice feeding-preference experiments: A hypothetical example with fruit-eating birds

I consider statistical problems in the analysis of multiple-choice food-preference experiments, and propose a univariate analysis of variance design for experiments of this type. I present an example experimental design, for a hypothetical comparison of fruit colour preferences between two frugivorous bird species. In each fictitious trial, four trays each containing a known weight of artificial fruits (red, blue, black, or green) are introduced into the cage, while four equivalent trays are left outside the cage, to control for tray weight loss due to other factors (notably desiccation). The proposed univariate approach allows data from such designs to be analysed with adequate power and no major violations of statistical assumptions. Nevertheless, there is no single “best” approach for experiments of this type: the best analysis in each case will depend on the particular aims and nature of the experiments.

Does landscape structure affect resource tracking by avian frugivores in a fragmented Afrotropical forest?

Frugivorous species heavily depend on patchy food resources and are believed to track these in space and time, thereby providing an important seed dispersal function that might be critical toward the regeneration of fruiting plants. However, isolation of suitable food patches due to habitat fragmentation or changes in landscape connectivity may hamper food tracking behaviour and adversely affect populations of both frugivores (through starvation) and food plants (through interruption of seed dispersal). We here test whether density fluctuations in four frugivorous Afrotropical bird species were larger and/or matched fluctuations in ripe fruit densities better in study plots embedded in large tracts of indigenous forest than in equally‐sized plots embedded in cultivated lands. We compared these results with those of four non‐frugivorous species (out‐group) which were not expected to track fruit resources. Whereas densities of both frugivores and fruit crops strongly fluctuated in space and time, these fluctuations were not synchronised, nor did the level of synchrony differ in relation to matrix type. For some but not all bird species, lower densities and smaller temporal fluctuations in forest plots surrounded by cultivation may reflect decreased mobility. The observed fluctuations in bird densities most likely reflect exchange with the surrounding landscape matrix, suggesting that small pockets of fruiting trees in farmland may comprise critical food resources for frugivores inhabiting highly fragmented landscapes, apart from increasing connectivity for both bird and seed dispersal.

Habitat and fig characteristics influence the bird assemblage and network properties of fig trees from Xishuangbanna, South-West China

Abstract:To understand how fruit tree characteristics and microhabitats shape the assemblage of birds on fig trees and the pattern of fig–bird interactions, we observed and recorded, over 96 d and 816 h, the frugivorous birds visiting 32 individual trees belonging to 14 species ofFicusthat were distributed across four different sites. A total of 30 bird species were recorded as eating figs, comprising 66.7% of the total number of frugivorous bird species recorded at the four sites. Small passerine birds such as bulbuls were the dominant frugivores for fig species. The number of bird species visiting different fig trees was significantly influenced by the crop size and canopy volume. Fruit colour and fruit size did not significantly influence the number of bird species, whereas habitats appeared to influence the composition of visiting birds. The fig–frugivorous bird interaction was asymmetrically structured, and the degree of nestedness appeared to be influenced by the forest type and degree of disturbance: the degree of nestedness in non-limestone forest tended to be higher than limestone forest; forest with less disturbance tend to be more nested compared with the open forest with high disturbance.

Reduced dispersal of native plant species as a consequence of the reduced abundance of frugivore species in fragmented rainforest

Frugivorous animals disperse the seeds of the majority of rainforest plant species and hence play a key role in the trajectory of rainforest regeneration. This study investigated whether changes in the species composition of the frugivore community in fragmented rainforest in subtropical Australia is likely to impact the dispersal of native plant species. The potential of frugivorous bird and bat species to disperse the seeds of plant species in fragmented rainforest was assessed using published dietary information together with field surveys of frugivore abundance within intact forest, forest fragments and patches of regrowth. Frugivore species with reduced abundance in fragmented rainforest were the only known dispersers of 27 of the 221 native plant species in the data set (12% of species). These frugivore species were also major dispersers of plant species producing fruits wider than 10 mm and species from the families Rubiaceae, Lauraceae, Myrtaceae, Meliaceae, Lamiaceae and Vitaceae. Except for Rubiaceae, these plant taxa are also potentially dispersed by two of the frugivore species that were widespread in fragmented rainforest, Lopholaimus antarcticus and Ptilonorhynchus violaceus, although dispersal rates are likely to be lower in fragmented than in extensive rainforest. Consistent with other regions, large-seeded plants are susceptible to reduced dispersal in fragmented rainforest in subtropical Australia. However, we predict a smaller deficit in seed dispersal in fragmented forests than has been reported from other regions, due to factors such as functional overlap among frugivore species, the ability of many Australian rainforest vertebrates to persist in fragmented rainforest, and a lack of hunting in these forests. Nevertheless, rainforest fragmentation has reduced the abundance of a suite of frugivorous rainforest fauna, which in turn is likely to reduce the dispersal of a certain plant taxa and may alter patterns of plant regeneration in subtropical Australian rainforest fragments.

The potential key seed-dispersing role of the arboreal marsupial Dromiciops gliroides

Marsupial seed dispersal is a rare phenomenon, although it may be ecologically significant in southern South America. The marsupial Dromiciops gliroides is endemic to the northern part of the temperate forest of South America. Here we describe the food habits and examine the potential role of D. gliroides as a seed disperser. We evaluated the diet of this marsupial in its natural habitat and in captivity. Dromiciops gliroides is omnivorous showing high consumption of a diversity of fruits. In captivity, D. gliroides consumed fruits from 80% of 22 native plant species we examined. Experiments conducted with fruits from two common understory shrubs show that seed passage through the digestive tract of D. gliroides enhances germination. Our results suggest that this species may have an important role as a seed disperser in the temperate forest of South America, which might offset a scarcity of frugivorous bird species.