Wallacea and its nectarivorous birds: nestedness and modules

Aim Wallacea, the vast oceanic boundary between the Oriental and Australian regions, contains 122 true nectarivorous bird species. It is the contact zone of the Oriental sunbirds and the Australian honeyeaters, and at least three more true nectarivorous families are resident in the region. An island–bird matrix for Wallacea was tested for the presence of two patterns, nestedness and modularity. If the matrix is modular, it consists of a number of densely linked subgroups or modules of islands and birds, which are weakly interconnected. These modules are used as a new tool in analysing biogeographical boundaries in Wallacea. Location Wallacea, Indonesia. Methods We constructed an island–bird matrix for Wallacea and used two algorithms, aninhado and sa , to test it for nestedness and modularity, respectively. aninhado calculates the matrix temperature and provides a null model, and sa is a module‐detecting program based on simulated annealing. The results of the sa were compared with those from a hierarchical cluster analysis. Results The matrix had a nested pattern, as is commonly the case for island–species matrices. The SA detected four modules in Wallacea, each consisting of a group of islands sharing a group of nectarivorous birds. The sa algorithm produced a more detailed pattern of the area than did the hierarchical cluster analysis. Main conclusions Modularity and nestedness do not preclude each other as biogeographical patterns. The boundaries of the modules detected by sa compared well with major boundaries from the existing literature and showed a clear division of Wallacea into modules of birds and islands closely linked together. Thus modules are biogeographical units of islands sharing a specific nectarivorous fauna. For some research questions, we suggest that modules may be more appropriate biogeographical units than single islands or traditionally perceived archipelagos. The nectarivorous families showed distinctly different distributions, indicating variation in their colonization history and speciation processes. We recommend sa as a tool for detecting fine‐grained biogeographical patterns.     

Sugar preferences of nectar feeding birds – a comparison of experimental techniques

Experiments to determine sugar preferences of nectarivorous animals have been conducted using a wide variety of experimental procedures, all of which aim at ensuring that the solutions offered in choices are “equivalent”. Each method used historically has controlled for a particular variable, such as number of molecules in solution, weight of sugar in solution, or amount of energy in solution, depending on what question the researchers have tried to answer. Biologists interpreting these results in terms of bird sugar preference have seldom taken these differences into account. The consequences of using different experimental procedures for sugar preferences exhibited by a nectarivorous bird, the malachite sunbird Nectarinia famosa, were examined using paired sucrose and hexose sugar solutions made up to be either equimolar, equiweight or equicaloric. We found the effect of methodology on bird sugar preference to be quite distinct, especially at low concentrations, where malachite sunbirds showed either sucrose preference, no preference, or hexose preference, depending on the method used. This study highlights the need for researchers to consider methodology when interpreting, or comparing among, results from previous studies.     

Sugar preferences, absorption efficiency and water influx in a Neotropical nectarivorous passerine, the Bananaquit (Coereba flaveola)

Nectarivory has evolved repeatedly in a number of unrelated bird taxa throughout the world and nectar feeding birds, regardless of their taxonomic affiliation, display convergent foraging and food processing adaptations that allow them to subsist on weak sugar solutions. However, phylogeny influences sugar type preferences of nectarivores. We investigated sugar preferences, assimilation efficiency and water flux in a Neotropical honeycreeper, the Bananaquit (Coereba flaveola; Coerebidae), a member of a radiation of tanagers and finches. Bananaquits showed no preference for nearly equicaloric (25% w/v) sucrose, glucose, fructose or glucose-fructose mixtures in pair-wise choice tests. In agreement with this lack of preference, they were equally efficient at absorbing sucrose and both hexoses. Apparent assimilation efficiency of these sugars was around 97.5%. In pair-wise tests, Bananaquits displayed a strong preference for the most concentrated sucrose solution when the lowest concentration ranged from 276 to 522 mM. Between 522 and 1120 mM sucrose solution concentrations, Bananaquits were able to adjust their volumetric food intake in order to maintain a constant energy intake. At solution concentration of 276 mM, birds could not maintain their rate of energy intake by increasing food consumption enough. We consider that at low sugar concentrations, Bananaquits faced a physiological constraint; they were unable to process food at a fast enough rate to meet their energy needs. We also explored the possibility that dilute nectars might be essential to sustain high water needs of Bananaquits by allowing them to control osmolarity of the food. Between 276 and 1120 mM sucrose solution concentrations, average amount of free water drunk by Bananaquits was independent of food concentration. They drank very little supplementary water and did not effectively dilute concentrated nectars. The evidence suggests that water bulk of dilute nectars is a burden to Bananaquits.     

The major ion chemistry of some southern African saline systems

Africa south of about 23° S has few natural athalassic lakes, saline or freshwater. South Africa, however, is rich in temporary pans, many of which are saline, while permanent saline springs occur along the coastal strip of the Namib Desert in Namibia. This paper examines the chemistry of the major ions in 67 Namibian waters, 47 of which have not previously been reported in the literature, and compares them with 66 South African waters, five of which have not previously been reported, and with saline lakes in East Africa.The highest value for total dissolved solids in South African waters was 276 g l^–1 (Koekiespan, south-western Cape) and the highest for Namibian waters were 160 g l^–1 (Hosabes, a small spring on a gypsous crust) and 302 g l^–1 (a salt pan at Oranjemund at the mouth of the Orange River). The dominant ions in fresh waters in the region are Ca²⁺ and HCO _inf3 ^– /CO _inf3 ^2– in the interior and in Namibia, and Na²⁺ and Cl⁺ on the south and east coasts. Regardless of the geochemistry of their substrata, the dominant ions in the saline waters throughout the region are Na⁺ and Cl^–. Thus differential precipitation of CaCO₃ and CaSO₄, as a result of evaporative concentration at high salinities, appears to be the determinant of the proportions of the major ions in these systems.The permanent springs on gypsous crusts along the coast of Namibia, although dominated by Na⁺ and Cl^– ions, contain considerable quantities of both Ca²⁺ and SO ₄ ^2– ions.     

Effectiveness of nectarivorous birds and honeybees as pollinators of Banksia spinulosa (Proteaceae)

Abstract The effectiveness of nectarivorous birds and honeybees (Apis mellifera) as pollinators of Banksia spinulosa (Proteaceae) was investigated. Birds visited inflorescences in the early, mid and late flowering seasons. In contrast, honeybees visited only on days in the late flowering period when maximum temperatures exceeded 15°C. Self pollen remained on pollen presenters of flowers for up to 5 days in the early and mid periods. In the late period, when honeybees visited inflorescences, self pollen was removed within 2 days. Pollen removal was similar for caged (birds excluded) and open inflorescences in the late period, indicating that most pollen was removed by honeybees. In the early and mid periods, honeyeaters pollinated 22% and 27% of flowers on open inflorescences, respectively. In the late period, when both birds and bees visited inflorescences, 64–73% of flowers on open inflorescences were pollinated. Foraging by honeybees resulted in pollen deposition as 38% of flowers on caged inflorescences were pollinated. Throughout the flowering season a similar number of pollen grains was deposited per stigma. There were 3.0–3.7 pollen grains per stigma on open inflorescences in the late period, although only 2.0 grains per stigma on caged inflorescences. In the early and mid periods, fewer caged than open inflorescences produced fruits, indicating the importance of honeyeaters to reproductive success at these times. In contrast, in the late period when honeybees visited inflorescences, fruit-set was similar on caged and open inflorescences. Overall, these results indicate that honeybees were effective pollinators of B. spinulosa.     

Prediction of mean adult survival rates of southern African birds from demographic and ecological covariates

Estimates of annual survival rates of birds are valuable in a wide range of studies of population ecology and conservation. These include modelling studies to assess the impacts of climatic change or anthropogenic mortality for many species for which no reliable direct estimates of survival are available. We evaluate the performance of regression models in predicting adult survival rates of birds from values of demographic and ecological covariates available from textbooks and databases. We estimated adult survival for 67 species using dead recoveries of birds ringed in southern Africa and fitted regression models using five covariates: mean clutch size, mean body mass, mean age at first breeding, diet and migratory tendency. Models including these explanatory variables performed well in predicting adult survival in this set of species, both when phylogenetic relatedness of the species was taken into account using phylogenetic generalized least squares (51% of variation in logit survival explained) and when it was not (48%). Two independent validation tests also indicated good predictive power, as indicated by high correlations of observed with expected values in a leave‐one‐out cross validation test performed using data from the 67 species (35% of variation in logit survival explained), and when annual survival rates from independent mark–recapture studies of 38 southern African species were predicted from covariates and the regression using dead recoveries (48%). Clutch size and body mass were the most influential covariates, both with and without the inclusion of phylogenetic effects, and a regression model including only these two variables performed well in both of the validation tests (39 and 48% of variation in logit survival explained). Our regression models, including the version with only clutch size and body mass, are likely to perform well in predicting adult survival rate for southern African species for which direct survival estimates are not available.     

Potential impacts of climatic change on southern African birds of fynbos and grassland biodiversity hotspots

Aim To examine potential impacts of climatic change on bird species richness of the fynbos and grassland biomes, especially on species of conservation concern, and to consider implications for biodiversity conservation strategy. Location Southern Africa, defined for this study as South Africa, Lesotho and Swaziland. Methods Climate response surfaces were fitted to model relationships between recorded distributions and reporting rates of 94 species and current bioclimatic variables. These models were used to project species’ potential ranges and reporting rates for future climatic scenarios derived from three general circulation models for 30‐year periods centred on 2025, 2055 and 2085. Results were summarized for species associated with each biome and examined in detail for 12 species of conservation concern. Results Species richness of fynbos and grassland bird assemblages will potentially decrease by an average of 30–40% by 2085 as a result of projected climatic changes. The areas of greatest richness are projected to decrease in extent and to shift in both cases. Attainment of projected shifts is likely to be limited by extent of untransformed habitat. Most species of conservation concern are projected to decrease in range extent, some by > 60%, and to decrease in reporting rate even where they persist, impacts upon their populations thus being greater than might be inferred from decreases in range extent alone. Two species may no longer have any areas of suitable climatic space by 2055; both already appear to be declining rapidly. Main conclusions Species losses are likely to be widespread with most species projected to decrease in range extent. Loss of key species, such as pollinators, may have far‐reaching implications for ecosystem function and composition. Conservation strategies, and identification of species of conservation concern, need to be informed by such results, notwithstanding the many uncertainties, because the certainties of climatic change make it essential that likely impacts not to be ignored.     

Molecular evidence for host specificity of parasitic nematode microfilariae in some African rainforest birds

Here we describe, determine the prevalence, and examine the host-specificity of some parasitic nematode microfilariae in selected bird species from West and Central Africa. We used microscopy to determine the prevalence of microfilariae in 969 host individuals representing 121 rainforest bird species from Cameroon, Côte d’Ivoire and Equatorial Guinea. Thirteen (11%) of these potential host species harboured microfilariae, and 35 individuals (3.6%) were infected. From the 35 infected individuals, we identified eight distinct morphological microfilarial forms. Sixteen of the 35 infected individuals were of one host species, the Fire-crested Alethe (Alethe diademata), at a prevalence rate of 62%. To examine host and geographical specificity, we sequenced a portion of the LSU rDNA gene from representative microfilariae drawn from different hosts and collecting locations. Identical sequences of the nematode LSU rDNA gene were found in A. diademata collected from locations in Côte d’Ivoire and Equatorial Guinea, locations separated by the Dahomey Gap and associated with different hypothesized refugial areas. In contrast, several other bird species collected at the same sites harboured different microfilaria lineages. We sequenced the mitochondrial ATP synthase genes of the host species A. diademata, and found a 5.4% sequence divergence between the birds sampled in Côte d’Ivoire, and those from Cameroon. Thus, despite this split between the two populations, they harbour microfilariae with identical lineages. These data provide evidence that the microfilariae found in A. diademata may be highly host specific. This apparent specificity may have important implications for the evolutionary and ecological interactions between parasitic nematodes and their avian hosts.     

How New Guinea rainforest flower resources vary in time and space: Implications for nectarivorous birds

Abstract Variability in spatial and temporal patterning of flowering by populations of rainforest trees fed upon by honeyeaters and flower-visiting parrots was studied for 2 years in lowland tropical hill forest in Papua New Guinea. All 2200 trees in a 3 ha plot were tagged, identified, mapped and monitored monthly. Of 274 tree species present, 86 flowered during the course of the study; during any given month, approximately 20% of the species flowering that month were visited by nectarivorous birds. Results showed that overall flower resources (total number of species, and number of bird-pollinated species, individuals and flowers) fluctuated during the year, decreased during the dry season and increased during the wet season. In addition, there was a wide range of temporal variation within and among tree species in length and timing of flowering period, percentage of each conspecific population flowering from year to year, and degree of synchrony among flowering conspecifics. Spatial dispersion of tree populations also varied, from clumps to scattered single individuals. Resident bird species were correlated with synchronously flowering trees, whereas nomadic bird species were correlated with asynchronously flowering trees. Resident birds were also associated with smaller blooming displays per tree, whereas nomadic birds were associated with trees that bloomed massively. There was no correlation between avian nomadism and spatial dispersion of tree populations. Thus nomadic birds seem to range in search of rich but unpredictable resources; resident birds may rely more on predictable, but smaller resources.     

Host specificity and incidence of Trypanosoma in some African rainforest birds: a molecular approach

Studies of host-parasite interactions in birds have contributed greatly to our understanding of the evolution and ecology of disease. Here we employ molecular techniques to determine the incidence and study the host-specificity of parasitic trypanosomes in the African avifauna. We developed a polymerase chain reaction (PCR)-based diagnostic test that amplified the small subunit ribosomal RNA gene (SSU rRNA) of Trypanosoma from avian blood samples. This nested PCR assay complements and corroborates information obtained by the traditional method of blood smear analysis. The test was used to describe the incidence of trypanosomes in 479 host individuals representing 71 rainforest bird species from Cameroon, the Ivory Coast and Equatorial Guinea. Forty-two (59%) of these potential host species harboured trypanosomes and 189 individuals (35%) were infected. To examine host and geographical specificity, we examined the morphology and sequenced a portion of the SSU rRNA gene from representative trypanosomes drawn from different hosts and collecting locations. In traditional blood smear analyses we identified two trypanosome morphospecies, T. avium and T. everetti. Our molecular and morphological results were congruent in that these two morphospecies had highly divergent SSU rRNA sequences, but the molecular assay also identified cryptic variation in T. avium, in which we found seven closely allied haplotypes. The pattern of sequence diversity within T. avium provides evidence for widespread trypanosome mixing across avian host taxa and across geographical locations. For example, T. avium lineages with identical haplotypes infected birds from different families, whereas single host species were infected by T. avium lineages with different haplotypes. Furthermore, some conspecific hosts from geographically distant sampling locations were infected with the same trypanosome lineage, but other individuals from those locations harboured different trypanosome lineages. This apparent lack of host or geographical specificity may have important consequences for the evolutionary and ecological interactions between parasitic trypanosomes and their avian hosts.     

A test of pollinator specificity and morphological convergence between nectarivorous birds and rainforest tree flowers in New Guinea

Interactions between flowering trees in a representative sample of vegetation, and the birds that fed at their flowers, were studied for 2 years in lowland tropical hill forest in New Guinea. All 2,200 trees in a 3-ha plot were tagged, identified, mapped, and monitored monthly. Approximately 60% of all individual trees flowered during the study; all species that these flowering individuals belonged to were evaluated for bird visitation. Approximately 13% of the 164 resident species of New Guinea avifauna at the study site, especially honeyeaters and parrots, visited flowers. In the forest inventory plot, approximately 15–22% of all 86 tree species that flowered during the study were visited by birds; most of these tree species were canopy species. Results showed that there was no statistically significant correlation between bird species grouped by bill morphology and flower species grouped as morphotypes and ranked by nectar accessibility, although strong but unexpected bird/plant associations were evident. These associations may be related to variables such as body mass or perch size. These results are discussed in comparison with results from the Neotropics and Australia, and in terms of morphological convergence and pollinator specificity in pollination systems.     

Bird pollination syndrome is the plant's adaptation to ornithophily,but nectarivorous birds are not so selective

Many tropical plants are pollinated by birds and several bird phylogenetical lineages have specialised to a nectar diet. The long-assumed, intimate ecological and evolutionary relationship between ornithophilous plants and phenotypically specialised nectarivorous birds has nevertheless been questioned in recent decades, where such plant–pollinator interactions have been shown to be highly generalised. In our study, we analysed two extensive interaction datasets: bird–flower and insect–flower interactions, both collected on Mt Cameroon, west-central Africa. We tested if: 1) insects and birds interact with distinct groups of plants; 2) plants with a typical set of ornithophilous floral traits (i.e. bird pollination syndrome) interact mainly with birds; 3) birds favour plants with bird pollination syndrome and; 4) if and how the individual floral traits and plant level nectar production predict bird visitation. Bird-visited plants were typically also visited by insects, while approximately half of the plants were visited by insects only. We confirmed the validity of the bird pollination syndrome hypothesis, as plants with bird-pollination syndrome traits were visited by birds at a higher rate and mostly hosted a lower frequency of visiting insects. However, these ornithophilous plants were not more attractive than the other plants for nectar-feeding birds. Nectar production per plant individual was a better predictor of bird visitation than any other floral trait traditionally related to the bird pollination syndrome. Our study thus demonstrated the highly asymmetrical relationship between ornithophilous plants and nectarivorous birds.