Malachite Sunbird Research Articles

Wing-moult and seasonal occurrence of sunbirds (Nectariniidae) captured at four sites in the Eastern Cape, South Africa

Ringing activity in the Eastern Cape province, South Africa, spanned 30 years, with three sites active concurrently over a 14-year period, and three sites over a 6-year period. In total, in the course of 714 ringing days, in all months, we handled 1 207 Amethyst Sunbirds, 708 Southern Double-collared Sunbirds, 707 Greater Double-collared Sunbirds, 381 Grey Sunbirds, 121 Malachite Sunbirds and 140 Collared Sunbirds. Although individuals of all six species were recaptured more than five years after ringing, and despite evidence of the seasonal passage of sunbirds at two sites near the Indian Ocean coast, no birds were recaptured away from the original ringing site. The extent of seasonal movement by these species remains unclear. All species have a complete post-breeding moult, with a period of eclipse plumage in males of the Malachite Sunbird and Southern Double-collared Sunbird. Primary wing-moult in adult Greater and Southern Double-collared Sunbirds extends over three months beginning in December. Inland populations of adult Amethyst Sunbirds and Malachite Sunbirds start primary moult in April. Moult apparently proceeds more rapidly in Malachite Sunbirds (70 days to completion) than in Amethyst Sunbirds (125 days), but the Malachite Sunbird is the only species that frequently displays interrupted/suspended moult in this region. Adult Amethyst Sunbirds in the coastal population evidently start moulting earlier, in late February, with a similar duration to completion as inland birds. Juvenile Amethyst Sunbirds start to moult some two months later than adults in each region and they may complete moult more quickly. Collared Sunbirds appear to have the most protracted moult, extending over five months from November, but estimates of moult parameters for this species and the Grey Sunbird (three months from December) are based on small samples.

Opportunistic avian nectarivory on flowering Aloe maculata with a review of visiting bird species

Eight bird species were recorded feeding on Aloe maculata (Soap Aloe) nectar at Biddulphsberg, Senekal, Free State, from 23–26 August 2021. Birds were mist-netted as part of a bird ringing study and aloe pollen was noticed on some birds. The flowering aloes attract mainly Malachite Nectarinia famosa and White-bellied Sunbirds Cinnyris talatala as well as Cape Zosterops virens and Orange River White-eyes Z. pallidus. Of the 108 birds ringed or collected, 34 birds (eight species) had aloe pollen on them. These species, including a first record of Black-chested Prinia Prinia flavicans, and a confirmed record of Streaky-headed Seedeaters Crithagra gularis, represent the first observations of birds probing A. maculata flowers.

Specialist and generalist avian nectarivores co-dominate visitation to a summer-flowering grassland aloe

Aloe reitzii var. reitzii is a summer-flowering (February–March) succulent, endemic to a restricted range within the heavily transformed grasslands of eastern South Africa. Floral structure and nectar properties suggest bird-pollination. This study investigated the temporal visitation events of birds to this aloe. Extensive camera observations during the 2017 flowering season (23 days) identified both specialist and generalist nectarivorous birds (n = four and five species respectively) as regular diurnal aloe visitors. Malachite Sunbirds (Nectarinia famosa) accounted for 49% of all visits, while Cape Weavers (Ploceus capensis) made up 41% of all visits; these species co-dominate visitation of the specialist and generalist avian feeding guilds respectively. In addition, visitation by each guild was separated temporally to some extent, with generalists mostly visiting early in the day, while specialists dominate afternoon visitation. Nectar volume (overall unbagged mean = 48.67 ± 4.70 µL) and concentration (overall unbagged mean = 10.68 ± 0.21% w/w) remains consistent throughout the day, and are within generalist nectar-feeding bird preferences, which may explain the abundance of Cape Weavers, despite floral morphological traits matching those of specialist nectar feeders. While many summer-flowering aloes are primarily insect- or sunbird-pollinated, Cape Weavers may be supplementing their diets with A. reitzii var. reitzii nectar, and potentially playing a crucial role in pollination.

Geographic variation of reproductive traits and competition for pollinators in a bird-pollinated plant.

Geographic variation in the reproductive traits of animal‐pollinated plants can be shaped by spatially variable selection imposed by differences in the local pollination environment. We investigated this process in Babiana ringens (Iridaceae), an enigmatic species from the Western Cape region of South Africa. B. ringens has evolved a specialized perch facilitating cross‐pollination by sunbirds and displays striking geographic variation in perch size and floral traits. Here, we investigate whether this variation can be explained by geographic differences in the pollinator communities. We measured floral and inflorescence traits, and abiotic variables (N, P, C, and rainfall) and made observations of sunbirds in populations spanning the range of B. ringens. In each population, we recorded sunbird species identity and measured visitation rates, interfloral pollen transfer, and whether the seed set of flowers was pollen limited. To evaluate whether competition from co‐occurring sunbird‐pollinated species might reduce visitation, we quantified nectar rewards in B. ringens and of other co‐flowering bird‐pollinated species in local communities in which populations occurred. Variation in abiotic variables was not associated with geographical variation of traits in B. ringens. Malachite sunbirds were the dominant visitor (97% of visits) and populations with larger‐sized traits exhibited higher visitation rates, more between‐flower pollen transfer and set more seed. No sunbirds were observed in four populations, all with smaller‐sized traits. Sunbird visitation to B. ringens was not associated with local sunbird activity in communities, but sunbird visitation was negatively associated with the amount of B. ringens sugar relative to the availability of alternative nectar sources. Our study provides evidence that B. ringens populations with larger floral traits are visited more frequently by sunbirds, and we propose that visitation rates to B. ringens may be influenced, in part, by competition with other sunbird‐pollinated species.

Narrow entrance of short-tubed Aloe flowers facilitates pollen transfer on long sunbird bills

Trade-offs are considered a major factor in the evolution of ecological specialization, as organisms can rarely specialize on more than one niche. Here we ask whether flowers can be specialized for more than one pollinator group. We studied an outcrossing plant, Aloe kraussii (Asphodelaceae), whose floral morphology is intermediate between that of exclusively bird- and exclusively insect-pollinated aloes. Previous field experiments showed that bees effectively pollinate A. kraussii; while sunbirds are frequent visitors their effectiveness as pollinators was unknown, especially as their long bills prevent head feathers—the normal location of pollen transfer by birds—from touching A. kraussii's relatively short anthers and stigmas. We tested whether sunbirds can pollinate A. kraussii, and whether this might be facilitated by flowers' narrow corolla opening, which could increase pollen transfer via narrow sunbird bills. Aviary experiments showed that a Malachite sunbird's bill can successfully pick up and deposit A. kraussii pollen, so long-billed sunbirds can be effective pollinators despite the apparent mismatch between bill and corolla length. Flowers with experimentally widened corolla openings experienced lower pollen removal and deposition by sunbirds than unmanipulated flowers with narrow openings. Aloe kraussii's floral morphology therefore enables dual specialization on two divergent pollinator guilds; short corollas facilitate bee pollination by enabling access to nectar, while narrow corolla openings facilitate pollen transfer via sunbird bills.

Notes on the flowering and pollination of the endemic grassland <i>Aloe reitzii</i> var. <i>reitzii</i> (Asphodelaceae)

Background: Aloe reitzii var. reitzii is a succulent with a restricted distribution in the montane grassland of eastern South Africa. It is a summer (late January–March) flowering succulent that grows on rocky outcrops at 1000 m–1600 m, and the conspicuous inflorescences suggest a pollination system focused towards birds.Objectives: To understand more about the pollination biology of A. reitzii var. reitzii.Methods: Nectar standing crop (flower volume and concentration) and the proportion of plants flowering were recorded. Camera traps and observations were used to record visitors to A. reitzii var. reitzii inflorescences.Results: Nectar volume was 36 μL ± 27 μL per flower (range 6 μL–93 μL; n = 27) and concentration was 16.5% ± 1.7% (range 13.5% – 19.5%). Camera trap observations, where 18.9% of all plants were observed flowering, recorded the three bird species Cape Weaver, Ploceus capensis, Malachite Sunbird, Nectarinia famosa and Greater Double-collared Sunbird, Cinnyris afer (60.4%, 27.1% and 12.5% of plant visits, respectively) visiting inflorescences.Conclusion: Because birds are important pollinators for many Aloe species, it is assumed that the bird species detected visiting A. reitzii var. reitzii are similarly important pollinators. At least 10 invertebrate species and sengi (Elephantulus sp.) were also recorded as visitors to flowers, but they may be less important pollinators than specialist and generalist avian nectarivores. This study provides further insight into the pollination biology of a diverse, and ecologically important, succulent genus in Africa.

Can short-billed nectar thieving sunbirds replace long-billed sunbird pollinators in transformed landscapes?

Pollinator specialisation through exploitation barriers (such as long floral tubes) does not necessarily mean a lack of pollination when the favoured pollinator is rare or absent. Theory predicts that suboptimal visitors will contribute to plant reproduction in the absence of the most effective pollinator. Here I address these questions with Chasmanthefloribunda a long-tubed plant species in the Cape Floristic Region, which is reliant on one species of pollinator, the long-billed Malachite Sunbird. In contrast to short-billed sunbirds, the Malachite Sunbird occurs in lower abundance or is absent in transformed landscapes. Short-billed sunbirds rob and thieve nectar from long-tubed flowers, but their potential contribution towards pollination is unknown. Experiments assessing seed set after single flower visits were performed to determine whether thieving short-billed sunbirds can act as substitute pollinators. To determine whether short-billed sunbirds reduce pollen limitation in transformed areas, pollen supplementation was done by hand and compared to natural fruit set. Short billed sunbirds are unable to act as substitute pollinators, and seed set is significantly lower in the flowers that they visited, compared to flowers visited by long-billed sunbirds. This is substantiated on a landscape scale, where fruit production in Chasmanthe floribunda could artificially be increased by 35% in transformed landscapes, but not so in natural areas. These findings have important consequences for the management and conservation of long-tubed bird-pollinated plant species that exist in recently transformed landscapes. The potential vulnerability of specialised plant species in transformed landscapes is highlighted.

Sunbird-pollination in the geoflorous species Hyobanche sanguinea (Orobanchaceae) and Lachenalia luteola (Hyacinthaceae)

Sunbird-pollinated plants display a suite of floral adaptations, for example, red tubular flowers, significant volumes of dilute nectar, or a suitable perch from which to forage flowers. In this study we show that two sunbird species were important for seed-set in low-growing, perchless plants of Hyobanche sanguinea and Lachenalia luteola on Kommetjie Slangkop, southern Cape Peninsula, South Africa. Remote video camera footage and field observations showed that malachite sunbirds (Nectarinia famosa) and orange-breasted sunbirds (Anthobaphes violacea) perched on the ground while visiting flowers of both plant species. Open inflorescences of both species yielded significantly higher seed-set than excluded inflorescences, which showed zero to near zero seed-set. Inflorescences shown on video to have been visited by sunbirds showed significantly higher seed-set than those for which video footage was not obtained, suggesting sunbirds are effective pollinators. Besides being the first documented pollinator information on these two species, our results expand upon the known traits associated with sunbird-pollination systems and suggest that low-growing sunbird-pollinated plants need not evolve perching structures in order to achieve effective visitation.

The importance of winter-flowering Aloe ferox for specialist and generalist nectar-feeding birds

The abundance of consumers and the availability of resources are often linked, and birds are known to track food resources at a variety of spatial and temporal scales. This study describes the seasonal influx of nectar-feeding birds during flowering in a 51-ha stand of Aloe ferox in the Eastern Cape, South Africa, over 5 years (2008–09 and 2011–13). Bimonthly point counts of birds were conducted before (April—May), during (June—July) and after (August) flowering, which occurs during the austral winter. The abundance of nectar-feeding birds increased significantly during flowering each year, whereas monthly abundances of non-nectarivores were unrelated to flowering. Models fitted to bird count-data revealed a significant interaction between feeding guild (nectarivorous versus non-nectarivorous species) and the percentage of flowering A. ferox over the 5 years of the study, confirming that these guilds responded differently to flowering events. Malachite Sunbirds (Nectarina famosa), which are specialist nectarivores, responded consistently to flowering of A. ferox each year, despite the low sugar concentrations of A. ferox nectar. The arrival of nectar-feeding birds en masse during flowering, and the number of bird species (16) observed feeding on A. ferox nectar, suggest that this plant is an important source of nutrition for birds at a time when other food resources are likely to be scarce.

Do pollinator distributions underlie the evolution of pollination ecotypes in the Cape shrub Erica plukenetii?

According to the Grant-Stebbins model of pollinator-driven divergence, plants that disperse beyond the range of their specialized pollinator may adapt to a new pollination system. Although this model provides a compelling explanation for pollination ecotype formation, few studies have directly tested its validity in nature. Here we investigate the distribution and pollination biology of several subspecies of the shrub Erica plukenetii from the Cape Floristic Region in South Africa. We analyse these data in a phylogenetic context and combine these results with information on pollinator ranges to test whether the evolution of pollination ecotypes is consistent with the Grant-Stebbins model. Pollinator observations showed that the most common form of E. plukenetii with intermediate corolla length is pollinated by short-billed Orange-breasted sunbirds. Populations at the northern fringe of the distribution are characterized by long corollas, and are mainly pollinated by long-billed Malachite sunbirds. A population with short corollas in the centre of the range was mainly pollinated by insects, particularly short-tongued noctuid moths. Bird exclusion in this population did not have an effect on fruit set, while insect exclusion reduced fruit set. An analysis of floral scent across the range, using coupled gas chromatography-mass spectrometry, showed that the scent bouquets of flowers from moth-pollinated populations are characterized by a larger number of scent compounds and higher emission rates than those in bird-pollinated populations. This was also reflected in clear separation of moth- and bird-pollinated populations in a two-dimensional phenotype space based on non-metric multidimensional scaling analysis of scent data. Phylogenetic analyses of chloroplast and nuclear DNA sequences strongly supported monophyly of E. plukenetii, but not of all the subspecies. Reconstruction of ancestral character states suggests two shifts from traits associated with short-billed Orange-breasted sunbird pollination: one towards traits associated with moth pollination, and one towards traits associated with pollination by long-billed Malachite sunbirds. The latter shift coincided with the colonization of Namaqualand in which Orange-breasted sunbirds are absent. Erica plukenetii is characterized by three pollination ecotypes, but only the evolutionary transition from short- to long-billed sunbird pollination can be clearly explained by the Grant-Stebbins model. Corolla length is a key character for both ecotype transitions, while floral scent emission was important for the transition from bird to moth pollination.

Reproductive ecology of Aloe plicatilis, a fynbos tree aloe endemic to the Cape Winelands, South Africa

While the pollination ecology of many Aloe species is well-documented, knowledge on aloe seed ecology, and hence aloe reproductive ecology in its entirety is limited. The aim of this study was to investigate the reproductive ecology of Aloe plicatilis, a Cape fynbos tree aloe endemic to the Cape Winelands, South Africa. Results from a pollinator exclusion experiment conducted at an A. plicatilis population on Paarl mountain suggests pollination primarily by insects, although bird visitation significantly increased seed set/fruit indicating possible co-pollination with insects. The species' long-tubed flowers and production of concentrated nectar, with observations of malachite sunbirds as the most common avian visitors to A. plicatilis flowers indicate the importance of long-billed specialist avian nectarivores as floral visitors. Analysis of the relationship between plant size and inflorescence production for five populations combined revealed a significant, positive linear relationship between plant size and the logarithm of the number of inflorescences/plant. Natural fruit and seed set determined for three populations (1325, 27,930 and 251,616 seeds/population) suggests low reproductive output compared to several other Aloe species. The smallest (31 individuals) and least dense (75plants/ha) A. plicatilis population produced the lowest seed set/plant (128 seeds) and per population (1325 seeds), suggesting an Allee effect. Evaluation of seed dispersal potential showed that potential dispersal distances were approximately three times the canopy height; however, the occurrence of A. plicatilis on mountains isolated from more continuous mountain ranges on which the species also occurs suggests the possibility of long-distance dispersal by strong, gusty, summer winds. Soil seed bank samples collected from 13 populations yielded close to zero seedling emergence, indicating the absence of persistent seed banks. A. plicatilis seeds stored under ambient laboratory conditions for 3, 18 and 24months were germinated in an environmental control chamber and a laboratory. High percentage germination was recorded for 18- and 24-month-seed (86 and 80%, respectively), while germination of 3-month-old seeds was three times lower, suggesting the need for after-ripening. Germination of fresh and one-year-old seed under ambient nursery conditions at the Karoo Desert National Botanical Garden in Worcester yielded emergence percentages of 67 and 44%, respectively, and were therefore less successful than germination under more controlled conditions. This is the first known study to investigate the reproductive ecology of a tree aloe species and that of a Cape fynbos aloe. The study highlights the importance of further studies on aloe seed ecology, particularly for rare and threatened species.

Sunbirds hover at flowers of Salvia and Lycium

Sunbirds usually perch when visiting flowers for nectar and only rarely hover. Except for three studies of sunbirds visiting introduced plants in South Africa and India as well as a native plant in Cameroon, there have been no quantitative studies of sunbird hovering behaviour. Here I present detailed observations of foraging behaviour in two sunbird species (Malachite Sunbird Nectarinia famosa and Southern Double-collared Sunbird Cinnyris chalybeus) at flowers of three Salvia species (Salvia africana-lutea, S. lanceolata and S. africana-caerulea; Lamiaceae) and one natural hybrid as well as Lycium afrum (Solanaceae) in South Africa. The birds not only perched, but also hovered (up to 28% of total visits) and sometimes hover-clasped (up to 3%). Other birds only rarely (Karoo Prinia Prinia maculosa) or never hovered during flower visits. These observations indicate that the foraging behaviour of specialist passerine nectarivorous birds overlaps with that of hummingbirds more than was previously thought.

Urbanization Drives a Reduction in Functional Diversity in a Guild of Nectar-feeding Birds

Urbanization is a widespread and rapidly growing threat to biodiversity, therefore we need a predictive understanding of its effects on species and ecosystem processes. In this paper we study the impact of urbanization on a guild of nectar-feeding birds in a biodiversity hotspot at the Cape of Africa. The guild of four bird species provides important ecosystem services by pollinating 320 plant species in the Cape Floral Region. Functional diversity within the guild is related to differences in bill length. The long-billed Malachite Sunbird (Nectarinia famosa) plays an irreplaceable role as the exclusive pollinator of plant species with long nectar tubes. We analyzed the composition of the guild in suburban gardens of Cape Town along a gradient of increasing distance from the nearest natural habitat. Urbanization reduces the functional diversity of the nectarivore guild. Malachite Sunbirds did not penetrate more than 1 km into the city, whereas only the short-billed Southern Double-collared Sunbirds (Cinnyris chalybea) occurred throughout the urbanization gradient. The lack of data precludes conclusions regarding the detailed responses of Orange-breasted Sunbirds (Anthobaphes violacea) and Sugarbirds (Promerops cafer), however their absence across the entire gradient is suggestive of high sensitivity. The functional diversity of this guild of pollinators can potentially be restored, but the pros and cons of this conservation action need to be considered.

The cost of being specialized: Pollinator limitation in the endangered geophyte Brunsvigia litoralis (Amaryllidaceae) in the Cape Floristic Region of South Africa

The impacts of habitat fragmentation and reduced population sizes on ecological processes deserve more attention. In this study we examine pollination in rural and urban populations of Brunsvigia litoralis (Amaryllidaceae), an endangered endemic and a flagship species for plant conservation in South Africa. B. litoralis has flowers conforming to the bird-pollination syndrome, but the only flower visitor at the urban sites, the Greater Double-collared Sunbird ( Cinnyris afra) (1.6 visits/flower/hour), is unable to access the nectar in the usual way due to a long perianth tube (38.8 mm) and resorts to robbing. Supplemental hand pollination was used to test for pollen limitation of seed set at the urban sites flowers were pollen-supplemented. Seed set in supplemented plants increased by more than an order of magnitude relative to controls. The longer-billed Malachite Sunbird ( Nectarinia famosa) was observed as the sole pollinator of B. litoralis at the rural site where seed set was significantly higher. Although B. litoralis plants are long lived, the absence of pollinators in these urban fragments might place populations at an extinction risk.

Nocturnal pectoral tuft display in the malachite sunbird

Diurnal birds generally sleep during the hours of darkness. Most male southern African sunbirds have pectoral tufts, although the function of these is not always understood. We examined nocturnal tuft display in male malachite sunbirds (Nectarinia famosa) and found that they display their pectoral tufts almost continuously throughout the night, whilst asleep. We suggest the possible function of this behaviour and suggest that these tufts might be a deterrent to predators, as they look like ‘eyes’ in the dark. A review of the use and occurrence of pectoral tufts in southern African sunbird species is also discussed. We suggest the ‘anti-predator’ hypothesis be investigated further.

Nocturnal Pectoral Tuft Display in the Malachite Sunbird

Diurnal birds generally sleep during the hours of darkness. Most male southern African sunbirds have pectoral tufts, although the function of these is not always understood. We examined nocturnal tuft display in male malachite sunbirds (Nectarinia famosa) and found that they display their pectoral tufts almost continuously throughout the night, whilst asleep. We suggest the possible function of this behaviour and suggest that these tufts might be a deterrent to predators, as they look like ‘eyes’ in the dark. A review of the use and occurrence of pectoral tufts in southern African sunbird species is also discussed. We suggest the ‘anti-predator’ hypothesis be investigated further.

Unexplained recurrent features of the plumage of birds

Unexplained recurrent features of the plumage of birds

Pollination of the red-hot poker Kniphofia laxiflora (Asphodelaceae) by sunbirds

Most of the species in the large African genus Kniphofia have floral traits that conform to the bird pollination syndrome, however there has been very little empirical work to confirm that birds are effective pollinators of Kniphofia species. From selective exclusion experiments, behavioural observations and pollen load analyses, we identified Amethyst Sunbirds ( Chalcomitra amethystina) and Malachite Sunbirds ( Nectarinia famosa) as the primary pollinators in two populations of Kniphofia laxiflora, with bees playing a smaller role. Bird visitors obtain moderate volumes (∼ 9 µl) of relatively concentrated (∼ 15%) hexose-rich nectar in the flowers. This species is shown to be genetically self-incompatible, and thus reliant on pollinator visits for seed set. Although mountain pride butterflies ( Aeropetes tulbaghia) have been identified as important pollinators of this species at two other populations, they did not occur at the two populations we studied.

Concentration-dependent Sugar Preferences of the Malachite Sunbird (Nectarinia famosa)

ABSTRACT. Sugar-type preferences of nectarivores may be an important selective factor in the evolution of sugar composition in floral nectar. We investigated sugar preferences of the Malachite Sunbird (Nectarinia famosa), using experiments in which birds were offered paired choices between energetically equivalent solutions over a range of sugar concentrations. The birds preferred hexose at low (5%) concentration and sucrose at high (25%) concentration; they showed no preference at 10%, 15%, and 20% concentrations. The birds regulated energy intake by adjusting volumetric consumption, except on a 5% concentration diet, where they failed to maintain energy balance. They also exhibited a strong preference for concentrated solutions, given a choice between 10%, 15%, 20%, and 25% sucrose solutions. We discuss the significance of these results in terms of the nectar composition of sunbird-pollinated plants.

Hyper-specialization for long-billed bird pollination in a guild of South African plants: the Malachite Sunbird pollination syndrome

A large diversity of floral morphological types exists within the bird pollination syndrome in the Cape Floral Region of South Africa. Here we focus on species with tubular flowers and ask: “Do differences in tube length among plant species correspond to differences in bill length among the birds that serve as pollinators?” To answer this question, we observed 1669 bird–plant interactions at thirteen bird-pollinated plant species across a spectrum of tube lengths. Only three nectar feeding bird species pollinated the focal plant species. The relatively short-billed species were the Southern Double-collared Sunbird ( Cinnyris chalybea) and Orange-breasted Sunbird ( Anthobaphes violacea); the only long-billed species was the Malachite Sunbird ( Nectarinia famosa). We found that the groups of plant species pollinated by the long- and short-billed birds differed significantly in floral tube length. Short-billed sunbirds nevertheless often robbed long-tubed flowers by piercing the corolla, and there was a significant difference in floral tube length among those species that were robbed, and those that were pollinated by short-billed sunbirds. The presence of territorial Malachite Sunbirds depressed robbing rates by short-billed sunbirds at long-tubed flowers. In turn, the absence of Malachite Sunbirds from short-tubed plant species might be explained by the observed positive correlation between tube length and nectar volume. Together, these data suggest that there is a subset of the bird-pollinated plants at the Cape that are pollinated solely by the long-billed Malachite Sunbird, a pollination service irreplaceable by the more abundant, short-billed sunbird species. To extrapolate this finding to a greater subset of species in the Cape Floral Region, we measured flowers on herbarium specimens of all tubular putatively bird-pollinated plants. We find that floral tube length has a bimodal distribution with 37 Cape species potentially dependent on pollination by Malachite Sunbirds.