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Sunbirds play a major role in the pollination of Old World nectivorous plants. However, with the exception of the Cape Floristic Region there is a major knowledge gap around African nectivore interaction networks—a stark contrast from the abundance of neotropical hummingbird–plant networks. Here, we describe a sunbird pollen transfer network (PTN) which we use in conjunction with a sunbird flower visitation network (FVN) to explore levels of sunbird specialization within an Afromontane forest habitat. Both networks were generalized compared with similar‐sized hummingbird networks, reflecting the wide range of flower types visited, the generalist diet, and bill characteristics of sunbirds. Three sunbird species from the genus Cinnyris accounted for 85% of flower visits and 77% of all pollen transported. Of the 17 plant species across both networks, 15 are predominantly pollinated by insects while Anthonotha noldeae (Fabaceae–Caesalpinioideae) and Globimetula braunii (Loranthaceae) depend on sunbirds for seed set. Sunbird species average bill lengths varied between 14.5 mm (the variable sunbird) and 23.6 mm (the Green‐headed Sunbird), but, while more pollen was carried on longer bills, we found no evidence for a relationship between bill length and type of flower visited. Both networks were nested. Some specialization was observed in both networks although this does not appear to be driven much by sunbird–flower trait matching. Overall, our results suggest that in contrast to nectivores elsewhere, factors such as phenology and/or environment, rather than morphology, may play important roles in limiting potential sunbird–flower interactions and need further investigation.

Loss of local, effective pollinators may potentially limit plant reproductive success but the plant–pollinator interactions could be rescued if the plant does not reject other pollen vectors. Firmiana kwangsiensis H.H. Hsue (Malvaceae) is an endangered tree endemic to limestone areas in South China. Although its preservation status is listed as “critically endangered”, its reproductive ecology is little known. We compared floral visitors in three wild populations and one transplanted population. Such a comparison allows us to see whether the pollinator assemblage varies geographically and to examine the plasticity of plant–pollinator interactions, informing sustainable ex situ conservation. Our pollination experiments indicated that fruit/seed set in F. kwangsiensis largely depended on pollinator visits, and was greatly reduced under hand self‐pollination or exclusion of bird visits. Floral visitors included sunbirds, butterflies, and bees (honeybee and wasp) but their visitation frequency varied in the four populations. The sunbird Nectarinia jugularis was the major pollinator in the three wild populations, but was replaced by the other sunbird Aethopyga christinae in the ex situ population. This tree is showy, with orange‐red flowers blooming before the leaves emerge. The calyx tube accumulates a large volume of dilute nectar (sugar concentration was 9.5%) in the morning, rewarding sunbird pollinators. Our investigations indicated that sunbirds rather than insects served as a functional group of pollinators for this endangered species. Successful ex situ conservation of this type of plant needs to consider the availability of potential pollinators.

PREMISE OF THE STUDY Properties of floral nectar have been used to predict if a plant species is pollinated by birds. To see whether winter-flowering plants evolve nectar properties corresponding to bird pollinators, nectar properties of several Camellia species (including the golden-flowered tea), as well as the role of floral visitors as effective pollinators, were examined. METHODS Potential pollinators of Camellia petelotii were identified at different times of day and under various weather conditions. A bird exclusion experiment was used to compare the pollination effectiveness of birds and insects. Nectar sugar components (fructose, glucose, and sucrose) from C. petelotii growing wild and another seven Camellia species and 22 additional cultivars (all in cultivation) were examined by high-performance liquid chromatography (HPLC). KEY RESULTS The sunbird Aethopyga siparaja and honeybees were the most frequent floral visitors to C. petelotii. Honeybee visits were significantly reduced in cloudy/rainy weather. The fruit and seed set of flowers with birds excluded were reduced by 64%, indicating that bird pollination is significant. For the wild populations of C. petelotii, a bagged flower could secrete 157 μL nectar; this nectar has a low sugar concentration (19%) and is sucrose-dominant (87%). The eight Camellia species and 22 cultivars had an average sugar concentration of around 30% and a sucrose concentration of 80%, demonstrating sucrose-dominant nectar in Camellia species. CONCLUSIONS The nectar sugar composition of Camellia species was characterized by sucrose dominance. In addition, the large reduction in seed set when birds are excluded in the golden-flowered tea also supports the suggestion that these winter-flowering plants may have evolved with birds as significant pollinators.

The long-standing paradigm that pollination systems adapted to hovering birds evolved only in the New World was recently challenged by the discovery of hovering pollination by Old World specialized passerine pollinators. This raises the possibility that hovering pollination may evolve more easily than previously believed, given sufficient selective pressure on plant traits, on nectarivory, or both. We observed foraging behavior by the sunbird Cyanomitra oritis at flowers of the native Old World plant Impatiens sakeriana. We measured the length of pedicels and peduncles (PedPed length), which can make the flowers difficult to reach while the bird perches on the stem, and determined if it influenced sunbird hovering or perching at a flower. Detailed analyses of video recordings showed that sunbirds only hovered at flowers with a long PedPed, whereas they employed both foraging modes when an adequate perch was available. A hovering sunbird could deplete nectar in a shorter time than a perching one. The frequency of visits was not greater at flowers with longer PedPed or with more open I. sakeriana flowers in the vicinity. Our study provides evidence that sunbird behavior does not follow simple energetic models, and that some sunbird pollination systems in the Old World resemble highly specialized hummingbird systems in the New World much more than expected, especially the overall adaptation of the system to bird hovering.

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 Chasmanthe floribunda 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.

Hermaphroditism is the most common se xual system in plants, occurring in approximately 72% of angiosperms ( de Jong and Klinkhamer, 2006 ). Despite the success of hermaphroditism in angiosperms, hermaphrodites still need to overcome compro-mises in both the quality and quantity of seed production owing to the close spatial proximity of male and female reproductive organs ( Barrett and Harder, 1996 ). As a result, hermaphroditic plants have evolved various forms of self-incompatibility (SI) and they often separate male and female reproductive function in space and time to reduce selfi ng and promote outcrossing ( de Nettancourt 1997 ; de Jong and Klinkhamer, 2006 ). Despite this, there is still potential for interference between sex functions. The most widely studied form of reproductive interference is pollen discounting (a form of female interference with male function) which occurs in both self-compatible and self-incompatible taxa ( Kohn and Barrett, 1994 ; Harder and Barrett, 1995 ; Eckert, 2000 ; Fishman, 2000 ). A much less well-studied phenomenon is ovule discounting, a form of male interference with female function where ovules penetrated by self-pollen tubes fail to develop, thus reducing opportunities for seed production ( Aizen and Harder, 2007 ). Ovule discounting can be diffi cult to quantify in the fi eld ( Aizen and Harder, 2007 ) and has often been considered to arise solely from early acting inbreeding depression ( Eckert et al., 2010 ). However, it could also arise from ovarian (late-acting) self-incompatibility in which ovules are penetrated by tubes from self-pollen, but then fail to develop ( Seavey and Bawa, 1986 ). Compared with pollen discounting, ovule discounting has sel-dom been quantifi ed in natural populations ( Waser and Price, 1991 ; V aughton and Ramsey, 2010 ). In plants prone to ovule dis-counting, experimental removal of self-pollen by emasculation should increase seed set ( Vaughton and Ramsey, 2010 ), but the outcomes of emasculation can be complex because it can nega-tively affect the rate of pollinator visitation if pollen is used as a reward ( Duffy and Johnson, 2011 ). In this study we consider whether experimental emascula-tion affects seed production in the perennial hermaphrodite, Kniphofi a linearifolia Baker (Xanthorrhoeaceae, formerly Aspho- delaceae). Studies of related species in this lineage have shown that ovules penetrated by self-pollen tubes uniformly fail to de-velop seeds, which suggests either late-acting self-incompatibility or strong early inbreeding depression ( Naaborgh and Willemse, 1991 ; Hargreaves et al., 2012 ; S. D. Johnson, unpublished data). As

 Premise of the study: The showiness of fl displays is usually explained as an adaptation to attract pollinators. However, selection for less attractive displays imposed by non-pollinating agents, particularly herbivores, may balance pollinator-driven selection for highly visible infl orescences. We investigated whether infl orescence architecture, particularly the unusual groundlevel fl owering associated with a specialized bird perch in Babiana ringens may have originated, in part, as an adaptive response to mammalian herbivory.  Methods: We measured levels of herbivory by antelope in populations of B. hirsuta , the putative sister species of B. ringens , which possesses the likely ancestral form of infl orescence architecture. To test for position-dependent effects of herbivory on fl owers, we compared the herbivory rates and seed production of manipulated infl orescences in a fi eld experiment. We predicted that fl owers at the base of infl orescences would suffer less herbivory than those in apical positions.  Results: We found herbivore damage to flin 50% of naturally occurring B. hirsuta plants. Manipulated infl orescences with only basal fl owers, and consequently similar infl orescence architecture to B. ringens , experienced signifi cantly lower herbivory and higher seed set than infl orescences manipulated to have only apical fl owers.  Conclusions: Our results are consistent with the hypothesis that position-dependent herbivory on infl orescences could have played a role in the evolution of infl orescence design. More specifi cally, position-dependent herbivory may have selected for the loss of apical fl owers. Position-dependent herbivory may have contributed toward the evolution of a naked infl orescence axis, a structure that characterizes B. ringens and functions as a bird perch facilitating cross-pollination by sunbirds.

We investigated the mechanism of coexistence of the rare Amani Sunbird (Hedydipna pallidigastra) and the widespread Collared Sunbird (H. collaris), within Brachystegia woodland in the Arabuko-Sokoke Forest, Kenya. We compared how prey abundance and search strategies affect resource exploitation by the two species. We used foraging theory to direct our measures of feeding activities as influenced by sunbird species, tree species and foraging height. We evaluated invertebrate abundance among tree species at different heights within trees. The Collared Sunbird primarily used the understory, and the Amani Sunbird primarily used the upper-canopy. Overall, the rate of prey attacks per flight of the Amani Sunbird was 2.8 times greater than that of the Collared Sunbird. The Amani Sunbird, however, used increased search and attack rates in the understory compared with the mid- and upper-canopies, but the Collared Sunbird foraged similarly throughout all strata. We hypothesize that the increased foraging rate of the Amani in the understory reflects increased foraging costs due to interference from the Collared Sunbird in that stratum. Furthermore, the Collared Sunbird exploits rich patches by moving frequently from place to place. The Amani Sunbird forages slowly, with reduced travel rates, and with a greater number of prey captures within a patch. Arthropod density did not differ among the vegetative strata, but was higher in Brachystegia spiciformis and Hymenaea verrucosa than in six other tree species. We hypothesize that the Amani Sunbird appears dependent upon continued tall B. spiciformis trees within the canopy of the Arabuko-Sokoke Forest.

On the island of Lombok, Indonesia, three nectarivorous birds partially coexist: the two closely related and very similar Lichmera honeyeaters and a sunbird (Cinnyris jugularis). We investigated how these species segregated ecologically in areas where they coexisted by evaluating foraging visits and aggressive interactions at rich and poor nectar resources in different habitats (forest and open areas) along an altitudinal gradient (800–1600 m asl). The two honeyeaters were partially segregated by altitude. In the zone of overlap, Lichmera limbata dominated the richest forest resources, while Lichmera lombokia dominated the richest resources in open land. The sunbird, C. jugularis, was only observed in open habitats and mostly at poor resource patches. In the three-species community in open habitats a dominance hierarchy was apparent with L. lombokia as the superior species and C. jugularis as the inferior species. Studies on how segregated species interact in their transition zone can help us to understand interactions between otherwise ecologically segregated species.

The winter-flowering succulent Aloe marlothii provides nectar for many opportunistic avian nectarivores in southern African savannas. We assessed the importance of A. marlothii nectar sugar for opportunistic nectarivores by analysing temporal changes in stable carbon isotope ratios (δ 13 C) in the tissues of birds in Suikerbosrand Nature Reserve, South Africa. The blood of the 11 most common non-granivorous opportunistic nectarivores at our site was enriched in 13 C by 3.4 ± 1.5‰, during the flowering period of A. marlothii, reflecting the enriched crassulacean acid metabolism (CAM) isotopic signature of nectar (-12.6 ± 0.5‰). This relatively small contribution of A. marlothii nectar to assimilated carbon in whole blood contrasted with that of exhaled CO 2 in African Red-eyed Bulbuls Pycnonotus nigricans and Cape White-eyes Zosterops capensis. In both these species, the δ 13 C of breath samples was significantly enriched compared with blood and feathers, and closely resembled that of the nectar, revealing combustion of ingested nectar rather than assimilation. Although our analysis was complicated by the presence of C 4 grasses, whose δ 13 C values are similar to those of CAM photosynthesizers, when considered with previously published feeding observations our data reveal that opportunistic nectarivores feeding on A. marlothii nectar obtain a relatively small fraction of their assimilated carbon, but most of their metabolized carbon, from this seasonally available carbohydrate food resource. Because the δ 13 C values of insects associated with C 3 plants also became enriched during the flowering season, some insect-eating opportunistic nectarivores may have assimilated A. marlothii carbon indirectly from insects. This study highlights the importance of understanding isotopic routing when assessing the nutritional significance of specific dietary items to consumer communities.

The nectarivory of sunbirds in the Old World and hummingbirds in the New World evolved independently. While both groups are specialised in their feeding apparatuses, hummingbirds are moreover famous for their adaptations to sustained hovering flight. Recently, an example of a pollination system of the invasive plant Nicotiana glauca has been used to show that less adapted sunbirds also are frequently able to hover. Nevertheless, the question has remained why plants adapted to bird hovering pollination do not occur outside the New World. In this paper we show that the long-peduncle Cameroonian Impatiens sakeriana is not capable of autonomous selfing and can be pollinated only by two often hovering sunbirds, the Cameroon sunbird Cyanomitra oritis and the northern double-collared sunbird Cinnyris reichenowi. Our study revealed that this plant is highly specialised for pollination by C. oritis. Cinnyris reichenowi hovers less frequently and often thieves nectar by piercing the flower spur when perching. This study shows that pollination systems occurring in the Old World follow similar evolutionary trends as systems including hovering hummingbirds in the New World.

We review digestion and osmoregulation in the avian gut, with an emphasis on the ways these different functions might interact to support or constrain each other and the ways they support the functioning of the whole animal in its natural environment. Differences between birds and other vertebrates are highlighted because these differences may make birds excellent models for study and may suggest interesting directions for future research. At a given body size birds, compared with mammals, tend to eat more food but have less small intestine and retain food in their gastrointestinal tract (GIT) for shorter periods of time, despite generally higher mass-specific energy demands. On most foods, however, they are not less efficient at digestion, which begs the question how they compensate. Intestinal tissue-specific rates of enzymatic breakdown of substrates and rates of active transport do not appear higher in birds than in mammals, nor is there a demonstrated difference in the extent to which those rates can be modulated during acclimation to different feeding regimes (e.g. diet, relative intake level). One compensation appears to be more extensive reliance on passive nutrient absorption by the paracellular pathway, because the avian species studied so far exceed the mammalian species by a factor of at least two- to threefold in this regard. Undigested residues reach the hindgut, but there is little evidence that most wild birds recover microbial metabolites of nutritional significance (essential amino acids and vitamins) by re-ingestion of faeces, in contrast to many hindgut fermenting mammals and possibly poultry. In birds, there is some evidence for hindgut capacity to breakdown either microbial protein or protein that escapes the small intestine intact, freeing up essential amino acids, and there is considerable evidence for an amino acid absorptive capacity in the hindgut of both avian and mammalian hindgut fermenters. Birds, unlike mammals, do not excrete hyperosmotic urine (i.e. more than five times plasma osmotic concentration). Urine is mixed with digesta rather than directly eliminated, and so the avian gut plays a relatively more important role in water and salt regulation than in mammals. Responses to dehydration and high- and low-salt loads are reviewed. Intestinal absorption of ingested water is modulated to help achieve water balance in one species studied (a nectar-feeding sunbird), the first demonstration of this in any terrestrial vertebrate. In many wild avian species the size and digestive capacity of the GIT is increased or decreased by as much as 50% in response to nutritional challenges such as hyperphagia, food restriction or fasting. The coincident impacts of these changes on osmoregulatory or immune function of the gut are poorly understood.

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.

Summary Monthly mist-netting of low-flying forest birds was conducted in three lake-shore forests in southern Uganda from September 1970 to July 1972. It was found that the edge of the forest formed a distinct ecological barrier that was rarely crossed by species on either side of it. Catches were concentrated in the hours of daylight, in two peaks, a morning peak at 09.00 hrs and an afternoon peak at 16.00 hrs (sun-time) for all birds combined, although there were slight species differences. Most bird species were found to be sedentary in a fixed home-range, and covered lateral distances of up to c. 300 m. No movement between the different forests was recorded. The most common birds such as bulbuls were often caught at heights between 0·6 and 1·8 m above the ground, but the upper limit of their vertical range was not determined. It is suggested that the bi-modality of flight activity may be intrinsic, even though it may be correlated with such extrinsic factors as light and radiation. On a month to month basis, the numbers of birds caught reflected breeding and moult activity. This was best shown by the Pygmy Kingfisher, taken in higher numbers towards the end of the first rainy season when a majority of the birds caught were young and many birds were moulting the remiges. On the other hand higher numbers of Olive Sunbird were found during the second rainy season, again at a time corresponding to a general moulting of remiges. The bulbuls showed fluctuations in numbers caught that were matched by an equally fluctuating pattern of moult. The role of food as a possible limiting factor in bird breeding is discussed.

Summary Owing to the regular alternation of wet and dry seasons and to the relatively simple arrangement of vegetation zones, migration is a well-developed phenomenon in the northern tropics of Africa. Nigeria is well placed for its study. While a vast amount remains to be learned, a systematic treatment of the 672 Nigerian bird species shows that at least 126 of them are migrant. Species newly shown to be migratory include the sunbird Nectarinia pulchella, the bunting Fringillaria (Emberiza) tahapisi, and the sparrow Gymnoris (Petronia) dentata, and corroborative evidence is adduced for many more. New interpretations are placed on the movements of the bustard Neotis denhami, the Painted Snipe Rostratula benghalensis, and other species. Most families that are migrant in the temperate zone (e.g. storks, cuckoos, nightjars, hirundines) have several migrants among their tropical representatives, except flycatchers, thrushes, warblers and shrikes. Important tropical migrant families include the kingfishers and sunbirds. The following ecological correlates emerge: migration appears to be more important at lower than higher trophic levels in the ecosystem; only one primary lowland rain forest and one montane forest species migrate; 95% of African migrants in Nigeria inhabit the five savanna zones, where the 120 migrants comprise 28% of the avifauna; most savanna migrants cross one, two or three vegetation zone boundaries; few are restricted within a single zone or cross four boundaries; twice as many savanna species are eurytopic (habitat-tolerant) as stenotopic (habitat-tied), and twice the proportion of eurytopic as stenotopic species are migrant; the majority of migrants move so as to avoid the winter drought in northern Nigeria (insectivores being little affected) and also the heaviest summer rains in southern savannas; migration is initiated by climatic factors such as rains, dry desert winds, etc. Three to six Nigerian species cross the Equator, but the stork Anastomus lamelligerus is shown to breed in Nigeria and the Chad basin and may not be a trans-equatorial migrant. A quail, a crake, a coucal and five cuckoos have space-time distribution patterns (motograms) in Nigeria that suggest equatorial migration. Motograms figured for 60 species show great variation. Nearly all land-bird migrants move with the progression of the sun and the inter-tropical front, north in spring and south in autumn. The basic pattern is thus a summer wet-season range at higher latitude than the winter dry-season range, and specific patterns vary according to the absolute and relative latitudinal limits af each season, and to speed and dates of migration. Comparison of congeneric migrants having different breeding seasons or motogram patterns suggests that a specific migration pattern is fixed by ecological necessity, and reproduction occurs at that time in the year when the species is stationary longest. Breeding seasons may span migration periods, leading to two-stage early-rains migration in e.g. the kingfisher Halcyon leucocephala. Water-bird migrations are complicated by opportunist breeding and responses to floods and changing water levels in rivers. A few species move with the typical land-bird pattern; others concentrate at perennial marshes in arid northern savannas, and may disperse in all directions from the few west African breeding stations.

Summary The male Splendid Sunbird has only one song type, each note of which has a simple frequency/time profile. An analysis of the songs of males from several localities near Legon (5.63° N, 0.19° N) showed that there are clear-cut song dialects characterizing each population. Those parts of the song giving rise to dialects are the time interval between consecutive pairs of notes (the time interval pattern) and the frequency/time profile of each note. The dialects were preserved over a period of three years (the duration of the study) and there was little variation in the song of a ringed bird over a period of two months. The boundary between dialects is apparently quite sharp, occurring perhaps within a distance of 50 m. Marked geographical variation in the song occurs, and is expected because of the mosaic of dialects that presumably exist throughout the sunbird's range in southern Ghana. For dialects to be effective in keeping populations together, those characteristics of the song which give rise to dialects should be readily and quickly discerned and need not require a statistical demonstration. This condition holds for the song of the Splendid Sunbird. The results are compared with the ideas of Nottebohm (1964) and Thielcke (1969) on the maintenance and usefulness of song dialects.

Floral nectar is offered by plants to animals as a reward for pollination. While nectar is typically a clear liquid containing sugar and trace amounts of amino acids, colored nectar has evolved in several plant families. Here we explore the functional significance of the phenolic compounds that impart a dark brown color to the nectar of the South African succulent shrub Aloe vryheidensis. Flowers of this aloe are visited for their nectar by a suite of short-billed birds that are occasional nectarivores, including bulbuls, white-eyes, rock thrushes, and chats. Dark-capped Bulbuls were more likely to probe model flowers containing dark nectar than those containing clear nectar, suggesting a potential signaling function for dark nectar. However, the main effect of the phenolics appears to be to repel "unwanted" nectarivores that find their bitter taste unpalatable. Nectar-feeding honey bees and sunbirds are morphologically mismatched for pollinating A. vryheidensis flowers and strongly reject its nectar. However, the frugivorous and insectivorous birds that effectively pollinate this aloe are seemingly unaffected by the nectar's bitter taste. Thus the dark phenolic component of the nectar appears to function as a floral filter by attracting some animals visually and deterring others by its taste.

Rhynchanthus beesianus W. W. Smith (Zingiberaceae) is an epiphytic tropical ginger with a very conspicuous floral display, but almost no fruit set under field conditions. The reproductive ecology encompassing phenology, floral biology, and pollination and breeding systems was investigated in an evergreen broad-leaved forest in Yunnan Province, Southwest China. The flowers possess a typical bird pollination syndrome, but no effective pollinators were observed during 138 h of observation. Female Black-breasted Sunbird (Aethopyga saturata) and bumblebees visited R. beesianus regularly, but they all played roles as nectar robbers. No fruit was found in the bagging treatment, and fruit set following manual self-pollination ((57.55 ± 4.08)%) was comparable with cross-pollination ((64.32 ± 4.42)%), suggesting that R. beesianus is self-compatible but spontaneous self-pollination in this species does not occur. Seed set of open-pollination ((26.42 ± 3.11)%) was significantly lower than manual self-pollination ((73.41 ± 4.16)%) and cross-pollination ((75.56 ± 4.52)%), confirming that R. beesianus was dependent on animals for fertilization and suffered a serious pollinator-limitation. (Managing editor: Wei Wang)

The evolutionary origins of the morphological and taxonomic diversity of angiosperms is poorly known. We used the genus Melianthus to explore the diversification of the southern African flora. Melianthus comprises eight species, and a phylogeny based on one nuclear and two plastid genes, as well as a morphological data set, confirmed that the genus is monophyletic. The two earliest diverging lineages are found in relatively mesic habitats, whereas the two terminal clades (an eastern and a western clade), each with three species, favor more arid habitats. The eastern clade is largely restricted to the summer-rainfall parts of southern Africa, and the western clade is found in winter-rainfall region. Molecular dating indicates a mid-Tertiary origin of the genus, with diversification of the eastern and western clades coincident with the Late Miocene-Pliocene uplift of the Escarpment mountains and the establishment of summer aridity along the west coast. The remarkably complex flowers are indicative of sunbird pollination, but many smaller birds can also visit. Speciation may be the consequence of allopatric divergence into edaphic-climatic niches. Divergence in flower and inflorescence morphology might be in response to the divergent pressures for nectar conservation in arid regions coupled with the need for signaling to avian pollinators in generally shrubby vegetation.

1. The nectars of hummingbird- and passerine-pollinated plants differ in both sugar type and concentration. Firstly, hummingbird nectars tend to be more concentrated than passerine nectars. Secondly, sucrose dominates hummingbird nectars, whereas glucose and fructose (hexose sugars) are the prevalent sugars in nectar of almost half the passerine-pollinated plants. It has been commonly assumed that these differences can be attributed to selection pressure from birds, largely determined by avian sugar preferences and digestive physiology. 2. Intake and preferences of Whitebellied Sunbirds Nectarinia talatala (A. Smith) and Broadtailed Hummingbirds Selasphorusplatycercus (Swainson) were examined across a range of sucrose and equicaloric hexose solutions at two ambient temperatures. Hummingbird energy balance was not affected by sugar type. Sunbird energy balance was only influenced by sugar type on a very dilute diet (0.1 mol l-1 sucrose equivalents, 'SE'), when the birds ingested 12% more sucrose than hexoses. Sunbirds and hummingbirds showed similar patterns in sugar preferences. Sunbirds preferred hexoses when offered dilute diets (0.1 mol l-1 SE at 21°C) and showed slight preference for sucrose when offered more concentrated diets (significant at 0.75 mol l-1 SE). Hummingbirds showed slight (non-significant) hexose preference when offered a dilute diet (0.25 mol l-1 SE at 10°C), but, in contrast to previous findings, hummingbirds showed no significant sucrose preference. 3. Our findings for Whitebellied Sunbirds and Broadtailed Hummingbirds do not support an ornithocentric explanation for nectar composition. Plant physiology and opportunist nectar feeders may also be influencing nectar sugars. To further address this question we discuss methodological considerations for researchers investigating how avian preferences and physiology may affect nectar composition.

1. Avian nectarivores consume a simple food which is generally dilute, but may vary widely in concentration and thus in water content. 2. Energy intake over 24 h was investigated in the Whitebellied Sunbird Nectarinia talatala (A. Smith) (mean mass 9·3 ± 1·0 SD g, n = 7) fed a wide range of sucrose concentrations (0·07–2·5 m), with and without access to supplementary water. 3. On diet concentrations between 0·25 and 2·5 m sucrose, birds showed perfect compensatory feeding by adjusting volumetric intake to maintain constant energy intake. 4. However, reduced intake on the two lowest concentrations of 0·07 and 0·1 m meant that the birds could not meet their energetic requirements and lost mass. We propose that physiological constraints associated with ingestion of large volumes of preformed water restrict intake at these very low concentrations. 5. Drinking of supplementary water varied greatly among individuals, but increased as diet concentration increased. This free water consumption effectively diluted the most concentrated diets of 1·5–2·5 m sucrose to an average value of 1·05 m, thus providing an indirect assessment of the birds’ concentration preferences.

Male orange-tufted sunbirds (Nectarinia osea) exhibit distinct song dialects throughout Israel. Recently, two distinct local dialects with a sharp boundary were discovered in a small (1.5 km 2 ) urban neighborhood densely inhabited by 63 territorial sunbird pairs. We conducted playback experiments to determine song dialect discrimination capability by sunbird males in this neighborhood. Males of both dialects responded significantly more strongly to playback of their own dialect than to that of the adjacent dialect. In spite of the extreme proximity between the two dialect areas, we found no effect of distance to the neighboring dialect on the intensity of any the behavioral responses. We suggest that due to the complex acoustic properties of this urban neighborhood, sunbirds are extremely limited in the number of neighboring males they can assess to establish what the local song is. A stronger response to one’s own dialect is therefore expected, and we discuss how local dialects could be maintained via this mechanism regardless of the very small distances between territories and dialect populations.

Road traffic is one of the most pervasive forms of anthropogenic disturbance, but its impact on pollination, a potentially sensitive ecosystem process, has not been investigated. Such an assessment is needed in order to evaluate the potential for roadside verges to act as biodiversity refugia and corridors in otherwise transformed landscapes. Here, we document the impact of a two-lane tar road on pollination by birds in the Cape fynbos of South Africa.To do so, we developed a quick and widely applicable method of determining pollination rates in bird-pollinated members of the large genus Erica. Experiments with caged birds showed that the status of the anther ring (broken/perfect) indicated a sunbird visit with 92% accuracy, while field surveys confirmed anther ring status also serves as a proxy for pollen receipt to stigmas. Using this technique we determined pollination rate in Erica perspicua at three distances from the road (0-10, 20-30 and 40-50 m). After controlling for flower colour, robbing rate and plant density, significantly fewer anther rings were disturbed in close proximity to the road.The documented twofold decline in pollination along roadsides could have important implications for the way we view and manage road verges as refugia for species and ecological processes.

Sunbirds (Nectarinia spp.) feeding at the East African mint Leonotis nepetifolia en- counter great variations in the nectar contents of flowers blooming in dense fields. The dispersion patterns of nectar are attributable to nectar removal from some flowers by the sunbirds themselves in earlier foraging and also to intrinsic floral variations. The problem facing the foraging sunbird is to increase its foraging efficiency (net energy gain per unit time) by avoiding recently visited, empty flowers and by visiting flowers with greater than average nectar volumes. Sunbirds patterned their foraging in 3 major ways. First, they used initial flowers probed on an inflorescence as an assay of what the rest of the flowers in that inflorescence contained and they rejected inflorescences with little nectar. Such rejection increased nectar intake per flower by as much as 15%. Second, territorial sunbirds preferentially fed at unvisited inflorescences, increasing nectar intake 25% relative to random foraging. This was accomplished at least in part by foraging at different heights on successive foraging bouts. Third, flight distances to the next flower changed in response to immediate reward levels in some species but not in others. In general, sunbirds feeding at Leonotis responded less to reward levels by differential turning and movement than some other organisms, possibly reflecting different prey distributions or boundary constraints on their foraging.

SUMMARY Nectar-feeding of birds was recorded during a phenological study of the woody vegetation at Zaria in the Northern Guinea Savanna of Nigeria. Throughout the dry season when it is in a non-breeding state, the Scarlet-breasted Sunbird Nectarinia senegalensis concentrates on the ornithophilous plants which flower in an overlapping sequence, and exploits the smaller-flowered species less frequently. As the flowering of the ornithophilous species decreases at the end of the dry season, the range of other plants exploited increases but, in the early rains as the flowering of the indigenous plants tails off, the sunbird switches to ornamental exotics and the indigenous, shrubby parasite, Tapinanthus globiferus. The bird is more conspicuously insectivorous during the wet season when it breeds. The Pygmy Sunbird Anthreptes platura is a breeding, dry-season visitor which exploits a somewhat different range of small-flowered, mainly entomophilous species and some exotics but also takes nectar from those ornithophilous species it can exploit, as well as the chiropterophilous Parkia clappertoniana. The bulk of the breeding population leaves the district before the flowering of the indigenous plant tails off. The five other species of sunbird recorded in the district are either very rare residents or more numerous wet-season visitors and passage migrants for which records of nectar-feeding are too few to draw conclusions about seasonal changes but the wet-season visitors appear to rely on the garden exotics in the comparative absence of flowering indigenous plants. Nectar-feeding on Bombax costatum and Parkia clappertoniana, where nectar is readily accessible and present in relatively large quantities, was noted for IS species of non-nectariniid birds, some of which were regular visitors. Some examples of flower consumption probably related to nectar-feeding are also mentioned.

SUMMARY Nectarinia osea (Nectariniidae) is a bird that bores holes into mature Malvaviscus flowers. Experiments with cut-off styles from flowers, and grafting of styles onto buds, show that the protruding style is the effective stimulus for sunbirds to bore holes in the Malvaviscus flowers.

A series of 2- to 3-h observations of two breeding male Malachite Sunbirds (Nectarinia famosa) territorial at Aloe gramninicola flowers was made in the highlands of Kenya. Average time budgeting, and hence energy budgeting, varied little between males, but each male showed significant differences in time and energy budgeting with stage of the nesting cycle. Empirical regression equations were used to estimate the total energy intake from nectar and the average caloric intake per flower visited per observation period. Male 1 generally took in more energy from nectar than it spent during an observation period; Male 2 regularly took in somewhat less energy than it expended. Both males probably supplemented energy intake from nectar with energy from insects. Multiple regression analyses supported the idea that the percentage of time a male spent foraging was primarily a function of (1) the amount of energy obtained per flower on the average during the observation period, and (2) the amount of time and hence of energy that was spent in chasing other birds from the nectar sources being defended and from the vicinity of the female while she was nest-building. There was no relation between percent time foraging and (1) the ambient temperatures during the observation period, or (2) the amount of time spent in flight activities other than chases. It is suggested that these males made relatively short-term adjustments in their foraging time as a function of energy intake and to some extent expenditures. However, the relation of foraging time to chase time may reflect also the impact of intruders on the energy content of the territory of the male.

Different concentrations of a sucrose solution vary the courtship song and behaviour of the male yellow-bellied sunbird Nectarinia venusta- the duration of subsong, total singing duration, and the absolute number of full song phrases. With high concentrations the sunbird sings more full song phrases but less subsong during the courtship season than otherwise. The various effects are described.