Nectar secretion dynamic links pollinator behavior to consequences for plant reproductive success in the ornithophilous mistletoe Psittacanthus robustus

The mistletoe Psittacanthus robustus was studied as a model to link flower phenology and nectar secretion strategy to pollinator behaviour and the reproductive consequences for the plant. The bright‐coloured flowers presented diurnal anthesis, opened asynchronously throughout the rainy season and produced copious dilute nectar as the main reward for pollinators. Most nectar was secreted just after flower opening, with little sugar replenishment after experimental removals. During the second day of anthesis in bagged flowers, the flowers quickly reabsorbed the offered nectar. Low values of nectar standing crop recorded in open flowers can be linked with high visitation rates by bird pollinators. Eight hummingbirds and two passerines were observed as potential pollinators. The most frequent flower visitors were the hummingbirds Eupetomena macroura and Colibri serrirostris, which actively defended flowering mistletoes. The spatial separation between anthers, stigma and nectar chamber promotes pollen deposition on flapping wings of hovering hummingbirds that usually probe many flowers per visit. Seed set did not differ between hand‐, self‐ and cross‐pollinated flowers, but these treatments set significantly more seeds than flowers naturally exposed to flower visitors. We suggest that the limitation observed in the reproductive success of this plant is not related to pollinator scarcity, but probably to the extreme frequency of visitation by territorial hummingbirds. We conclude that the costs and benefits of plant reproduction depend on the interaction strength between flowers and pollinators, and the assessment of nectar secretion dynamics, pollinator behaviour and plant breeding system allows clarification of the complexity of such associations.     

The Behavior and Interactions of Birds Visiting Erythrina fusca Flowers in the Colombian Amazon1

I observed 22 species of birds visiting flowering Erythrina fusca trees at Matamatá, Amazonas, Colombia. The large orange flowers of E. fusca are adapted for pollination by birds and are protected from illegitimate visits by a petal that covers the nectaries and anthers until displaced by a foraging bird. Experiments with flowers bagged to exclude potential pollinators demonstrated that the flowers do not open without assistance. At Matamatá, parrots are the most frequent visitors to flowering E. fusca, and two species, Dusky‐headed Parakeet (Aratinga weddellii) and Cobalt‐winged Parakeet (Brotogeris cyanoptera), appear to be the main pollinators. This is only the fourth report of Neotropical parrots acting as pollinating agents. At least five other parrot species fed on the nectar or flowers of E. fusca but destroyed the flowers in the process. Orange‐backed Troupials (Icterus jamacaii) were the only other species observed opening E. fusca flowers nondestructively and are likely to be pollinators. Hummingbirds were common visitors to E. fusca flowers and some species were found to carry E. fusca pollen; however, hummingbirds were unable to open the flowers themselves and relied on other visitors to open the flowers for them. The number of hummingbird visits to a flowering E. fusca tree was positively correlated with the number of visits by parrots and icterids, but not with the number of mature flowers, indicating that legitimate visitors facilitate access by hummingbirds.     

Breeding system of Macromeria viridiflora (Boraginaceae) and geographic variation in pollinator assemblages

This study explores the association between variation in pollinator type and flower size in Macromeria viridiflora (Boraginaceae) by studying the breeding system of the plant and the pollinator effectiveness of floral visitors. Studies were conducted at two sites where plants differ in flower size and floral visitors. Breeding system studies showed that while plants are self-compatible and occasionally produce seed autogamously, pollinators are important for reproductive success in the plants. However, plants are not pollinator-limited at these sites. Combining visitation rate and pollen deposition as measures of pollinator effectiveness, I found hummingbirds to be the most effective pollinators at both sites. Although hawkmoths also pollinate the flowers, they visit the flowers less frequently and, at one of the two sites, deposit less pollen. These results are consistent with the hypothesis that geographic variation in corolla size is the result of selection by different hummingbird species.     

The assembly of plants used as nectar sources by hummingbirds in a Cerrado area of Central Brazil

Studies on hummingbird–plant interactions commonly use a pollination approach emphasizing mutualistic relationships. But floral resources are often used opportunistically by these birds. Plant–pollinator assemblies and pollination sustainability will depend both on the well-adapted plants and other potential floral resources. The Cerrado, Neotropical savannas of Central Brazil, has ca. 7.5 % of its flora supposedly adapted to hummingbird pollination. But detailed information about flowers effectively used by hummingbirds at community level is still lacking. Hence, we recorded all plant species visited by hummingbirds, to determine how these nectariferous flowers were distributed in time and space in different plant formations of a Cerrado area, and also the hummingbird species that visit them. The study was conducted between March 2007 and December 2008 in the Panga Ecological Station. Data regarding flowering phenology, floral morphology and visitation were collected monthly. Forty-six nectariferous species from 39 genera and 17 families were recorded, most with annual flowering dynamics and tubular flowers. But only 21 species had a combination of traits fitting classic ornithophilous syndrome. For the remaining species hummingbird visitation was ascertained from observations at the study site or other sites in the region. Eight hummingbird species occurred in the area and were recorded visiting directly 36 plant species. The study area presented a relatively low number of ornithophilous plants, but a great habitat diversity and many non-ornithophilous plants that hummingbirds used as nectar sources. Therefore, in the studied Cerrado, the diversity of environments and nectariferous plants favour the maintenance of resident and migrant hummingbirds.     

Aechmea pectinata: a hummingbird-dependent bromeliad with inconspicuous flowers from the rainforest in south-eastern Brazil

The pollination biology of Aechmea pectinata (Bromeliaceae) was studied in a submontane rainforest in south-eastern Brazil. This species has a mainly clumped distribution and its aggregated individuals are likely to be clones. From October to January, during the flowering period, the distal third of its leaves becomes red. The inflorescence produces 1-15 flowers per day over a period of 20-25 d. The flowers are inconspicuous, greenish-white coloured, tubular shaped with a narrow opening, and the stigma is situated just above the anthers. Anthesis begins at 0400 h and flowers last for about 13 h. The highest nectar volume and sugar concentration occur between 0600 and 1000 h, and decrease throughout the day. Aechmea pectinata is self-incompatible and therefore pollinator-dependent. Hummingbirds are its main pollinators (about 90 % of the visits), visiting flowers mainly in the morning. There is a positive correlation between the number of hummingbird visits per inflorescence and the production of nectar, suggesting that the availability of this resource is important in attracting and maintaining visitors. The arrangement of the floral structures favours pollen deposition on the bill of the hummingbirds. Flowers in clumps promote hummingbird territoriality, and a consequence is self-pollination in a broader sense (geitonogamy) as individuals in assemblages are genetically close. However, trap-lining and intruding hummingbirds promote cross-pollination. These observations suggest that successful fruit set of A. pectinata depends on both the spatial distribution of its individuals and the interactions among hummingbirds.     

Flowering patterns of long-lived Heliconia inflorescences: implications for visiting and resident nectarivores

Summary Flowering patterns of four Heliconia (Heliconiaceae) species in Trinidad, West Indies were examined for their predictability and availability to the nectarivores that rely on Heliconia floral nectar. Principal flower visitors are trapling hermit hummingbirds; inflorescences are inhabited by nectarivorous hummingbird flower mites that move between inflorescences by riding in the hummingbirds' nares. Heliconia inflorescences flower for 40–200 days, providing long-term sources of copious nectar (30–60 l per flower), but each Heliconia flower lasts only a single day. As an inflorescence ages the interval increases between open flowers within a bract; wet-season inflorescences produce open flowers more slowly than dry-season conspecifics.Estimated daily energy expenditures for hermit hummingbirds demonstrate that slow production of short-lived open flowers plus low inflorescence density preclude territorial defense of Heliconia by the hermits. Heliconia flowering patterns are viewed as a means of (i) regulating reproductive investment by the plants through staggered flower production over long periods of time, and (ii) maintaining outcrossing by necessitating a traplining visitation pattern by its hummingbird pollinators. I suggest that Heliconia exhibit a two-tiered pollination system by using hermit hummingbirds primarily for outcrossing and using hummingbird flower mites primarily for self-pollination.     

A comparison of distances flown by different visitors to flowers of the same species

Summary The morphologically complex flowers of Delphinium nelsonii, D. barbeyi, and Ipomopsis aggregata are visited by a wide variety of animals. Visitors to each species range from small insects, such as worker bumblebees and solitary bees, to hummingbirds, and thus span roughly an order of magnitude in body mass and metabolic rate while flying; they also differ in type of food collected and in their efficacy as pollinators. Despite these differences, all the visitors to a given plant species fly similar, short distances between successively visited flowers and plants. There are no significant relationships between mean flight distance and metabolic rate or body mass among the visitors to any plant species. Thus there is no evidence that flight characteristics depend on anything as straightforward as whether flower visitors have high or low energetic requirements.     

Phenological patterns and pollination network structure in a Venezuelan páramo: a community-scale perspective on plant-animal interactions

ABSTRACT

Background: Little information is available about life history of páramo plants such as phenology and plant-animal interactions.

Aims: We analysed phenological patterns of flowering and characterised the structure of a plant-pollinator network in a Venezuelan páramo in order to identify key species in this ecosystem.

Methods: We counted the number of individuals with flowers of 76 native plant species and recorded their pollinators in 16 permanent plots between 3000 and 4200 m monthly for three years. We used this dataset to develop a plant-pollinator network, on which nine different metrics related to structural properties were calculated.

Results: The flowering of most species concentrated during the rainy season (between May and November), however some species have continuous flowering. The guild of floral visitors included hummingbirds, flower piercers, bumblebees, Diptera and Lepidoptera. The plant – flower visitor interaction network did not exhibit nestedness, but showed a significant specialization index (H2) and high values of functional complementarity.

Conclusions: Páramo plants have the capacity of maintaining a resident nectarivorus fauna (bumblebees and hummingbirds) because of continuous flower offer during the year. However, the plant – pollinator network identified could be very sensitive to the loss component species, owing to high levels of specialisation and functional complementarity.     

Does Invasion of Exotic Plants Promote Invasion of Exotic Flower Visitors? A Case Study from the Temperate Forests of the Southern Andes

Habitat disturbance, particularly of human origin, promotes the invasion of exotic plants, which in turn might foster the invasion of alien-interacting animals. Here we assess whether the invasion of exotic plants – mostly mediated by habitat disturbance – facilitates the invasion of exotic flower visitors in temperate forests of the southern Andes, Argentina. We recorded visit frequencies and the identity of visitors to the flowers of 15 native and 15 exotic plant species occurring in different highly disturbed and less disturbed habitats. We identified three alien flower visitors, the hymenopterans Apis mellifera, Bombus ruderatus, and Vespula germanica. We found significantly more visitation by exotic insects in disturbed habitats. This pattern was explained, at least in part, by the association between alien flower visitors and flowers of exotic plants, which occurred more frequently in disturbed habitats. However, this general pattern masked different responses between the two main alien flower visitors. Apis mellifera exploited almost exclusively the flowers of a subset of herbaceous exotic plants that thrive under disturbance, whereas B. ruderatus visited equally flowers of both exotic and native plants in both disturbed and undisturbed habitats. We did not find any strong evidence that flowers of exotic plants were more generalist than those of native plants, or that exotic flower visitors were more generalist than their native counterparts. Our results suggest that alien plant species could facilitate the invasion of at least some exotic flower visitors to disturbed habitats. Because flowering plants as well as flower visitors benefit from this mutualism, this association may enhance, through a positive feedback, successful establishment of both exotic partners.     

Pollinating birds differ in spectral sensitivity

Pollinating animals and their angiosperm hosts often show strong co-adaptation in traits that increase the likelihood of a successful transfer of pollen and nutrient rewards. One such adaptation is the reported colour difference caused by unequal distribution of anthocyanidin pigments amongst plant species visited by hummingbirds and passerines. This phenomenon has been suggested to reflect possible differences in the colour vision of these pollinating birds. The presence of any such difference in colour vision would arguably affect the ecological and evolutionary interactions between flowers and their visitors, accentuating differences in floral displays and attractiveness of plants to the favoured avian pollinators. We have tested for differences in colour vision, as indicated by the amino acid present at certain key positions in the short-wavelength-sensitive type 1 (SWS1) visual pigment opsin, between the major groups of pollinating birds: the non-passerine Trochilidae (hummingbirds), the passerine Meliphagidae (honeyeaters) and Nectariniidae (sunbirds) plus five other Passerida passerine families. The results reveal gross spectral sensitivity differences between hummingbirds and honeyeaters, on the one hand, and the Passerida species, on the other.     

Hummingbird avoidance of nectar-robbed plants: spatial location or visual cues

Broad-tailed and rufous hummingbirds avoid plants and flowers that have recently been visited by nectar-robbing bees. However, the cues the hummingbirds use to make such choices are not known. To determine the proximate cues hummingbirds use to avoid visiting nectar-robbed plants, I conducted multiple field experiments and one aviary study using the nectar-robbed, hummingbird-pollinated plant Ipomopsis aggregata . In the first field experiment, free-flying hummingbirds were presented with plants in which I manipulated nectar volume and the presence of nectar-robber holes. Hummingbirds visited significantly more plants with nectar and probed more available flowers on those plants, regardless of the presence of nectar-robber holes. Thus, I hypothesized that hummingbirds may avoid robbed plants based on their spatial memory of unrewarding plants and/or visual cues that nectar absence provides. In an aviary study, I removed spatial cues by re-randomizing the position of plants after each hummingbird-foraging bout, but hummingbirds still selected plants with nectar. Nectar may provide a visual cue in I. aggregata flowers because corollas are translucent, and nectar is visible through the side of the corolla. To determine if hummingbirds use this visual cue to avoid plants with no nectar, I masked corolla translucence in a field study by painting flowers with acrylic paint. Hummingbirds still visited significantly more plants with nectar and probed more flowers on those plants, whether or not the corollas were painted. These results suggest that hummingbirds use nectar as a proximate cue to locate and avoid non-rewarding, nectar-robbed plants, even in the absence of spatial cues and simple visual cues.     

Effects of the availability of floral resources and neighboring plants on nectar robbery in a specialized pollination system

Many plants pollinated by nectar-foraging animals have to maintain a balance between legitimate visitor attraction strategies and mechanisms that minimize illegitimate visits. This study investigated how floral display and neighboring species composition influences nectar robbing by hummingbirds in the tropical ornithophilous herb Heliconia spathocircinata. We tested the role of inflorescence display, flower abundance, and neighboring species in the reduction of nectar robbing in H. spathocircinata. Our results indicate that nectar robbing hummingbird activity was higher in moderately large inflorescence displays and that the frequency of nectar robbing in H. spathocircinata decreases with increased flower abundance and the presence of neighboring plant species. Neighboring non-ornithophilous plants decreased the frequency of nectar robbing in H. spathocircinata flowers to a greater extent than ornithophilous ones. These results suggest that nectar robbing hummingbirds are attracted to similar conditions that attract legitimate visitors and that spatial aggregation and mixed-species displays may represent a mechanism to dilute nectar robbing effects at an individual level.     

Reproductive ecology of distylous Palicourea Padifolia (Rubiaceae) in a tropical montane cloud forest. I. Hummingbirds' effectiveness as pollen vectors

The adaptiveness of distyly has been typically investigated in terms of its female function, specifically pollen receipt. However, pollen loads on stigmas can only provide moderate support for Darwin's hypothesis of the promotion of legitimate crosses. To determine the effectiveness of hummingbirds as pollen vectors between floral morphs and the consequences in terms of male (pollen transfer) and female function (pollen receipt) in Palicourea padifolia (Rubiaceae), floral visitors, their foraging modes, and temporal patterns of floral visitation were observed and documented. Differences in pollen and stigma morphology, pollen flow, rates of pollen deposition, and/or stigmatic pollen loads were then evaluated for their contribution toward differences in reproductive output between floral morphs. A pollination experiment with stuffed hummingbirds that varied in bill size was done to evaluate the contribution of bill variation toward differences between floral morphs in pollen receipt and pollen transfer and female reproductive output. Anthers of long-styled flowers contained significantly more and smaller pollen grains than those of short-styled flowers, independently of corolla and anther lengths. The shape and orientation of the stigma lobes differed between morphs and were significantly longer among short-styled flowers. Hummingbird visitation rates did not differ significantly between floral morphs, and foraging movements from focal plants towards neighboring plants were independent of floral morph. Stigmatic pollen loads under field conditions and those after controlled hummingbird visitation, along with rates of pollen accumulation through the day indicated that stigmas of short-styled flowers receive proportionately more legitimate (intermorph) pollen grains than did those of long-styled flowers. However, the species of hummingbird was marginally significant in explaining variation in pollen deposition on stigmas. Lastly, intermorph pollinations of P. padifolia resulted in significant differences in fruit production between floral morphs, independent of pollination treatment and pollinator species; short-styled flowers proportionately developed almost twice the number of fruits developed by long-styled flowers.     

An Assemblage of Hummingbird-pollinated Flowers in a Montane Forest in Southeastern Brazil

Relationships between ornithophilous flowers and hummingbirds have been little studied in southern South America, where hummingbird species richness is low. We studied an ornithophilous flower assemblage and the hummingbird pollinators in a montane forest in southeastern Brazil. Twenty-three native hummingbird-pollinated plant species in 21 genera and 14 families were observed. Bromeliaceae, Fabaceae, Gesneriaceae, and Lobeliaceae are represented by more than one species within the assemblage. Flower shapes vary from narrow tube to bowl-shape, but tubular flowers prevail. The variety of flower shapes and sizes results in diverse pollen placement on the body parts of hummingbird visitors, although pollen is deposited mostly on the bill. Sugar concentration in nectar averages 22.1%, and nectar volume per flower averages 16.9 μl. The plant populations bloom for one month to year-round, and their flowering approaches the steady-state pattern. Four flower subsets may be defined within the assemblage, each subset related to the bill size and foraging habits of the most frequent bird visitor. Of the six species of hummingbirds recorded at the study site, four are common and largely resident. The four hummingbirds differ in bill size, body mass, and favoured foraging sites, attributes which reflect their favoured flower subsets. One hermit and one trochiline hummingbird share most of the flower species they use, these two birds being the major pollinators within the flower assemblage. This montane forest community may be viewed as medium-rich in ornithophilous flower species and poor in hummingbird species.     

Hummingbird responses to gender-biased nectar production: are nectar biases maintained by natural or sexual selection?

Pollinators mediate the evolution of secondary floral traits through both natural and sexual selection. Gender-biased nectar, for example, could be maintained by one or both, depending on the interactions between plants and pollinators. Here, I investigate pollinator responses to gender-biased nectar using the dichogamous herb Chrysothemis friedrichsthaliana (Gesneriaceae) which produces more nectar during the male floral phase. Previous research showed that the hummingbird pollinator Phaethornis striigularis visited male-phase flowers more often than female-phase flowers, and multiple visits benefited male more than female fecundity. If sexual selection maintains male-biased rewards, hummingbirds should prefer more-rewarding flowers independent of floral gender. If, however, differential rewards are partially maintained through natural selection, hummingbirds should respond to asymmetry with visits that reduce geitonogamy, i.e. selfing and pollen discounting. In plants with male biases, these visit types include single-flower visits and movements from low to high rewards. To test these predictions, I manipulated nectar asymmetry between pairs of real or artificial flowers on plants and recorded foraging behaviour. I also assessed maternal costs of selfing using hand pollinations. For plants with real flowers, hummingbirds preferred more-rewarding flowers and male-phase morphology, the latter possibly owing to previous experience. At artificial arrays, hummingbirds responded to extreme reward asymmetry with increased single-flower visits; however, they moved from high to low rewards more often than low to high. Finally, selfed flowers did not produce inferior seeds. In summary, sexual selection, more so than geitonogamy avoidance, maintains nectar biases in C. friedrichsthaliana, in one of the clearest examples of sexual selection in plants, to date.     

Intraseasonal variation in pollination intensity and seed set in an alpine population of Ranunculus acris in southwestern Norway

I studied aspects of the pollination and reproduction ecology of an alpine population of the circurnpolar Ranunculus acris (Ranunculaceae) at Hardangervidda, southwest Norway Dipteran families, mainly Muscidae and Anthomyudae, were the most frequent flower visitors and pollinators A single visit by these insects resulted in a seed set of c 18% of the total potential Visitation rates were highest early m the flowering season The longevity of individual flowers of early flowering plants was c 3 d shorter than that of mid-season flowering individuals Insect pollinators moved short distances between flowers and they mostly visited near neighbour plants Expenments showed that Ranunculus acris was self-incompatible and thus dependent on insect visitation for seed production Early flowering individuals had a very high seed set relative to individuals flowering in mid- and late season, suggesting a strong selection pressure for early flowering in the population Seed production in this Ranunculus acris population seems to be limited by severe climatic conditions and a low pollination intensity     

Pollination ecology of Agave macroacantha (Agavaceae) in a Mexican tropical desert. I. Floral biology and pollination mechanisms

In a study of sexual reproduction in long-lived semelparous plants, we observed Agave macroacantha in the tropical desert of Tehuacán-Cuicatlán, Mexico, describing duration of flowering, flower phenology, and nectar production patterns. We also performed two manipulative experiments evaluating (a) the seed production efficiency of different crossing systems (selfing, cross-pollination, apomixis, and control), and (b) the effect of different pollinators (diurnal exposure to pollinators, nocturnal exposure, exclusion, and control) on the seeds produced. Flowering occurred from early May to late July and had a mean duration of 29 days in the individual rosettes. The flowers were protandrous; anthesis occurred in the afternoon of the third day after floral opening, and the pistils matured in the afternoon of the fifth day. The stigmas remained receptive from dusk to the following morning. Pollination was mostly allogamous. Nectar was produced principally during the night, from the first stages of floral aperture until the stigmas wilted and flowering ceased. The flowers were visited during the day by hymenoptera, butterflies, and hummingbirds and during the night by bats and moths. Only the nocturnal visitors, however, were successful pollinators. Agave macroacantha is extremely dependent on nocturnal pollinators for its reproductive success.     

Pollination Ecology and Effect of Nectar Removal in Macleania bullata (Ericaceae)1

The floral syndrome of Macleania bullataYeo (Ericaceae) reflects its adaptation to hummingbird pollination. Its flowers, however, are subject to high levels of nectar robbing. I examined the floral visitor assemblage of M. bullata in a tropical montane wet forest in southwestern Colombia, focusing on the behavior of the visitors. I also tested for the presence of nocturnal pollination and the effects of nectar removal on new nectar production. The principal floral visitors were the nectar robbing hummingbirds Ocreatus underwoodii (19.1% of visits) and Chlorostilbon mellisugus (18.9%). Only two species of long–billed hummingbirds visited the flowers of M. bullata as “legitimate” pollinators: Coeligena torquata (14.7% of visits) and Doryfera ludoviciae (14.3%). The remaining visits constituted nectar robbing by bees, butterflies, and other species of hummingbirds. Nocturnal pollination took place, although fruit set levels were 2.4 times higher when only diurnal pollination was allowed as opposed to exclusively nocturnal pollination. Nectar robbers removed floral nectar without pollinating the flower. Treatments of experimental nectar removal were carried out to examine if flowers synthesize more nectar after nectar removal. Nectar removal increased the total volume of nectar produced by each flower without affecting sugar concentration. Thus, nectar robbing can impose a high cost to the plants by forcing them to replace lost nectar.     

An exotic magnet plant alters pollinator abundance and behavior: a field test with a native mistletoe

Exotic species can threaten biodiversity by disrupting ecological interactions among native species. Highly-attractive exotic species can exert a ‘magnet effect’ by attracting native pollinators, which may have either competitive or facilitative effects on co-flowering native plants. However, those effects may be context-dependent. We used a mistletoe-hummingbird pollination system in the Valdivian rainforest (southern Chile) to test whether the exotic tree Eucalyptus globulus (a highly attractive species to pollinators) acts as a magnet species, affecting the co-flowering native mistletoe. We compared hummingbird abundance, visitation rates, and activity patterns between native forest and abandoned E. globulus plantations. We found that hummingbirds were more abundant and visited more flowers at the plantation irrespective of E. globulus flowering. We observed a significant change of pollinator activity at the native habitat during E. globulus flowering, as hummingbirds visited mistletoe flowers more frequently early in the morning at the plantations and in the afternoon at the native forests. Our results showed that E. globulus acts as an exotic magnet species and can alter pollinator abundance and behavior. Our findings demonstrate the importance of considering local- and landscape-scale processes to understand the effects of magnet species on native plants and suggest that magnet species may influence even highly-attractive plants.

     

The relative importance of birds and insects as pollinators of the New Zealand flora

Native birds may have been underestimated as pollinators of the New Zealand flora due to their early decline in abundance and diversity on the mainland. This paper reconsiders the relative importance of birds and insects as pollinators to eight native flowering plants, representing a range of pollination syndromes, on two offshore island refuges. Experimental manipulations were made on five of these plant species to assess the relative effectiveness of bird and insect visitors as pollinators. In addition, foraging behaviour and the respective morphologies of flowers and visitors were measured at all eight plants to identify the main pollinators. The experimental measures showed that percentage fruit set was significantly higher in flowers exposed to birds than flowers from which birds were excluded in all manipulated plants. The observational measures revealed that for six of the flowering species (Sophora microphylla, Vitex lucens, Pittosporum crassifolium, Pittosporum umbellatum, Pseudopanax arboreus and Dysoxylum spectabile) the endemic honeyeaters were most likely to meet the conditions necessary for successful pollination. For the remaining two species (Metrosideros excelsa and Geniostoma ligus trifolium) the contribution by honeyeaters and insects to pollination was equivalent. The results suggest that the role of the endemic honeyeaters in pollination of the New Zealand flora, and the subsequent regeneration of native forest ecosystems, should be important considerations in ecosystem management.