Nectar Feeding Research Articles

Nectar-Feeding Behavior in the Mallee Ringneck, Barnardius zonarius barnardi.

Opportunistic nectarivory occurs in many avian lineages around the world. In order to understand the implications of this behavior to plant reproduction via pollination and to other nectarivores via competition, more thorough descriptions of opportunistic nectar-feeding behavior are necessary. We observed nectar feeding of the mallee ringneck, Barnardius zonarius barnardi, on flowers of the spotted emu bush, Eremophila maculata, in the temperate mallee of South Australia. Here, we describe the nectar-feeding behavior of B. zonarius barnardi and discuss the implications for competition with honeyeaters and the reproduction of E. maculata. We also compare the morphology of the feeding apparatus of B. zonarius barnardi with that of nectarivorous parrots, lorikeets and lories, to determine whether they share convergent morphological features to facilitate the consumption of nectar. Finally, we suggest avenues for future natural history work to better document opportunistic avian nectarivory in Australian ecosystems.

Upper bill bending as an adaptation for nectar feeding in hummingbirds.

Observations of maxillary (upper bill) bending in hummingbirds have been considered an optical illusion, yet a recent description of out-of-phase opening and closing between their bill base and tip suggests a genuine capacity for bill bending. We investigate bill kinematics during nectar feeding in six species of hummingbirds. We employed geometric morphometrics to identify bending zones and combined these data with measurements of bill flexural rigidity from micro-computed tomography scans to better understand the flexing mechanism. We found that the mandible remains in place throughout the licking cycle, while the maxilla undergoes significant shape deformation, such that the distal portion of the upper bill bends upwards. We propose that bill bending is a key component of the drinking mechanism in hummingbirds, allowing the coordination of bill function (distal wringing and basal expansion) and tongue function (raking/squeegeeing) during intra-oral transport. We present a fluid analysis that reveals a combination of pressure-driven (Poiseuille) and boundary-driven (Couette) flows, which have previously been thought to represent alternative drinking mechanisms. Bill bending allows for separation of the bill tips while maintaining a tightly closed middle section of the bill, enabling nectar exploitation in long and narrow flowers that can exclude less efficient pollinators.

Effect of gradual pollen presentation on pollination efficiency and reproduction of Vaccinium corymbosum Berkeley in two habitats

IntroductionGradual pollen presentation is a reproductive strategy for plants to improve the efficiency and accuracy of pollen export and acceptance as well as to promote outcrossing. Vaccinium corymbosum Berkeley has a typical mechanism of gradual pollen presentation.MethodsIn this study, we used indoor and outdoor observations to investigate the floral characteristics, pollination characteristics and breeding system of this species in open ground and greenhouse.ResultsThe results showed that the single white, inverted bell-shaped flower of V. corymbosum was able to effectively avoid the negative effects of rainfall, nectar dilution and pollen removal by wind, and improved pollen viability and the duration of stigma receptivity. The setting rate of ‘Northland’ is higher than open ground by artificial pollination in greenhouse, therefore, greenhouses are more suitable for ‘Northland’ reproduction. The gradual pollen presentation prolongs dispersal time, promotes pollinator participation in the pollination process, increases staminate fitness, and provides for nectar feeding by pollinators as well as pollen export. Bombus spp. and A. m. ligustica were effective pollinators in the open ground and greenhouse, and the pollination efficiency of Bombus spp. was higher than that of A. m. ligustica, and greenhouse pollination is more efficient than open ground. The coincidence of the peak period of pollinator visits with the period of highest pollen viability and optimal pollination of stigmas, as well as the high nectar production, could maximize the frequency of pollinator visits and increase the chances of successful pollination as well as the pollination efficiency.DiscussionTherefore, it is important to study the floral characteristics of V. corymbosum Berkeley and the mechanism of gradual pollen presentation in order to improve the pollination efficiency and promote the success of outcrossing, which can provide a theoretical basis for the breeding of V. corymbosum.

Fuel provisioning for pollen collection by solitary bee, Andrena taraxaci orienticola

Female solitary bees collect pollen for their brood at the expense of using sugars in the nectar as fuel for flight. When flowers provide both pollen and nectar, solitary bees can refuel from the flowers to sustain pollen foraging. However, not all flowers provide both pollen and nectar. This study investigates how females of the solitary bee Andrena taraxaci orienticola secure fuel to sustain pollen foraging when flowers provide scarce nectar. By using DNA barcoding, we identified the Japanese dandelion Taraxacum platycarpum as their primary food source. This dandelion produces almost no nectar in the early morning when female bees collect almost no nectar but collect substantial amounts of pollen. We also found that these bees leave the nest with significantly more nectar at the first flight of the day than at later flights. When we restricted their fuel load by preventing nectar feeding, significantly more females failed to collect pollen on the first flight of the following day. These results suggest females hold back some part of the nectar collected at the end of a day’s foraging and use it the following morning as fuel to sustain pollen foraging from flowers providing little nectar.

Nectar Feeding and Dearth Period Management in Indian Honey Bee <i>Apis cerana</i> (F)

There have been many attempts to reduce the loss of Indian honey bee Apis cerana (F) colonies during the dearth period by supplementing nectar feeding substitutes. An experiment on development and evaluation of nectar feeding substitutes was conducted at an apiary maintained at the Division of Entomology, SKUAST-K, Shalimar from July to September during 2020-21. Syrup containing apple juice, sugar and mixture of both were evaluated as a diet supplement to develop an efficient feeding substitute. These include: T1 - apple juice and sugar in the ratio of 1:1; T2 - apple juice and sugar in the ratio of 1.5:1; T3- apple juice alone and T4 - sugar syrup in the ratio of 1:1 and compared with T5 natural feeding to determine their impact on desirable attributes of colonies. A gradual increase in the colony performance index (CPI), space covered by eggs (sq cm), larvae (sq cm) and pupae (sq cm) was observed, which were maximum with apple juice and sugar in the ratio of 1.5:1 viz; CPI (13.28); space covered by eggs (204.25 sq cm); larvae (296.12 sq cm); pupae (484.41 sq cm). All parameters were found to be least in T5 (natural feeding). Thus, apple juice and sugar in the ratio of 1.5:1 (T2 ) was the best nectar feeding substitute.

Unveil the sugar diet and associated environmental compounds in the crop of the mosquito Culex pipiens

Culex pipiens (Linnaeus, 1758) mosquitoes search plant sources of sugars to cope with the energetic demand of various physiological processes. The crop as part of the digestive system is devoted to the storage of sugar-based meal obtained from various nectars sources. The profiling of sugars and metabolites in the Culex pipiens’ crop is scarce, and only few studies used Liquid Chromatography – Mass Spectrometry (LC-MS), which provides broad detection for biomonitoring environmental substances and even contaminants in the sugar diet of mosquitoes populations.Therefore, sugar and metabolite profiling were performed on crops obtained from mosquitoes exposed to plant nectar under laboratory or natural conditions by Ultra High-Performance LC-MS (UHPLC-MS). This method allowed us a precise quantitative and qualitative identification of sugar diet and associated environmental compounds in the crop of the mosquito C. pipiens. Under laboratory condition, mosquitoes were allowed to feed on either glucose solution, commercially-available flowers or field collected flowers. In addition, we collected mosquitoes from the field to compare those crop metabolomes with metabolome patterns occurring after nectar feeding in the lab.The sugar quantities and quality obtained from the crops of mosquitoes collected in the field were similar to those crops obtained from mosquitoes that fed on commercially-available flowers and from field collected flowers with a limit of detection of 10 μg/L for sucrose, glucose and sucrose. Next to sugar compounds, we identified 2 types of amino acids, 12 natural products, and 9 pesticides.Next to the diversity of sugar compounds, we could confirm that secondary metabolites and environmental pollutants are typically up taken from floral nectar sources by C. pipiens. The in-depth knowledge on mosquito–plant interactions may inspire the development and further optimization of mosquito trap systems and arboviral surveillance systems.

Effects of heavy metal pollution on population dynamics of another important pollinator insect group: Horseflies (Diptera: Tabanidae)

Horseflies represent important agents of pollination as well as other pollinator insects, like butterflies, bees and wasps. Horseflies belong to the genera Atylotus, Dasyramphis, Glaucops, Pangonius, Philoliche, Chrysops, Hybomitra, and Tabanus species are exclusive nectar feeders. Glucose, fructose and sucrose are major components of plant nectars which are used nourishing for developing eggs. Because of these features horseflies have a significant role in pollination of phanerogams. This study was conducted to investigate the effects of toxic heavy metals on the population dynamics of horsefly species. Monthly changes on the accumulation of heavy metals in the larval habitats of horsefly species were determined with Perkin Elmer Optical Spectrophotometer and also correlations between concentrations of heavy metals and population fluctuations of horse fly species were observed. The results demonstrated that lead, iron and cadmium have statistically important negative effects on the population dynamics of horsefly species.

Illuminating the Mysteries of the Smallest Birds: Hummingbird Population Health, Disease Ecology, and Genomics.

Hummingbirds share biologically distinctive traits: sustained hovering flight, the smallest bird body size, and high metabolic rates fueled partially by nectar feeding that provides pollination to plant species. Being insectivorous and sometimes serving as prey to larger birds, they fulfill additional important ecological roles. Hummingbird species evolved and radiated into nearly every habitat in the Americas, with a core of species diversity in South America. Population declines of some of their species are increasing their risk of extinction. Threats to population health and genetic diversity are just beginning to be identified, including diseases and hazards caused by humans. We review the disciplines of population health, disease ecology, and genomics as they relate to hummingbirds. We appraise knowledge gaps, causes of morbidity and mortality including disease, and threats to population viability. Finally, we highlight areas of research need and provide ideas for future studies aimed at facilitating hummingbird conservation.

Male-biased night foraging by bumblebees (Hymenoptera, Apidae, Bombus spp.) in Taiwan

Known nocturnal behaviors of bees in the superfamily Apoidea, including the genus Bombus, were almost exclusively of females. Here we report observations of active free-ranging male Bombus at night in the plant nursery of the Fushan Research Center, Taiwan, in April 2022. Nectar feeding by males at inflorescences was confirmed by tongue-licking in the absence of pollen collecting. The numbers of active female and male bumblebees during the daytime were close to equal. In contrast, only males were found to be active in the night. Our observations suggest that such nocturnal activity is facultative. This finding not only provides a rare case of nocturnal activity in free-ranging Bombus, but also demonstrates that such behaviors can vary between the sexes.

Fine structure of sensilla on the proboscis of the Indian Honey Bee Apis cerana indica Fabricius (Insecta: Hymenoptera: Apidae)

Honey bees feed on flowers from which they collect nectar and pollen and their mouth parts are designed for fluid-feedingfrom flowers. The proboscis consists of a ‘tongue’ that includes a long glossa and ends in a spoon-shaped labellum, labial palp, galea and mandibles. The sensilla on the proboscis assists in nectar feeding. A study of the chemosensory hairs on the proboscis was carried out in Apis cerana indica collected from apiaries at the foot of Western Ghats, India. Light- and scanning electron microscopy were employed. In addition, silver staining was carried out to distinguish different types of chemosensilla. The glossa has 60 sensilla chaetica that stain by silver nitrate technique. The length (110 μ), width (2 μ) and spacing of microtrichia on glossa and forked hairs on the labellum are suited for the collection of nectar due to viscosity and to reduce leakiness while feeding. The length of the glossa being short suggests that A. cerana indica feeds on small-sized flowers that are not tubular. The labial palp has sensilla chaetica A and sensilla chaetica B distinguished by their length and sensilla basiconica, all of which are silver nitrate-positive and thus chemosensory in nature. Distal galea has sensilla basiconica, sensilla chaetica A and B and sensilla coeloconica. The maxillary palp is a mechanosensory structure. The bulge on the galea near the maxillary palp has chemosensory sensilla chaetica. Mandibular hairs did not stain with silver and are hence mechanosensory. The sensilla on proboscis in A. cerana indica is comparable to mouth part sensilla in Apis mellifera and Apis florea. The position of the chemosensilla at different regions suggests their role in tasting nectar, detecting the flow of nectar, and the dimensions of the flower and pollen.

How do honeyeaters drink nectar?

We investigated the kinematics and biomechanics of nectar feeding in five species of honeyeater (Phylidonyris novaehollandiae, Acanthagenys rufogularis, Ptilotula penicillata, Certhionyx variegatus, Manorina flavigula). There is abundant information on honeyeater foraging behaviors and ecological relationships with plants, but there has never been an examination of their nectar-feeding from kinematic and biomechanical perspectives. We analyzed high-speed video of feeding in captive individuals to describe the kinematics of their nectar feeding, with specific focus on describing tongue movements and bill-tongue coordination, and to characterize the mechanism of nectar uptake in the tongue. We found clear interspecific variation in kinematics and tongue filling mechanics. Species varied in lick frequency, tongue velocity, and protrusion and retraction duration, which, in some cases, are relevant for differences in tongue filling mechanisms. We found support for the use of capillary filling in Certhionyx variegatus only. By contrast, Phylidonyris novaehollandiae, Acanthagenys rufogularis, Ptilotula penicillata, and Manorina flavigula employed a modified version of the expansive filling mechanism seen in hummingbirds, as there was dorsoventral expansion of the tongue body, even the portions that remain outside the nectar, once the tongue tip entered the nectar. All species use fluid trapping in the distal fimbriated portion of the tongue, which supports previous hypotheses describing the honeyeater tongue as a "paintbrush."

Monitoring resistance to methomyl and synergism in the non-target Musca domestica from cotton fields of Punjab and Sindh provinces, Pakistan

Insecticides are an integral part of most of the cropping systems worldwide; however, these usually exert negative impact on the environment and non-target insects as well. Non-target insects are prone to develop resistance to insecticides due to prolonged and repeated lethal and sublethal exposures. Musca domestica is a common non-target, pollinator and nectar feeder species in cotton ecosystem, besides its status as a public health pest in human habitations. In the present work, resistance to methomyl, one of the major insecticides used for cotton pest management, was assessed in 20 M. domestica strains from the major cotton producing areas of the Punjab and Sindh provinces of Pakistan. The results revealed that toxicity values of methomyl for Punjabi and Sindhi strains ranged from 28.07 to 136.16 µg fly−1 and 29.32 to 136.87 µg fly−1, respectively. Among Punjabi strains, D.G. Khan, Lodhran, Bahawalpur, Toba Tek Singh, Bahawalnagar, Rajanpur and Jhang strains exhibited very high levels of resistance (RR > 100) to methomyl; Bhakkar, Kasur, Vehari, Layyah, Muzaffargarh and R.Y. Khan showed high resistance (RR = 51–100 fold), while the Mianwali strain showed a moderate level of resistance to methomyl (RR = 36.45 fold). In case of Sindhi strains, very high levels of resistance (> 100 fold) were reported for Sukkar and Sanghar strains, high levels of resistance (RR 51–100 fold) for Khairpur, Jamshoro and Ghotki, and moderate resistance to methomyl (38.08 fold) in the Dadu strain. There was a significant synergism of methomyl toxicity in all field strains when methomyl bioassayed along with piperonyl butoxide (PBO) and S,S,S-tributylphosphorotrithioate (DEF) providing clues of metabolic-based mechanisms of resistance to methomyl. In conclusion, insecticides used in crop farming can cause resistance development in non-target M. domestica. It is necessary to adopt the pest management activities that are safe for the environment and non-target insect species.

Nectar feeding beyond the tongue: hummingbirds drink using phase-shifted bill opening, flexible tongue flaps and wringing at the tips.

Hummingbirds are the most speciose group of vertebrate nectarivores and exhibit striking bill variation in association with their floral food sources. To explicitly link comparative feeding biomechanics to hummingbird ecology, deciphering how they move nectar from the tongue to the throat is as important as understanding how this liquid is collected. We employed synced, orthogonally positioned, high-speed cameras to describe the bill movements, and backlight filming to track tongue and nectar displacements intraorally. We reveal that the tongue base plays a central role in fluid handling, and that the bill is neither just a passive vehicle taking the tongue inside the flower nor a static tube for the nectar to flow into the throat. Instead, we show that the bill is actually a dynamic device with an unexpected pattern of opening and closing of its tip and base. We describe three complementary mechanisms: (1) distal wringing: the tongue is wrung out as soon as it is retracted and upon protrusion, near the bill tip where the intraoral capacity is decreased when the bill tips are closed; (2) tongue raking: the nectar filling the intraoral cavity is moved mouthwards by the tongue base, leveraging flexible flaps, upon retraction; (3) basal expansion: as more nectar is released into the oral cavity, the bill base is open (phase-shifted from the tip opening), increasing the intraoral capacity to facilitate nectar flow towards the throat.

Sugar Detection in Mosquitoes via Anthrone Tests.

Adult mosquitoes feed on plant sugar, frequently in the form of floral nectar. However, because of spatial and temporal variation in this behavior, as well as to the predilection of most mosquitoes to alter their behavior in the presence of a researcher, observing mosquito nectar feeding and similar behaviors directly in real time is not always feasible. In this protocol, I describe methods for hot and cold anthrone tests, which can be used to quantify the degree to which mosquito sugar feeding occurs in nature.

Hummingbird community structure and nectar resources modulate the response of interspecific competition to forest conversion

On-going land-use change has profound impacts on biodiversity by filtering species that cannot survive in disturbed landscapes and potentially altering biotic interactions. In particular, how land-use change reshapes biotic interactions remains an open question. Here, we used selectivity experiments with nectar feeders in natural and converted forests to test the direct and indirect effects of land-use change on resource competition in Andean hummingbirds along an elevational gradient. Selectivity was defined as the time hummingbirds spent at high resource feeders when feeders with both low and high resource values were offered in the presence of other hummingbird species. Selectivity approximates the outcome of interspecific competition (i.e., the resource intake across competing species); in the absence of competition, birds should exhibit higher selectivity. We evaluated the indirect effect of forest conversion on selectivity, as mediated by morphological dissimilarity and flower resource abundance, using structural equation models. We found that forest conversion influenced selectivity at low and mid-elevations, but the influence of morphological dissimilarity and resource availability on selectivity varied between these elevations. At mid-elevation, selectivity was more influenced by the presence of morphologically similar competitors than by resource abundance while at low-elevation resource abundance was a more important predictor of selectivity. Our results suggest that selectivity is influenced by forest conversion, but that the drivers of these changes vary across elevation, highlighting the importance of considering context-dependent variation in the composition of resources and competitors when studying competition.

Variable evidence for convergence in morphology and function across avian nectarivores.

Nectar-feeding birds provide an excellent system in which to examine form-function relationships over evolutionary time. There are many independent origins of nectarivory in birds, and nectar feeding is a lifestyle with many inherent biophysical constraints. We review the morphology and function of the feeding apparatus, the locomotor apparatus, and the digestive and renal systems across avian nectarivores with the goals of synthesizing available information and identifying the extent to which different aspects of anatomy have morphologically and functionally converged. In doing so, we have systematically tabulated the occurrence of putative adaptations to nectarivory across birds and created what is, to our knowledge, the first comprehensive summary of adaptations to nectarivory across body systems and taxa. We also provide the first phylogenetically informed estimate of the number of times nectarivory has evolved within Aves. Based on this synthesis of existing knowledge, we identify current knowledge gaps and provide suggestions for future research questions and methods of data collection that will increase our understanding of the distribution of adaptations across bodily systems and taxa, and the relationship between those adaptations and ecological and evolutionary factors. We hope that this synthesis will serve as a landmark for the current state of the field, prompting investigators to begin collecting new data and addressing questions that have heretofore been impossible to answer about the ecology, evolution, and functional morphology of avian nectarivory.

Biomechanics of nectar feeding explain flower orientation in plants pollinated by long-proboscid flies.

The function of flower orientation is much debated, with adaptation to pollinator mouthparts being a particularly compelling explanation, but also one that has lacked empirical support from broad-scale comparative studies. The two families of long-proboscid fly pollinators show similar hovering behaviour while feeding on nectar but differ in the biomechanics of their proboscides which can be up to 80mm in length: Tabanidae have a fixed forward-pointing proboscis while Nemestrinidae can swivel their proboscis downwards. We predicted that this difference has implications for the evolution of flower orientation. We established the flower angles of 156 South African plant species specialised for pollination by long-proboscid flies. Using a phylogenetically corrected analysis, we found that flowers pollinated by Tabanidae tend to be horizontally orientated, while those pollinated by Nemestrinidae tend to be more variable in orientation and more often vertically orientated. These results confirm the importance of pollinator biomechanics for the evolution of floral traits and highlight a potential mechanism of reproductive isolation between sympatric plant species pollinated by different long-proboscid fly families.

The impacts of seasonal variation and climate on food utilization in a population of critically endangered cotton-top tamarins (Saguinus oedipus) in Colombia: A 22-year longitudinal study.

To examine how precipitation patterns and climate change impact feeding choices made by a population of critically endangered cotton-top tamarins (Saguinus oedipus), we examined 22 years of feeding data (1999-2020) from 21 groups collected at Parque Natural Regional Bosque Seco El Ceibal Mono Tití in Santa Catalina, Colombia. We describe the diet and examine the role of seasonal rainfall and annual variation in rainfall on diet. Rainfall is highly seasonal (mean annual rainfall 1562 mm [range 940-2680 mm]) with a dry, early rainy, and late rainy season in each year. Over 80 species of plants formed part of the fruit, nectar, and exudate components of the diet. Fruits, although available year-round, were more commonly available and consumed during the late rainy seasons (August-November). Exudates were consumed more frequently in the dry season (December-March) and invertebrate consumption was stable across the year. Nectar feeding from a single species (Combretum fruticosum) peaked in November. Rainfall varied over the years, with 13 years exceeding the 99% confidence intervals for mean rainfall. Ten of these extreme years (both drought and extremely wet) occurred in the last 11 years. Fruit consumption did not vary between extreme and average years, but cotton-top tamarins consumed more invertebrates and exudates in wet years. Presently, cotton-top tamarins appear to be able to cope with these extreme variations in rainfall due to their highly varied diet. However, the forests that these primates depend upon for survival are threatened by human exploitation making it critically important to maintain a generalist feeding strategy for survival as many fruiting trees that compose a large proportion of the diet are removed. As conservation efforts continue, plant species consumed by cotton-top tamarins provide useful data when selecting species for habitat restoration programs.

Methods to Assess Blood and Nectar Meals in Aedes aegypti Mosquitoes.

Male and female Aedes aegypti mosquitoes survive by feeding on floral nectar for metabolic energy, but females require blood protein, obtained from biting a host, for egg development. Although males exclusively derive energy from nectar sugars, females must select the meal that best matches their present metabolic and reproductive needs. In females, blood and nectar promote independent feeding behaviors with distinct sensory appendages, meal sizes, digestive tract targets, and metabolic fates. Understanding how male and female mosquitoes recognize, locate, and metabolize nutrients is essential for characterizing the survival and reproductive capabilities of this mosquito. Here, we provide an introduction to blood versus nectar feeding and methods to quantify nectar and blood meal sizes in individual Ae. aegypti mosquitoes. Precise quantification of meal size is crucial for ensuring consistency in assays that record events downstream of feeding behavior, including host attraction or fecundity.

Dying for love: Illegal international trade in hummingbird love charms

AbstractHummingbirds (family Trochilidae) are among the most recognizable groups of birds, due to their tiny size, supremely maneuverable flight, and iridescent plumage. They are essential pollinators in ecosystems throughout the New World, and are welcome visitors to gardens and nectar feeders in every corner of the United States. Despite this familiarity, few people are aware that hummingbirds are the objects of active illegal international trade. The practice of incorporating the bodies of hummingbirds in love charms, known aschuparrosacharms, is a centuries‐old tradition in Mexico. The practice has now spread to the United States. This report summarizes investigations of the hummingbird trade by the U.S. Fish and Wildlife Service from 2013 to 2021. A total of 905 hummingbird carcasses were recovered in these investigations, representing 22 different species, 18 of which are protected by the Migratory Bird Treaty Act. While it appears that all hummingbirds were killed and packaged in Mexico, many originated from migratory U.S. populations. The species most frequently identified inchuparrosaswas Ruby‐throated Hummingbird, which nests entirely in the United States and occurs in Mexico only in the non‐breeding season. Much remains to be learned about the dimensions of thechuparrosatrade, and its possible impacts on hummingbird populations.