Optimal foraging in bumblebees: Calculation of net rate of energy intake and optimal patch choice

To test many predictions of “optimal foraging theory” it is necessary to calculate the rate of net energy intake of a foraging animal. Equations are derived for the calculation of the rate of net energy intake of a foraging bumblebee. The assumptions that form the basis of these energy equations are discussed. As examples, the rates of net energy intake are calculated for Bombus flavifrons workers foraging on neighboring patches of Aconitum columbianum and Delphinium barbeyi. If the bumblebees forage optimally, their net rates of energy intake in the two patches should be equal. The observed rates are consistent with this hypothesis. The application of an optimality approach to pollination biology is briefly discussed.     

Optimal body size in bumblebees

Summary It is hypothesized that the body size of a bumblebee will be that size which maximizes its average net rate of energy intake while collecting nectar. A mathematical model is developed with the result that the net rate of energy intake of a nectar-collecting bumblebee is expressed as a function of the body size of the bumblebee. From this model the body size which maximizes the net rate of energy intake (i.e., optimal body size) is found (as the solution of an implicit equation). In this situation the advantage of large size is that larger bumblebees fly faster and hence take less flight time than smaller bumblebees. The disadvantage of larger size is greater energetic costs.The parameters of the model are estimated using data obtained from the foraging behavior of bumblebees on monkshood (Aconitum columbianum). The optimal body size is then calculated for workers of Bombus appositus which obtained almost all their nectar from monkshood. The observed and expected (i.e., optimal) body size are found to be close and not significantly different.The model also predicts that, from the bumblebee's point of view, there should be a positive correlation between the size of the bumblebee and the average amount of nectar obtained per flower. Evidence of this correlation is presented and the possible significance of the correlation from the plant's point of view is discussed. A possible extension of the model to general relationships between predator body size, prey size and prey density is discussed.     

The effect of sugar solution type,sugar concentration and viscosity on the imbibition and energy intake rate of bumblebees

Nectar is an essential resource for bumblebees and many other flower-visiting insects. The main constituents of nectar are sugars, which vary in both composition and concentration between plant species. We assessed the influence of sugar concentration, sugar solution viscosity and sugar solution composition on the imbibition and energy intake rate of bumblebees, Bombus impatiens Cresson (Hymenoptera: Apidae). To do this, we measured their rate of solution intake for 49 different sugar solution treatments, which varied in both sugar composition and concentration. In general, the imbibition rates of bumblebees were found to increase with increasing sugar concentration, probably due to their preference for high sugar concentrations, up to a concentration of 27% (w/w), at which point solutions reached a threshold viscosity of approximately 1.5–1.6 mPa.s. Above this threshold, the increasing viscosity of the solutions physically inhibited the imbibition rates of bees, and imbibition rate began to decrease as the concentration increased. Nevertheless, bumblebee energy intake rate increased with increasing concentration up to about 42–56%. Although we found that sugar solution composition had an impact on both imbibition and energy intake rate, its effect was not as straightforward as that of sugar concentration and viscosity.     

Optimal foraging in bumblebees: Hunting by expectation

The foraging behaviour literature contains three hypotheses concerned with hunting by expectation. These suggest possible rules animals use to decide when to leave particular feeding sites and search in other places for food. Predictions of the three hypotheses were tested experimentally by varying the quality of plants (amount and distribution of nectar) encountered by bumblebees (Bombus appositus). Results support only a rate expectation hypothesis. Bees left multiflowered plants when the amount of nectar found in the first flower was below a threshold volume. Bees stayed on plants if they received greater than the threshold volume. This threshold nectar volume is close to the amount predicted if a bee forages to maximize its rate of net energy intake.     

Estimating nest locations of bumblebee <Emphasis Type="Italic">Bombus ardens</Emphasis> from flower quality and distribution

The central-place forager in a social-insect colony, e.g., the bumblebee, has been expected to maximize its net rate of energy gain to increase the success of its colony. In addition to foraging behavior, the nest location is an important factor for the success of the colony. The bumblebee’s nest location would be affected by the spatial distribution of flowers and their food quality. In this study, we constructed a model to estimate bumblebee nest sites, using the net energy intake rate at available food sites for workers foraging from the nest site. We hypothesized that the probability of colony establishment at a site in coordinates (x, y) was high as the sum of the net energy intake rate I(x, y) increased. To obtain I(x, y), nectar standing crop, sugar concentration, and foraging time were measured for ten plant species in the study site covering 6.25 km². As available flowers changed seasonally, I(x, y) was calculated for three periods: the end of April, the beginning of May, and the middle of May. To verify our hypothesis, we compared the estimations in our model with the actual nest sites of Bombus ardens found in the beginning of May and June by means of tracking bumblebees. From the results, we considered that the net energy intake rate at mid-May might represent the probability of colony establishment, because it could affect colony persistence and reproductive success.     

Pollinator shift to managed honeybees enhances reproductive output in a bumblebee-pollinated plant

Introduced honeybees have had a large impact on native ecosystems by disrupting native plant–pollinator interactions. However, little is known of the effect of honeybees on reproduction of bumblebee-pollinated plants. Seasonal displacement of native bumblebees by introduced honeybees (Apis mellifera and A. cerana) was observed in Pedicularis densispica, endemic to Hengduan Mountains, China, providing an opportunity for honeybee presence/absence comparisons. Five-year field surveys were conducted in one frequently disturbed population at Yila Pasture (YP). We compared pollination effectiveness (combinations of visitation rate, efficiency in pollen transfer, and potential geitonogamy) between native and introduced managed bees. The total visitation rate of native bees and subsequent reproductive output decreased progressively, but honeybee introduction resulted in at least twofold increase in visitation and 70 % increase in seed set. In general, native bumblebees, which have larger bodies and longer proboscises and spent more time probing single flowers, were more efficient than honeybees in terms of pollen removal and pollen deposition during first visits to virgin flowers. Compared with bumblebees, honeybees visited markedly fewer flowers in sequence within individual plants, potentially reducing geitonogamous pollination. Our data highlight that introduced honeybees can provide pollination service in terms of both quantity and quality for P. densispica. We suggest honeybee introduction as an effective way to augment pollination of P. densispica at disturbed and isolated sites.     

Exploring the predation of UK bumblebees (Apidae, <Emphasis Type="Italic">Bombus</Emphasis> spp.) by the invasive pitcher plant <Emphasis Type="Italic">Sarracenia purpurea</Emphasis>: examining the effects of annual variation,seasonal variation,plant density and bumblebee gender

Invasive carnivorous plant species can impact the native invertebrate communities on which they prey. This article explores the predation of native UK bumblebees (Bombus spp.) by the invasive pitcher plant species Sarracenia purpurea and discusses the potential effect of S. purpurea on native bumblebees. Specifically, it evaluates whether the extent to which bumblebees are captured varies (i) over successive years, (ii) across June and July, (iii) with density of distribution of pitchers or (iv) with bumblebee gender. Pitcher contents were examined from an established population of Sarracenia purpurea growing in Dorset, UK. Results show that the total extent to which bumblebees were captured differed over the years 2012–2014 inclusive. A 1-year study in 2013 showed that more bumblebees were caught in July than in June and more bumblebees were captured when pitchers grew at high density. Results from 2013 also showed that more pitchers caught more than one bumblebee than would be expected based on a normal probability distribution and that this phenomenon affects female and male bumblebees equally. We discuss possible reasons for these results including that the bumblebees may be using S. purpurea as a resource. Further work is required to establish the exact underpinning mechanisms and the relative roles of plant and bumblebee behaviour within the relationship. Such interaction complexity may have consequences for consideration in invasive carnivorous plant management.     

Optimal foraging: Random movement by pollen collecting bumblebees

Summary Two bumblebee species, Bombus bifarius and B. flavifrons, forage randomly with respect to direction when gathering pollen on Potentilla gracilis. Bees avoid revisiting flowers by being able to differentiate recently visited from unvisited flowers. This recognition occurs while bees are flying over open flowers and appears to be a response to the amount of available pollen within flowers. Random foraging with respect to direction is the optimal strategy when the probability of flower revisitation is low. Bumblebees appear to be moving preferentially between nearest neighbors, again as predicted by foraging theory. This behavior causes the establishment of pollen patches in the P. gracilis population. Unlike other pollinators studied in similar situations, bumblebees on P. gracilis do not forage utilizing an area-restricted searching behavior. Because floral reward quality can be assessed at low cost by bees foraging on P. gracilis, their tendency to move to nearby flowers even after encountering a poor quality blossom apparently yields a higher rate of net energy intake than does area-restricted searching. The data indicate that bumblebees exhibit great plasticity in foraging behavior and that they are able to forage efficiently under a wide range of environmental conditions.     

A new mathematical model for combining growth and energy intake in animals: The case of the growing pig

A simultaneous model for analysis of net energy intake and growth curves is presented, viewing the animal's responses as a two dimensional outcome. The model is derived from four assumptions: (1) the intake is a quadratic function of metabolic weight; (2) the rate of body energy accretion represents the difference between intake and maintenance; (3) the relationship between body weight and body energy is allometric and (4) animal intrinsic variability affects the outcomes so the intake and growth trajectories are realizations of a stochastic process. Data on cumulated net energy intake and body weight measurements registered from weaning to maturity were available for 13 pigs. The model was fitted separately to 13 datasets. Furthermore, slaughter data obtained from 170 littermates was available for validation of the model. The parameters of the model were estimated by maximum likelihood within a stochastic state space model framework where a transform-both-sides approach was adopted to obtain constant variance. A suitable autocorrelation structure was generated by the stochastic process formulation. The pigs’ capacity for intake and growth were quantified by eight parameters: body weight at maximum rate of intake (149-281 kg); maximum rate of intake (25.7-35.7 MJ/day); metabolic body size exponent (fixed: 0.75); the daily maintenance requirement per kg metabolic body size (0.232-0.303 MJ/(day×kg^0.75)); reciprocal scaled energy density ; a dimensional exponent, θ₆ (0.730-0.867); coefficient for animal intrinsic variability in intake (0.120-0.248 MJ^0.5) and coefficient for animal intrinsic variability in growth (0.029-0.065 kg^0.5). Model parameter values for maintenance requirements and body energy gains were in good agreement with those obtained from slaughter data. In conclusion, the model provides biologically relevant parameter values, which cannot be derived by traditional analysis of growth and energy intake data.     

Optimal foraging in bumblebees and coevolution with their plants

Summary The aims of this paper were to consider the coevolution between bumblebee movement patterns within plants and various properties of the plants such as the spatial distribution of their flowers, and to determine the extent to which the bumblebees and the plants can be considered to be maximally adaptive or optimal. Attention was restricted to plants which have flowers arranged on vertical inflorescences and to the bumblebees which visit these plants.It was found that the bumblebees tend to commence foraging at the bottom of each infloresence, that they tend to move from one flower to the closest vertically higher flower, that they miss flowers as they move upwards and that they tend to leave each inflorescence before reaching the top. It was also found for the four common plant species considered that nectar abundance per flower decreases with flower height on an inflorescence, that the flowers with receptive stigmas are restricted to the bottoms of the inflorescences while the flowers shedding pollen occur above them, and that the flowers are arranged approximately in spirals on the inflorescences.The pattern of movements of the bumblebees and the various properties of the plants appear to represent coevolved adaptations. Furthermore the bumblebees' movement patterns appear to be optimal in the sense that they result in the maximum net rate of energy gain to the bumblebees. Further studies are necessary, however, to determine whether or not the plants can be considered to be optimal.An exception to the above scheme is provided by a plant which is quite uncommon in the study area. This plant also has flowers on vertical inflorescences and appears to be pollinated by bumblebees. However, while the pattern of movements of the bumblebees on this plant species are extremely similar to those on the four common species, this plant species exhibits quite different properties from the other four. Two possible explanations for this exception are presented.     

Plant Defenses and Predation Risk Differentially Shape Patterns of Consumption,Growth, and Digestive Efficiency in a Guild of Leaf-Chewing Insects

Herbivores are squeezed between the two omnipresent threats of variable food quality and natural enemy attack, but these two factors are not independent of one another. The mechanisms by which organisms navigate the dual challenges of foraging while avoiding predation are poorly understood. We tested the effects of plant defense and predation risk on herbivory in an assemblage of leaf-chewing insects on Solanum lycopersicum (tomato) that included two Solanaceae specialists (Manduca sexta and Leptinotarsa decemlineata) and one generalist (Trichoplusia ni). Defenses were altered using genetic manipulations of the jasmonate phytohormonal cascade, whereas predation risk was assessed by exposing herbivores to cues from the predaceous stink bug, Podisus maculiventris. Predation risk reduced herbivore food intake by an average of 29% relative to predator-free controls. Interestingly, this predator-mediated impact on foraging behavior largely attenuated when quantified in terms of individual growth rate. Only one of the three species experienced lower body weight under predation risk and the magnitude of this effect was small (17% reduction) compared with effects on foraging behavior. Manduca sexta larvae, compensated for their predator-induced reduction in food intake by more effectively converting leaf tissue to body mass. They also had higher whole-body lipid content when exposed to predators, suggesting that individuals convert energy to storage forms to draw upon when risk subsides. In accordance with expectations based on insect diet breadth, plant defenses tended to have a stronger impact on consumption and growth in the generalist than the two specialists. These data both confirm the ecological significance of predators in the foraging behavior of herbivorous prey and demonstrate how sophisticated compensatory mechanisms allow foragers to partially offset the detrimental effects of reduced food intake. The fact that these mechanisms operated across a wide range of plant resistance phenotypes suggests that compensation is not always constrained by reduced food quality.     

Empirical prediction of net splanchnic release of ketogenic nutrients,acetate, butyrate and β-hydroxybutyrate in ruminants: a meta-analysis

For energy feeding systems for ruminants to evolve towards a nutrient-based system, dietary energy supply has to be determined in terms of amount and nature of nutrients. The objective of this study was to establish response equations of the net hepatic flux and net splanchnic release of acetate, butyrate and β-hydroxybutyrate to changes in diet and animal profiles. A meta-analysis was applied on published data compiled from the FLuxes of nutrients across Organs and tissues in Ruminant Animals database, which pools the results from international publications on net splanchnic nutrient fluxes measured in multi-catheterized ruminants. Prediction variables were identified from current knowledge on digestion, hepatic and other tissue metabolism. Subsequently, physiological and other, more integrative, predictors were obtained. Models were established for intakes up to 41 g dry matter per kg BW per day and diets containing up to 70 g concentrate per 100 g dry matter. Models predicted the net hepatic fluxes or net splanchnic release of each nutrient from its net portal appearance and the animal profile. Corrections were applied to account for incomplete hepatic recovery of the blood flow marker, para-aminohippuric acid. Changes in net splanchnic release (mmol/kg BW per hour) could then be predicted by combining the previously published net portal appearance models and the present net hepatic fluxes models. The net splanchnic release of acetate and butyrate were thus predicted from the intake of ruminally fermented organic matter (RfOM) and the nature of RfOM (acetate: residual mean square error (RMSE)=0.18; butyrate: RMSE=0.01). The net splanchnic release of β-hydroxybutyrate was predicted from RfOM intake and the energy balance of the animals (RMSE=0.035), or from the net portal appearance of butyrate and the energy balance of the animals (RMSE=0.050). Models obtained were independent of ruminant species, and presented low interfering factors on the residuals, least square means or individual slopes. The model equations highlighted the importance of considering the physiological state of animals when predicting splanchnic metabolism. This work showed that it is possible to use simple predictors to accurately predict the amount and nature of ketogenic nutrients released towards peripheral tissues in both sheep and cattle at different physiological status. These results provide deeper insight into biological processes and will contribute to the development of improved tools for dietary formulation.     

Optimal foraging,plant density and the marginal value theorem

Summary The stochastic, discrete analogue of the marginal value theorem predicts that as the cost of moving between plants increases, bees should increase the percentage of the available flowers which they visit per plant. This prediction was tested using two populations of Polemonium foliosissimum and their primary pollinators Bombus flavifrons and B. bifarius. The results of these tests were equivocal. Bees did not perform exactly as the marginal value theorem predicted they should to maximize their rate of net energy intake. Instead of visiting more flowers per plant as movement costs increased bees were observed to alter their behavior in other ways in an attempt to maximize their rate of net energy intake. They were demonstrated to be flying randomly with respect to direction, flying short flight distances relative to the plant spacing distances encountered, flying predominately between nearest neighbor plants, and to be visiting flowers of other plant species while enroute from one P. foliosissimum flower to another P. foliosissimum flower. Such behavioral flexibility strongly implies that optimal foraging models which predict a shift in any particular behavior in response to environmental conditions are too simplistic to accurately predict foraging behavior.     

Fatty acid oxidation and fatty acid synthesis in energy restricted rats

The importance of fat oxidation and fatty acid synthesis were examined in rats fed approximately one half their ad libitum food intake for a period of 13 days followed by 7 days of ad libitum feeding (refed rats). This study was undertaken because previous reports demonstrated that refed rats rapidly accumulated body fat. Our results confirmed this observation: refed rats accrued body fat and body weight at rates that were approximately 3 times higher than controls. Evidence for a period of increased metabolic efficiency was demonstrated by measuring the net energy requirement for maintenance over the refeeding period: refed rats had a reduced metabolic rate during the period of energy restriction (approximately 30% lower than control) and this persisted up to 2 days after the reintroduction of ad libitum feeding. The major factor responsible for the rapid fat gain was a depressed rate of fatty acid oxidation. Calculations of protein and carbohydrate intake over the refeeding period showed that the simplest explanation for the decrease in fatty acid oxidation is fat sparing. This is possible because of the large increase in dietary carbohydrate and protein intake during the refeeding period when metabolic rates are still depressed. The increased carbohydrate and protein may adequately compensate for the increasing energy requirements of the ER rats over the refeeding period affording rats the luxury of storing the excess dietary fat energy.     

Feed intake patterns nor growth rates of pigs are affected by dietary resistant starch,despite marked differences in digestion

Current feed evaluation systems often assume that fermented starch (i.e. resistant starch (RS)) yields less energy than digested starch. However, growth rates of pigs fed low and high RS diets are often the same when feed is available ad libitum. This may be explained by its effect on digestive processes changing feeding behavior, and consequently energy utilization. This study aims to investigate the effect of RS on nutrient digestion and digesta passage rate in pigs, in combination with its effect on feeding behavior and growth performance under ad libitum conditions. In experiment 1, 20 male pigs (40 ± 2.82 kg) were fed diets containing either 50% waxy maize starch (low in RS (LRS)) or high-amylose maize starch (high in RS (HRS)), and soluble and insoluble indigestible markers. After 14 days of adaptation to the diets, pigs were fed hourly to reach steady state (6 h), dissected, and digesta were collected from eight segments. From the collected samples, nutrient digestion and passage rate of the solid and liquid digesta fraction were determined. In experiment 2, 288 pigs (80 ± 0.48 kg; sex ratio per pen 1 : 1; boar : gilt) were housed in groups of 6. Pigs were ad libitum-fed one of the experimental diets, and slaughtered at approximately 115 kg. Feed intake, growth and carcass parameters were measured. Ileal starch digestibility was greater for LRS-fed than for HRS-fed pigs (98.0% v. 74.0%; P < 0.001), where the additional undigested starch in HRS-fed pigs was fermented in the large intestine. No effects of RS on digesta passage rate of the solid or liquid digesta fraction and on feeding behavior were observed. Growth rate and feed intake did not differ between diets, whereas feed efficiency of HRS-fed pigs was 1%-unit higher than that of LRS-fed pigs (P = 0.041). The efficiency of feed used for carcass gain did not differ between diets indicating that the difference in feed efficiency was determined by the non-carcass fraction. Despite a 30% greater RS intake (of total starch) with HRS than with LRS, carcass gain and feed efficiency used for carcass gain were unaffected. RS did not affect digesta passage rate nor feeding behavior suggesting that the difference in energy intake between fermented and digested starch is compensated for post-absorptively. Our results indicate that the net energy value of fermented starch currently used in pig feed evaluation systems is underestimated and should be reconsidered.     

Bumblebee death associated with Tilia x europaea L

For more than six decades, bumblebee death, which mainly occurs in August, has been assumed to be associated with intake of presumed toxic nectar from linden trees (Tilia spp.), a hypothesis which has been sustained by observations of a significant number of dead bumblebees under these trees during their flowering season. Several theories exist in current literature to account for these observations. The nectar has been assumed to contain compound(s) toxic to the bumblebees including the monosaccharide mannose, which cannot be metabolized by bumblebees. The presence of toxic compounds such as the alkaloid nicotine or pesticides of anthropogenic origin has also been indicated. However, none of the above suggested compounds have hitherto been properly characterized from the nectar. In the current paper we report on characterization of the composition of nectar of linden trees, under which a significant number of dead bumblebees were observed. The structure determinations were performed by selective 1D TOCSY NMR and extensive applications of 2D NMR spectroscopy. The nectar of the linden flowers was readily available in significant amounts during the entire period when dead bumblebees were observed under these trees. The nectar only contained non-toxic sugars such as α-glucopyranose, β-glucopyranose, sucrose, fructose and minor amounts of xylose. The nectar did not contain mannose, nor alkaloids or pesticides. Initial toxicity studies using brine shrimp lethality assay showed that the nectar did not exhibit any toxic effects even at concentrations higher than 1 mg/ml dry weight, providing disproving evidence against the assumption of the nectar's toxic character.     

Estimation of the maintenance energy requirements,methane emissions and nitrogen utilization efficiency of two suckler cow genotypes

Seventeen non-lactating dairy-bred suckler cows (LF; Limousin×Holstein-Friesian) and 17 non-lactating beef composite breed suckler cows (ST; Stabiliser) were used to study enteric methane emissions and energy and nitrogen (N) utilization from grass silage diets. Cows were housed in cubicle accommodation for 17 days, and then moved to individual tie-stalls for an 8-day digestibility balance including a 2-day adaption followed by immediate transfer to an indirect, open-circuit, respiration calorimeters for 3 days with gaseous exchange recorded over the last two of these days. Grass silage was offered ad libitum once daily at 0900 h throughout the study. There were no significant differences (P>0.05) between the genotypes for energy intakes, energy outputs or energy use efficiency, or for methane emission rates (methane emissions per unit of dry matter intake or energy intake), or for N metabolism characteristics (N intake or N output in faeces or urine). Accordingly, the data for both cow genotypes were pooled and used to develop relationships between inputs and outputs. Regression of energy retention against ME intake (r²=0.52; P<0.001) indicated values for net energy requirements for maintenance of 0.386, 0.392 and 0.375 MJ/kg^0.75 for LF+ST, LF and ST respectively. Methane energy output was 0.066 of gross energy intake when the intercept was omitted from the linear equation (r²=0.59; P<0.001). There were positive linear relationships between N intake and N outputs in manure, and manure N accounted for 0.923 of the N intake. The present results provide approaches to predict maintenance energy requirement, methane emission and manure N output for suckler cows and further information is required to evaluate their application in a wide range of suckler production systems.     

光周期和高脂食物对雌性高山姬鼠能量代谢和产热的影响

为了研究光周期和高脂食物对小型哺乳动物能量代谢和产热的影响,将成年雌性高山姬鼠分别驯化于长光照低脂、高脂食物和短光照低脂、高脂食物条件下,7周后测定动物的体重、能量摄入、产热、身体组成、血清瘦素浓度以及体脂含量等参数。结果发现:1)短光照抑制体重增长,降低血清瘦素浓度,增加非颤抖性产热;2)高脂食物使摄入能减少,消化率和体脂含量提高,但未显著影响体重、基础代谢率、非颤抖性产热和血清瘦素浓度;3)血清瘦素浓度与摄入能不相关,但与体脂重量正相关。结果暗示:短光照下瘦素作用敏感性增加和产热能力增强,可能介导了抵抗高脂食物诱导的肥胖。在野外条件下,高山姬鼠能通过能量代谢和产热的适应性调节避免体重的过度增长,有利于降低捕食风险,增强生存能力。     

Focal Plant Observations as a Standardised Method for Pollinator Monitoring: Opportunities and Limitations for Mass Participation Citizen Science

BackgroundRecently there has been increasing focus on monitoring pollinating insects, due to concerns about their declines, and interest in the role of volunteers in monitoring pollinators, particularly bumblebees, via citizen science.

Methodology / Principal Findings

The Big Bumblebee Discovery was a one-year citizen science project run by a partnership of EDF Energy, the British Science Association and the Centre for Ecology & Hydrology which sought to assess the influence of the landscape at multiple scales on the diversity and abundance of bumblebees. Timed counts of bumblebees (Bombus spp.; identified to six colour groups) visiting focal plants of lavender (Lavendula spp.) were carried out by about 13 000 primary school children (7–11 years old) from over 4000 schools across the UK. 3948 reports were received totalling 26 868 bumblebees. We found that while the wider landscape type had no significant effect on reported bumblebee abundance, the local proximity to flowers had a significant effect (fewer bumblebees where other flowers were reported to be >5m away from the focal plant). However, the rate of mis-identifcation, revealed by photographs uploaded by participants and a photo-based quiz, was high.

Conclusions / Significance

Our citizen science results support recent research on the importance of local flocal resources on pollinator abundance. Timed counts of insects visiting a lure plant is potentially an effective approach for standardised pollinator monitoring, engaging a large number of participants with a simple protocol. However, the relatively high rate of mis-identifications (compared to reports from previous pollinator citizen science projects) highlights the importance of investing in resources to train volunteers. Also, to be a scientifically valid method for enquiry, citizen science data needs to be sufficiently high quality, so receiving supporting evidence (such as photographs) would allow this to be tested and for records to be verified.     

Honeyeater foraging: A test of optimal foraging theory

Honeyeaters (Meliphagidae) were observed foraging for nectar from Lambertia formosa inflorescences, each of which has seven flowers. The frequency distribution of numbers of flowers probed per visit to an inflorescence was found to be bimodal, with one peak at two and the other at seven. It is hypothesized that this frequency distribution results from a rule of departure from inflorescences that maximizes the net rate of energy gain. Patterns of nectar distribution were determined for a large sample of inflorescences. In addition the extent to which the honeyeaters re-probe flowers during a visit to an inflorescence was estimated. From these data and from field measurements of the times required by the honeyeaters to perform the various foraging behaviours, computer simulations of honeyeater foraging were constructed. These simulations led in turn to optimal frequency distributions of numbers of flowers probed per inflorescence that were bimodal but had peaks at 1 and 7 instead of 2 and 7. Although the observed and predicted behaviour were consequently similar, the difference between them was nevertheless significant. This difference could have been due to the birds' transient occupancy of the study area.