Bumblebee Habitat Research Articles

Unveiling of climate change-driven decline of suitable habitat for Himalayan bumblebees

Insect pollinators, especially bumblebees are rapidly declining from their natural habitat in the mountain and temperate regions of the world due to climate change and other anthropogenic activities. We still lack reliable information about the current and future habitat conditions of bumblebees in the Himalaya. In this study, we used the maximum entropy algorithm for SDM to look at current and future (in 2050 and 2070) suitable habitats for bumblebees in the Himalaya. We found that the habitat conditions in the Himalayan mountain range do not have a very promising future as suitable habitat for most species will decrease over the next 50 years. By 2050, less than 10% of the Himalayan area will remain a suitable habitat for about 72% of species, and by 2070 this number will be raised to 75%. During this time period, the existing suitable habitat of bumblebees will be declined but some species will find new suitable habitat which clearly indicates possibility of habitat range shift by Himalayan bumblebees. Overall, about 15% of the Himalayan region is currently highly suitable for bumblebees, which should be considered as priority areas for the conservation of these pollinators. Since suitable habitats for bumblebees lie between several countries, nations that share international borders in the Himalayan region should have international agreements for comprehensive pollinator diversity conservation to protect these indispensable ecosystem service providers.

Determining Minnesota bee species' distributions and phenologies with the help of participatory science.

The Minnesota Bee Atlas project contributed new information about bee distributions, phenologies, and community structure by mobilizing participatory science volunteers to document bees statewide. Volunteers submitted iNaturalist (©2016 California Academy of Sciences) photograph observations, monitored nest-traps for tunnel-nesting bees, and conducted roadside observational bumble bee surveys. By pairing research scientists and participatory science volunteers, we overcame geographic and temporal challenges to document the presence, phenologies, and abundances of species. Minnesota Bee Atlas project observations included new state records for Megachile inimica, Megachile frugalis, Megachile sculpturalis, Osmia georgica, Stelis permaculata, and Bombus nevadensis, nesting phenology for 17 species, a new documentation of bivoltinism for Megachile relativa in Minnesota, and over 500 observations of the endangered species Bombus affinis. We also expanded known ranges for 16 bee species compared with specimens available from the University of Minnesota (UMN) Insect Collection. Surveys with standardized effort across the state found ecological province associations for six tunnel-nesting species and lower bumble bee abundance in the Prairie Parkland ecological province than the Laurentian Mixed Forest or Eastern Broadleaf Forest ecological provinces, indicating potential benefit of a focus on bumble bee habitat management in the Prairie Parkland. Landcover analysis found associations for four tunnel-nesting species, as well as a possible association of B. affinis with developed areas. These data can inform management decisions affecting pollinator conservation and recovery of endangered species. By engaging over 2,500 project volunteers and other iNaturalist users, we also promoted conservation action for pollinators through our educational programs and interactions.

Positive impact of postfire environment on bumble bees not explained by habitat variables in a remote forested ecosystem.

Bumble bees are important pollinators in temperate forested regions where fire is a driving force for habitat change, and thus understanding how these insects respond to fire is critical. Previous work has shown bees are often positively affected by the postfire environment, with burned sites supporting greater bee abundance and diversity, and increased floral resources. The extent to which fire impacts variation in bumblebee site occupancy is not well-understood, especially in higher latitude regions with dense, primarily coniferous forests. Occupancy models are powerful tools for biodiversity analyses, as they separately estimate occupancy probability (likelihood that a species is present at a particular location) and detection probability (likelihood of observing a species when it is present). Using these models, we tested whether bumblebee site occupancy is higher in burned locations as a result of the increasein canopy openness, floral species richness, and floral abundance. We quantified the impact of fire, and associated habitat changes, on bumblebee species' occupancy in an area with high wildfire frequency in British Columbia, Canada. The burn status of a site was the only significant predictor for determining bumblebee occurrence (with burned sites having higher occupancy); floral resource availability and canopy openness only impacted detection probability (roughly, sample bias). These findings highlight the importance of controlling for the influence of habitat on species detection in pollinator studies and suggest that fire in this system changes the habitat for bumble bees in positive ways that extend beyond our measurements of differences in floral resources and canopy cover.

Bees in the six: Determinants of bumblebee habitat quality in urban landscapes.

With growing urbanization, it is becoming increasingly important to design cities in a manner that sustains and enhances biodiversity and ecosystem services. Native bees are critical pollinators that have experienced substantive declines over the past several decades. These declines have captured the attention of the public, particularly urbanites, prompting a large interest in protecting pollinators and their habitats in cities across North America and Europe. Unfortunately, we currently lack research about specific features of urban environments that can enhance the fitness of pollinators. We carried out an intensive study of Bombus impatiens, the Common Eastern Bumblebee, in the city of Toronto (Canada's largest city), to better understand landscape parameters that provide high‐quality habitat for this species and likely other generalist bees. We divided the city into 270 grid cells and sampled a large number of worker bees, which were then genotyped at twelve hypervariable microsatellite loci. The genetic data allowed us to quantify the effective number of colonies and foraging distance for bumblebees in our study area. We then asked how the city's landscape and human population demography and income are associated with the availability of high‐quality habitat for B. impatiens. Several aspects of Toronto's landscape influenced colony density and foraging range. Urbanization had a clear effect on both colony density and foraging distance of workers. On the other hand, functional (i.e., not cosmetic) green space was often associated with higher quality habitats for bumblebees. Our study suggests several planning strategies to enhance habitat quality for bumblebees and other pollinators in cities.

Bumble Bee (Bombus spp.) Abundance in New York Highway Roadsides across Levels of Roadside Mowing and Road Traffic

Bombus spp. (Bumble bees) face population declines, in part due to habitat loss. Roadside rights-of-way (ROWs) are potential habitats; however, they are highly disturbed due to roadside mowing and on-road traffic. We investigated whether these factors are associated with variation in abundance of bumble bees in highway roadside ROWs across New York State. We used sweep netting and photography along 30 highways with different mowing pattern (control, reduced) and traffic level (low, medium, high) treatments in 2019 and 2020. Very few bumble bees were observed (98% of n = 916 observations found 0). This result was potentially due to insufficient foraging plants or nesting areas. Further investigation is needed to understand how highway roadside ROWs can be high quality habitat for bumble bees.

Contrasting effects of land cover on nesting habitat use and reproductive output for bumble bees

AbstractUnderstanding habitat quality is central to understanding the distributions of species on the landscape, as well as to conserving and restoring at‐risk species. Although it is well known that many species require different resources throughout their life cycles, pollinator conservation efforts focus almost exclusively on forage resources. In this study, we evaluate nesting habitat for bumble bees by locating nests directly on the landscape. We compared colony density and colony reproductive output for Bombus impatiens, the common eastern bumble bee, across three different land cover types (hay fields, meadows, and forests). We also assessed nesting habitat associations for all Bombus nests located during surveys to tease apart species‐specific patterns of habitat use. We found that B. impatiens nested under the ground in two natural land cover types, forests, and meadows, but found no B. impatiens nests in hay fields. Though B. impatiens nested at similar densities in both meadows and forests, colonies in forests had much higher reproductive output. In contrast, B. griseocollis tended to nest on the surface of the ground and was almost always found in meadows. B. perplexis was the only species to nest in all three habitat types, including hay fields. For some bumble bee species in this system, meadows, the habitat type with abundant forage resources, may be sufficient to maintain them throughout their life cycles. However, B. impatiens might benefit from heterogeneous landscapes with forests and meadows. Results for B. impatiens emphasize the longstanding notion that habitat use is not always positively correlated with habitat quality (as measured by reproductive output). Our results also show that habitat selection by bumble bees at one spatial scale may be influenced by resources at other scales. Finally, we demonstrate the feasibility of direct nest searches for understanding bumble bee distribution and ecology.

Reduction in the potential distribution of bumble bees (Apidae:Bombus) in Mesoamerica under different climate change scenarios: Conservation implications

Bumble bees are an ecologically and economically important group of pollinating insects worldwide. Global climate change is predicted to affect bumble bee ecology including habitat suitability and geographic distribution. Our study aims to estimate the impact of projected climate change on 18 Mesoamerican bumble bee species. We used ecological niche modeling (ENM) using current and future climate emissions scenarios (representative concentration pathway 4.5, 6.0, and 8.5) and models (CCSM4, HadGEM2-AO, and MIROC-ESM-CHEM). Regardless of the scenario and model applied, our results suggest that all bumble bee species are predicted to undergo a reduction in their potential distribution and habitat suitability due to projected climate change. ENMs based on low emission scenarios predict a distribution loss ranging from 7% to 67% depending on the species for the year 2050. Furthermore, we discovered that the reduction of bumble bee geographic range shape will be more evident at the margins of their distribution. The reduction of suitable habitat is predicted to be accompanied by a 100-500m upslope change in altitude and 1-581km shift away from the current geographic centroid of a species' distribution. On average, protected natural areas in Mesoamerica cover ~14% of each species' current potential distribution, and this proportion is predicted to increase to ~23% in the high emission climate change scenarios. Our models predict that climate change will reduce Mesoamerican bumble bee habitat suitability, especially for rare species, by reducing their potential distribution ranges and suitability. The small proportion of current and future potential distribution falling in protected natural areas suggests that such areas will likely have marginal contribution to bumble bee habitat conservation. Our results have the capacity to inform stakeholders in designing effective landscape management for bumble bees, which may include developing restoration plans for montane pine oak forests habitats and native flowering plants.

One‐size does not fit all: at‐risk bumble bee habitat management requires species‐specific local and landscape considerations

AbstractDeclining bumble bees are threatened by habitat loss, pathogens and climate change. Despite policy and management recommendations to create pollinator habitat, the habitat requirements for at‐risk bumble bees remains unclear. Most studies on bumble bee habitat are descriptive, focus on floral resources, occur at one spatial scale, or do not examine at‐risk species.We provide the first thorough habitat description for two North American bumblebee species (Bombus terricolaandBombus pensylvanicus) at‐risk of extinction. We asked the following questions: (i) What characterisesB. terricolaandB. pensylvanicushabitat? (ii) Are landscape variables, local variables, or flowering plant species more important determinants of habitat? (iii) do important variables change throughout the season?Surveys were conducted at 25 sites with a recent occurrence of eitherB. terricola,B. pensylvanicus, or both species across southern Ontario, Canada. Landscape variables were extracted from a 1‐km buffer around each site. Local variables related to bumble bee resource requirements (floral, nesting and overwintering) and flowering species cover were measured in spring, mid‐summer, and late‐summer.We found that the proportion of different land cover classes at 1 km was a more important predictor ofB. terricolaandB. pennsylvanicuspresence than local transect based variables such as floral richness or the patchiness of floral cover. We did not find any evidence of important variables changing temporally, but floral resources were consistently important throughout the season. Our results highlight that management of at‐risk pollinator species requires consideration of species‐specific habitat requirements.

The queen is led? Bumblebee (Bombus spp.) nest-searching on sea wall banks may be influenced by cutting and sward height

English sea wall flood defences support an important grassland habitat for bumblebees (Bombus spp.). However, annual cutting in midsummer (July–August) could negatively affect them. The mowing regime on a sea wall at Goldhanger Creek in Essex was changed to a late cut (after 15 September) and nest-searching behaviour was compared with an adjacent sea wall cut in midsummer (normal cut in August). Sward height and the number of queens nest-searching were significantly higher on the normal cut sea wall than on the late cut one. Tall grass swards resulting from a cut early in the previous summer may be important for nest-searching compared to those mown late, although there is probably an interaction with sea wall aspect and soil type. The landward slope was also more attractive for nesting than the flat folding (berm) due to the longer vegetation where nests under construction were located (of Bombus humilis and B. terrestris).

Agricultural field margins provide food and nesting resources to bumble bees (Bombus spp., Hymenoptera: Apidae) in Southwestern Ontario, Canada

Abstract Bumble bees are declining globally, largely due to habitat loss driven by agricultural intensification. Within agriculturally dominated landscapes, semi‐natural habitats (e.g. meadows, wetland edges) are fragmented, increasing the value of uncropped agricultural field margins for providing a source of food, nesting, and hibernation resources to bumble bees. We compared bumble bee communities sampled in agricultural field margins and semi‐natural habitats across Southwestern Ontario, Canada in order to assess differences in habitat quality. We then examined the effect of floral resources and soil characteristics on the bumble bee communities present in each site, independent of the habitat type classification. Our data revealed that bumble bee abundance, diversity, and community composition did not differ between habitat types. However, when examined independently of habitat type, bumble bee abundance and diversity increased with floral abundance, floral diversity, the number of rodent holes, and sandy soil texture. These results suggest that agricultural field margins are not inherently degraded bumble bee habitat and have the potential to provide food and nesting resources comparable to semi‐natural habitats in a fragmented agricultural landscape. Ensuring field margins contain the necessary floral resources and soil characteristics for bumble bees has implications for conservation and mitigating habitat loss caused by the agricultural fields themselves.

The influence of garden flowers on pollinator visits to forest flowers: comparison of bumblebee habitat use between urban and natural areas

As garden plants in urbanized environments provide considerable diverse floral resources to pollinators, the availability of floral resources has changed as a consequence of increasing urbanization. Although pollinators often forage at different sites in response to spatiotemporal variations in floral resources, little is known about the differences in pollinator foraging between urban and nearby natural environments. We monitored the foraging patterns of bumblebees in open and forest habitats in two areas with and without urban gardens with respect to flowering phenology and the availability of floral resources in each habitat. Floral richness in the forest habitat decreased as the season progressed, with a peak in late spring to early summer, whereas floral resources in the open habitat increased late in the season. Thus, floral resources in the open habitat could compensate for seasonal declines in forest floral resources. In the urban area, which contained green gardens, floral richness in the open habitat was much greater than that in the forest habitat. This resulted in a relatively high density of bumblebees in the open habitat in the urban area compared with those in the natural area, which lacked green gardens. Visitation frequency of bumblebees to forest flowers decreased as the floral richness of the open habitat increased. These results suggest that although urban gardens are important foraging sites for pollinators, the high attractiveness of garden flowers reduces pollinator visits to wildflowers in nearby forests. This may result in reduced pollination of native flowers.

A systematic review of the nesting and overwintering habitat of bumble bees globally

Some bumble bee species are in decline globally. Declines have been attributed to many factors including habitat loss. Habitat is an integral component of any species and should be a central focus of conservation efforts to protect at risk species. However, the habitat of bumble bee species is not fully understood. We conducted a systematic review of the peer-reviewed literature using Web of Science to summarize articles that have described the habitat of bumble bee species. In total, 55 nesting and 10 overwintering habitat studies are described in this review. We described common patterns associated with bumble bee studies including overwintering habitat, landscape type, and ground position. We found that bumble bee nests are more frequently found underground and that studies were biased towards the United Kingdom and agricultural habitats. There are some preferences in nesting and overwintering habitat, but further research is needed to draw any substantial conclusions. Detection of nesting and overwintering site studies may be improved using citizen science initiatives and possibly through employing detection dogs or radio-telemetry. Increasing the detection of nesting and overwintering sites is an important priority to improve our understanding of bumble bee habitat. It is critical that we identify all aspects of bumble bee habitat to ensure the protection, restoration and creation of important resources to ensure their conservation.

The effect of mass-flowering orchards and semi-natural habitat on bumblebee colony performance

Bumblebees are important pollinators for agricultural crops and wild plants. However, agricultural intensification and loss of semi-natural habitat may have adverse effects on colony performance. While mass-flowering crops may serve as food sources, landscapes dominated by intensive agriculture may be a poor bumblebee habitat compared to landscapes dominated by semi-natural habitat, such as forests and species-rich grasslands. We investigated the effect of different land use classes on bumblebee colony performance at two periods of time during the flying season. We expected mass-flowering crops to have a positive influence on colony performance during flowering. After mass-flowering, presence of semi-natural habitat was hypothesized to be essential for colony development. We placed artificial colonies of Bombus terrestris in 28 apple and pear orchards during and after mass-flowering. We measured colony growth and took pollen samples from foraging workers. Causal relationships between land-use, pollen quality, amount of pollen collected and colony performance were analyzed. Contrary to our expectations, we found a negative correlation between orchard cover and amount of pollen collected in spring, during mass-flowering, resulting in a lower colony performance. During mass-flowering, colony performance and pollen diversity were positively correlated with cover of open semi-natural habitat, while after mass-flowering, colony performance was positively correlated with forest cover. After mass-flowering, pollen sources were more diverse and colony growth was related to land use classes at a larger spatial scale, indicating that bumblebees foraged further. We did not find a correlation between the performances of colonies at one specific site that were placed during and after mass-flowering. Landscapes dominated by mass-flowering orchards represent inferior habitats for bumblebees during flowering. Heterogenous landscapes, containing a mix of various types of semi-natural habitat increase the habitat quality for bumblebees. We advise to maintain these diverse patches of semi-natural habitat, as mass-flowering crops alone are insufficient to support bumblebee colonies.

Experimental rewilding enhances grassland functional composition and pollinator habitat use

Abstract Semi‐natural grasslands are rich in biodiversity and thus important habitats for conservation, yet they are experiencing rapid declines due to agricultural intensification and abandonment. Promoting a more diverse mammalian herbivore community, including large and megaherbivores, may result in positive cascade effects for biodiversity and ecosystem functioning. Therefore, reintroducing an ecologically functional substitute of an extinct large herbivore could mitigate current biodiversity declines and foster semi‐natural grassland conservation. To test this hypothesis, we set up a 3‐year rewilding experiment where 12 feral horses were introduced in three 10‐hectare enclosure replicates (four horses per enclosure). We used community‐weighted mean plant functional traits to elucidate plant community changes induced by grazing through time. We also investigated the effects of this experimental treatment on insect pollinated plants and on pollinator habitat use. The grassland community exerted a mixed tolerance/avoidance response to grazing. This resulted in plant functional compositional changes which favoured prostrate plant species with higher specific leaf area, characteristic of ruderal communities. Plant species richness was higher in grazed compared to ungrazed areas. Butterfly and bumblebee habitat use, as well as feeding and resting activities were also higher in grazed areas. Moreover, the number of pollinators increased with plant species richness. Synthesis and applications. This study demonstrates that, to enhance the diversity of a given herbivore community with ecological replacements of extinct wild horses can have significant effects on the functional composition of grasslands. It can also mitigate plant species declines, in particular bee‐dependent plants, and boost pollinator habitat use. Novel management alternatives are urgently needed to reverse the negative effect of land abandonment in European agricultural landscapes. Thus, rewilding interventions with large mammalian herbivores may offset current biodiversity declines by maintaining important functional links between plants and pollinators in grassland ecosystems.

A Preliminary Assessment of Bumble Bee (Hymenoptera: Apidae) Habitat Suitability Across Protected and Unprotected Areas in the Philippines

The Philippines is a biodiversity hotspot and is home to thousands of endemic species, including at least two understudied bumble bee species: Bombus flavescens Smith, 1952 and Bombus irisanensis Cockerell, 1910. Since the 1990s, there have been virtually no studies published on the biology, ecology, and taxonomy of Philippine bumble bees—evidence of the dearth of basic entomological investigations on these important insects. In this preliminary study, our objective is to briefly summarize the geographic distribution of bumble bee habitat suitability (HS) in the Philippines across protected and unprotected areas. Maximum entropy species distribution models (SDMs) of B. flavescens and B. irisanensis were constructed using 19 unique occurrence records and 11 bioclimatic variables to estimate HS in the Philippines. Our SDMs estimated that minimum HS for B. flavescens and B. irisanensis covers ~28,066 and ~24,603 km2 of the 114 protected land parcels in the Philippines, respectively. Across unprotected areas, our SDMs estimated that minimum HS for B. flavescens and B. irisanensis covers ~146,063 and ~156,674 km2, respectively. As predicted, high-elevation habitats have the highest HS relative to low-elevation habitats (r = 0.61, P = 0.003). While our SDMs predicts an extensive distribution of both species across both protected and unprotected areas, it is important to note that nearly 80% of the Philippines is deforested. Our study identifies high-elevation protected areas as places where bumble bees may still thrive, and survey effort should be prioritized to these places to determine the status of Philippine bumble bees.

The effect of management practices on bumblebee densities in hedgerow and grassland habitats

Large-scale declines in pollinator species are a concern at present. Such declines have been attributed to a range of factors that act in tandem, rather than in isolation. Some of the most pervasive factors affecting pollinator populations are habitat loss and degradation, which results in the loss of floral resources, nesting sites and landscape connectivity. Intensification of agriculture and urbanisation are two major causes of such habitat alterations. Hedgerows and grasslands are two vital habitats for pollinators in European landscapes. When managed appropriately, these habitats may provide abundant floral resources and nesting opportunities, as well as connectivity between habitats in a fragmented landscape. This study examined the effects that management practices of hedgerows and grasslands may have on bumblebee species, an important group of wild pollinators. Bumblebee abundance was recorded using transect walks in managed and unmanaged sites, including both hedgerows and grasslands. Greater densities of bumblebees were found in unmanaged grasslands in comparison to managed grasslands. Unmanaged hedgerows were also found to have a greater density of bumblebees than managed hedgerows. These results indicate that sites which are less intensively managed provide a more suitable habitat for bumblebees. Therefore, our study underlines the importance of (a) enforcing restrictions on hedge-cutting, and (b) reducing the management intensity of grasslands to provide adequate habitat for pollinators.

Source‐sink dynamics of bumblebees in rapidly changing landscapes

Abstract Bumblebees inhabit spatially heterogeneous landscapes that are likely characterized by population sources and sinks. To date, most studies of bumblebee habitat requirements have examined static relationships between worker abundance and habitat characteristics. However, if habitat types are linked by dispersal, source‐sink dynamics could alter overall population sensitivity to habitat loss, changing conclusions from static approaches. Here, we used empirically derived spatial matrix models to study source‐sink population dynamics of bumblebees in heterogeneous environments. We used these models to assess population sensitivity to habitat loss and to examine the population dynamics that could occur under rapid habitat change. Loss of natural habitat reduced long‐term population growth rates, and more natural habitat was required to sustain bumblebee species with long‐distance dispersal than species with short‐distance dispersal. The long‐term relative density of colonies in each habitat type depended on landscape structure and bumblebee dispersal ability. Under most conditions, high‐quality habitat contained higher densities of colonies than low‐quality habitats. However, low‐quality habitat could contain higher densities than high‐quality habitats if populations were in long‐term decline. Rapid loss or restoration of natural habitat produced transient population dynamics that differed from long‐term dynamics. After large landscape perturbations that affected population structure, transient dynamics persisted for 4–8 years and were longest for species with short dispersal in highly aggregated landscapes. While transient dynamics were short in duration, they caused large effects on long‐term population density. Synthesis and applications. When habitats are linked by dispersal or populations have recently experienced perturbations, patterns of abundance on the landscape may not reflect variation in habitat quality. Spatially structured matrix population models are practical tools than can be used to account for nonequilibrium and source‐sink dynamics. For bumblebees, population sensitivity to habitat loss and the duration of transient dynamics depend on dispersal ability and landscape configuration. Demographic approaches such as ours can help to disentangle population patterns from processes and will therefore be valuable for guiding conservation and management.

The potential of electricity transmission corridors in forested areas as bumblebee habitat.

Declines in pollinator abundance and diversity are not only a conservation issue, but also a threat to crop pollination. Maintained infrastructure corridors, such as those containing electricity transmission lines, are potentially important wild pollinator habitat. However, there is a lack of evidence comparing the abundance and diversity of wild pollinators in transmission corridors with other important pollinator habitats. We compared the diversity of a key pollinator group, bumblebees (Bombus spp.), between transmission corridors and the surrounding semi-natural and managed habitat types at 10 sites across Sweden's Uppland region. Our results show that transmission corridors have no impact on bumblebee diversity in the surrounding area. However, transmission corridors and other maintained habitats such as roadsides have a level of bumblebee abundance and diversity comparable to semi-natural grasslands and host species that are important for conservation and ecosystem service provision. Under the current management regime, transmission corridors already provide valuable bumblebee habitat, but given that host plant density is the main determinant of bumblebee abundance, these areas could potentially be enhanced by establishing and maintaining key host plants. We show that in northern temperate regions the maintenance of transmission corridors has the potential to contribute to bumblebee conservation and the ecosystem services they provide.

Bumblebees depend on ericaceous species to survive in temperate heathlands

Abstract Bumblebees are the predominant wild pollinators for many plant species in temperate regions. A bumblebee colony requires pollen and nectar throughout its lifetime, but degraded and fragmented habitats may have gaps in the temporal and spatial continuity of floral resources. Heathlands are open biotopes that provide favourable habitat for bumblebees like Bombus jonellus, a declining species in Belgium. In heathlands, ericaceous species are the main plants that provide pollen and nectar for bumblebees. Although the nectar composition of ericaceous species has been previously studied, data on pollen composition remain scarce. We examined bumblebee diets (composition of their pollen loads) in Belgian heathlands over the course of a colony lifetime to assess the fidelity of bumblebees for ericaceous species. We compared nutritional values by investigating the chemical composition (amino acids, polypeptides and sterols) of the pollen of the ericaceous and dominant non‐ericaceous species present in pollen loads. No relationship was detected between the abundance of a particular plant species in bumblebee loads and its pollen composition. The successive flowering periods and the nutritional quality of pollen of ericaceous species offer valuable resources for bumblebees. Ericaceous species represent a large part of bumblebee diets in heathlands, especially in early spring and late summer when the diversity of other flowering species was low. Bumblebee pollen loads also contained non‐ericaceous flowering species that grow outside heathlands. Thus, land planning must incorporate conservation strategies for the different elements of the landscape matrix, including heathlands, peatlands, meadows and margins.

Effects of habitat composition and landscape structure on worker foraging distances of five bumble bee species

Bumble bees (Bombus spp.) are important pollinators of both crops and wildflowers. Their contribution to this essential ecosystem service has been threatened over recent decades by changes in land use, which have led to declines in their populations. In order to design effective conservation measures, it is important to understand the effects of variation in landscape composition and structure on the foraging activities of worker bumble bees. This is because the viability of individual colonies is likely to be affected by the trade-off between the energetic costs of foraging over greater distances and the potential gains from access to additional resources. We used field surveys, molecular genetics, and fine resolution remote sensing to estimate the locations of wild bumble bee nests and to infer foraging distances across a 20-km² agricultural landscape in southern England, UK. We investigated five species, including the rare B. ruderatus and ecologically similar but widespread B. hortorum. We compared worker foraging distances between species and examined how variation in landscape composition and structure affected foraging distances at the colony level. Mean worker foraging distances differed significantly between species. Bombus terrestris, B. lapidarius, and B. ruderatus exhibited significantly greater mean foraging distances (551, 536, and 501 m, respectively) than B. hortorum and B. pascuorum (336 and 272 m, respectively). There was wide variation in worker foraging distances between colonies of the same species, which was in turn strongly influenced by the amount and spatial configuration of available foraging habitats. Shorter foraging distances were found for colonies where the local landscape had high coverage and low fragmentation of semi-natural vegetation, including managed agri-environmental field margins. The strength of relationships between different landscape variables and foraging distance varied between species, for example the strongest relationship for B. ruderatus being with floral cover of preferred forage plants. Our findings suggest that management of landscape composition and configuration has the potential to reduce foraging distances across a range of bumble bee species. There is thus potential for improvements in the design and implementation of landscape management options, such as agri-environment schemes, aimed at providing foraging habitat for bumble bees and enhancing crop pollination services.