Collected Evidence: Collected Evidence: Practise wildlife gardening A site comparison study in one city in the UK found more species of bumblebee in domestic city gardens with lower intensity of management, a measure reflecting the tidiness of the garden and the use of garden pesticides. Solitary bees were not affected by this measure.  Collected, 18 May 2010 07:40:30 +0100Collected Evidence: Collected Evidence: Protect brownfield sites We have captured no evidence for the effects of interventions to protect brownfield sites from insensitive re-development. 'No evidence' for an action means we have not yet found any studies that directly and quantitatively tested this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.    Collected, 18 May 2010 14:57:41 +0100Collected Evidence: Collected Evidence: Plant parks and gardens with appropriate flowersTwo replicated trials in the USA and Canada have found more wild bees (either more species or more individuals) in gardens planted with bee forage or native plants, relative to conventionally managed gardens. Another USA trial found more bee species after the addition of bee forage plants to a community garden. Three trials in the UK or USA have shown that native flowering plants or bee forage plants are well used by wild bees when planted in gardens. A UK trial demonstrated that some popular non-native or horticulturally modified garden flowers are not frequently visited by insects, despite providing nectar in some cases.  Collected, 18 May 2010 15:19:40 +0100Collected Evidence: Collected Evidence: Manage land under power lines for wildlifeOne replicated trial in Maryland, USA found more bee species under power lines managed as scrub than in equivalent areas of annually mown grassland.  Collected, 20 May 2010 01:34:31 +0100Collected Evidence: Collected Evidence: Exclude bumblebee nest predators such as badgers and mink We have captured no evidence demonstrating the effects of excluding mammalian predators from natural bumblebee nesting areas. 'No evidence' for an action means we have not yet found any studies that directly and quantitatively tested this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.    Collected, 20 May 2010 01:35:01 +0100Collected Evidence: Collected Evidence: Provide artificial nest sites for bumblebees We have captured 11 replicated trials of bumblebee nest boxes. Several different types of nest box have been shown to be acceptable to bumblebees, including wooden or brick and tile boxes at the ground surface, underground tin, wooden or terracotta boxes and boxes attached to trees.   Three replicated trials since 1989 in the UK have shown very low uptake rates (0-2.5%) of various nest box designs (not including underground nest boxes), while seven trials in previous decades in the UK, USA or Canada, and one recent trial in the USA, showed overall uptake rates between 10% and 48%.   Wooden surface or above ground nest boxes of the kind currently marketed for wildlife gardening are not the most effective design. Eight studies test this type of nest box. Five (pre-1978, USA or Canada) find 10-40% occupancy. Three (post-1989, UK) find very low occupancy of 0-1.5%. The four replicated trials that have directly compared wooden surface nest boxes with other types all report that underground, false underground or aerial boxes are more readily occupied.   Nest boxes entirely buried 5-10 cm underground, with a 30-80 cm long entrance pipe, are generally the most effective. Seven replicated trials in the USA, Canada or the UK have tested underground nest boxes and found between 6% and 58% occupancy.   We have captured no evidence for the effects of providing nest boxes on bumblebee populations.  Collected, 20 May 2010 02:19:20 +0100Collected Evidence: Collected Evidence: Prevent spread of the small hive beetleOne replicated trial in the USA tested the effect of using mite-killing strips in commercial honey bee Apis mellifera transport packages, to reduce the spread of small hive beetle. More than half the beetles escaped the packages and were not killed by the strip.  Collected, 20 May 2010 04:31:44 +0100Collected Evidence: Collected Evidence: Manage wild honey bees sustainablyWe can find no evidence of the impact of reduced honey-hunting or improved harvesting methods on wild honey bee populations. One trial in southern Vietnam, showed that occupancy of artificial rafters by the giant honey bee Apis dorsata can be over 85% when rafters are placed by a large clearing greater than 25 m in diameter.  Collected, 20 May 2010 05:25:33 +0100Collected Evidence: Collected Evidence: Exclude ants from solitary bee nesting sitesOne replicated controlled trial showed that excluding ants from solitary nests of the endemic Australian bee Exonuera nigrescens increased production of offspring.  Collected, 20 May 2010 06:43:55 +0100Collected Evidence: Collected Evidence: Provide artificial nest sites for solitary beesWe have captured 30 replicated trials of nest boxes for solitary bees in 10 countries, including Europe, North and South America and Asia. Twenty-nine of these trials showed occupancy by bees. Many species of solitary bee readily nest in the boxes, including some species considered endangered in a study on farmland in Germany, oil-collecting species of the genus Centris in South America and a recently discovered species in lowland tropical forest in Costa Rica. One trial in temperate forest in Canada recorded no bees using nest boxes. A set of replicated experiments in Germany estimated that four medium to large European species of solitary bee have a foraging range of 150 to 600 m, so nest boxes must be within this distance of foraging resources. Twenty-three replicated trials have shown nest boxes of cut hollow stems or tubes being occupied by solitary bees. Eleven trials demonstrated occupation of blocks of wood drilled with holes. Two trials in Neotropical secondary forest (one in Brazil, one in Mexico) showed that particular solitary bee species will nest in wooden boxes, without stems or confining walls inside. Two replicated trials have compared reproductive success in different nest box designs. One showed that reed stem and wooden grooved-board nest boxes produced more bees/nest than four other types. Nest boxes with plastic-lined holes, or plastic or paper tubes were much less productive, due to parasitism or mould. The other, a small trial, found nests of the oil-collecting bee Centris analis in Brazil were more productive in cardboard straws placed in drilled wooden holes than in grooved wooden boards stacked together. Three trials on agricultural land, one on a carpenter bee in India, one on a range of species in Germany and one on species of Osmia in the USA, have shown that the number of occupied solitary bee nests can double over three years with repeated nest box provision at a given site. One small replicated trial compared populations of solitary bees in blueberry fields in the USA with and without nest boxes over three years. The estimated number of foraging Osmia bees had increased in fields with nest boxes, compared to fields without nest boxes. Eleven replicated trials have recorded solitary bees in nest boxes being attacked by parasites or predators. Rates of mortality and parasitism have been measured in 10 studies. Mortality rates range from 13% mortality for cavity-nesting bees and wasps combined in Germany (2% were successfully parasitized), or 2% of bee brood cells attacked in shade coffee and cacao plantations in central Sulawesi, Indonesia, to 36% parasitism and 20% other mortality (56% mortality overall) for the subtropical carpenter bee Xylocopa fenestrata in India. Two replicated trials of the use of drilled wooden nest boxes by bees in California, USA, showed that introduced European earwigs Forficula auricularia and introduced European leafcutter bee species use the boxes. In one trial, these introduced species more commonly occupied the boxes than native bees. A small trial tested three soil-filled nest boxes for the mining bee Andrena flavipes in the UK, but they were not occupied.Collected, 20 May 2010 07:16:20 +0100Collected Evidence: Collected Evidence: Increase the use of clover leys on farmlandWe have captured no evidence that increasing the use of clover leys can enhance wild bee populations. One replicated trial in Germany showed that fields planted with a white clover grass mixture do not attract solitary bees to nest preferentially on site. A trial in Switzerland showed that if white clover is mowed during flowering, injuries and mortality of bees can be reduced by avoiding the use of a processor attached to the mower.  Collected, 20 May 2010 08:48:02 +0100Collected Evidence: Collected Evidence: Legally protect large native treesA study in degraded savannah in Minas Gerais, Brazil showed that the stingless bee species Melipona quadrifasciata selectively nested in the protected cerrado tree Caryocar brasiliense, evidence that protecting this species from logging or wood harvesting has helped to conserve stingless bees.  Collected, 20 May 2010 09:28:04 +0100Collected Evidence: Collected Evidence: Exclude introduced European earwigs from nest sitesIn California, USA, a replicated controlled trial showed that numbers of introduced European earwigs Forficula auricularia resting in solitary bee nest boxes can be reduced using a sticky barrier Tanglefoot. This treatment increased the use of the boxes by native bees.  Collected, 20 May 2010 10:20:05 +0100Collected Evidence: Collected Evidence: Leave field margins unsprayed within the crop (conservation headlands)Two replicated controlled trials in England showed that conservation headlands do not attract more foraging bumblebees than conventional crop fields. One replicated trial found fewer bees on conservation headlands than in naturally regenerated, uncropped field margins in England.  Collected, 20 May 2010 13:15:26 +0100Collected Evidence: Collected Evidence: Prevent escape of commercial bumblebees from greenhouses One small replicated trial in Canada showed that a plastic greenhouse covering that transmits ultraviolet light (so transmitted light is similar to daylight) reduced the numbers of bumblebees from managed colonies escaping through open gutter vents. One trial in Japan showed that externally mounted nets and zipped, netted entrances can keep commercial bumblebees inside greenhouses as long as they are regularly checked and maintained.  Collected, 20 May 2010 13:55:19 +0100Collected Evidence: Collected Evidence: Keep pure breeding populations of native honey bee subspeciesOne replicated trial in Switzerland found that pure breeding populations of the European black honey bee Apis mellifera mellifera contained a significant proportion (28%) of hybrids with an introduced subspecies Apis mellifera carnica.  Collected, 20 May 2010 14:49:31 +0100Collected Evidence: Collected Evidence: Introduce mated females to small populations to improve genetic diversityOne trial in Brazil showed that genetic diversity can be maintained in small isolated populations of stingless bees Melipona scutellaris by regularly introducing inseminated queens.  Collected, 20 May 2010 15:23:26 +0100Collected Evidence: Collected Evidence: Increase the proportion of natural or semi-natural habitat in the farmed landscape We found no evidence demonstrating the effects of restoring natural or semi-natural habitat on bee diversity or abundance in neighbouring farms. 'No evidence' for an action means we have not yet found any studies that directly and quantitatively tested this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.  Collected, 20 May 2010 15:31:52 +0100Collected Evidence: Collected Evidence: Introduce agri-environment schemes to benefit wild beesFour replicated trials in Europe have shown enhanced diversity and/or abundance of foraging wild bees on land managed under various European agri-environment schemes, relative to conventionally-managed fields or field margins. These schemes were the Swiss Ecological Compensation Areas (one replicated trial), the German organic arable farming option (one replicated trial), the Dutch botanical and meadow bird agreements (one replicated trial, very low numbers of bee species) and the Scottish Rural Stewardship Scheme (one replicated trial, also included nest-searching queen bumblebees). Four replicated trials in Europe found that the number of bees and/or bee species is not enhanced on land managed under agri-environment schemes, including meadow bird agreements in wet grassland in the Netherlands, measures to protect steppe-living birds and compensation measures around a National Park in Spain, and 6 m wide grass field margin strips in England (one replicated trial for each). On a wider landscape scale, two replicated trials in the UK have found bumblebee populations were not enhanced on farmland managed under agri-environment schemes. One trial compared the reproductive success of colonies of the buff-tailed bumblebee Bombus terrestris, the other compared queen bumblebee numbers in spring in conventionally managed field margins, on farms with and without agri-environment schemes.  Collected, 20 May 2010 16:11:07 +0100Collected Evidence: Collected Evidence: Leave arable field margins uncropped with natural regenerationFour replicated trials in the UK have found more bumblebees (and more bee species in two trials) foraging on uncropped field margins than on cropped margins. One small unreplicated trial found similar bee species richness on a naturally regenerated margin as on margins sown with wildflowers. A small replicated trial found that neither abundance nor diversity of bumblebees were higher on naturally regenerated margins than on cropped margins. Two trials note that the value of naturally regenerated uncropped field margins is based on thistle species considered to be pernicious weeds requiring control. Two trials found that the value of naturally regenerated uncropped field margins for bees was not consistent from year to year. We have captured no evidence on the effects of field margin management on solitary bees.  Collected, 20 May 2010 16:57:57 +0100Collected Evidence: Collected Evidence: Increase the diversity of nectar and pollen plants in the landscape for beesOne large replicated controlled trial showed that the average abundance of long-tongued bumblebees on field margins was positively correlated with the number of pollen and nectar agri-environment agreements in a 10 km grid square.  Collected, 20 May 2010 18:33:50 +0100Collected Evidence: Collected Evidence: Increase areas of rough grassland for bumblebee nestingOne replicated controlled trial on lowland farms in Scotland showed that grassy field margins attracted nest-searching queen bumblebees in spring at higher densities than cropped field margins, managed or unmanaged grasslands or hedgerows.  Collected, 20 May 2010 18:37:48 +0100Collected Evidence: Collected Evidence: Protect existing natural or semi-natural habitat to prevent conversion to agriculture We have captured no evidence for the effects of protecting areas of natural or semi-natural habitat on bee populations or communities. 'No evidence' for an action means we have not yet found any studies that directly and quantitatively tested this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.    Collected, 20 May 2010 19:58:47 +0100Collected Evidence: Collected Evidence: Plant dedicated floral resources on farmlandFourteen trials in Europe and North America have recorded substantial numbers of wild bees foraging on perennial or annual sown flowering plants in the agricultural environment. Ten trials (eight replicated) have monitored bees foraging on patches sown with a high proportion of phacelia Phacelia tanacetifolia on farmland and all but one found substantial numbers of foraging wild (non-Apis) bees, particularly bumblebees Bombus spp. Six of these trials recorded the number of foraging bee species, which ranged from eight to 35. One replicated trial shows that phacelia is not very attractive to wild bees in Greece. One replicated controlled trial in the UK showed that planted perennial leguminous herbs, including clovers, were more attractive to bumblebees in landscapes with a greater proportion of arable farming. Four replicated trials have quantified the wider response of wild bee populations to planted flower patches by measuring reproductive success, numbers of nesting bees or numbers foraging in the surrounding landscape. One trial showed that planted patches of bigleaf lupine Lupinus polyphyllus in commercial apple orchards in Novia Scotia, Canada, significantly enhanced the reproductive success of blue orchard mason bees Osmia lignaria. One trial in the Netherlands showed that bee numbers and species richness are not higher in farmland 50-1,500 m away from planted flower patches. Two trials in Germany found no or relatively few species of solitary bee nesting on set-aside fields sown with phacelia or clover respectively.  Collected, 20 May 2010 20:02:31 +0100Collected Evidence: Collected Evidence: Manage hedges to benefit beesOne replicated controlled trial showed that hedges managed under the Scottish Rural Stewardship scheme do not attract more nest-searching or foraging queen bumblebees in spring than conventionally managed hedgerows.  Collected, 20 May 2010 21:16:02 +0100
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What Works in Conservation

What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence, in synopses. Subjects covered so far include amphibians, birds, mammals, forests, peatland and control of freshwater invasive species. More are in progress.

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