Collected 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: Eradicate existing populations of invasive non-native speciesOne replicated trial in Louisiana, USA, demonstrated that colonies of invasive Africanized honey bees Apis mellifera can be killed by providing insecticide (acephate)-laced syrup for 30 minutes. One replicated controlled before-and-after trial attempted to eradicate European buff-tailed bumblebees Bombus terrestris from trial sites in Japan by catching and killing foraging bees. The treatment led to an increase in numbers of two native bumblebee species, but did not eradicate B. terrestris.  Collected, 20 May 2010 04:54:57 +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: Replace honey-hunting with apiculture  One study reported that a programme to enhance take-up of stingless beekeeping in southern Mexico increased the number of managed colonies in the area. Five trials contributed to scientific improvement of stingless beekeeping methods. Two controlled trials showed that either brewer's yeast (one trial) or a mix with 25% pollen collected by honey bees Apis mellifera (one trial) can be used as a pollen substitute to feed Scaptotrigona postica in times of pollen scarcity. A study on the island of Tobago found a wooden hive design with separate, different-shaped honey and brood chambers allowed honey to be extracted without damaging the brood. One trial showed that 50 g of comb with mature pupae is enough to start a new daughter colony of S. mexicana. One trial found brood growth was higher in traditional log hives than in box hives with internal volumes exceeding 14 litres, and recommended smaller box hives. We have captured no clear evidence about whether these activities help conserve bees or enhance native bee populations.    Collected, 20 May 2010 06:29:24 +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: 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: Provide nest boxes for stingless beesOne replicated trial tested nest boxes placed in trees for the stingless bee Melipona quadrifasciata in Brazil and found no uptake.  Collected, 20 May 2010 11:16:43 +0100Collected Evidence: Collected Evidence: Ensure commercial hives/nests are disease freeOne randomised controlled trial in Canada found that the antibiotic fumagillin is not effective against Nosema bombi infection in managed colonies of the western bumblebee Bombus occidentalis. One replicated controlled trial in South Korea found that Indian meal moth Plodia interpunctella in commercial bumblebee colonies can be controlled with the insect pathogen Bacillus thuringiensis (Bt) Aizawai strain, at a strength of 1 g Bt/litre of water.  Collected, 20 May 2010 11:17:19 +0100Collected Evidence: Collected Evidence: Retain dead wood in forest managementWe have found no evidence on the impact of retaining dead wood in forests or woodlands on wild bee communities or populations.  '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 12:43:18 +0100Collected Evidence: Collected Evidence: Control fire risk using mechanical shrub control and/or prescribed burningOne replicated controlled trial in mixed temperate forest in the USA showed that for bee conservation, it is best to control fire using cutting and burning combined. This increases herbaceous plant cover in subsequent years.  Collected, 20 May 2010 12:49:47 +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: Control deployment of hives/ nests We have found no direct evidence for the effects of excluding Apis mellifera hives, or nests of other managed pollinators, on populations of wild bees. '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 13:54:55 +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: Restrict certain pesticidesOne site comparison study in Italy showed that a reduction in the number of solitary bee species in late summer associated with repeated applications of the insecticide fenitrothion can be avoided by not applying the insecticide.  Collected, 20 May 2010 17:07:09 +0100Collected Evidence: Collected Evidence: Reduce fertilizer run-off into marginsWe have captured no evidence on the effects of specific interventions to reduce fertilizer run off into field margins. '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 17:48:38 +0100Collected Evidence: Collected Evidence: Restore species-rich grassland on road vergesOne replicated controlled trial showed that road verges planted with native prairie vegetation in Kansas, USA supported a greater number and diversity of bees than frequently mown grassed verges.  Collected, 20 May 2010 18:38:51 +0100Collected Evidence: Collected Evidence: Re-plant native forest We have found no evidence on the impact of reforestation on wild bee communities or populations. '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 18:51:39 +0100Collected Evidence: Collected Evidence: Reduce pesticide or herbicide use generallyOne replicated trial in the USA showed that numbers of foraging bees on squash farms are not affected by the responsible use of pesticides.  Collected, 20 May 2010 19:22:20 +0100Collected Evidence: Collected Evidence: Rear declining bumblebees in captivityWe have captured 22 trials from 13 countries documenting captive rearing of bumblebee colonies by confining mated queens alone (eight trials), with one or more bumblebee workers (seven trials), honey bee workers (one trial), male bumblebee pupae (three trials) or following anaesthetisation with CO2 (four trials). One trial found that over four years of artificial rearing, Bombus terrestris queens gradually decreased in weight. Three trials have tried to rear North American bumblebees now declining or thought to be declining. Two induced spring queens of the half-black bumblebee B. vagans to rear adults in captivity, one trial induced queen yellow-banded bumblebees B. terricola (attempted in all three trials) and red-belted bumblebees B. rufocinctus (only attempted in one trial) to rear adults in captivity. All three trials tried to rear the yellow bumblebee B. fervidus and in all cases the queens laid eggs but the larvae died before becoming adults. One trial found the same pattern for the rusty-patched bumblebee and the American bumblebee B. pensylvanicus. One study reports rearing the large garden bumblebee B. ruderatus, a Biodiversity Action Plan species in the UK. Two trials have reported laboratory rearing of a pocket-making bumblebee, the Neotropical B. atratus. Three replicated trials demonstrated that the pollen diet of captively reared bumblebees influences reproductive success. In one trial, buff-tailed bumblebee B. terrestris colonies fed on freshly frozen pollen produced larger queens that survived better and produced larger colonies themselves than colonies fed on dried, frozen pollen. Two replicated trials demonstrated that B. terrestris workers can produce more offspring when fed types of pollen with a higher protein content. Two replicated experiments showed that an artificial light regime of eight hours light, 16 hours darkness, can reduce the time taken for artificially reared queen B. terrestris to lay eggs, relative to rearing in constant darkness. We have captured two replicated trials examining the effect of different artificial hibernation regimes in B. terrestris. One showed that hibernation of queens at 4-5°C for 45 days enhanced egg-laying and colony formation rates, but hibernated queens produced smaller colonies than non-hibernated queens. The second showed that queens should weigh more than 0.6 g (wet weight) and be hibernated for four months or less to have a good chance of surviving.Collected, 20 May 2010 20:22:36 +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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