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What Works in Conservation 2015

 | 
William J. Sutherland
, 
Lynn V. Dicks
, 
Nancy Ockendon
, 
et al.

3. Bird Conservation

3.4. Threat: Agriculture

Texte intégral

3.4.1 All farming systems

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for all farming systems?

Beneficial

● Plant wild bird seed or cover mixture
● Provide (or retain) set-aside areas in farmland

Likely to be beneficial

● Create uncultivated margins around intensive arable or pasture fields
● Increase the proportion of natural/semi-natural habitat in the farmed landscape
● Manage ditches to benefit wildlife
● Pay farmers to cover the costs of conservation measures
● Plant grass buffer strips/margins around arable or pasture fields
● Plant nectar flower mixture/ wildflower strips
● Leave refuges in fields during harvest
● Reduce conflict by deterring birds from taking crops: use bird scarers
● Relocate nests at harvest time to reduce nestling mortality
● Use mowing techniques to reduce mortality

Unknown effectiveness (limited evidence)

● Control scrub on farmland
● Offer per clutch payment for farmland birds
● Manage hedges to benefit wildlife
● Plant new hedges
● Reduce conflict by deterring birds from taking crops: use repellents
● Take field corners out of management

Likely to be ineffective or harmful

● Mark bird nests during harvest or mowing

No evidence found (no assessment)

● Cross compliance standards for all subsidy payments
● Food labelling schemes relating to biodiversity friendly farming
● Manage stone-faced hedge banks to benefit birds
● Plant in-field trees
● Protect in-field trees
● Reduce field size (or maintain small fields)
● Support or maintain low-intensity agricultural systems
● Tree pollarding, tree surgery

Beneficial

Plant wild bird seed or cover mixture

1Seven of 41 studies found that fields or farms with wild bird cover had higher diversity than other sites, or that wild bird cover held more species than other habitats. Thirty-two studies found that populations, or abundances of some or all species were higher on wild bird cover than other habitats, or that wild bird cover was used more than other habitats. Four of these studies investigated several interventions at once. Thirteen studies found that bird populations or densities were similar on wild bird cover and other habitats that some species were not associated with wild bird cover, or that birds rarely used wild bird cover. Three studies found higher productivities of birds on wild bird cover than other habitats. Two found no differences for some or all species studied. Two studies found that survival of grey partridge or artificial nests increased on wild bird cover; one found lower partridge survival in farms with wild bird cover than other farms. Five studies from the UK found that some wild bird cover crops were used more than others. A study and a review found that the arrangement of wild bird cover in the landscape affected its use by birds. Assessment: beneficial (effectiveness 81%; certainty 81%; harms 0%).

2http://www.conservationevidence.com/​actions/​187

Provide (or retain) set-aside areas in farmland

3Four out of 23 studies from Europe and North America found more species on set-aside than on crops. One study found fewer. Twenty-one studies found that some species were at higher densities on set-aside than other habitats, or that they used set-aside more often. Four found that some species were found at lower densities on set-aside than other habitats. Three studies found that waders and Eurasian skylarks had higher productivities on set-aside than other crops. One study found that skylarks on set-aside had lower similar or lower productivities than on crops. One study from the UK found that rotational set-aside was used more than non-rotational set-aside, another found no difference. A review from North America and Europe found that naturally regenerated set-aside held more birds and more species than sown set-aside. Assessment: beneficial (effectiveness 70%; certainty 75%; harms 0%).

4http://www.conservationevidence.com/​actions/​175

Likely to be beneficial

Create uncultivated margins around intensive arable or pasture fields

5One of eight studies found that three sparrow species found on uncultivated margins on a site in the USA were not found on mown field edges. A replicated study from Canada found fewer species in uncultivated margins than in hedges or trees. Three studies found that some bird species were associated with uncultivated margins, or that birds were more abundant on margins than other habitats. One study found that these effects were very weak and four studies of three experiments found that uncultivated margins contained similar numbers of birds as other habitats in winter, or that several species studied did not show associations with margins. A study from the UK found that yellowhammers used uncultivated margins more than crops in early summer. Use fell in uncut margins later in the year. A study from the UK found that grey partridge released on uncultivated margins had high survival. Assessment: likely to be beneficial (effectiveness 45%; certainty 55%; harms 0%).

6http://www.conservationevidence.com/​actions/​190

Increase the proportion of natural/semi-natural habitat in the farmed landscape

7Two studies from Switzerland and Australia, of the five we captured, found that areas with plantings of native species, or areas under a scheme designed to increase semi-natural habitats (the Swiss Ecological Compensation Areas scheme), held more bird species than other areas. One study from Switzerland found that populations of three bird species increased in areas under the Ecological Compensation Areas scheme. A third Swiss study found that some habitats near Ecological Compensation Areas held more birds than habitats further away, but the overall amount of Ecological Compensation Area had no effect on bird populations. A study from the UK found no effect of habitat-creation on grey partridge populations. Assessment: likely to be beneficial (effectiveness 45%; certainty 44%; harms 0%).

8http://www.conservationevidence.com/​actions/​171

Manage ditches to benefit wildlife

9One study of four from the UK found that bunded ditches were visited more often by birds than non-bunded ditches. Three studies found that some birds responded positively to ditches managed for wildlife, but that other species did not respond to management, or responded negatively. Assessment: likely to be beneficial (effectiveness 40%; certainty 49%; harms 14%).

10http://www.conservationevidence.com/​actions/​180

Pay farmers to cover the costs of conservation measures

11Three out of 31 studies found national population increases in three species after payment schemes targeted at their conservation. One found that many other species continued declining. Twenty-two studies found that at least some species were found at higher densities on sites with agri-environment schemes; some differences were present only in summer or only in winter. Fifteen studies found some species at similar densities on agri-environment schemes and non-agri-environment scheme sites or appeared to respond negatively to agri-environment schemes. One study found that grey partridge survival was higher in some years on agri-environment scheme sites. Two studies found higher productivity on agri-environment scheme sites for some species, one found no effect of agri-environment schemes. A review found that some agri-environment schemes options were not being used enough to benefit many species of bird. A study from the UK found that there was no difference in the densities of seed-eating birds in winter between two agri-environment scheme designations. Assessment: likely to be beneficial (effectiveness 56%; certainty 80%; harms 0%).

12http://www.conservationevidence.com/​actions/​172

Plant grass buffer strips/margins around arable or pasture fields

13One of 15 studies found more bird species in fields in the USA that were bordered by grass margins than in unbordered fields. Two studies from the UK found no effect of margins on species richness. One study found that more birds used grass strips in fields than used crops. Even more used grass margins. Nine studies from the USA and UK found that sites with grass margins had more positive population trends or higher populations for some birds, or that some species showed strong habitat associations with grass margins. Three studies found no such effect for some or all species. Two studies found that species used margins more than other habitats and one found that birds used cut margins more than uncut during winter, but less than other habitats during summer. A study from the UK found that grey partridge broods were smaller on grass margins than other habitat types. Assessment: likely to be beneficial (effectiveness 47%; certainty 54%; harms 0%).

14http://www.conservationevidence.com/​actions/​191

Plant nectar flower mixture/wildflower strips

15Three of seven studies found that birds used wildflower strips more than other habitats; two found strips were not used more than other habitats. A study from Switzerland found that Eurasian skylarks were more likely to nest in patches sown with annual weeds than in crops and were less likely to abandon nests. A study from the UK found that management of field margins affected their use more than the seed mix used. Assessment: likely to be beneficial (effectiveness 55%; certainty 45%; harms 0%).

16http://www.conservationevidence.com/​actions/​189

Leave refuges in fields during harvest

17One study found that fewer gamebirds came into contact with mowing machinery when refuges were left in fields. A study from the UK found that Eurasian skylarks did not nest at higher densities in uncut refuges than in the rest of the field. Assessment: likely to be beneficial (effectiveness 50%; certainty 41%; harms 0%).

18http://conservationevidence.com/​actions/​193

Reduce conflict by deterring birds from taking crops (using bird scarers)

19A controlled paired study in the USA found reduced levels of damage to almond orchards when American crow distress calls were broadcast. A study in Pakistan found that four pest species were less abundant when reflector ribbons were hung above crops compared to where ribbons were not used. Assessment: likely to be beneficial (effectiveness 66%; certainty 44%; harms 0%).

20http://www.conservationevidence.com/​actions/​199

Relocate nests at harvest time to reduce nestling mortality

21A study from Spain found that Montagu’s harrier clutches had higher hatching and fledging rates when they were temporarily moved during harvest than control nests that were not moved. Assessment: likely to be beneficial (effectiveness 55%; certainty 42%; harms 0%).

22http://www.conservationevidence.com/​actions/​195

Use mowing techniques to reduce mortality

23One of three studies from the UK found a large increase in the national population of corncrakes after a scheme to delay mowing and promote corncrake-friendly mowing techniques. Two studies found lower levels of corncrake and Eurasian skylark mortality when wildlife-friendly mowing techniques were used. Assessment: likely to be beneficial (effectiveness 85%; certainty 50%; harms 0%).

24http://www.conservationevidence.com/​actions/​192

Unknown effectiveness (limited evidence)

Control scrub on farmland

25A study from the UK found farms with a combined intervention that included scrub control had lower numbers of young grey partridge per adult. Assessment: unknown effectiveness – limited evidence (effectiveness 7%; certainty 9%; harms 1%).

26http://www.conservationevidence.com/​actions/​197

Offer per clutch payment for farmland birds

27One of two studies from the Netherlands found slightly higher breeding densities of waders on farms with per clutch payment schemes but this and another study found no higher numbers overall. One study found higher hatching success on farms with payment schemes. Assessment: unknown effectiveness – limited evidence (effectiveness 43%; certainty 35%; harms 0%).

28http://conservationevidence.com/​actions/​196

Manage hedges to benefit wildlife

29One of seven studies found no differences in the number of species in a UK site with wildlife-friendly hedge management and sites without. Seven studies found that some species increased in managed hedges or were more likely to be found in them than other habitats. One investigated several interventions at the same time. Four studies found that some species responded negatively or not at all to hedge management or that effects varied across regions of the UK. Assessment: unknown effectiveness – limited evidence (effectiveness 39%; certainty 38%; harms 3%).

30http://www.conservationevidence.com/​actions/​177

Plant new hedges

31A study from the USA found that populations of northern bobwhites increased following several interventions including the planting of new hedges. Assessment: unknown effectiveness – limited evidence (effectiveness 23%; certainty 19%; harms 0%).

32http://www.conservationevidence.com/​actions/​178

Reduce conflict by deterring birds from taking crops (using repellents)

33A replicated, randomised and controlled ex situ study in the USA found that dickcissels consumed less rice if it was treated with two repellents compared to controls. Assessment: unknown effectiveness – limited evidence (effectiveness 29%; certainty 27%; harms 0%).

34%20http://www.conservationevidence.com/​actions/​200

Take field corners out of management

35A study from the UK found that overwinter survival of grey partridge was positively correlated with taking field corners out of management, but this relationship was only significant in one of three winters. There was no relationship with measures of productivity (brood size, young: adult). Assessment: unknown effectiveness – limited evidence (effectiveness 30%; certainty 15%; harms 0%).

36http://www.conservationevidence.com/​actions/​198

Likely to be ineffective or harmful

Mark bird nests during harvest or mowing

37A study from the Netherlands found that fewer northern lapwing nests were destroyed when they were marked with bamboo poles than when they were unmarked. Assessment: likely to be ineffective or harmful (effectiveness 30%; certainty 45%; harms 20%).

38http://www.conservationevidence.com/​actions/​148

No evidence found (no assessment)

39We have captured no evidence for the following interventions:

  • Cross compliance standards for all subsidy payments
  • Food labelling schemes relating to biodiversity-friendly farming
  • Manage stone-faced hedge banks to benefit birds
  • Plant in-field trees
  • Protect in-field trees
  • Reduce field size (or maintain small fields)
  • Support or maintain low-intensity agricultural systems
  • Tree pollarding, tree surgery

3.4.2 Arable farming

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for arable farming systems?

Likely to be beneficial

● Create ʹskylark plotsʹ
● Leave overwinter stubbles
● Leave uncropped cultivated margins or fallow land (includes lapwing and stone curlew plots)
● Sow crops in spring rather than autumn
● Undersow spring cereals, with clover for example

Trade-off between benefit and harms

● Reduce tillage

Unknown effectiveness (limited evidence)

● Implement mosaic management
● Increase crop diversity to benefit birds
● Plant more than one crop per field (intercropping)

Unlikely to be beneficial

● Create beetle banks

Likely to be ineffective or harmful

● Plant cereals in wide-spaced rows
● Revert arable land to permanent grassland

No evidence found (no assessment)

● Add 1% barley into wheat crop for corn buntings
● Create corn bunting plots
● Leave unharvested cereal headlands within arable fields
● Plant nettle strips

Likely to be beneficial

Create ʹskylark plotsʹ (undrilled patches in cereal fields)

40One study of seven found that the Eurasian skylark population on a farm increased after skylark plots were provided. Another found higher skylark densities on fields with plots in. Two studies from the UK found that skylark productivity was higher for birds with skylark plots in their territories, a study from Switzerland found no differences. Two studies from Denmark and Switzerland found that skylarks used plots more than expected, but a study from the UK found that seed-eating songbirds did not. Assessment: likely to be beneficial (effectiveness 65%; certainty 60%; harms 0%).

41http://www.conservationevidence.com/​actions/​214

Leave overwinter stubbles

42Three of fourteen studies report positive population-level changes in two species after winter stubble provision. All investigated several interventions at once. Eight studies found that some farmland birds were found on stubbles or were positively associated with them, three investigated several interventions and one found no more positive associations than expected by chance. A study from the UK found that most species did not preferentially use stubble, compared to cover crops and another found that a greater area of stubble in a site meant lower grey partridge brood size. Five studies from the UK found that management of stubbles influenced their use by birds. One study found that only one species was more common on stubbles under agri-environment schemes. Assessment: likely to be beneficial (effectiveness 40%; certainty 60%; harms 0%).

43http://www.conservationevidence.com/​actions/​203

Leave uncropped cultivated margins or fallow land (includes lapwing and stone curlew plots)

44Three of nine studies report that the UK population of Eurasian thick-knees increased following a scheme to promote lapwing plots (and other interventions). A study from the UK found that plots did not appear to influence grey partridge populations. Four studies from the UK found that at least one species was associated with lapwing plots, or used them for foraging or nesting. One study found that 11 species were not associated with plots, another that fewer used plots than used crops in two regions of the UK. Two studies found that nesting success was higher on lapwing plots and fallow than in crops. A third found fewer grey partridge chicks per adult on sites with lots of lapwing plots. Assessment: likely to be beneficial (effectiveness 59%; certainty 55%; harms 15%).

45http://www.conservationevidence.com/​actions/​213

Sow crops in spring rather than autumn

46One study from Sweden, of three examining the effects of spring-sown crops, found that more birds were found on areas with spring, rather than autumn-sown crops. A study from the UK found that several species used the study site for the first time after spring-sowing was started. All three studies found that some populations increased after the start of spring sowing. A study from the UK found that some species declined as well. A study from Sweden found that hatching success of songbirds and northern lapwing was lower on spring-sown, compared with autumn-sown crops. Assessment: likely to be beneficial (effectiveness 55%; certainty 67%; harms 10%).

47http://conservationevidence.com/​actions/​207

Undersow spring cereals, with clover for example

48Four of five studies from the UK found that bird densities were higher on undersown fields or margins than other fields, or that use of fields increased if they were undersown. Two studies of the same experiment found that not all species nested at higher densities in undersown habitats. A study from the UK found that grey partridge populations were lower on sites with large amounts of undersown cereal. Assessment: likely to be beneficial (effectiveness 60%; certainty 45%; harms 10%).

49http://www.conservationevidence.com/​actions/​208

Trade-off between benefit and harms

Reduce tillage

50Six of ten studies found that some or all bird groups had higher species richness or diversity on reduced-tillage fields, compared to conventional fields in some areas. Two studies found that some groups had lower diversity on reduced-tillage sites, or that there was no difference between treatments. Nine studies found that some species were found at higher densities on reduced tillage fields, six found that some species were at similar or lower densities. Three studies found evidence for higher productivities on reduced-tillage fields. One found that not all measures of productivity were higher. Assessment: trade-offs between benefits and harms (effectiveness 50%; certainty 48%; harms 51%).

51http://www.conservationevidence.com/​actions/​211

Unknown effectiveness (limited evidence)

Implement mosaic management

52One of two studies from the Netherlands found that northern lapwing population trends, but not those of three other waders, became more positive following the introduction of mosaic management. The other found that black-tailed godwit productivity was higher under mosaic management than other management types. Assessment: unknown effectiveness – limited evidence (effectiveness 20%; certainty 33%; harms 0%).

53 http://www.conservationevidence.com/​actions/​130

Increase crop diversity to benefit birds

54A study from the UK found that more barnacle geese used a site after the amount of land under cereals was decreased and several other interventions were used. Assessment: unknown effectiveness – limited evidence (effectiveness 20%; certainty 19%; harms 0%).

55http://conservationevidence.com/​actions/​201

Plant more than one crop per field (intercropping)

56A study from the USA found that 35 species of bird used fields with intercropping, with four nesting, but that productivity from the fields was very low. Assessment: unknown effectiveness – limited evidence (effectiveness 30%; certainty 36%; harms 18%).

57http://www.conservationevidence.com/​actions/​209

Unlikely to be beneficial

Create beetle banks

58Two of six studies from the UK found that some bird populations were higher on sites with beetle banks. Both investigated several interventions at once. Two studies found no relationships between bird species abundances or populations and beetle banks. Two studies (including a review) from the UK found that three bird species used beetle banks more than expected, one used them less than expected. Assessment: unlikely to be beneficial (effectiveness 30%; certainty 41%; harms 0%).

59http://www.conservationevidence.com/​actions/​217

Likely to be ineffective or harmful

Plant cereals in wide-spaced rows

60One of three studies from the UK found that fields with wide-spaced rows held more Eurasian skylark nests than control fields. One study found that fields with wide-spaced rows held fewer nests. Both found that fields with wide-spaced rows held fewer nests than fields with skylark plots. A study from the UK found that skylark chicks in fields with wide-spaced rows had similar diets to those in control fields. Assessment: likely to be ineffective or harmful (effectiveness 20%; certainty 44%; harms 20%).

61http://www.conservationevidence.com/​actions/​216

Revert arable land to permanent grassland

62All five studies looking at the effects of reverting arable land to grassland found no clear benefit to birds. The studies monitored birds in winter or grey partridges in the UK and wading birds in Denmark. They included three replicated controlled trials. Assessment: likely to be ineffective or harmful (effectiveness 0%; certainty 64%; harms 10%).

63http://www.conservationevidence.com/​actions/​210

No evidence found (no assessment)

64We have captured no evidence for the following interventions:

  • Add 1% barley into wheat crop for corn buntings
  • Create corn bunting plots
  • Leave unharvested cereal headlands within arable fields
  • Plant nettle strips

3.4.3 Livestock farming

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for livestock farming systems?

Likely to be beneficial

● Delay mowing date on grasslands
● Leave uncut rye grass in silage fields
● Maintain species-rich, semi-natural grassland
● Maintain traditional water meadows
● Mark fencing to avoid bird mortality
● Plant cereals for whole crop silage
● Reduce grazing intensity
● Reduce management intensity of permanent grasslands

Trade-off between benefit and harms

● Exclude livestock from semi-natural habitat

Unknown effectiveness (limited evidence)

● Create open patches or strips in permanent grassland
● Maintain upland heath/moor
● Protect nests from livestock to reduce trampling
● Provide short grass for waders
● Raise mowing height on grasslands

Unlikely to be beneficial

● Use traditional breeds of livestock

No evidence found (no assessment)

● Maintain lowland heathland
● Maintain rush pastures
● Maintain wood pasture and parkland
● Plant Brassica fodder crops
● Use mixed stocking

Likely to be beneficial

Delay mowing date on grasslands

65Two of five studies (both reviews) found that the UK corncrake populations increased following two schemes to encourage farmers to delay mowing. A study from the Netherlands found no evidence that waders and other birds were more abundant in fields with delayed mowing. Another study from the Netherlands found that fields with delayed mowing held more birds than other fields, but differences were present before the scheme began and population trends did not differ between treatments. A study from the USA found that fewer nests were destroyed by machinery in late-cut fields, compared with early-cut fields. Assessment: likely to be beneficial (effectiveness 45%; certainty 52%; harms 0%).

66http://www.conservationevidence.com/​actions/​223

Leave uncut rye grass in silage fields

67All four studies from the UK (including two reviews) found that seed-eating birds were benefited by leaving uncut (or once-cut) rye grass in fields, or that seed-eating species were more abundant on uncut plots. Three studies found that seed-eating birds were more abundant on uncut and ungrazed plots than on uncut and grazed plots. A study from the UK found that the responses of non-seed-eating birds were less certain than seed-eating species, with some species avoiding uncut rye grass. Assessment: likely to be beneficial (effectiveness 67%; certainty 56%; harms 8%).

68http://www.conservationevidence.com/​actions/​224

Maintain species-rich, semi-natural grassland

69One of two studies found that the populations of five species increased in an area of the UK after the start of management designed to maintain unimproved grasslands. A study from Switzerland found that wetland birds nested at greater densities on managed hay meadows than expected, but birds of open farmland used hay meadows less. Assessment: likely to be beneficial (effectiveness 41%; certainty 44%; harms 0%).

70http://www.conservationevidence.com/​actions/​218

Maintain traditional water meadows

71One of four studies (from the UK) found that the populations of two waders increased on reserves managed as water meadows. Two studies from the Netherlands found that there were more waders or birds overall on specially managed meadows or 12.5 ha plots, but one found that these differences were present before management began, the other found no differences between individual fields under different management. Two studies from the UK and Netherlands found that wader populations were no different between specially and conventionally managed meadows, or that wader populations decreased on specially-managed meadows. A study from the UK found that northern lapwing productivity was not high enough to maintain populations on three of four sites managed for waders. Assessment: likely to be beneficial (effectiveness 50%; certainty 52%; harms 0%).

72http://www.conservationevidence.com/​actions/​229

Mark fencing to avoid bird mortality

73A study from the UK found that fewer birds collided with marked sections of deer fences, compared to unmarked sections. Assessment: likely to be beneficial (effectiveness 65%; certainty 46%; harms 0%).

74http://www.conservationevidence.com/​actions/​238

Plant cereals for whole crop silage

75Three studies of one experiment found that seed-eating birds used cereal-based wholecrop silage crops more than other crops in summer and winter. Insect-eating species used other crops and grassland more often. Assessment: likely to be beneficial (effectiveness 55%; certainty 43%; harms 0%).

76http://www.conservationevidence.com/​actions/​225

Reduce grazing intensity

77Nine of eleven studies from the UK and USA found that the populations of some species were higher on fields with reduced grazing intensity, compared to conventionally-grazed fields, or found that birds used these fields more. Three studies investigated several interventions at once. Five studies from Europe found that some or all species were no more numerous, or were less abundant on fields with reduced grazing. A study from the UK found that black grouse populations increased at reduced grazing sites (whilst they declined elsewhere). However, large areas with reduced grazing had low female densities. A study from the USA found that the number of species on plots with reduced grazing increased over time. A study from four European countries found no differences in the number of species on sites with low-or high-intensity grazing. Assessment: likely to be beneficial (effectiveness 46%; certainty 55%; harms 0%).

78http://www.conservationevidence.com/​actions/​220

Reduce management intensity of permanent grasslands

79Seven of eight European studies found that some or all birds studied were more abundant on grasslands with reduced management intensity, or used them more than other habitats for foraging. Five studies of four experiments found that some or all species were found at lower or similar abundances on reduced-management grasslands, compared to intensively-managed grasslands. Assessment: likely to be beneficial (effectiveness 65%; certainty 46%; harms 0%).

80http://www.conservationevidence.com/​actions/​219

Trade-off between benefit and harms

Exclude livestock from semi-natural habitat

81Two studies from the USA, out of 11 overall, found higher species richness on sites with grazers excluded. A study from Argentina found lower species richness and one from the USA found no difference. Seven studies from the USA found that overall bird abundance, or the abundances of some species were higher in sites with grazers excluded. Seven studies from the USA and Argentina found that overall abundance or the abundance of some species were lower on sites without grazers, or did not differ. Three studies found that productivities were higher on sites with grazers excluded. In one, the difference was only found consistently in comparison with improved pastures, not unimproved. Assessment: trade-offs between benefits and harms (effectiveness 50%; certainty 57%; harms 30%).

82http://../www.conservationevidence.com/actions/236

Unknown effectiveness (limited evidence)

Create open patches or strips in permanent grassland

83A study from the UK found that Eurasian skylarks used fields with open strips in, but that variations in skylark numbers were too great to draw conclusions from this finding. Assessment: unknown effectiveness – limited evidence (effectiveness 20%; certainty 19%; harms 0%).

84http://www.conservationevidence.com/​actions/​239

Maintain upland heath/moor

85A study from the UK found that bird populations in one region were increasing with agri-environment guidelines on moor management. There were some problems with overgrazing, burning and scrub encroachment. Assessment: unknown effectiveness – limited evidence (effectiveness 30%; certainty 15%; harms 0%).

86http://www.conservationevidence.com/​actions/​230

Protect nests from livestock to reduce trampling

87One of two studies found that a population of Chatham Island oystercatchers increased following several interventions including the erection of fencing around individual nests. A study from Sweden found that no southern dunlin nests were trampled when protected by cages; some unprotected nests were destroyed. Assessment: unknown effectiveness – limited evidence (effectiveness 56%; certainty 19%; harms 0%).

88http://www.conservationevidence.com/​actions/​237

Provide short grass for waders

89A study from the UK found that common starlings and northern lapwing spent more time foraging on areas with short swards, compared to longer swards. Assessment: unknown effectiveness – limited evidence (effectiveness 41%; certainty 32%; harms 0%).

90%20http://www.conservationevidence.com/​actions/​221

Raise mowing height on grasslands

91One of two studies from the UK found that no more foraging birds were attracted to plots with raised mowing heights, compared to plots with shorter grass. A review from the UK found that Eurasian skylarks had higher productivity on sites with raised mowing heights, but this increase was not enough to maintain local populations. Assessment: unknown effectiveness – limited evidence (effectiveness 20%; certainty 36%; harms 0%).

92http://www.conservationevidence.com/​actions/​222

Unlikely to be beneficial

Use traditional breeds of livestock

93A study from four countries in Europe found no differences in bird abundances in areas grazed with traditional or commercial breeds. Assessment: unlikely to be beneficial (effectiveness 0%; certainty 44%; harms 0%).

94http://www.conservationevidence.com/​actions/​233

No evidence found (no assessment)

95We have captured no evidence for the following interventions:

  • Maintain lowland heathland
  • Maintain rush pastures
  • Maintain wood pasture and parkland
  • Plant Brassica fodder crops
  • Use mixed stocking

3.4.4 Perennial, non-timber crops

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for perennial, non-timber crops?

Unknown effectiveness (limited evidence)

● Maintain traditional orchards

No evidence found (no assessment)

● Manage perennial bioenergy crops to benefit wildlife

Unknown effectiveness (limited evidence)

Maintain traditional orchards

96Two site comparison studies from the UK and Switzerland found that traditional orchards offer little benefit to birds. In Switzerland only one breeding bird species was associated with traditional orchards. In the UK, the population density of cirl bunting was negatively related to the presence of orchards. Assessment: unknown effectiveness – limited evidence (effectiveness 10%; certainty 24%; harms 0%).

97http://www.conservationevidence.com/​actions/​240

No evidence found (no assessment)

98We have captured no evidence for the following interventions:

99• Manage perennial bioenergy crops to benefit wildlife

3.4.5 Aquaculture

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for aquaculture?

Likely to be beneficial

● Deter birds from landing on shellfish culture gear – suspend oyster bags under water
● Deter birds from landing on shellfish culture gear – use spikes on oyster cages
● Disturb birds at roosts
● Provide refuges for fish within ponds
● Use electric fencing to exclude fish-eating birds
● Use ʹmussel socksʹ to prevent birds from attacking shellfish
● Use netting to exclude fish-eating birds

Unknown effectiveness (limited evidence)

● Increase water turbidity to reduce fish predation by birds
● Translocate birds away from fish farms
● Use in-water devices to reduce fish loss from ponds

Unlikely to be beneficial

● Disturb birds using foot patrols
● Spray water to deter birds from ponds

Likely to be ineffective or harmful

● Scare birds from fish farms

Likely to be beneficial

Deter birds from landing on shellfish culture gear

100A study from Canada found that fewer birds landed on oyster cages fitted with spikes than control cages. The same study found that fewer birds landed on oyster bags suspended 6 cm, but not 3 cm, underwater, compared to bags on the surface. Assessment for using spikes on oyster cages: likely to be beneficial (effectiveness 60%; certainty 43%; harms 0%). Assessment for suspending oyster bags under water: likely to be beneficial (effectiveness 55%; certainty 43%; harms 0%).

101http://www.conservationevidence.com/​actions/​257

102http://www.conservationevidence.com/​actions/​256

Disturb birds at roosts

103One study from the USA found reduced fish predation after fish-eating birds were disturbed at roosts. Five studies from the USA and Israel found that birds foraged less near disturbed roosts, or left the area after being disturbed. One found the effects were only temporary. Assessment: likely to be beneficial (effectiveness 67%; certainty 45%; harms 0%).

104http://www.conservationevidence.com/​actions/​245

Provide refuges for fish within ponds

105A study from the UK found that cormorants caught fewer fish in a pond with fish refuges in, compared to a control pond. Assessment: likely to be beneficial (effectiveness 65%; certainty 43%; harms 0%).

106http://www.conservationevidence.com/​actions/​253

Use electric fencing to exclude fish-eating birds

107Two before-and-after trials from the USA found lower use of fish ponds by herons after electric fencing was installed. Assessment: likely to be beneficial (effectiveness 60%; certainty 49%; harms 0%).

108http://www.conservationevidence.com/​actions/​247

Use ʹmussel socksʹ to prevent birds from attacking shellfish

109A study from Canada found that mussel socks with protective sleeves lost fewer medium-sized mussels (but not small or large mussels), compared to unprotected mussel socks. Assessment: likely to be beneficial (effectiveness 50%; certainty 41%; harms 0%).

110http://www.conservationevidence.com/​actions/​250

Use netting to exclude fish-eating birds

111Two studies from Germany and the USA, and a review, found that netting over ponds reduced the loss of fish to predatory birds. Two studies from the USA and the Netherlands found that birds still landed on ponds with netting, but that they altered their behaviour, compared to open ponds. Two studies from Germany and Israel found that some birds became entangled in netting over ponds. Assessment: likely to be beneficial (effectiveness 60%; certainty 59%; harms 15%).

112http://www.conservationevidence.com/​actions/​248

Unknown effectiveness (limited evidence)

Increase water turbidity to reduce fish predation by birds

113An ex situ study from France found that egret foraging efficiency was reduced in more turbid water. Assessment: unknown effectiveness – limited evidence (effectiveness 50%; certainty 23%; harms 0%).

114http://www.conservationevidence.com/​actions/​252

Translocate birds away from fish farms

115A study from the USA found that translocating birds appeared to reduce bird numbers at a fish farm. A study from Belgium found that it did not. Assessment: unknown effectiveness – limited evidence (effectiveness 20%; certainty 33%; harms 0%).

116http://www.conservationevidence.com/​actions/​251

Use in-water devices to reduce fish loss from ponds

117A study from the USA found that fewer cormorants used two ponds after underwater ropes were installed; a study from Australia found that no fewer cormorants used ponds with gill nets in. Assessment: unknown effectiveness – limited evidence (effectiveness 34%; certainty 35%; harms 0%).

118http://www.conservationevidence.com/​actions/​254

Unlikely to be beneficial

Disturb birds using foot patrols

119Two replicated studies from Belgium and Australia found that using foot patrols to disturb birds from fish farms did not reduce the number of birds present or fish consumption. Assessment: unlikely to be beneficial (effectiveness 0%; certainty 45%; harms 0%).

120http://www.conservationevidence.com/​actions/​249

Spray water to deter birds from ponds

121A study from Sweden found that spraying water deterred birds from fish ponds, but that some birds became habituated to the spray. Assessment: unlikely to be beneficial (effectiveness 31%; certainty 43%; harms 0%).

122http://www.conservationevidence.com/​actions/​255

Likely to be ineffective or harmful

Scare birds from fish farms

123One study from Israel found a population increase in fish-eating birds after efforts to scare them from fish farms, possibly due to lower persecution. One of two studies found evidence for reduced loss of fish when birds were scared from farms. Two studies from Australia and Belgium found that disturbing birds using foot patrols was not effective. Ten of 11 studies from across the world found some effects for acoustic deterrents, five of seven found that visual deterrents were effective. In both cases some studies found that results were temporary, birds became habituated or that some deterrents were effective, whilst others were not. One study found that trained raptors were effective, one found little evidence for the effectiveness of helicopters or light aircraft. Assessment: likely to be ineffective or harmful (effectiveness 36%; certainty 64%; harms 0%).

124http://www.conservationevidence.com/​actions/​244

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