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What Works in Conservation 2015

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

3. Bird Conservation

3.11. Threat: Invasive alien and other problematic species

Texte intégral

1This assessment method for this chapter is described in Walsh, J. C., Dicks, L. V. & Sutherland, W. J. (2015) The effect of scientific evidence on conservation practitionersʹ management decisions. Conservation Biology, 29: 88-98. No harms were assessed for this section.

3.11.1 Reduce predation by other species

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for reducing predation by other species?

Beneficial

● Control mammalian predators on islands
● Remove or control predators to enhance bird populations and communities

Likely to be beneficial

● Control avian predators on islands

Unknown effectiveness (limited evidence)

● Control invasive ants on islands
● Reduce predation by translocating predators

Evidence not assessed

● Control predators not on islands

2NB. No harms assessed for this section

Beneficial

Control mammalian predators on islands

3Of the 33 studies from across the world, 16 described population increases or recolonisations in at least some of the sites studied and 18 found higher reproductive success or lower mortality (on artificial nests in one case).

4Two studies that investigated population changes found only partial increases, in black oystercatchers Haematopus bachmani and two gamebird species, respectively. Eighteen of the studies investigated rodent control; 12 cat Felis catus control and 6 various other predators including pigs Sus scrofa and red foxes Vulpes vulpes. The two that found only partial increases examined cat, fox and other larger mammal removal. Assessment: beneficial (effectiveness 81%; certainty 78%).

5http://www.conservationevidence.com/​actions/​373

Remove or control predators to enhance bird populations and communities

6Both a meta-analysis and a systematic review (both global) found that bird reproductive success increased with predator control and that either post-breeding or breeding-season populations increased. The systematic review found that post-breeding success increased with predator control on mainlands, but not islands. Assessment: beneficial (effectiveness 66%; certainty 71%).

7http://www.conservationevidence.com/​actions/​371

Likely to be beneficial

Control avian predators on islands

8Five out of seven studies from across the world found that bird populations increased, had higher reproductive success, or lower mortality following avian predator control. However, although two discussed multiple interventions, so changes couldn’t be linked to predator control, and one found that no birds returned to the site the following year. All five that reported positive effects were studies of seabird populations. The two that found little evidence studied the effects of crow removal on gamebirds or birds of prey. Assessment: likely to be beneficial (effectiveness 50%; certainty 45%).

9http://www.conservationevidence.com/​actions/​372

Unknown effectiveness (limited evidence)

Control invasive ants on islands

10A single study in the USA found that controlling the invasive tropical fire ant Solenopsis geminata, but not the big-headed ant Pheidole megacephala, led to lower rates of injuries and temporarily higher fledging success than on islands without ant control. The authors note that very few chicks were injured by P. megacephala on either experimental or control islands. Assessment: unknown effectiveness – limited evidence (effectiveness 10%; certainty 15%).

11http://www.conservationevidence.com/​actions/​383

Reduce predation by translocating predators

12Two studies from France and the USA found local population increases or reduced predation following the translocation of predators away from an area. Assessment: unknown effectiveness – limited evidence (effectiveness 27%; certainty 20%).

13http://www.conservationevidence.com/​actions/​393

Evidence not assessed

Control predators not on islands

14A study from the UK found higher bird community breeding densities and fledging success rates in plots with red fox Vulpes vulpes and carrion crow Corvus corone control. Of the 25 taxa-specific studies, only five found evidence for population increases with predator control, whilst one found a population decrease (with other interventions also used); one found lower or similar survival, probably because birds took bait. Nineteen studies found some evidence for increased reproductive success or decreased predation with predator control, with three studies (including a meta-analysis) finding no evidence for higher reproductive success or predation with predator control or translocation from the study site. One other study found evidence for increases in only three of six species studied. Most studies studied the removal of a number of different mammals, although several also removed bird predators, mostly carrion crows and gulls Larus spp. Assessment: this intervention has not been assessed.

15http://www.conservationevidence.com/​actions/​384

3.11.2 Reduce incidental mortality during predator eradication or control

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for reducing incidental mortality during predator eradication or control predation

Unknown effectiveness (limited evidence)

● Distribute poison bait using dispensers
● Use coloured baits to reduce accidental mortality during predator control
● Use repellents on baits

Evidence not assessed

● Do birds take bait designed for pest control?

16NB. No harms assessed for this section

Unknown effectiveness (limited evidence)

Distribute poison bait using dispensers

17A study from New Zealand found that South Island robin survival was higher when bait for rats and mice was dispensed from feeders, compared to being scattered. Assessment: unknown effectiveness – limited evidence (effectiveness 40%; certainty 25%).

18http://www.conservationevidence.com/​actions/​157

Use coloured baits to reduce accidental mortality during predator control

19Two out of three studies found that dyed baits were consumed at lower rates by songbirds and kestrels. An ex situ study from Australia found that dyeing food did not reduce its consumption by bush thick-knees. Assessment: unknown effectiveness – limited evidence (effectiveness 20%; certainty 30%).

20http://www.conservationevidence.com/​actions/​182

Use repellents on baits

21A study in New Zealand found that repellents reduced the rate of pecking at baits by North Island robins. A study from the USA found that treating bait with repellents did not reduce consumption by American kestrels.

22Assessment: unknown effectiveness – limited evidence (effectiveness 10%; certainty 10%).

23http://www.conservationevidence.com/​actions/​159

Evidence not assessed

Do birds take bait designed for pest control?

24Two studies from New Zealand and Australia, one ex situ, found no evidence that birds took bait meant for pest control. Assessment: this intervention has not been assessed.

25http://www.conservationevidence.com/​actions/​395

3.11.3 Reduce nest predation by excluding predators from nests or nesting areas

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for reducing nest predation by excluding predators from nests or nesting areas

Likely to be beneficial

● Physically protect nests from predators using non electric fencing
● Physically protect nests with individual exclosures/barriers or provide shelters for chicks
● Protect bird nests using electric fencing
● Use artificial nests that discourage predation

Unknown effectiveness (limited evidence)

● Guard nests to prevent predation
● Plant nesting cover to reduce nest predation
● Protect nests from ants
● Use multiple barriers to protect nests
● Use naphthalene to deter mammalian predators
● Use snakeskin to deter mammalian nest predators

No evidence found (no assessment)

● Play spoken-word radio programs to deter predators
● Use ʹcat curfewsʹ to reduce predation
● Use lion dung to deter domestic cats
● Use mirrors to deter nest predators
● Use ultrasonic devices to deter cats

Evidence not assessed

● Can nest protection increase nest abandonment?
● Can nest protection increase predation of adults and chicks?

Likely to be beneficial

Physically protect nests from predators using non-electric fencing

26Two of four studies from the UK and the USA found that fewer nests failed or were predated when predator exclusion fences were erected. Two studies found that nesting and fledging success was no higher when fences were used, one found that hatching success was higher. Assessment: likely to be beneficial (effectiveness 45%; certainty 48%).

27http://www.conservationevidence.com/​actions/​183

Physically protect nests with individual exclosures/barriers or provide shelters for chicks

28Nine of 23 studies found that fledging rates or productivity were higher for nests protected by individual barriers than for unprotected nests. Two found no higher productivity. Fourteen studies found that hatching rates or survival were higher, or that predation was lower for protected nests. Two found no differences between protected and unprotected nests and one found that adults were harassed by predators at protected nests. One study found that chick shelters were not used much and a review found that some exclosure designs were more effective than others. Assessment: likely to be beneficial (effectiveness 50%; certainty 50%).

29http://conservationevidence.com/​actions/​397

30http://conservationevidence.com/​actions/​398

31http://conservationevidence.com/​actions/​399

32http://conservationevidence.com/​actions/​400 Protect bird nests using electric fencing Two of six studies found increased numbers of terns or tern nests following the erection of an electric fence around colonies. Five studies found higher survival or productivity of waders or seabirds when electric fences were used and one found lower predation by mammals inside electric fences. One study found that predation by birds was higher inside electric fences. Assessment: likely to be beneficial (effectiveness 60%; certainty 59%).

33http://www.conservationevidence.com/​actions/​188

Use artificial nests that discourage predation

34Three out of five studies from North America found lower predation rates or higher nesting success for wildfowl in artificial nests, compared with natural nests. An ex situ study found that some nest box designs prevented racoons from entering. A study found that wood ducks avoided antipredator nest boxes but only if given the choice of unaltered nest boxes. Assessment: likely to be beneficial (effectiveness 59%; certainty 54%).

35http://www.conservationevidence.com/​actions/​402

Unknown effectiveness (limited evidence)

Guard nests to prevent predation

36Nest guarding can be used as a response to a range of threats and is therefore discussed in ʹGeneral responses to small/declining populationsʹ. Assessment: unknown effectiveness – limited evidence (effectiveness 50%; certainty 30%).

37http://www.conservationevidence.com/​actions/​411

Plant nesting cover to reduce nest predation

38Studies relevant to this intervention are in ‘ Threat: Agriculture’. Assessment: unknown effectiveness – limited evidence (effectiveness 28%; certainty 30%).

39http://www.conservationevidence.com/​actions/​405

Protect nests from ants

40A study from the USA found that vireo nests protected from ants with a physical barrier and a chemical repellent had higher fledging success than unprotected nests. Assessment: unknown effectiveness – limited evidence (effectiveness 45%; certainty 17%).

41http://www.conservationevidence.com/​actions/​410

Use multiple barriers to protect nests

42One of two studies found that plover fledging success in the USA was no higher when an electric fence was erected around individual nest exclosures, compared to when just the exclosures were present. A study from the USA found that predation on chicks was lower when one of two barriers around nests was removed early, compared to when it was left for three more days. Assessment: unknown effectiveness – limited evidence (effectiveness 7%; certainty 17%).

43http://www.conservationevidence.com/​actions/​404

Use naphthalene to deter mammalian predators

44A study from the USA found that predation rates on artificial nests did not differ when naphthalene moth balls were scattered around them. Assessment: unknown effectiveness – limited evidence (effectiveness 0%; certainty 10%).

45http://www.conservationevidence.com/​actions/​408

Use snakeskin to deter mammalian nest predators

46A study from the USA found that flycatcher nests were predated less frequently if they had a snakeskin wrapped around them. Assessment: unknown effectiveness – limited evidence (effectiveness 33%; certainty 15%).

47http://www.conservationevidence.com/​actions/​406

No evidence found (no assessment)

48We have captured no evidence for the following interventions:

  • Play spoken-word radio programmes to deter predators
  • Use ʹcat curfewsʹ to reduce predation
  • Use lion dung to deter domestic cats
  • Use mirrors to deter nest predators
  • Use ultrasonic devices to deter cats

Evidence not assessed

Can nest protection increase nest abandonment?

49One of four studies (from the USA) found an increase in abandonment after nest exclosures were used. Two studies from the USA and Sweden found no increases in abandonment when exclosures were used and a review from the USA found that some designs were more likely to cause abandonment than others. Assessment: this intervention has not been assessed.

50http://www.conservationevidence.com/​actions/​401

Can nest protection increase predation of adults and chicks?

51Four of five studies from the USA and Sweden found that predation on chicks and adults was higher when exclosures were used. One of these found that adults were harassed when exclosures were installed and the chicks rapidly predated when they were removed. One study from Sweden found that predation was no higher when exclosures were used. Assessment: this intervention has not been assessed.

52http://www.conservationevidence.com/​actions/​403

3.11.4 Reduce mortality by reducing hunting ability or changing predator behaviour

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for reducing mortality by reducing hunting ability or changing predator behaviour

Unknown effectiveness (limited evidence)

● Reduce predation by translocating nest boxes
● Use collar-mounted devices to reduce predation
● Use supplementary feeding of predators to reduce predation

Unlikely to be beneficial

● Use aversive conditioning to reduce nest predation

Unknown effectiveness (limited evidence)

Reduce predation by translocating nest boxes

53Two European studies found that predation rates were lower for translocated nest boxes than for controls. Assessment: unknown effectiveness – limited evidence (effectiveness 48%; certainty 25%).

54http://www.conservationevidence.com/​actions/​420

Use collar-mounted devices to reduce predation

55Two replicated randomised and controlled studies in the UK and Australia found that fewer birds were returned by cats wearing collars with anti-hunting devices, compared to cats with control collars. No differences were found between different devices. Assessment: unknown effectiveness – limited evidence (effectiveness 48%; certainty 35%).

56http://www.conservationevidence.com/​actions/​416

Use supplementary feeding to reduce predation

57One of three studies found that fewer grouse chicks were taken to harrier nests when supplementary food was provided to the harriers, but no effect on grouse adult survival or productivity was found. One study from the USA found reduced predation on artificial nests when supplementary food was provided. Another study from the USA found no such effect. Assessment: unknown effectiveness – limited evidence (effectiveness 13%; certainty 20%).

58http://www.conservationevidence.com/​actions/​417

Unlikely to be beneficial

Use aversive conditioning to reduce nest predation

59Nine out of 12 studies found no evidence for aversive conditioning or reduced nest predation after aversive conditioning treatment stopped. Ten studies found reduced consumption of food when it was treated with repellent chemicals, i. e. during the treatment. Three, all studying avian predators, found some evidence for reduced consumption after treatment but these were short-lived trials or the effect disappeared within a year. Assessment: unlikely to be beneficial (effectiveness 9%; certainty 60%).

60http://www.conservationevidence.com/​actions/​418

61http://www.conservationevidence.com/​actions/​419

3.11.5 Reduce competition with other species for food and nest sites

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for reducing competition with other species for food and nest sites?

Likely to be beneficial

● Reduce inter-specific competition for food by removing or controlling competitor species

Unknown effectiveness (limited evidence)

● Protect nest sites from competitors
● Reduce competition between species by providing nest boxes
● Reduce inter-specific competition for nest sites by modifying habitats to exclude competitor species
● Reduce inter-specific competition for nest sites by removing competitor species: ground nesting seabirds
● Reduce inter-specific competition for nest sites by removing competitor species: songbirds
● Reduce inter-specific competition for nest sites by removing competitor species: woodpeckers

Likely to be beneficial

Reduce inter-specific competition for food by removing or controlling competitor species

62Three out of four studies found that at least some of the target species increased following the removal or control of competitor species. Two studies found that some or all target species did not increase, or that there was no change in kleptoparasitic behaviour of competitor species after control efforts. Assessment: likely to be beneficial (effectiveness 44%; certainty 40%; harms 0%).

63http://www.conservationevidence.com/​actions/​428

Unknown effectiveness (limited evidence)

Protect nest sites from competitors

64Two studies from the USA found that red-cockaded woodpecker populations increased after the installation of ʹrestrictor platesʹ around nest holes to prevent larger woodpeckers for enlarging them. Several other interventions were used at the same time. A study from Puerto Rico found lower competition between species after nest boxes were altered. A study from the USA found weak evidence that exclusion devices prevented house sparrows from using nest boxes and another study from the USA found that fitting restrictor plates to red-cockaded woodpecker holes reduced the number that were enlarged by other woodpeckers. Assessment: unknown effectiveness – limited evidence (effectiveness 39%; certainty 24%; harms 5%).

65http://www.conservationevidence.com/​actions/​426

Reduce competition between species by providing nest boxes

66A study from the USA found that providing extra nest boxes did not reduce the rate at which common starlings usurped northern flickers from nests. Assessment: unknown effectiveness – limited evidence (effectiveness 0%; certainty 16%; harms 0%).

67http://www.conservationevidence.com/​actions/​427

Reduce inter-specific competition for nest sites by modifying habitats to exclude competitor species

68A study from the USA found that clearing midstorey vegetation did not reduce the occupancy of red-cockaded woodpecker nesting holes by southern flying squirrels. Assessment: unknown effectiveness – limited evidence (effectiveness 0%; certainty 12%; harms 0%).

69http://www.conservationevidence.com/​actions/​425

Reduce inter-specific competition for nest sites by removing competitor species (ground nesting seabirds)

70Four studies from Canada and the UK found increased tern populations following the control or exclusion of gulls, and in two cases with many additional interventions. Two studies from the UK and Canada found that controlling large gulls had no impact on smaller species. Two studies from the USA and UK found that exclusion devices successfully reduced the numbers of gulls at sites, although one found that they were only effective at small colonies and the other found that methods varied in their effectiveness and practicality. Assessment: unknown effectiveness – limited evidence (effectiveness 41%; certainty 31%; harms 14%).

71http://www.conservationevidence.com/​actions/​422

Reduce inter-specific competition for nest sites by removing competitor species (songbirds)

72Two studies from Australia found increases in bird populations and species richness after control of noisy miners. A study from Italy found that blue tits nested in more nest boxes when hazel dormice were excluded from boxes over winter. Assessment: unknown effectiveness – limited evidence (effectiveness 50%; certainty 22%; harms 0%).

73http://www.conservationevidence.com/​actions/​424

Reduce inter-specific competition for nest sites by removing competitor species (woodpeckers)

74Two studies in the USA found red-cockaded woodpecker populations increased following the removal of southern flying squirrels, in one case along with other interventions. A third found that red-cockaded woodpecker reintroductions were successful when squirrels were controlled. One study found fewer holes were occupied by squirrels following control efforts, but that occupancy by red-cockaded woodpeckers was no higher. Assessment: unknown effectiveness – limited evidence (effectiveness 34%; certainty 28%; harms 0%).

75http://www.conservationevidence.com/​actions/​423

3.11.6 Reduce adverse habitat alteration by other species

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for reducing adverse habitat alteration by other species?

Likely to be beneficial

● Control or remove habitat-altering mammals
● Reduce adverse habitat alterations by excluding problematic species (terrestrial species)

Unknown effectiveness (limited evidence)

● Reduce adverse habitat alterations by excluding problematic species (aquatic species)
● Remove problematic vegetation
● Use buffer zones to reduce the impact of invasive plant control

Likely to be beneficial

Control or remove habitat-altering mammals

76Four out of five studies from islands in the Azores and Australia found that seabird populations increased after rabbits or other species were removed, although three studied several interventions at the same time. Two studies from Australia and Madeira found that seabird productivity increased after rabbit and house mouse eradication. Assessment: likely to be beneficial (effectiveness 61%; certainty 41%; harms 0%).

77http://www.conservationevidence.com/​actions/​431

Reduce adverse habitat alterations by excluding problematic species (terrestrial species)

78Three studies from the USA and the UK found higher numbers of certain songbird species and higher species richness in these groups when deer were excluded from forests. Intermediate canopy-nesting species in the USA and common nightingales in the UK were the species to benefit. A study from Hawaii found mixed effects of grazer exclusion. Assessment: likely to be beneficial (effectiveness 48%; certainty 40%; harms 0%).

79http://www.conservationevidence.com/​actions/​429

Unknown effectiveness (limited evidence)

Reduce adverse habitat alterations by excluding problematic species (aquatic species)

80A study in the USA found that waterbirds preferentially used wetland plots from which grass carp were excluded but moved as these became depleted over the winter. Assessment: unknown effectiveness – limited evidence (effectiveness 30%; certainty 14%; harms 0%).

81http://www.conservationevidence.com/​actions/​430

Remove problematic vegetation

82One of four studies (from Japan) found an increase in a bird population following the removal of an invasive plant. One study from the USA found lower bird densities in areas where a problematic native species was removed. One study from Australia found the Gould’s petrel productivity was higher following the removal of native bird-lime trees, and a study from New Zealand found that Chatham Island oystercatchers could nest in preferable areas of beaches after invasive marram grass was removed. Assessment: unknown effectiveness – limited evidence (effectiveness 43%; certainty 23%; harms 0%).

83http://www.conservationevidence.com/​actions/​432

Use buffer zones to reduce the impact of invasive plant control

84A study from the USA found that no snail kite nests (built above water in cattail and bulrush) were lost during herbicide spraying when buffer zones were established around nests. Assessment: unknown effectiveness – limited evidence (effectiveness 40%; certainty 10%; harms 0%).

85http://www.conservationevidence.com/​actions/​433

3.11.7 Reduce parasitism and disease

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for reducing parasitism and disease?

Likely to be beneficial

● Remove/control adult brood parasites

Trade-off between benefit and harms

● Remove/treat endoparasites and diseases

Unknown effectiveness (limited evidence)

● Alter artificial nest sites to discourage brood parasitism
● Exclude or control ʹreservoir speciesʹ to reduce parasite burdens
● Remove brood parasite eggs from target species ’ nests
● Remove/treat ectoparasites to increase survival or reproductive success: reduce nest ectoparasites by providing beneficial nesting material
● Remove/treat ectoparasites to increase survival or reproductive success: remove ectoparasites from feathers
● Use false brood parasite eggs to discourage brood parasitism

Unlikely to be beneficial

● Remove/treat ectoparasites to increase survival or reproductive success: remove ectoparasites from nests

Likely to be beneficial

Remove/control adult brood parasites

86One of 12 studies, all from the Americas, found that a host species population increased after control of the parasitic cowbird, two studies found no effect. Five studies found higher productivities or success rates when cowbirds were removed, five found that some or all measures of productivity were no different. Eleven studies found that brood parasitism rates were lower after cowbird control. Assessment: likely to be beneficial (effectiveness 48%; certainty 61%; harms 0%).

87http://www.conservationevidence.com/​actions/​441

Trade-off between benefit and harms

Remove/treat endoparasites and diseases

88Two out of five studies found that removing endoparasites increased survival in birds and one study found higher productivity in treated birds. Two studies found no evidence, or uncertain evidence, for increases in survival with treatment and one study found lower parasite burdens, but also lower survival in birds treated with antihelmintic drugs. Assessment: trade-offs between benefits and harms (effectiveness 48%; certainty 51%; harms 37%).

89http://www.conservationevidence.com/​actions/​434

Unknown effectiveness (limited evidence)

Alter artificial nest sites to discourage brood parasitism

90A replicated trial from Puerto Rico found that brood parasitism levels were extremely high across all nest box designs tested. Assessment: unknown effectiveness – limited evidence (effectiveness 0%; certainty 13%; harms 0%).

91http://www.conservationevidence.com/​actions/​446

Exclude or control ʹreservoir speciesʹ to reduce parasite burdens

92One of two studies found increased chick production in grouse when hares (carries of louping ill virus) were culled in the area, although a comment on the paper disputes this finding. A literature review found no compelling evidence for the effects of hare culling on grouse populations. Assessment: unknown effectiveness – limited evidence (effectiveness 13%; certainty 20%; harms 0%).

93http://www.conservationevidence.com/​actions/​435

Remove brood parasite eggs from target speciesʹ nests

94One of two studies found lower rates of parasitism when cowbird eggs were removed from host nests. One study found that nests from which cowbird eggs were removed had lower success than parasitised nests. Assessment: unknown effectiveness – limited evidence (effectiveness 24%; certainty 20%; harms 21%).

95http://www.conservationevidence.com/​actions/​443

Remove/treat ectoparasites to increase survival or reproductive success (provide beneficial nesting material)

96A study in Canada found lower numbers of some, but not all, parasites in nests provided with beneficial nesting material, but that there was no effect on fledging rates or chick condition. Assessment: unknown effectiveness – limited evidence (effectiveness 15%; certainty 13%; harms 0%).

97http://www.conservationevidence.com/​actions/​439

Remove/treat ectoparasites to increase survival or reproductive success (remove ectoparasites from feathers)

98A study in the UK found that red grouse treated with spot applications had lower tick and disease burdens and higher survival than controls, whilst birds with impregnated tags had lower tick burdens only. A study in Hawaii found that CO2 was the most effective way to remove lice from feathers, although lice were not killed. Assessment: unknown effectiveness – limited evidence (effectiveness 42%; certainty 16%; harms 0%).

99http://www.conservationevidence.com/​actions/​437

Use false brood parasite eggs to discourage brood parasitism

100A study from the USA found that parasitism rates were lower for redwinged blackbird nests with false or real cowbird eggs placed in them, than for control nests. Assessment: unknown effectiveness – limited evidence (effectiveness 35%; certainty 19%; harms 0%).

101http://www.conservationevidence.com/​actions/​444

Unlikely to be beneficial

Remove/treat ectoparasites to increase survival or reproductive success (remove ectoparasites from nests)

102Six of the seven studies found lower infestation rates in nests treated for ectoparasites, one (that used microwaves to treat nests) did not find fewer parasites. Two studies from the USA found higher survival or lower abandonment in nests treated for ectoparasites, whilst seven studies from across the world found no differences in survival, fledging rates or productivity between nests treated for ectoparasites and controls. Two of six studies found that chicks from nests treated for ectoparasites were in better condition than those from control nests. Assessment: unlikely to be beneficial (effectiveness 25%; certainty 58%; harms 0%).

103http://www.conservationevidence.com/​actions/​438

3.11.8 Reduce detrimental impacts of other problematic species

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for reducing detrimental impacts of other problematic species?

Unknown effectiveness (limited evidence)

● Use copper strips to exclude snails from nests

Unknown effectiveness (limited evidence)

Use copper strips to exclude snails from nests

104A study from Mauritius found no mortality from snails invading echo parakeet nests after the installation of copper strips around nest trees. Before installation, four chicks were killed by snails. Assessment: unknown effectiveness – limited evidence (effectiveness 47%; certainty 15%; harms 0%).

105http://www.conservationevidence.com/​actions/​447

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