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What Works in Conservation 2018

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

3. Bird conservation

3.15 Captive breeding, rearing and releases (ex situ conservation)

Texte intégral

3.15.1 Captive breeding

Likely to be beneficial

● Artificially incubate and hand-rear birds in captivity (raptors)

1Six studies from across the world found high success rates for artificial incubation and hand-rearing of raptors. A replicated and controlled study from France found that artificially incubated raptor eggs had lower hatching success than parent-incubated eggs but fledging success for hand-reared chicks was similar to wild chicks. A study from Canada found that hand-reared chicks had slower growth and attained a lower weight than parent-reared birds. A replicated study from Mauritius found that hand-rearing of wild eggs had higher success than hand-rearing captive-bred chicks. Three studies that provided methodological comparisons reported that incubation temperature affected hatching success and adding saline to the diet of falcon chicks increased their weight gain. Assessment: likely to be beneficial (effectiveness 60%; certainty 52%; harms 5%).

2http://www.conservationevidence.com/​actions/​614

● Artificially incubate and hand-rear birds in captivity (seabirds)

3Five studies from across the world found evidence for the success of hand-rearing seabirds. One small study in Spain found that one of five hand-reared Audouin’s gulls successfully bred in the wild. Four studies found that various petrel species successfully fledged after hand-rearing. One controlled study found that fledging rates of hand-reared birds was similar to parent-reared birds, although a study on a single bird found that the chick fledged at a lower weight and later than parent-reared chicks. Assessment: likely to be beneficial (effectiveness 67%; certainty 45%; harms 2%).

4http://www.conservationevidence.com/​actions/​604

● Artificially incubate and hand-rear birds in captivity (songbirds)

5Four studies from the USA found high rates of success for artificial incubation and hand-rearing of songbirds. One study found that crow chicks fed more food had higher growth rates, but these rates never matched those of wild birds. Assessment: likely to be beneficial (effectiveness 51%; certainty 44%; harms 1%).

6http://www.conservationevidence.com/​actions/​616

● Artificially incubate and hand-rear birds in captivity (waders)

7Three out of four replicated and controlled studies from the USA and New Zealand found that artificially incubated and/or hand-reared waders had higher hatching and fledging success than controls. One study from New Zealand found that hatching success of black stilt was lower for artificially-incubated eggs. Assessment: likely to be beneficial (effectiveness 64%; certainty 41%; harms 4%).

8http://www.conservationevidence.com/​actions/​611

● Use captive breeding to increase or maintain populations (raptors)

9Three small studies and a review from around the world found that raptors bred successfully in captivity. Two of these studies found that wild-caught birds bred in captivity after a few years, with one pair of brown goshawks producing 15 young over four years, whilst a study on bald eagle captive breeding found low fertility in captive-bred eggs, but that birds still produced chicks after a year. A review of Mauritius kestrel captive breeding found that 139 independent young were raised over 12 years from 30 eggs and chicks taken from the wild. An update of the same programme found that hand-reared Mauritius kestrels were less successful if they came from captive-bred eggs compared to wild ‘harvested’ eggs. Assessment: likely to be beneficial (effectiveness 50%; certainty 41%; harms 10%).

10http://www.conservationevidence.com/​actions/​596

Unknown effectiveness (limited evidence)

● Artificially incubate and hand-rear birds in captivity (bustards)

11Two reviews of a houbara bustard captive breeding programme in Saudi Arabia found no difference in survival between artificially and parentally incubated eggs, and that removing eggs from clutches as they were laid increased the number laid by females. Assessment: unknown effectiveness — limited evidence (effectiveness 31%; certainty 10%; harms 0%).

12http://www.conservationevidence.com/​actions/​610

● Artificially incubate and hand-rear birds in captivity (cranes)

13Two studies from the USA found that hand-reared birds showed normal reproductive behaviour and higher survival than parent-reared birds. Assessment: unknown effectiveness — limited evidence (effectiveness 76%; certainty 31%; harms 0%).

14http://www.conservationevidence.com/​actions/​609

● Artificially incubate and hand-rear birds in captivity (gamebirds)

15A study in Finland found that hand-reared grey partridges did not take off to fly as effectively as wild-caught birds, potentially making them more vulnerable to predation. Assessment: unknown effectiveness — limited evidence (effectiveness 11%; certainty 10%; harms 50%).

16http://www.conservationevidence.com/​actions/​607

● Artificially incubate and hand-rear birds in captivity (parrots)

17Two studies from South America describe the successful hand-rearing of parrot chicks. A review of the kakapo management programme found that chicks could be successfully raised and released, but that eggs incubated from a young age had low success. A study from the USA found that all hand-reared thick-billed parrots died within a month of release: significantly lower survival than for wild-caught birds translocated to the release site. Assessment: unknown effectiveness — limited evidence (effectiveness 19%; certainty 30%; harms 11%).

18http://www.conservationevidence.com/​actions/​615

● Artificially incubate and hand-rear birds in captivity (penguins)

19Two replicated and controlled studies from South Africa found that hand-reared and released African penguins had similar survival and breeding success as birds which were not hand-reared. Assessment: unknown effectiveness — limited evidence (effectiveness 41%; certainty 15%; harms 0%).

20http://www.conservationevidence.com/​actions/​605

● Artificially incubate and hand-rear birds in captivity (rails)

21A controlled study from New Zealand found that post-release survival of hand-reared takahe was as high as wild-reared birds and that six of ten released females raised chicks. Assessment: unknown effectiveness — limited evidence (effectiveness 64%; certainty 13%; harms 0%).

22http://www.conservationevidence.com/​actions/​608

● Artificially incubate and hand-rear birds in captivity (storks and ibises)

23A small study in the USA describes the successful artificial incubation and hand-rearing of two Abdim’s stork chicks, whilst a review of northern bald ibis conservation found that only very intensive rearing of a small number of chicks appeared to allow strong bonds, thought to be important for the successful release of birds into the wild, to form between chicks. Assessment: unknown effectiveness — limited evidence (effectiveness 18%; certainty 10%; harms 0%).

24http://www.conservationevidence.com/​actions/​612

● Artificially incubate and hand-rear birds in captivity (vultures)

25A study in Peru found that hand-reared Andean condors had similar survival to parent-reared birds after release into the wild. Assessment: unknown effectiveness — limited evidence (effectiveness 30%; certainty 10%; harms 0%).

26http://www.conservationevidence.com/​actions/​613

● Artificially incubate and hand-rear birds in captivity (wildfowl)

27Two studies in Canada and India found high success rates for hand-rearing buffleheads and bar-headed geese in captivity. Eggs were artificially incubated or incubated under foster parents. A replicated, controlled study in England found that Hawaiian geese (nene) chicks showed less well-adapted behaviours if they were raised without parental contact. Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 20%; harms 10%).

28http://www.conservationevidence.com/​actions/​606

● Freeze semen for artificial insemination

29Two small trials from the USA found that using thawed frozen semen for artificial insemination resulted in low fertility rates. A small trial from the USA found that a cryprotectant increased fertility rates achieved using frozen semen. Assessment: unknown effectiveness — limited evidence (effectiveness 10%; certainty 10%; harms 45%).

30http://www.conservationevidence.com/​actions/​602

● Use artificial insemination in captive breeding

31A replicated study from Saudi Arabia found that artificial insemination could increase fertility in houbara bustards. A study of the same programme and a review found that repeated inseminations increased fertility, with the review arguing that artificial insemination had the potential to be a useful technique. Two studies from the USA found that artificially-inseminated raptors had either zero fertility, or approximately 50%. Assessment: unknown effectiveness — limited evidence (effectiveness 33%; certainty 21%; harms 0%).

32http://www.conservationevidence.com/​actions/​601

● Use captive breeding to increase or maintain populations (bustards)

33Four studies of a captive breeding programme in Saudi Arabia reported that the houbara bustard chicks were successfully raised in captivity, with 285 chicks hatched in the 7th year of the project after 232 birds were used to start the captive population. Captive birds bred earlier and appeared to lay more eggs than wild birds. Forty-six percent of captive eggs hatched and 43% of chicks survived to ten years old. Assessment: unknown effectiveness — limited evidence (effectiveness 41%; certainty 16%; harms 5%).

34http://www.conservationevidence.com/​actions/​592

● Use captive breeding to increase or maintain populations (cranes)

35A study from Canada over 32 years found that whooping cranes successfully bred in captivity eight years after the first eggs were removed from the wild. Assessment: unknown effectiveness — limited evidence (effectiveness 51%; certainty 17%; harms 6%).

36http://www.conservationevidence.com/​actions/​591

● Use captive breeding to increase or maintain populations (pigeons)

37A review of a captive-breeding programme on Mauritius and in the UK found that 42 pink pigeons were successfully bred in captivity. Assessment: unknown effectiveness — limited evidence (effectiveness 69%; certainty 21%; harms 0%).

38http://www.conservationevidence.com/​actions/​597

● Use captive breeding to increase or maintain populations (rails)

39A study from Australia found that three pairs of Lord Howe Islandwoodhens successfully bred in captivity, with 66 chicks being produced over four years. Assessment: unknown effectiveness — limited evidence (effectiveness 26%; certainty 11%; harms 5%).

40http://www.conservationevidence.com/​actions/​590

● Use captive breeding to increase or maintain populations (seabirds)

41A study from Spain found that a single pair of Audouin’s gulls successfully bred in captivity. Assessment: unknown effectiveness — limited evidence (effectiveness 20%; certainty 4%; harms 5%).

42http://www.conservationevidence.com/​actions/​589

● Use captive breeding to increase or maintain populations (songbirds)

43Three studies from Australia and the USA found that three species of songbird bred successfully in captivity. Four out of five pairs of wild-bred, hand-reared puaiohi formed pairs and laid a total of 39 eggs and a breeding population of helmeted honeyeaters was successfully established through a breeding programme. Only one pair of loggerhead shrikes formed pairs from eight wild birds caught and their first clutch died. Assessment: unknown effectiveness — limited evidence (effectiveness 77%; certainty 31%; harms 5%).

44http://www.conservationevidence.com/​actions/​598

● Use captive breeding to increase or maintain populations (storks and ibises)

45We captured a small study and a review both from the USA describing the captive breeding of storks. The study found that a pair bred; the review found that only seven of 19 species had been successfully bred in captivity. A review of bald ibis conservation found that 1,150 birds had been produced in captivity from 150 founders over 20 years. However, some projects had failed, and a study from Turkey found that captive birds had lower productivity than wild birds. Assessment: unknown effectiveness — limited evidence (effectiveness 31%; certainty 30%; harms 8%).

46http://www.conservationevidence.com/​actions/​595

● Use captive breeding to increase or maintain populations (tinamous)

47A replicated study from Costa Rica found that great tinamous successfully bred in captivity, with similar reproductive success to wild birds. Assessment: unknown effectiveness — limited evidence (effectiveness 51%; certainty 15%; harms 5%).

48http://www.conservationevidence.com/​actions/​588

● Use puppets to increase the success of hand-rearing

49Three studies from the USA and Saudi Arabia found that crows and bustards raised using puppets did not have higher survival, dispersal or growth than chicks hand-reared conventionally. Assessment: unknown effectiveness — limited evidence (effectiveness 4%; certainty 20%; harms 0%).

50http://www.conservationevidence.com/​actions/​617

● Wash contaminated semen and use it for artificial insemination

51A replicated, controlled study from Spain found that washed, contaminated semen could be used to successfully inseminate raptors. Assessment: unknown effectiveness — limited evidence (effectiveness 31%; certainty 15%; harms 0%).

52http://www.conservationevidence.com/​actions/​603

Evidence not assessed

● Can captive breeding have deleterious effects?

53We captured no studies investigating the effects of captive-breeding on fitness. Three studies using wild and captive populations or museum specimens found physiological or genetic changes in populations that had been bred in captivity. One found that changes were more likely to be caused by extremely low population levels than by captivity.

54http://www.conservationevidence.com/​actions/​599

3.15.2 Release captive-bred individuals

Likely to be beneficial

● Provide supplementary food after release

55All three studies captured found that released birds used supplementary food provided. One study from Australia found that malleefowl had higher survival when provided with food and a study from Peru found that supplementary food could be used to increase the foraging ranges of Andean condors after release. Assessment: likely to be beneficial (effectiveness 45%; certainty 48%; harms 0%).

56http://www.conservationevidence.com/​actions/​639

● Release captive-bred individuals into the wild to restore or augment wild populations (cranes)

57Four studies of five release programmes from the USA and Russia found that released cranes had high survival or bred in the wild. Two studies from two release programmes in the USA found low survival of captive-bred eggs fostered to wild birds compared with wild eggs, or a failure to increase the wild flock size. A worldwide review found that releases of migratory species were more successful if birds were released into existing flocks, and for non-migratory populations. One study from the USA found that birds released as sub-adults had higher survival than birds cross-fostered to wild birds. Assessment: likely to be beneficial (effectiveness 55%; certainty 50%; harms 5%).

58http://www.conservationevidence.com/​actions/​621

● Release captive-bred individuals into the wild to restore or augment wild populations (raptors)

59Five studies of three release programmes from across the world found the establishment or increase of wild populations of falcons. Five studies from the USA found high survival of released raptors although one study from Australia found that a wedge-tailed eagle had to be taken back into captivity after acting aggressively towards humans, and another Australian study found that only one of 15 brown goshawks released was recovered. Assessment: likely to be beneficial (effectiveness 69%; certainty 56%; harms 10%).

60http://www.conservationevidence.com/​actions/​626

● Release captive-bred individuals into the wild to restore or augment wild populations (songbirds)

61A study in Mauritius describes the establishment of a population of Mauritius fody following the release of captive-bred individuals. Four studies of three release programmes on Hawaii found high survival of all three species released, with two thrush species successfully breeding. A replicated, controlled study from the USA found that shrike pairs with captive-bred females had lower reproductive success than pairs where both parents were wild-bred. Assessment: likely to be beneficial (effectiveness 42%; certainty 40%; harms 5%).

62http://www.conservationevidence.com/​actions/​630

● Release captive-bred individuals into the wild to restore or augment wild populations (vultures)

63Four studies of two release programmes found that release programmes led to large population increases in Andean condors in Colombia and griffon vultures in France. A small study in Peru found high survival of released Andean condors over 18 months, with all fatalities occurring in the first six months after release. Assessment: likely to be beneficial (effectiveness 73%; certainty 54%; harms 0%).

64http://www.conservationevidence.com/​actions/​625

Unknown effectiveness (limited evidence)

● Clip birds’ wings on release

65Two of four studies found that bustards and geese had lower survival when released into holding pens with clipped wings compared to birds released without clipped wings. One study found no differences in survival for clipped or unclipped northern bald ibis. One study found that adult geese released with clipped wings survived better than geese released before they were able to fly. Assessment: unknown effectiveness — limited evidence (effectiveness 10%; certainty 30%; harms 5%).

66http://www.conservationevidence.com/​actions/​633

● Release birds as adults or sub-adults not juveniles

67Three out of nine studies from across the world found that birds released as sub-adults had higher survival than those released as juveniles. Two studies found lower survival of wing-clipped sub-adult geese and bustards, compared with juveniles and one study found lower survival of all birds released as sub-adults, compared to those released as juveniles. Three studies found no differences in survival for birds released at different ages, although one found higher reproduction in birds released at greater ages. Assessment: unknown effectiveness — limited evidence (effectiveness 35%; certainty 15%; harms 19%).

68http://www.conservationevidence.com/​actions/​636

● Release birds in groups

69A study from New Zealand found that released stilts were more likely to move long distances after release if they were released in larger groups. Assessment: unknown effectiveness — limited evidence (effectiveness 32%; certainty 26%; harms 2%).

70http://www.conservationevidence.com/​actions/​634

● Release captive-bred individuals into the wild to restore or augment wild populations (bustards)

71Three reviews of a release programme for houbara bustard in Saudi Arabia found low initial survival of released birds, but the establishment of a breeding population and an overall success rate of 41%. The programme tested many different release techniques, the most successful of which was release of sub-adults, which were able to fly, into a large exclosure. Assessment: unknown effectiveness — limited evidence (effectiveness 34%; certainty 26%; harms 5%).

72http://www.conservationevidence.com/​actions/​622

● Release captive-bred individuals into the wild to restore or augment wild populations (gamebirds)

73One of five studies from across the world found that releasing gamebirds established a population or bolstered an existing population. A review of a reintroduction programme in Pakistan found some breeding success in released cheer pheasants, but habitat change at the release site then excluded released birds. Three studies from Europe and the USA found that released birds had low survival, low reproductive success and no impact on the wild population. Assessment: unknown effectiveness — limited evidence (effectiveness 5%; certainty 35%; harms 1%).

74http://www.conservationevidence.com/​actions/​619

● Release captive-bred individuals into the wild to restore or augment wild populations (owls)

75A study in the USA found that a barn owl population was established following the release of 157 birds in the area over three years. A replicated, controlled study in Canada found that released burrowing owls had similar reproductive output but higher mortality than wild birds. Assessment: unknown effectiveness — limited evidence (effectiveness 24%; certainty 15%; harms 0%).

76http://www.conservationevidence.com/​actions/​627

● Release captive-bred individuals into the wild to restore or augment wild populations (parrots)

77A study from Venezuela found that the population of yellow-shouldered amazons increased significantly following the release of captive-bred birds along with other interventions. A study in Costa Rica and Peru found high survival and some breeding of scarlet macaw after release. Three replicated studies in the USA, Dominican Republic and Puerto Rico found low survival in released birds, although the Puerto Rican study also found that released birds bred successfully. Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 30%; harms 3%).

78http://www.conservationevidence.com/​actions/​629

● Release captive-bred individuals into the wild to restore or augment wild populations (pigeons)

79A single review of a captive-release programme in Mauritius found that that released pink pigeons had a first year survival of 36%. Assessment: unknown effectiveness — limited evidence (effectiveness 20%; certainty 5%; harms 1%).

80http://www.conservationevidence.com/​actions/​628

● Release captive-bred individuals into the wild to restore or augment wild populations (rails)

81One study from Australia found that released Lord Howe Island woodhens successfully bred in the wild, re-establishing a wild population and a study from the UK found high survival of released corncrake in the first summer after release. A replicated study in New Zealand found very low survival of North Island weka following release, mainly due to predation. Assessment: unknown effectiveness — limited evidence (effectiveness 26%; certainty 16%; harms 0%).

82http://www.conservationevidence.com/​actions/​620

● Release captive-bred individuals into the wild to restore or augment wild populations (storks and ibises)

83A replicated study and a review of northern bald ibis release programmes in Europe and the Middle East found that only one of four resulted in a wild population being established or supported, with many birds dying or dispersing, rather than forming stable colonies. Assessment: unknown effectiveness — limited evidence (effectiveness 20%; certainty 20%; harms 2%).

84http://www.conservationevidence.com/​actions/​624

● Release captive-bred individuals into the wild to restore or augment wild populations (waders)

85A review of black stilt releases in New Zealand found that birds had low survival (13–20%) and many moved away from their release sites. Assessment: unknown effectiveness — limited evidence (effectiveness 10%; certainty 5%; harms 15%).

86http://www.conservationevidence.com/​actions/​623

● Release captive-bred individuals into the wild to restore or augment wild populations (wildfowl)

87Two studies of reintroduction programmes of ducks in New Zealand found high survival of released birds and population establishment. A study from Alaska found low survival of released cackling geese, but the population recovered from 1,000 to 6,000 birds after releases and the control of mammalian predators. A review of a reintroduction programme from Hawaii found that the release of Hawaiian geese (nene) did not result in the establishment of a self-sustaining population. Two studies from Canada found very low return rates for released ducks with one finding no evidence for survival of released birds over two years, although there was some evidence that breeding success was higher for released birds than wild ones. Assessment: unknown effectiveness — limited evidence (effectiveness 30%; certainty 24%; harms 0%).

88http://www.conservationevidence.com/​actions/​618

● Release chicks and adults in ‘coveys’

89Two out of three studies found that geese and partridges released in coveys had higher survival than young birds released on their own or adults released in pairs. A study from Saudi Arabia found that bustard chicks had low survival when released in coveys with flightless females. Assessment: unknown effectiveness — limited evidence (effectiveness 40%; certainty 36%; harms 6%).

90http://www.conservationevidence.com/​actions/​635

● Use ‘anti-predator training’ to improve survival after release

91Both studies captured found higher survival for birds given predator training before release, compared with un-trained birds. One found that using a live fox, but not a model, for training increased survival in bustards, but that several birds were injured during training. Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 20%; harms 9%).

92http://www.conservationevidence.com/​actions/​637

● Use appropriate populations to source released populations

93Two studies from Europe found that birds from populations near release sites adapted better and in one case had higher reproductive productivity than those from more distant populations. Assessment: unknown effectiveness — limited evidence (effectiveness 53%; certainty 31%; harms 0%).

94http://www.conservationevidence.com/​actions/​631

● Use ‘flying training’ before release

95A study from the Dominican Republic found that parrots had higher first-year survival if they were given pre-release flying training. Assessment: unknown effectiveness — limited evidence (effectiveness 30%; certainty 10%; harms 0%).

96http://www.conservationevidence.com/​actions/​638

● Use holding pens at release sites

97Three of four studies from North America and Saudi Arabia found that birds released into holding pens were more likely to form pairs or had higher survival than birds released into the open. One study found that parrots released into pens had lower survival than those released without preparation. A review of northern bald ibis releases found that holding pens could be used to prevent birds from migrating from the release site and so increase survival. Assessment: unknown effectiveness — limited evidence (effectiveness 51%; certainty 36%; harms 2%).

98http://www.conservationevidence.com/​actions/​632

● Use microlites to help birds migrate

99A study from Europe found that northern bald ibises followed a microlite south in the winter but failed to make the return journey the next year. Assessment: unknown effectiveness — limited evidence (effectiveness 3%; certainty 5%; harms 5%).

100http://www.conservationevidence.com/​actions/​640

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