How To Prepare Animals For Release Into The Wild
Release captive-bred individuals into the wild to restore or augment wild populations of cranes
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Overall effectiveness category Likely to be benign
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Number of studies: 6
Study locations
Cardinal messages
- Four studies of five release programmes from the U.s.a. and Russia, from a total of eight programmes, found that released cranes had high survival or bred in the wild. Two studies from 2 release programmes in the U.s. constitute 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 establish that releases of migratory species only tended to exist successful if birds were released into existing flocks, with higher success for non-migratory populations.
- One written report from the USA establish that birds released every bit sub-adults had higher survival than birds cross-fostered to wild birds.
- One study from the Usa plant that 73% of all mortalities occurred in the get-go year after release.
Almost key letters
Key messages provide a descriptive index to studies we have constitute that test this intervention.
Studies are not direct comparable or of equal value. When making decisions based on this prove, you should consider factors such as report size, study design, reported metrics and relevance of the report to your situation, rather than merely counting the number of studies that support a particular interpretation.
Supporting show from individual studies
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A replicated report describing the success of releasing captive-bred Mississippi sandhill cranes Grus canadensis pulla onto a moisture pine savanna site in Mississippi, U.s.a. (Zwank & Wilson 1987) plant that, of xl birds released between 1979 and 1985, 46% were alive at the terminate of the study (between 1 and 6 years after release). Of the 22 mortalities, 16 (73%) occurred during the first year afterwards release, with iii during each of the 2nd and third years. Predation and human-caused bloodshed were the primary causes. Birds were bred in captivity and parent-raised before beingness rendered temporarily flightless with wing brails and moved to acclimatisation pens. They were between iv months and one year one-time at release.
Report and other actions tested -
A replicated study as part of the planning for a whooping crane Grus americana reintroduction program, a study in Florida, USA, in 1986-vii (Nesbitt & Carpenter 1993) found that greater sandhill cranes Grus canadensis tabida released as sub-adults in a 'soft release' programme had higher survival than birds fostered to Florida sandhill cranes G. c. pratensis (56% of 27 birds surviving for one year vs. 39% survival for 34 fostered birds, discussed in 'Foster eggs or chicks with wild non-conspecifics (cantankerous-fostering)'). The nine to x calendar month-sometime cranes were prevented from flying and kept in an open up-topped 1.5 ha enclosure for four to six weeks until they were released. Nutrient was provided until the birds no longer returned to the enclosure. Greater sandhill cranes are migratory, whilst Florida sandhill cranes are not. Migratory movements of released birds were larger than a control group of Florida sandhill cranes, merely not significantly and then.
Report and other actions tested -
A replicated study in Idaho, USA, between 1975 and 1991 (Kuyt 1996) establish that 215 wild-sourced whooping crane Grus americana eggs that were cross-fostered into sandhill crane G. canadensis nests had higher hatching success than 73 captive-bred whooping crane eggs, fostered at the same time (77% hatching success for wild-sourced eggs vs. sixty% for convict-bred). This study is also discussed in 'Use captive breeding to increment or maintain populations', 'Foster eggs or chicks with wild conspecifics' and 'Foster eggs or chicks with wild non-conspecifics (cross-fostering)'.
Study and other actions tested -
A 1998 review (Davis 1998) found that crane Grus spp. reintroduction programmes have had mixed success, with reintroductions of migratory species generally failing when birds were not released into existing flocks. Reintroductions of Siberian cranes One thousand. leucogeranus has non increased wild flock size, with no reintroduced birds existence seen after migration and high mortality during rearing, high poaching levels and few wild birds to guide migration. Releases of semi-wild carmine-crowned cranes Chiliad. japonensis and white-naped cranes G. vipio in southeast Russia establish that 4 of ten released birds migrated successfully, and at least ii pairs nested, one successfully. At least 84% of 38 greater sandhill cranes G. canadensis tabida survived for a yr after release in Michigan, U.s.a., 74% returned afterwards migration and iv males nested. Non-migratory releases by and large had higher success: offset-year survival of non-migratory whooping cranes G. americana has increased from approximately 34% (1993-4) to 71% (1996), although the population remains very small and may rely on continued releases. Convict-reared Mississippi sandhill cranes G. c. pulla had an overall commencement-yr survival of 70%, an adult survival over 91% following release and in 1992 represented 80% of the wild population. In 1996 there were 13 nesting pairs (the most recorded), with threescore% of known pairs having at least ane captive-reared individuals. The population, even so, remains dependent on releases. The author argues that post-release monitoring is vital to identify causes of mortality.
Study and other actions tested -
A replicated, controlled study in a breeding heart in Mississippi, USA, between 1989 and 1996 (Ellis et al. 2000) institute that first year survival of captive-bred Mississippi sandhill cranes Grus canadensis pulla was high, with approximately 80% of 132 birds surviving. Birds were released either in mixed flocks (both manus-reared and parent-reared birds) or not-mixed flocks (with just one rearing type). Survival rates over four years were highest for hand-reared birds in mixed flocks (approximately 95% survival for 17 birds), followed by parent-reared birds in mixed flocks (89% of 31 birds), mitt-reared in non-mixed flocks (78% of 39 birds) and were everyman in parent-reared, non-mixed flocks (56% of 45). By the end of the report, notwithstanding, differences betwixt parent and manus-reared birds were no longer statistically pregnant, although mixed flock birds all the same had higher survival. Birds were kept in 'cohorts' for four to five weeks, before being moved to the release site and kept for a calendar month in uncovered pens earlier wing brails (which prevent flying) were removed in December. Details of hand-rearing are found in 'Artificially incubate and hand-rear birds in captivity'.
Study and other deportment tested -
A replicated study of a whooping crane Grus americana reintroduction programme in 2001-v in wetlands in Florida, U.s. (Urbanek et al. 2010), found that winter-releases of this migratory bird proved constructive. Boilerplate outset-year survival of 71 wintertime-released juvenile birds was 87%, and was higher in later years as techniques improved. Birds were reared past humans wearing costumes (to avoid imprinting on homo carers, meet 'Use puppets to increment the survival or growth of hand-reared chicks' for studies on this intervention) and guided to the release site by an ultralight aircraft. Once at that place they were kept in property pens by costumed caretakers. When the habitat prevented this, the juveniles were vulnerable to bobcat Lynx rufus predation, merely this problem was overcome by vegetation clearance. Winter releases of this type were advantageous considering the intensive care reduced predation by bobcats, juveniles were kept away from harassment by developed birds and juveniles did non lose their fear of humans through contact with tame sandhill cranes K. canadensis. Once released, juveniles showed ordinary migratory and summer behaviour.
Report and other deportment tested
Please cite as:
Williams, D.R., Child, Grand.F., Dicks, L.V., Ockendon, N., Pople, R.G., Showler, D.A., Walsh, J.C., zu Ermgassen, E.M.H.J. & Sutherland, W.J. (2020) Bird Conservation. Pages 137-281 in: W.J. Sutherland, Fifty.V. Dicks, S.O. Petrovan & R.K. Smith (eds)What Works in Conservation 2020. Open Book Publishers, Cambridge, Great britain.
Bird Conservation - Published 2013
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