Action Synopsis: Bird Conservation About Actions

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

How is the evidence assessed?
  • Effectiveness
  • Certainty
  • Harms

Study locations

Key messages

A replicated study and a review of northern bald ibis Geronticus eremita release programmes in Europe and the Middle East found that only one of four had resulted in a wild population being established or supported, with many birds dying or dispersing, rather than forming stable colonies.


About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

  1. A replicated study in southeast Turkey in 1977-88 (Akçakaya 1990) found that northern bald ibis Geronticus eremita bred or kept in captivity did not increase the Turkish population. From 1981-88, 67 individuals were released and 12 (18%) migrated with the wild population (note: this excludes 1984, 1986 and 1987, for which data were not available). There was high winter mortality among birds that did not migrate and also high mortality on migration. The wild population in the study area declined over the study period, with five pairs in 1986, seven in 1987 and only four birds returning in 1988. This study is also described in ‘Use captive breeding to increase or maintain populations’ and ‘Provide artificial nesting sites’.

    Study and other actions tested
  2. A 2007 review of northern bald ibis (waldrapp) Geronticus eremita conservation (Bowden et al. 2007) found varying success in release programmes, dependent on the techniques used. Trials in Israel using a variety of techniques (described in ‘Release birds as adults or sub-adults, not juveniles’ and ‘Clip birds’ wings on release’) found that all 56 birds released became emaciated and disorientated and formed poor social bonds. Similarly, the release of 73 birds in Spain between 2004 and 2006 has not resulted in the formation of a stable colony. However, the release of 43 birds in Austria has led to the establishment of a colony in the wild. This study is also discussed in ‘Use captive breeding to increase or maintain populations’, ‘Artificially incubate and hand-rear birds in captivity’, ‘Use holding pens at release sites’, ‘Release birds as adults or sub-adults, not juveniles’, ‘Clip birds’ wings on release’, ‘Use microlites to help birds migrate’ and ‘Foster birds with non-conspecifics’.

    Study and other actions tested
Please cite as:

Williams, D.R., Child, M.F., Dicks, L.V., Ockendon, N., Pople, R.G., Showler, D.A., Walsh, J.C., zu Ermgassen, E.K.H.J. & Sutherland, W.J. (2020) Bird Conservation. Pages 137-281 in: W.J. Sutherland, L.V. Dicks, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2020. Open Book Publishers, Cambridge, UK.


Where has this evidence come from?

List of journals searched by synopsis

All the journals searched for all synopses

Bird Conservation

This Action forms part of the Action Synopsis:

Bird Conservation
What Works 2021 cover

What Works in Conservation

What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence, in synopses. Subjects covered so far include amphibians, birds, mammals, forests, peatland and control of freshwater invasive species. More are in progress.

More about What Works in Conservation

Download free PDF or purchase
The Conservation Evidence Journal

The Conservation Evidence Journal

An online, free to publish in, open-access journal publishing results from research and projects that test the effectiveness of conservation actions.

Read the latest volume: Volume 21

Go to the CE Journal

Discover more on our blog

Our blog contains the latest news and updates from the Conservation Evidence team, the Conservation Evidence Journal, and our global partners in evidence-based conservation.

Who uses Conservation Evidence?

Meet some of the evidence champions

Endangered Landscape ProgrammeRed List Champion - Arc Kent Wildlife Trust The Rufford Foundation Save the Frogs - Ghana Mauritian Wildlife Supporting Conservation Leaders
Sustainability Dashboard National Biodiversity Network Frog Life The international journey of Conservation - Oryx Cool Farm Alliance UNEP AWFA Bat Conservation InternationalPeople trust for endangered species Vincet Wildlife Trust