Action: Release captive-bred individuals into the wild to restore or augment wild populations of bustards
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- Three reviews of a release programme for houbara bustard Chlamydotis undulata macqueenii in Saudi Arabia and a replicated trial as part of the same programme 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, discussed elsewhere, with releases being most successful if sub-adults were released, able to fly, into a large exclosure.
Captive breeding is normally used to provide individuals which can then be released into the wild to either restore a population in part of the species’ former range, or to augment an existing population.
Release techniques vary considerably, from ‘hard releases’ involving the simple release of individuals into the wild to ‘soft releases’ which involve a variety of adaptation and acclimatisation techniques before release or post-release feeding and care. The following section includes studies describing the overall effects of release projects. Studies that compare specific release techniques are described elsewhere (‘Use holding pens at release sites’, ‘Use ‘anti-predator training’ to improve survival after release’ etc).
Supporting evidence from individual studies
A review of a captive breeding programme in southwest Saudi Arabia (Seddon et al. 1995) reported that, of six houbara bustards Chlamydotis undulata macqueenii released in three separate trials in 1991-2, only two survived, of which one was recaptured. This programme is discussed in more detail in ‘Use captive breeding to increase or maintain populations’, ‘Use artificial insemination in captive breeding’ and ‘Artificially incubate and hand-rear birds in captivity’.
A review (Jaime et al. 1996) of the same release programme as in Seddon et al. 1995 found that houbara bustard Chlamydotis undulata macqueenii releases were most successful when sub-adult birds were released into a large (4 km2) fenced enclosure, compared with releases of birds without an enclosure, releases of chicks or releases of sub-adult birds with clipped wings. Four adults and sub-adults were released without an enclosure in 1991 and all were killed within three days by foxes. This study is also discussed in ‘Use captive breeding to increase or maintain populations’ and ‘Use artificial insemination in captive breeding’. The other release techniques are discussed in ‘Release birds in ‘coveys’, ‘Use holding pens at site of release’ and ‘Use holding pens at site of release and clip birds’ wings’.
A review (Gelinaud et al. 1997) of the same release programme as in Seddon et al.1995 reports a houbara bustard Chlamydotis undulata macqueenii population established in southwest Saudi Arabia through releases of captive-bred birds in 1993-4 (discussed in Combreau & Smith 1998), bred for the first time in 1995. Of 22 females and 13 males in the population, three females and one male were confirmed as breeding. One yearling female raised three chicks to fledging (at 38-42 days old) whilst two other females laid a total of three eggs, all of which were infertile. The authors suggest that infertility may be caused by a low density of males and inexperienced females. One infertile brood was replaced with fertile eggs, discussed in ‘Foster eggs or chicks with wild conspecifics’.
A replicated trial (Combreau & Smith 1998) as part of the same release programme as in Seddon et al. 1995 and Gelinaud et al. 1997 found that 35 of 85 houbara bustards Chlamydotis undulata macqueenii (41%) released at a desert steppe site in southwest Saudi Arabia were successfully introduced. This study investigates how different release techniques affected survival, discussed in ‘Release birds as sub-adults or adults, not juveniles’ and ‘Use holding pens at release sites’. The effect of predator removal is discussed in ‘Control predators not on islands’.
- Seddon P.J., Saint Jalme M., van Heezik Y., Paillat P., Gaucher P. & Combreau O. (1995) Restoration of houbara bustard populations in Saudi Arabia: developments and future directions. Oryx, 29, 136-142
- Jaime M.S., Combreau O., Seddon P.J., Paillat P. & van Heezik Y. (1996) Restoration of Chlamydotis undulata macqueenii (Houbara Bustard) Populations in Saudi Arabia: A Progress Report. Restoration Ecology, 4, 81-87
- Gelinaud G., Combreau O. & Seddon P.J. (1997) First breeding by captive-bred houbara bustards introduced in central Saudi Arabia. Journal of Arid Environments, 35, 527-534
- Combreau O. & Smith T.R. (1998) Release techniques and predation in the introduction of houbara bustards in Saudi Arabia. Biological Conservation, 84, 147-155