Individual study: Red kite Milvus milvus reintroductions to the UK are successful, evidence on corncrake Crex crex reintroductions is lacking
Carter I. & Newbery P. (2004) Reintroduction as a tool for population recovery of farmland birds. Ibis, 146, 221-229
This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.
Release captive-bred individuals into the wild to restore or augment wild populations of rails
A 2004 review of a corncrake Crex crex release programme in a wet grassland site in eastern England (Carter & Newbery 2004) found that only six chicks could be released into the wild in 2002 (due to predation in captivity), and that none was seen in the area the following year. From 140 eggs laid in 2003, 52 chicks were released during summer. Survival was apparently high, but data on overwinter survival and subsequent reproduction were not available. Captive birds were kept in a flock in autumn and winter and then paired off in the spring. Eggs were removed before hatching and incubated artificially. Once hatched, they were hand-fed until they could feed themselves and then released into a pen at the release site when ten days old before being released at 28 days old. This paper also discusses the translocation of red kites Milvus milvus to the UK, discussed in ‘Translocate individuals’.
A 2004 review (Carter & Newbery 2004) of the same red kite Milvus milvus translocation programmes to the UK as in (3,4) found that the release of 518 subadult birds (between 69 and 103 at each site) between 1989 and 2004 resulted in the establishment of one population of at least 177 breeding pairs (from 93 birds released), four populations of between 16 and 35 breeding pairs and one population of just four pairs (90 birds released, beginning in 2001). Productivity in 2003 was comparable to other parts of their range (1.8-2.0 young/breeding pair) for all populations except the smallest (0.25 young/breeding pair). High mortality rates in the less successful sites are thought to be due to illegal poisoning. Birds were taken from large populations across Europe when 4-6 weeks old, kept in aviaries for a further eight weeks (with minimal human contact) and then released. This paper also discusses the release of captive-bred corncrakes Crex crex, discussed in ‘Release captive-bred individuals’.