The birds fledge from the artificial nest-site at the usual fledging age and develop
their flying and hunting skills gradually at ages comparable to wild-reared birds.
During this learning period, food is provided on or near the nest until it is no
longer taken.
The hacking technique is not suitable for some other groups of birds that are
incapable of feeding themselves from provisioned food until after fledging.
Hence, they are usually kept in captivity until they have been fully weaned, and
released.
Released birds are unlikely to do as well as young reared in the wild. There
are exceptions, however, for survival of released birds of prey is very high and
in Mauritius Kestrels is comparable to that of wild fledged birds. Survival in
reintroduced captive-reared Takahe was also equal to that of wild reared birds
(Maxwell and Jamieson 1997), as was that of Pink Pigeons, although for the pigeons
additional food was provided and predators were controlled (Swinnerton 2001).
For most species, the earlier in the post-fledging period they can be released,
the better their subsequent survival. In the Pink Pigeon, 68% of 196 birds
released before reaching 150 days survived for at least a year post-release, com-
pared to 56% of 52 birds released at a greater age (Swinnerton 2001). Griffon
Vultures Gyps fulvuswere unusual in that birds released as adults survived bet-
ter than those released as juveniles (Sarrazin et al. 1994). In this social species,
the released vultures joined previously released birds from which they presum-
ably learned their survival skills. These vultures were artificially provisioned with
food (Terrase et al. 1994). In all social species, releases seemed more successful if
there were other birds from previous releases nearby from which newcomers
could learn.
Once the birds have been free for a designated period, food and water are gradu-
ally reduced and the birds are left to fend for themselves. The degree of post-release
care is variable between projects and some also provide close guarding, individual
monitoring, veterinary backup, and predator control. Some species need to be
supported long-term following release, especially if the release environment is sub-
optimal in some way. Some social species, such as parrots and hornbills may, in some
cases, have to be supported for at least a generation post-release, especially if there are
no wild or previously released conspecifics established in the area to pass on appro-
priate social and survival skills.
12.5.2Translocations
Translocations involve the movement of wild birds from one area of habitat to
another. The most appropriate birds to move are usually juveniles, using the same
release and post-release management as for captive-raised birds. Adults are more
290 |Conservation management of endangered birds