focal species. Young captive Pink Pigeons reared by domestic pigeons Columba
liviadied when they contracted pigeon herpesvirus from their foster parents
(Snyder et al. 1985).
Birds intended for reintroduction should be raised and kept away from unnec-
essary contact with other captive birds, which may be carrying a disease to which
the population is naive. Concerns about the risks of introducing disease into the
wild by restocking with captive bred birds need to be set against a background of
disease in the existing population. If a disease is already present, we may be less
concerned about introducing that disease from captivity (Greenwood 1996).
There are disease risks associated with many management procedures, although
these risks are often small. Fieldworkers may transmit parrot viruses on their
clothes. Many of the problems can be minimized by good hygiene. Supplemental
feeding stations need to be kept clean and only good quality food used. The
spread of salmonellosis among British wild birds concentrated at garden feeding
tables is well recognized (Wilson and Macdonald 1967). At the supplementary
feeding stations used by free-living Echo Parakeets and Pink Pigeons, the
hoppers have been designed to exclude most other species. A high incidence of
trichomoniasis in young Pink Pigeons was believed to have been exacerbated by
exotic doves drinking and feeding from the same hoppers (Greenwood 1996).
The incidence of trichomoniasis decreased when the exotic doves were excluded.
Disease management can reduce mortality and some parasitic diseases can
be treated in the field, especially at nest-sites. Tropical Nest Fly Passeromyia
heterochaetalarvae feed on nestling Echo Parakeets and can be major source of
mortality (Jones and Duffy 1993). This problem was eliminated by the addition
of an insecticide dust (5% carbaryl) to the nest substrate at the beginning of the
season, and every 2 weeks during the nestling period. Similarly, insecticide
powder was applied to Black Robin nests to reduce the build-up of mites that, if
unchecked, could cause brood desertion and mortality (Butler and Merton
1992). At Echo Parakeet nest cavities, the substrate was also treated with the
abendazole to control fungal diseases such as aspergillosis.
12.3.4Predator control
Predator control is a component of many bird restoration projects. When causes
of predation are unknown, the approach should be protective, to minimize the
possible impact of predators, and reactive, responding to any detected predation.
The indiscriminate killing of even common predators is not recommended, as it
may lead to unforeseen problems. An exception is when dealing with exotic
predators known to be a problem elsewhere. In restoring native bird species on
278 |Conservation management of endangered birds