The level of intervention and management is dictated by the rarity of the
species. The IUCN criteria for threatened species; Critically Endangered,
Endangered, and Vulnerable (IUCN 1994) provide a guide to the degree and
intensity of management required. The process of restoration goes through sev-
eral stages when the emphasis and priorities may change. Five broad overlapping
stages provide a conceptual framework in which to develop restoration work.
12.2.1 Stage one: know your species
For many endangered species, we still know only cursory details of their life
history and biology. Several early attempts to restore populations failed because
not enough was known about their ecology to address, in an effective manner, the
problems they were encountering. Thus the first stage is to know the life history,
ecology, distribution, and numbers of the species concerned. A study of a small
number of pairs will answer questions about the diet, habitat needs, and nest suc-
cess. Studies of captive individuals have often been used to supplement studies in
the wild, if necessary using related species to develop techniques and train staff.
12.2.2 Stage two: diagnose causes of population decline and test
remedial action
There are several approaches to this problem (see Green 1995, 2002; Sutherland
2000 for useful background). Collation of existing knowledge is essential to
assess previous distribution and population trends, especially information on
mortality, productivity, causes of breeding failure, age structure, survival in
different habitats, the impacts of weather, and other factors of possible relevance.
Review any ecological changes that may have impacted upon the species, espe-
cially those brought about by recent human action.
From these exercises and information learnt in stage one, it is possible to list
all the possible reasons for decline and to propose hypotheses on causes of rarity
that can be tested in the field. For species where nest-sites might be limiting, this
possibility can be tested by providing artificial sites or enhancing natural ones.
Where food might be limiting, the provision of supplemental food, and moni-
toring the response of the population can give an indication of the extent and
nature of the problem. (For details of previous experiments involving food and
nest manipulations see Newton 1994, 1998).
For many threatened bird species on islands, it can be assumed a priorithat
known exotic mammal predators (often rats and feral cats) are likely to be affecting
bird populations. On the basis of past experience, these species can be considered
guilty until proven innocent, but data must be collected during any control
program to evaluate its effect, and management should be modified accordingly.
All management needs to be based on evidence.
270 |Conservation management of endangered birds