13. Exploitation
Michael C. Runge, William L. Kendall, and James D. Nichols
13.1 Introduction: assessment of exploitation
13.1.1Taking a conservative approach
Many bird populations are exploited for human purposes, through subsistence
or commercial harvest, or live collection, for food, recreation, medicine, orna-
ments, pets, or to reduce crop damage, or predation on game animals. While the
motivations and methods are varied, they share one consequence—removal of
birds from wild populations. Often, this removal and the consequences to the
population are not quantified, but the outcome can be dire. Overkill is one of an
“Evil Quartet” of causes of recent extinctions (Diamond 1989).
The conservation biologist or wildlife manager wishing to prevent loss of bio-
diversity and extinction due to exploitation is often faced with uncertainty regarding
the status of the population, the level of harvest, and the dynamics of the population
in question. How should one proceed? There are two kinds of error to guard against:
doing nothing when exploitation is having a negative impact; and implementing
unnecessary restrictions when exploitation is already sustainable. The focus of this
chapter is to describe an assessment approach and monitoring tools to guard against
the former error; that is, to take a conservative approach in the face of uncertainty.
Exploitation of bird and mammal populations has tremendous economic and
cultural importance, and managing exploitation requires careful consideration
of those forces (Bennett and Robinson 2000). The conservation biologist needs
to bring robust data and defensible analyses to the discussion. The three general
types of information required are: minimum estimates of population size, estim-
ates of harvest levels, and an understanding of population dynamics.
13.1.2Minimum estimates of population size
The effect of harvest on a population depends in large part on the magnitude of
the harvest relative to the population size. In addition, the effect of harvest can be
mediated by density-dependent dynamics. For these reasons, an estimate of the