1
Bird diversity survey methods
Colin J. Bibby
1.1 Introduction
The perfect bird census would locate and identify every individual bird at an
instant in time. This is the approach used every 10 years to count humans in the
United Kingdom. But individuals in many bird species are dispersed and hard
to find. Rigorous counting might be achieved in a small area and is easier for
some species than others. Bibby et al. (2000) give the whole subject of counting
birds a more detailed treatment and many more references than is possible in
two chapters in this book. A shorter practical guide book (Bibby, Jones, and
Marsden1998) is freely available at http://www.conservation.bp.com/advice/field.asp
There is no rigid distinction between survey (this chapter) and census
(Chapter 2), but some general gradients can be perceived singly or in combina-
tion (See Table 1.1).
Multispecies surveys may be appropriate where the aim of study is to describe
the birds of a relatively poorly known area. In this case, an assessment of the
species complement of the avifauna may be sufficient, with abundance estimates
being at best qualitative or relative. Questions might be biogeographic, asking
about the factors affecting the distribution and diversity of birds. Atlas studies are
a powerful way of describing the distribution of birds over large areas. Here the
primary aim is to produce distribution maps species by species and quantifica-
tion, though possible, is relatively less important. A study aiming to compare the
conservation importance of known sites might similarly be satisfied with a survey
approach. Questions may concern the impact of habitat variation on the fauna
where the habitat variation is either natural or human-induced. Studies of the
impact of logging in forests would be a typical example. Assessment of the
number of species in an area is often important in studies looking at habitat frag-
mentation, using an island biogeographic model. Formal monitoring programs
have to date tended to use more sophisticated census approaches. It is possible