Work in shifting cultivation landscapes suggests some important patterns
in the characteristics of bird communities. Terborgh and Weske (1969, Ama-
zonian Peru), Johns (1991, Amazonian Brazil), Andrade and Rubio-Torgler
(1994, Amazonian Colombia), Vieira et al. (1996, Amazonian Brazil), and
Anderson (2001, Mesoamerica) have carried out studies of birds in neotropi-
cal shifting cultivation landscapes. Studies from Africa and Asia are less
numerous but include Blankenspoor (1991, Liberia) and Shankar Raman et
al. (1998, northeastern India). The numbers of habitat types included in com-
parisons and the landscape contexts in which shifting cultivation communities
were analyzed vary between studies. The fields and fallows where Johns,
Andrade and Rubio-Torgler, and Anderson worked were embedded in a pri-
mary forest matrix, for example, whereas Vieira et al. (1996) worked in the
Bragantina landscape of Pará State, Brazil, where fallow and secondary forest
is the dominant land cover type and only a single 200-ha fragment of dryland
forest could be found for comparisons with fallows. Sampling methods also
vary between studies and affect the comparability of the results. The scale of
these studies should be considered the patch, with the exception of that of
Anderson, which related the characteristics of the raptor community to land-
scape characteristics. In common with the studies of vegetation cited previ-
ously, all these authors used a chronosequence approach to sampling, working
simultaneously in fallows of different ages and assuming that any differences
between them represent patterns over time in a single habitat patch.
No single, clear-cut pattern of bird species richness and diversity emerges
from these studies; we will consider compositional patterns later in this chap-
ter. Neither Terborgh and Weske (1969) nor Andrade and Rubio-Torgler
(1994) found between-habitat differences of species diversity per 100 individ-
uals in understory mist net captures, although total numbers of species
observed by all methods differed between habitats in the former study and
were lowest in second growth and a cocoa plantation. Adding to this indica-
tion that bird species richness may be lower in fallow vegetation than in pri-
mary forest, Vieira et al. (1996) caught fewer species in 10-year and 20-year
fallows than in their primary forest fragment. They also found more forest
bird species in the 20-year fallow than in the 10-year one, and, similarly, bird
species richness increased markedly between fallows of increasing age in both
the African (Blankenspoor 1991) and the Asian (Shankar Raman et al. 1998)
studies cited. In contrast, however, fallow was the mostspecies-rich habitat at
Johns’s (1991) site. On a much larger spatial scale, the abundance and diver-
sity of raptors observed by Anderson (2001) increased with the increasing
structural heterogeneity contributed to the landscape by shifting cultivation,
with primary forest being the least structurally diverse landscape. Such a rela-
tionship seems likely to be observed on many different scales in many groups
of organisms as long as the number of disturbed-habitat species gained
- The Biodiversity and Conservation Potential of Shifting Cultivation Landscapes 175