Walia Special Edition on the Bale Mountains (2011) - Zoologische ...

of a community there must be a premise of shared resource exploitation (Simberloff et al. 1992;
Rice and Kronlund 1997). This excludes lumping a species that serves as a resource with another
that exploits in one community or those that do not have any direct relationship at all. Within this
context it is essential for the scientist to determine which group of species is naturally predisposed
to form a community.
Using multivariate ordination techniques various workers have determined groups of
interrelated species based on evaluation of ecological and morphological attributes (Holmes et al.
1979; Shirley and Smith 2005; Askins and Philbrik 1987; Wilson 1974; Simberloff et al. 1992).
Holmes et al. (1979) differentiated a set of 22 (the total bird list is 29 as per Richard et al. (1986)
which apparently may mean the whole breeding bird assemblage of the site is made of only an
insectivorous group) insectivorous bird species of the Hubbard Brooks of West Hampshire, USA
in to 4 groups of foraging guilds. They determined a guild by limiting its definition to a group that
contains species that exploit the same foraging resource in a similar manner. The authors showed
that these four groups were subcomponents of an insectivorous bird community of their study area.
In some cases species classification was undertaken with clear intention of describing ecological
guilds in a community focusing on their trophic boundaries (Teborgh et al. 1990; Wilson 1974). Data
in Askin and Philbrick (1987), was analyzed for each group of species they determined separately.
But it must be noted that criteria that reflect proximate interspecifc interaction may not explain the
observed structuring of a large set of species completely. In some case studies it was shown that
long-term temporal scale patterns of structure, even at small spatial scale, can not be fully explained
by interspecifc interaction alone (Richard et al. 1986). For larger bird assemblages particularly in
some regions of the northern hemisphere, additional attributes such as migratory status was used
in classifying large sets of birds (Böhning-Gaese and Bauer 1995; Akins and Philbrick 1987). In
some instances the nativity of species has been used as classification criteria (Mills et al. 1989).
All these studies tend to lump all species as parts of the same community even in situations where
some actually are predators of a large proportion of the species in the assemblage (a case in point
is Böhning-Gaese and Bauer 1995; Askin and Philbrick 1987; Wethered and Lawes 2005). It is
the theoretical and empirical relevance of such a tendency that our current paper explored and
improvised on.
We examined the value of application of the fundamental principles of community ecology
to define highland bird communities in the Bale Mountains National Park of Ethiopia to test how
well this may be reflected on the ground using bird census data. Since preparation of a species total
list at the continental or regional scale (although this is most preferable) is impractical at this stage
due to lack of species specific distributional data at some finer scale, we decided to use only the
NP’s total species list of resident birds for this purpose. Our analysis of attributes related to dietary
preferences and bill morphology of the 117 resident bird assemblage of the BMNP demonstrated,
species were significantly grouped in to five assemblages representing at least some proportion
of a vertebrate community. We refrained from strongly suggesting that each of this group is a
complete community because there are instances of easily observable holes in some of the groups.
<strong>Walia</strong>-<strong>Special</strong> <strong>Edition</strong> on the Bale Mountains 25