International Journal of Molecular Evolution and Biodiversity 2016, Vol. 6, No. 1, 1-12
3
placement was proportional to the area of the habitat type (Bibby et al., 1998; Lambert et al., 2009).
For each of the two blocks of riverine forest randomly selected (Kiltu Banti and Lophi), a total of thirty point
count stations; fifteen point count stations in each block were laid. All the thirty point count stations were
surveyed four times (two times both in the wet and dry seasons) during the study period. The Point count stations
in a sample block were 200m apart to avoid double counting (Ralph et al. 1985). To minimize disturbance during
count, a waiting period of 3 to 5 minutes prior to counting were applied (Hosteler, 2001).
Two sessions of data collection were carried out for both wet and dry seasons. For the wet season, data was
collected from July to September 2013 for first session and March to May 2014 for second session. First session
of data collection for the dry season was carried out from November to December 2013 and from January to
February 2014 for the second session. Data were collected early in the morning from 6:30 a.m. to 10:00 a.m. and
late in the afternoon from 3:30 p.m. to 6:00 p. m (Spencer, 1963; Centerbury et al., 2000). Birds flying over the
area were also observed to identify species. For larger flocks and for rapidly moving flocks, members of
individual species were recorded by estimation methods (Bibby et al., 1998). Common methods when estimating
very large flock is to count, say 10, 20, 50, 100, or 500 birds and then estimate the proportion of the larger flock
were used. Species observed during the survey were identified and taxonomically classified following Sinclair and
Ryan (2003), Avibase: Bird Checklist of the World (Lepage, 2013) and Avibase; Bird checklists of the world
(Lepage, 2008). Photographs were taken for further confirmation of species.
2.3 Data Analysis
The species diversity of each habitat in the two seasons was analyzed using Shannon diversity Index (Shannon
and Wiener, 1949). Species evenness was evaluated using Shannon-Wiener evenness Index (E) (Southwood and
Henderson, 2000). Simpson’s similarity index (Simpson, 1949) was used to assess the similarity of species
between two different habitat types. The relative abundance of avian species was determined using encounter rates
that give crude ordinal scales of abundance as abundant, common, frequent, uncommon and rare (Bibby et al.,
1998). Accordingly bird species with encounter rates <0.1, 0.1–2.0, 2.1–10.0, 10.1–40.0 and 40.0+ were classified
as rare, uncommon, frequent, common and abundant respectively. Chi-square test (χ2 test) was used to compare
variations in the number of species in the same habitat between seasons at 0.05 level of significance.
3 Results
3.1 Species composition
A total of 124 bird species belonging to 18 Orders and 50 Families were recorded during the study period
(Appendix I). Among the recorded species, Wattled ibis (Bostrychia carunculata), Banded barbet (Lybius undatus)
and Erlanger's lark (Calandrella erlangeri) are endemic to Ethiopia and Eritrea. The highest number of bird species
was recorded from the family Accipitridae (14 species) followed by Columbidae, Nectariniidae and Ciconiidae
each with nine, six and five species, respectively (Appendix I). Seasonal variation was observed in the number of
species and abundance of individual species among the different habitat types. Among 124 bird species recorded,
114 and 111 bird species were recorded during wet and dry season, respectively. One hundred bird species were
common to both seasons, but 11 and 13 species were exclusive to the wet and dry seasons, respectively.
3.2 Species richness, evenness and species diversity indices
Variation in the number of bird species was observed among the three habitats and between seasons in the same
habitat. The highest number of species was recorded from woodland both during wet (67) and dry (49) seasons
followed by wetland with 41species during wet season and 48 species during the dry season. During both seasons,
the highest number of bird species was recorded from woodland (87) followed by riverine forest (53) (Table 1).
But, variation in the number of species in the same habitat was not statistically significant (p=0.458 > 0.05 in
wetland; p=0.095>0.05 in woodland; p=0.117>0.05 in riverine forest).
Variations were also observed in species diversity among the different habitat types during the wet and dry
seasons. The woodland supported the highest avian diversity both during wet (H’= 3.96) and dry (H’= 3.71)
