Figure 1: here
2.2. Methods
Field equipment and materials used during data collection period include
binoculars, digital photo camera, GPS, and data sheet. Bird guidebooks
(Stevenson & Fanashawe, 2002, Redman et al. , 2009; Ayanlem,
2013) were used for bird identification. Preliminary survey was
conducted in May 2016 to gather relevant information about the study
area. In this survey, an overall view of the study area was assessed.
Global Positioning System readings were used to locate the positions and
to identify the altitudinal ranges of the study area.
Based on the habitat type, the study area was classified into swampy,
open-land, and forest patch. Sampling units representing each habitat
type was selected based on stratified random sampling method. The
technique involved dividing the study area into blocks by choosing the
location of each habitat with random numbers as adapted from Sutherland
(1996).
Point count method was used to record the presence and abundance of bird
species (Bibby et al., 2000). Data were taken on 30 sampling points of
which 13 sampling points on swampy habitats, 9 on forest patches, and 8
on open habitats. In each point count station, a minimum distance of
150-200m was maintained using GPS to avoid double counting (Vielliard,
2000). Point count method was undertaken from a fixed location within
the sample unit of radius of 25m at a fixed time interval consisting of
5-10 minutes depending up on the difficulties of the area and the type
of bird species to be identified and enumerated (Vielliard, 2000;
Buckland, 2006). To minimize disturbance during counts, a waiting period
of 3–5minutes prior to counting were applied (Hostler & Martine,
2001). All birds seen were recorded, except birds flying over the canopy
and not stopping within the 25m radius.
Data were recorded in the morning from 06:30–10:00 a.m. and late in the
afternoon from 15:00–18.00 p.m. for five consecutive days per month for
six months both during the wet and dry seasons. Wet season data were
collected during June, July, and August 2016, while data for the dry
season were collected during February, March, and April 2017.
Identification of avian species was carried out using plumage pattern,
size, shape, and color of birds (Aynalem & Bekele 2009). Photographs
were taken to confirm identification of some of the avian species which
were not easily identified in the field. The taxonomic groups of birds
were categorized based on field guides (Stevenson & Fanashawe, 2002,
Redman et al. , 2009; Ayanlem, 2013).
2.3. Data analysis
Data for the abundance of birds and the effect of habitat types and
season on birds were analyzed using ANOVA, and avian diversity was
analyzed using Shannon-Wiener Diversity Index (H’). Simpson′s Index of
Diversity (D) was used to evaluate the relative abundance of avian
species in each habitat type. Species evenness was assessed using
Shannon’s equitability index (E). Relative abundance of avian species
was determined using encounter rates (Bibby et al., 1998), and
avian community similarity were assessed using Sorensen’s coefficient as
adopted from Jeffery et al. (2004). SAS (Version 9.2) software
program was used to run the analysis and Tukey’s HSD test at α=0.05 was
used to test significant differences.
3. RESULTS
A total of 131 bird species belonging to 15 orders and 53 families were
identified of which 122 and 108 species were recorded during the wet and
dry seasons, respectively. Among the total avian species, 99 species
were recorded both during the wet and dry seasons, 23 species were
recorded only during the wet season, and 9 species only during the dry
season (Table 1).