Research Article

Avian Diversity in Dhati Walel National Park of Western Ethiopia  

Megersa Tsegaye , Tsegaye Gadisa , Gelaye G/Micchael
Department of Biology, Jimma University, P.O. Box 378, Ethiopia
Author    Correspondence author
International Journal of Molecular Evolution and Biodiversity, 2016, Vol. 6, No. 1   doi: 10.5376/ijmeb.2016.06.0001
Received: 15 Jan., 2016    Accepted: 29 Feb., 2016    Published: 09 Mar., 2016
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Preferred citation for this article:

Tsegaye M., Gadisa T. and G/Micchael G., 2016, Avian Diversity in Dhati Walel National Park of Western Ethiopia, International Journal of Molecular Evolution and Biodiversity, 2016, 6(1), 1-12 (doi: 10.5376/ijmeb.2016.06.0001)


Knowledge on species diversity, distribution and abundance are among prerequisite ecological information to design sound conservation strategy. The present study was carried out to assess diversity, distribution and relative abundance of avian fauna in Dhati Walel National Park, western Ethiopia. Data were collected from June 2013 to May 2014 from three habitat types: wetland, woodland, and riverine forest. Data were collected using the method of line transects in wetland and woodland and point count method in riverine forest. A total of 124 avian species belonging to 18 orders and 50 families were recorded during the whole study period. Twenty-three families were from order Passeriformes. Three species: Banded barbet (Lybius undatus), Erlanger’s lark (Calandrella erlangeri) and Wattled ibis (Bostrychia carunculata), are endemic to Ethiopia and Eritrea. The highest number of species (14) was recorded from the family Accipitridae (order Accipitriformes). Families Columbidae (order Columbiformes), Nectariniidae (order Passeriformes) and Ciconiidae (order Charadriiformes) were represented with nine, six and five species, respectively. Woodland supported the highest avian diversity both during wet (H’ = 3.96) and dry (H’= 3.71) seasons.  Wetland was the least diversified (H’= 2.93, wet and H’ = 3.07, dry) in both seasons. Similarity of bird species was more between woodland and riverine forest both during the wet (SI=0.44) and dry (SI=0.31) seasons. There were no rare species and many frequent (33 species wet and 38 species dry seasons) and common (23 wet) species were recorded in the woodland. Awareness creation to reduce human pressure and research on the remaining habitat of the park are recommended.
Abundance; Avifauna; Dhati Walel National Park; Distribution; Diversity

1 Introduction

Among 2100 bird species so far recorded in Africa (Sinclair and Ryan, 2003), Ethiopia harbors 926 species (Lepage, 2006) of which 21 species are endemic and 19 species are globally threatened (Redman et al., 2009). Out of the threated bird species of the country, two species are critically endangered, five species endangered, and 12 species vulnerable (Collar et al., 1994). Seventy-three hot spots have been identified in the country represented by three conservation categories: 19 critical sites, 23, urgent sites and 31 highly sited areas (Mengistu, 2003).


Birds have long been popular with naturalists, amateurs and professionals and hence their systematics and distributions are better known than any other comparable groups of animals, with the possible exception of large mammals (Furness and Greenwood, 1993). They are one of the most important components of biodiversity with immense ecological, economic and esthetic values. Birds are technologically advanced, highly motivated, extremely efficient and cost-effective insect pest controllers (Pschorn-Walker, 1977). Fruit-eating birds help in dispersal of seeds and seeds may sprout wherever the droppings fall (Clout and Hay, 1989) and certain birds like hummingbirds and sunbirds pollinate flowers that produce nectar. Birds through the ages have been the source of considerable fascination and folklore and have been used as symbols. They are arguably the most universally celebrated form of nature, found in pictures, photographs, sculptures, word and song (Clifford et al., 1998). On the other hand, few bird species like Quelea (Quelea quelea) cause major agricultural loss in some regions of the world (Elliott, 1989).

In the tropics, Ethiopia not being exception, habitat losses and habitat degradation are causing rapid declines in bird species, which in turn caused reductions in ecosystem processes, services and benefits (Sekercioglu et al., 2012). Agriculture puts 1 065 threatened birds at risk, logging and wood harvesting impacting 668 species and invasive species threaten 625 of the threatened species (Bird Life International, 2008). In Ethiopia particularly in the Afromontane rain forests, habitat destruction and degradation due to anthropogenic activities are reducing the forest cover and the associated biodiversity (Yeshitila, 2001). Ongoing reductions in bird abundance and species richness are likely to have far-reaching ecological consequences, with diverse societal impacts ranging from the spread of disease and loss of agricultural pest control to plant extinctions and trophic cascades (Gaston et al., 2000).
Dhati Walel is a newly established National Park in Ethiopia with little ecological information. The area is believed to be rich in faunal diversity (Gonfa et al. 2015). However, there is an accelerated reduction in its faunal diversity including avian species as a result of man-made pressure and activities, such as uncontrolled hunting, habitat destruction for agricultural expansion, pressure by domestic animals and heavy encroachment by human being.  Knowledge about avian diversity, distribution and relative abundance is very essential for the development of sound management plan for a given protected area. However, no research has been carried out to investigate the diversity, distribution and relative abundance of avian species of Dhati Walel National Park. Thus, this study was carried out with the objective of gathering baseline information on the diversity, distribution and relative abundance of the avian fauna of the area.
2 Materials and Methods
2.1 Study area
Dhati Walel National Park (established in 2010) is located in western lowlands of Ethiopia, about 647 km from Addis Ababa, the capital city of Ethiopia (OFWE, 2012). The park lies between the coordinates of 67° 55' 49'' to 72° 45' 03'' E and 10° 05' 25'' to 10° 51' 01''N, covering an area of about 1035 km2 (103,500 ha) (OFWE, 2012). The elevation in the Park ranges from1390m around Dhati River to 1500m at the peak of mount Walel. There are four major habitat types: wetland, woodland, riverine forest and grassland. The mean monthly maximum temperature of the area ranges between 270 C and 290 C and the mean minimum temperature of the area ranges between150 C and 170 C. The mean annual rainfall of the area is 1 350 mm (Figure 1).


Figure 1 Location Dhati Walel National Park and study sites


2.2 Method
Wetland, woodland and riverine forest were surveyed in this particular study. To make the results representative, 20 to 25% of each habitat was assessed as suggested by Bibby et al., (1992). Wetland and woodland habitats were surveyed using the method of line transects while point count method was used in the riverine forest (Buckland et al., 2001). For the three blocks of wetland randomly selected (Burka Sabato, Doleti and Dhati), twenty lines transects, seven line transects each for Burka Sabato and Doleti and six transects for Dhati were laid. For the three blocks randomly selected from woodland (Bada Toko, Tullu Shimala and Kumbabe), twenty line transects, eight transects for Bada Toko, nine transects for Tullu Shimala and three line transects for Kumbabe were established. The length of transects varied based on the size and accessibility of the block sampled. Accordingly, in wetland, the length of transects was 2 km and in the woodland the length was 1.5 km. Bird species were recorded by walking at the center of a line transect from both right and left. Line transects were 250-300 m apart to avoid double counting (Hostler and Martin, 2006) and were placed by random sampling approach in which transect 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). 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). 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).


Table 1 Species richness, evenness and diversity indexes among the three habitats in different seasons


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) seasons. The riverine forest and wetland supported the least diversity of avian during the wet (H’= 2.93) and dry (H’= 3.07) seasons respectively. The highest and the lowest even distribution were observed in woodland during both wet (E=0.94) and dry (E=0.95) seasons (Table 1).
3.3 Species similarity
The highest similarity of bird species (SI=0.92) within the same habitat between wet and dry seasons was observed in the wetland followed by riverine forest (SI=0.68). The similarity of bird species between wet and dry seasons was the least in woodland (SI=0.5) (Table 2).


Table 2 Seasonal species similarity (SI) within the same habitat


Among the three habitat types, similarity of birds species was the highest between woodland and riverine forest during both during the dry (SI=0.31) and wet (SI=0.44) seasons. The combined data of wet and dry seasons also showed high similarity between bird species of woodland and riverine forest (SI=0.76) (Table 3).


Table 3 Species similarity among the three habitats types in different seasons


3.4 Abundance
During the wet season, 20, 11 and 7 species were uncommon and 16, 33 and 9 species were frequent in the wetland, woodland and riverine forest respectively. During the dry season, 23, 8 and 20 species were uncommon and 8, 3 and 11 species were common in the wetland, woodland and riverine forest respectively. In both seasons, there were no rare species and 2 abundant species were recorded during the wet season from the riverine forest (Table 4).


Table 4 Abundance of avian species during the wet and dry seasons using encounter rates


4 Discussion
The difference in species diversity, number of species and number of individuals of species among the different habitat types of the present study could be associated with differences in habitat characteristics and feeding habits of birds as suggested by Smith (1992). Among the three studied habitats, the most diversified habitat in avian species was the woodland (H’max= 4.47) followed by riverine forest (H’max =3.97). This variation could be due to variation in habitat heterogeneity. The more heterogeneous vegetation and vegetation strata in the woodland and riverine forest compared to the wetland could have provided several niches for birds making the woodland and riverine forest with high diversity of birds. The importance of the availability of different vegetation strata for different bird species is also supported by other studies. For example, Cueto and Casenava (1999) reported positive correlation between bird species richness and the availability of vegetation strata. Similarly, Erdelen (1984) indicated significant correlation between bird species diversity and vegetation structure. Chace et al. (2006) reported that birds respond to changes in vegetation composition and structure, which in turn affects their food resources.
The variations in species composition recorded during the wet and dry seasons were not significantly different. This is in line with Shimelis and Bekele (2008) who reported the negligible effect of season or the role of climate in affecting the diversity of birds of a particular habitat. Within the same habitat, the highest seasonal similarity of bird species was observed in the wetland (SI=0.92). This might be due to the availability of similar and stable food resources both in the wet and dry seasons in the wetland than the other two habitat types. The relatively small seasonal similarity of bird species observed in woodland (SI=0.5) may be due to local migration of birds to the riverine forest and wetland when resources are scare in the woodland as many bird species migrate thereby optimizing availability of food sources and breeding habitats.
Among the three habitat types, more similarity of birds species was recorded from woodland and riverine forest both during dry (SI=0.31) and wet (SI=0.44) seasons. This is probably due to the similarity of vegetation structure between the two habitat types. Study carried out by Erdelen (1984) also showed significant correlation between diversity of bird species and the vegetation structure. As the vegetation layer increases, the number of available niches for birds also increases and so does the diversity of avian species. This is due to the different feeding habit of birds leading to niche separation (MacArthur, 1964). 
In the present study, the highest number of bird species was recorded in the woodland (87 species) followed by riverine forest (53 species). This might be due to higher vegetation complexity of the woodland and riverine forest than wetland. This finding is in line with MacArthur (1972) and Smith (1974), who reported that habitats with complex vegetation can provide stable source of food, nesting and cover from predator for different avian species. Tellaria and Santos (1994), also pointed out that habitat structure affects distribution of individual species of birds. Besides, foraging modes (Marone, 1991) and floristic composition (Wiens and Rotenberry, 1981) have influence on the distribution of birds. Besides, habitat size (Willis, 1979) has influence on the distribution of avian. The small size of the riverine forest in the study area might have contributed to the less number of species compared to the woodland.
The seasonal variation in the availability of food resources result in seasonal changes in the species abundance of birds (Karr and Roth 1971; Gaston et al., 2000). The uncommon species may be related to the breeding nature, large home range and niche of the species. In addition, degradation of the habitat might be a reason for the species to be uncommon (Ryan and Owino, 2006). The abundance of many bird species are determined by the composition of the vegetation that forms a major element of their habitats. As vegetation changes along complex geographical and environmental gradients, a particular bird species may appear, increase or decrease in number, and disappear as the habitat changes (Lee and Rotenberry, 2005).
The number of bird species (124) recorded in this study does not represent all the avian species present in the study area, but can update some of the avian species present in the study area. If an exhaustive survey is made in all the habitats (including grassland) by increasing the length of the study period and the sampling area, the number of species identified will be more. This underlines the area could be one of the areas with high avian diversity in Ethiopia.
We thank Jimma University for the financial support. Oromia Regional State Park Development Office and Dhati Walel National Park warden and all scout members need to be acknowledged for creating a homely working environment and their unlimited friendly relationship during the field investigations in the Park.
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