Community composition, relative abundance and habitat association of avian species in Apini and Dikuma forest patches, Awi Administrative Zone, Ethiopia

Study on community composition, relative abundance and habitat association of avifauna in Apini and Dikuma forest patches, Awi Administrative Zone, Ethiopia, was carried out from September 2013 to April 2014. The main objective of this study was to investigate diversity, relative abundance, and habitat association of avian species in the study area. Data were collected using point count method, and analyzed using Shannon Weiner index, Simpson ́s diversity index and Sorensen ́s coefficient. A total of 95 avian species belonging to 44 families and 11orders were identified. Among 95 bird species, 93 are residents, one is intra-African migrant and one is Palaearctic migrant, and of the 93 resident birds, seven are endemic to Ethiopia, and ten shared between Ethiopia and Eritrea. In the present study, 79 and 83 bird species were recorded during the wet and dry seasons, respectively. Dikuma forest patch had the highest avian diversity during the dry season (H ́=3.84) and Apini had the lowest (H ́=3.59) in the same season. Habitat association of birds among the vegetation strata showed the highest species similarity occurred between forest interior and forest edge (CC=0.65), followed by forest edge and shrub (CC=0.62), and the least was between forest interior and shrub (CC=0.3). Species richness and composition are important parameters to maintain stability and functioning of an ecosystem. To conserve the rich avian diversity of Apini and Dikuma forest patches, the anthropogenic disturbances in the area should be minimized.


INTRODUCTION
Ethiopia has diverse sets of ecosystems, ranging from humid forests and extensive wetlands to deserts and supporting a wide variety of life forms Ethiopian Wildlife and Natural History Society (EWNHS), 1996; Viveropol, 2001). The altitudinal difference with the highest peak of Ras Dashen (4543m a.s.l.) and the lowest in the Afar depression (120m below sea level) is the main reason for the highest biodiversity in Ethiopia (Shibru Tedela, 1995;EWNHS, 1996). These wide ranges of altitudes have given the country a variety of ecologically distinct and isolated areas *Corresponding author: dessalegn_ejigu@yahoo.com edge species because they are favoured by forest fragmentation (Angelstam, 1992). Habitat edges can affect species directly due to altered habitat characteristics and indirectly by facilitating movement or creating habitat for competitors, predators and parasites (Watson et al., 2004).
Furthermore, the natural heterogeneity found in many parts of the forest structure such as abundance of large trees, dead wood and multilayered stands, canopy openness, the kinds and amounts of resources available for breeding and foraging activities can also affect avian communities (Naka and Cintra, 2012).
A study in the extremely fragmented and dry northern part of Ethiopia showed the occurrence of more species and a higher number of unique species in the forest patches than in open fields (Aerts et al., 2008). Therefore, understanding the effect of habitat disturbance on bird community structure is important to prioritize future conservation of biodiversity that are under great pressure either due to natural or human induced disturbances (Girma Mengesha et al., 2011).
In terms of avifauna, Ethiopia is one of the most significant countries in Africa, and the availability of different habitat types contribute for their diversity. Thus in Ethiopia, there are more than 857 avian species of which 20 are endemic, 29 are globally threatened and one introduced species (Lepage, 2014). A number of variables have been found to influence bird species diversity within a landscape. Some landscapes exhibit high richness in biological diversity than others. Mountain ecosystems are usually recognized as biodiversity hotspots harbouring rich biota often with high number of endemic species (Thapliyal et al., 2012).
Much of the Ethiopian landscape is altered by agricultural activities, deforestation and over-grazing (Aerts et al., 2008). Habitat deterioration is particularly threatening quality of the ecosystems.
Avian studies have great value to determine the importance of the site, habitat requirement of the species, and to understand the population dynamics (Gibbons et al., 1996). Seasonal variation in avian community structure decreases with increasing vegetation complexity (Symth, 1974;Karr, 1976). This is apparently due to the increased buffering of the physical environment by more complex vegetation.
Forests attract a large number of avifauna because of the habitat suitability for most of them (Hosetti and Harisha, 2009

Description of the study area
The present study was conducted in two forest patches of Awi Administrative Zone, namely Apini interval depending up on the difficulties of the area and the type of bird species to be identified and enumerated (Vielliard, 2000). All birds seen and heard from 25m radius were recorded. The survey was conducted along a series of point counting stations by counting the number of birds detected on each point counting station (Buckland, 2006 (Sutherland, 1996). Thus, eight sample blocks were selected at random to be representative of the whole study area.
Point count method was used to record the presence or abundance of bird species (Bibby et al., 2000;Buckland et al., 2001). Censuses were taken on 32 sampling points of which 12 were from forest interiors, 8 from shrubs, and 12 from forest edges. In each point count station, a minimum distance of 150 -200m was maintained using GPS to avoid double counting (Vielliard, 2000). To

Data analysis
Birds' species 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. Evenness (E) was used to quantify the unique representation of a species against a given hypothetical community in which all species are equally common (Krebs, 1999). Relative abundance of avian species was determined using encounter rates following Bibby et al. (1998).

Species diversity
The highest number of avian species was recorded in Dikuma forest patch both during the wet and dry seasons. The Shannon-Weiner diversity index revealed that more avian species diversity (H′=3.84) was recorded in Dikuma during the dry season and the least (H′ =3.59) was recorded in Apini in the same season (Table 1). Avian species were evenly distributed in these areas as indicated by the evenness value (E=0.89).

Distribution of avian species
The three habitat types namely forest interiors, shrubs, and forest edges varied in the number of avian species diversity and abundance. During the wet and dry seasons, the highest number of species was recorded in the forest edges, followed by forest  Species similarity between the two forest patches indicated that the maximum value of seasonal species similarity was observed in Apini forest patch (Table 3).
Species similarity between the two forest patch communities were CC= 0.77 and CC= 0.79 in the dry and wet seasons, respectively. The overall community similarity of the two forest patches were (CC= 0.73).
Community similarity among the three habitat types during both the wet and dry seasons indicated that relatively high similarity was recorded between forest interior and forest edge (CC= 0.65). Similarity between shrubs and forest edge was (CC= 0.62), and the lowest species similarity was obtained between forest interior and shrubs (CC=0.3).
interior, and the lowest was observed in shrubs.
Shrubs had less avian diversity than other habitats regardless of season and site. Apini, forest interior and forest edge did not show difference in bird species diversity (Figure 2).

Relative abundance
Relative This indicated that there were more uncommon species in Apini during the wet season and frequent species in Dikuma during the dry season (Table 2).   (Scott et al., 2003). Over grazing in the shrub habitat results in flushing of nests by rain due to the absence of hay material for nesting birds.
Unavailability of hay causes exposure which allows the birds of prey to approach the eggs or chicks of breeding birds (Ali and Bibi, 2013). tend to concentrate to forest edges. This variation in abundance and occupancy over time was also observed even in species with a relatively stable population (Gaston et al., 2000).
Some of the most common species in the two forest patches were mountain thrush (Turdus abyssinicus),

RECOMMENDATIONS
The present study showed that Apini and Dikuma forest patches support diversified bird species belonging to different families and orders. Family Ploceidae, Columbidae, and Accipitridae are the most widely distributed families in the area.
Seven endemic bird species of Ethiopia and ten endemic species shared with Eritrea are identified in the study area. Diversity and abundance of avian species are relatively higher at forest edges than forest interiors and shrubs. Regardless of various avian species and other faunas available in the present study area, the attention given to conserve its biota is not significant. Forests are managed for human uses primarily for livestock grazing and firewood rather than for biodiversity conservation.
Therefore, habitat disturbance due to various anthropogenic activities have a prominent impact on the abundance and diversity of birds in the study area.
As the conservation effort in the area is minimal, Redman, N., Stevenson, T and Fanshawe, J. (2009).