EFFECTS OF FRAGMENTATION ON AVIFAUNAL COMPOSITION, DIVERSITY AND FLUCTUATING ASYMMETRY IN THE EASTERN MAU FOREST: A CASE STUDY OF RIVER NJORO WATERSHED, KENYA

ABSTRACT
Fragmentation and its effects on avifauna is a study that was conducted in upper River Njoro watershed covering about 280km2. The watershed is under threat from increasing human activities that have led to rapid changes in land cover and deterioration of environmental and habitat conditions for birds. These include replacement of indigenous trees with exotic types, clearing of riparian vegetation, cultivation of river banks, deforestation and forest fragmentation. The study’s main objective was examination of effects of forest fragmentation and environmental degradation on composition, diversity and fluctuating asymmetry of avifauna in natural and plantation forest fragments in the River Njoro watershed. Mist netting was used as the method of data collection. Length of sampling time per station depended on rate of capture. Captured birds were ringed and studied with detailed data recorded in Ringing Book. Statistical and descriptive analyses were performed using windows based MINITAB (Version 13.1) software. Diversity Indices were calculated for different forest fragments and data subjected to Analysis of Variance and F-test. A total of 238 individual birds from 49 species, 17 Families and 4 Orders were captured. Results show that larger continuous forest fragments have more birds and higher diversity than smaller ones, forest generalist birds are more than forest specialist birds, natural forest fragments have a higher diversity of birds than plantation forests (P<0.05), fluctuating asymmetry was, however, not observed in the birds. Based on these key findings, several conclusions are made. These include a difference in composition of birds between the forest fragments, a significant difference in diversity of birds between natural forest fragments and plantation forest fragments and environmental degradation has not caused significant genetic stress in the avifauna of River Njoro watershed since fluctuating asymmetry was not observed. The study recommends; that forest policies on plantation establishment be reviewed by Kenya Forest Service and all stakeholders to discourage establishment of monoculture plantations in the midst of natural forests, that a similar study is carried out during the dry season to capture weather variations, that regular monitoring of environmental conditions and birds be carried out to monitor trends, and lastly, long term research on genetics of birds be carried out in the watershed to serve as early warning signals and thus provide guidance on informed management decisions.

CHAPTER ONE
INTRODUCTION
1.1. Background of the Study
Since the development of agriculture, natural vegetation cover of every continent has been extensively modified (Taku, 2000) resulting to extensive removal of native vegetation, and leave fragmented patches across the landscape (Tompkins and Kotiaho, 2002). This process is commonly known as habitat fragmentation, a process which brings about climatical changes that include temporal and spatial patterns of temperature, and precipitation that influence natural ecosystems (Brown et al., 1982). After fragmentation some of the biota within the remnant areas is influenced and changes seen in behaviour, morphology and distribution. In extreme cases, species that are incapable of adapting to the changes are either forced to migrate or they die and eventually get extirpated (Wiens, 1989).

Habitat fragmentation is defined as the process by which large, continuous habitat blocks become subdivided into smaller, more or less isolated fragments (Lund, 2006). Studies of the effects of habitat fragmentation on spatial structure and genetic variation of populations across a variety of taxa continue to identify dispersal as a key process in both population regulation and spatial distribution (Mladenoff et al., 1993). In birds, effects of such habitat and climatic changes are expressed in altered morphological formations, a manifestation of genetic alteration (Anciaes and Marini, 2000). This manifestation is measured by an index of condition called Fluctuating Asymmetry (Krissman, 2006).

Fluctuating asymmetry is described by Tomkins and Kotiaho (2002) as the deviation from perfect bilateral symmetry caused by environmental stresses, developmental instability and genetic problems during development. The condition also refers to small random deviations from perfect symmetry in bilaterally paired structures. It reflects an organism's ability to cope with genetic and environmental stress during development. The use of Fluctuating Asymmetry as an indicator of such stresses is based on the assumption that perfect symmetry is a priori expectation for the ideal state of bilateral structures (Leary and Allendorf, 1989). Fluctuating asymmetry has been used as an indicator of individual quality in studies of natural and sexual selection and as a bio-indicator tool for environmental monitoring and conservation biology (Bradley, 1980).

Eastern Mau Forest has been heavily and destructively logged and degraded (Ngugi et al., 2005), and as reported by Shivoga et al., (2003), this has drastically altered the ecosystem. Since the changes are not happening in isolation, they affect all the other players in the tropical forest ecosystem. As this continues, the functions of the ecosystem are impaired, with concomitance ecosystem imbalances and declines in biodiversity. In Kenya, threatened biodiversity extends well beyond the currently gazetted protected areas (Bennun and Njoroge, 1999). Indeed, Important Birds Areas (IBAs) (places of international significance for the conservation of birds at the global, regional or sub regional level) designated in Kenya, so far cover most of these protected areas and some substantial area outside. Mau forest complex is one such IBA. According to Bennun and Njoroge (1999) the forest holds one of the richest examples of a central East African montane avifauna and 72% of the Kenya’s Afrotropical Highland biome species.

River Njoro watershed which covers the eastern escarpment of Mau is one of the parts in the Mau Forest Complex that has been extensively degraded and fragmented (KFWG, 2001). The watershed area under forest progressively declined from 47% in 1970 to about 15% in 1998 (SAPS, 2002). Between 1986 and 2005, the watershed lost 10% and 9% of indigenous and plantation forests, respectively (Baldyga et al., 2004). Despite all these changes, very little is known on the present status of birds in Eastern Mau forest and more particularly in River Njoro watershed. Bird communities play major roles in the functioning of ecosystems and are very sensitive to slight environmental changes. Changes in general character of vegetation cover of a given region almost inevitably would be followed by changes in bird distribution.

This study was undertaken in upper River Njoro watershed of Eastern Mau forest with the principal aim of studying the relationships between environmental stress (fragmentation and degradation) and genetic stress (fluctuating Asymmetry) in birds. Afro tropical forest bird species in fragmented landscape manifested environmental stress in morphometric differentiation. Furthermore the study gave an estimate of the density and population structure of the forest dependent birds in upper River Njoro watershed.

Statement of the Problem
River Njoro watershed is part of the Mau forest complex, which is one of the five major water towers for Kenya. Mau Forest complex has five main Forest Reserves; Eastern Mau (66,000ha), Western Mau (22,700ha), South-western Mau (84,000ha), Trans Mara (34,400ha), and Ol Pusimoru (17,200ha). The forest complex covers a substantial area of the south-western highlands of Kenya, and represents the largest remaining near-continuous block of montane indigenous forest in East Africa (Bennun and Njoroge, 1999). Mau Forest Complex generally has a rich highland bird community, characteristic of the central Kenya highlands (Bennun and Njoroge, 1999). It is designated as an Important Bird Area since it has global and regional significance in birds conservation. This is proven by the fact that Mau complex is categorized among the richest examples of Central East African montane avifauna (Fishpool, 1996). Further to this, forty-nine of the Kenya’s 67 Afrotropical Highland biome species are known to occur in Mau, making 72% of Kenya’s Afro-tropical Highland biome species (Bennun and Njoroge, 1999).

The forest also harbours eight species of birds that are Vulnerable and Regionally Threatened. These are Ayre's Hawk Eagle, African Crowned Eagle, African Grass Owl, Cape Eagle Owl, Red-chested Owlet, Least Honey guide, Grey-winged Robin, and Purple-throated Cuckoo-shrike. The Hartlaub’s Turaco is endemic in Mau escarpment while Hunter’s Cisticola and Jackson’s Francolin are restricted-range species in the complex forest (Zimmerman et al., 1996). In spite of this, the forest and its rich biodiversity are threatened by human interference. As reported by Bennun and Njoroge (1999), among the most vulnerable parts of Mau Forest for bird conservation, are the high montane forests on the Eastern Mau. This is where River Njoro watershed is located.

Eastern Mau forest as a whole and River Njoro watershed in particular is under threat from increasing human activities that have led to rapid changes in land cover and deterioration of environmental and habitat condition. The major degrading activities include replacement of indigenous tree species with exotic types, clearing of riparian vegetation, cultivation of river banks, deforestation and forest fragmentation. The increasing human population in the watershed translates to a greater need for agricultural produce and settlement land. About two-thirds of the river’s drainage basin is already used for agricultural purposes, mainly for intensive small-scale cultivation (WWF, 1998). The remaining forest mainly along the river bank has also been fragmented into small forest parcels.

The environmental degradation in Eastern Mau Forest is a threat to biodiversity and subsequent loss including birds’ species. To prevent the undesired loss, intervention to control the degradation is necessary. To ensure interventions have the desired outcome, it is indispensable to establish the current status of the biodiversity which would serve as the beginning point for measuring any impacts of the intervention and establishing trends. Prior to this study, not much was known about birds in River Njoro watershed. Research work on biotic communities carried out previously in the watershed focused on composition, abundance and distribution of aquatic macro-invertebrates, fish, frogs, phytoplankton, and zooplankton, (Milbrink, 1977; Vareschi, 1979, 1982; Vareschi and Vareschi, 1984; Vareschi and Jacobs, 1984; Kairu, 1994; Leichtfried and Shivoga, 1995; Bretschko, 1995 and 1996; and Shivoga, 1999a, b, c, d). None of the studies focused on birds.

This study therefore was conducted to establish baseline status of birds with the main objective being to examine the effects of forest fragmentation and environmental degradation on composition, diversity, and fluctuating asymmetry of avifauna in upper River Njoro watershed. The research focused on birds in the fragmented forest blocks using mist nets and ringing procedures, compared and contrasted the status of birds for the different fragments. The guiding objectives were as outlined below.

The General Objective
The general objective of this study was to provide a clear and broad understanding of the effects of forest fragmentation and environmental degradation on composition, diversity, and fluctuating asymmetry of avifauna in upper River Njoro watershed

Specific Objectives
The main objective was broken down into specific objectives namely;

(i) To determine the composition of avifauna in each forest fragment in River Njoro watershed

(ii) To assess the diversity of avifauna in both plantation and natural forest fragments in River Njoro watershed

(iii) To measure fluctuating asymmetry of avifauna in River Njoro watershed

Hypothesis
The following hypotheses guided the study:

H0: There is no difference in composition of the avifauna found in the various forest fragments in River Njoro watershed

H0: There is no difference in the diversity of avifauna found in plantation forest compared to those in natural forest in River Njoro watershed

H0: There is no fluctuating asymmetry in avifauna of River Njoro watershed

Justification and Significance of the Study
Birds are an integral component of the ecosystem since they serve many important functions, including: control of insect and rodent population, distribution of seeds and pollination of flowers that leads to forest conservation, food sources for bird predators, scavenge carcasses and recycle nutrients back into the earth. Ecosystems such as forests provide us with food, medicines and important raw materials. Humans depend on these ecosystems for survival because they keep the climate stable, oxygenate the air and transform pollutants into nutrients. Birds play an important role in the effective functioning of these systems.

Birds live in a variety of habitats; their conservation highlights the diversity of different habitats and is critical to the richness and diversity of the planet. Birds occupy a higher position in the food chain and are therefore good indicators of the general state of our biodiversity. Extirpation of birds is an indicator that something is wrong with the local environment and that action needs to be taken to restore the affected environment. Birds are also indicators of climate change; their behaviour and disappearance are a response to change in the prevailing environment. Driscoll (2013) describes birds as having a psychosocial significance to humans and states that, “birds feed our spirits, marking for us the passage of seasons, moving us to create art and poetry, inspiring us to flight and reminding us that we are not only on, but of, this earth”. Many people derive great pleasure, fulfilment and inspiration from watching birds and listening to them.

Given the importance of birds, effects of the observed fragmentation and habitat degradation in River Njoro watershed needed investigation. The finding of this study will lead to information and decisions that will lead to conservation of biodiversity. This study is justified because it forms a beginning point for further conservation work in River Njoro watershed.

Scope, Limitations, Assumptions and Challenges,
1. The scope of this study was birds that can be captured by mist netting. As such, it did not focus on breeding and nestlings of the birds studied. The birds that were captured by the mist net formed the sample used for analysis and conclusion.

2. Mist netting as the main data collection tool is limited to the extent that it does not capture birds that soar high above the height of the net which would be about five meters from the ground.

3. The study did not study effects of climate change on the birds’ densities and composition. It assumed that all the observed trends are attributed to fragmentation

4. The study assumed that any observed fluctuating asymmetry is brought about by environmental stress that originates from habitat fragmentation. It did not consider other sources of environmental stress including pollution from agrochemicals used in the surrounding agricultural land.

5. This study did not consider effects of other factors related to urbanisation, land use and land use change and human settlements in specificity other that it brings about fragmentation.

6. The study was carried out during the day therefore may have not captured nocturnal birds

Operationalization of Terms
The list below has definitions of key terms described in the context of this study.

Avifauna: The term has two words in one, fauna refering to organisms in Kingdom Animalia and aves which is another name for all animals in the birds’ branch so avifauna refers to all birds’ species. The term has been used to generate other terms e.g. Avitourism, refereeing to the ecotourism that focuses on bird watching. In this study Avaifauna refers to birds’ species and individuals observed in the watershed. This is the main subject of study.

Composition: refers to species found in the ecosystem and their characteristics including age, sex, and population structure. Composition in this study focuses on characteristics in terms of age (adult, juvenile, breeding), sex (male and female) and forest dependency.

Diversity: refers to the unique collection of bird species in a unique ecosystem setting that probably cannot be replicated and that cannot be moved to another site because of the environmental drivers. The term in this study is used to describe the total variety of bird species living in River Njoro watershed.

Fluctuating Asymmetry (FA): the differences observed in the sizes of a pair of limbs/tarsi of individual birds. It is a measure of condition of individual birds’ morphological formation following exposure to environmental stress (in this case forest fragmentation) which in turn affects the genetic formation. The observed difference could be between the two parts of the pair and/or the standard measurements for the species in question. This study uses the term to refer to any difference in the length of tarsus of an individual bird resulting from any cause.

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Item Type: Kenyan Material  |  Attribute: 84 pages  |  Chapters: 1-5
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