ABSTRACT
Populations of avian species continue to decline worldwide due to the various types of habitat degradation. This is the case with Hinde’s Babbler which is listed as Vulnerable in the IUCN Red List with isolated populations confined to some parts of central and eastern Kenya. The purpose of this study was to asses and compare its current population status in MNP, Ngaya Forest Reserve and agricultural landscapes. This survey was conducted between June and December, 2015 covering dry and wet season. Data was collected at points along predetermined transects where playback of Hinde’s Babbler was used to elicit response of Hinde’s Babbler groups. A cumulative transect length of 19km was surveyed in the three landscapes where quadrats of 20 x20m were set at constant intervals. At each point of detection, total number of adults, offsprings, disturbances, threats and vegetation attributes were recorded. Mann-Whitney, Kruskal Wallis, mean, frequencies and Spearman Rank Test were used to analyze data. The results indicated a mean group size of 4.7 at Ngaya Forest Reserve, 4.6 in MNP and 3.4 at the AS during dry season. These resulted in a population estimate of 127 individuals (Ngaya), 91 individuals (MNP) and 98 individuals (AL). During wet season the mean group size in Ngaya Forest Reserve was 5.2, 3.9 in MNP and 4.0 in AS. This resulted in population estimate of 84 individuals at Ngaya Forest, 123 in MNP and 38 individuals at AS. There was no significant statistical difference between group density during dry and wet sampling season (W = 241.5, P =0.08). In terms of relationship with habitat, only shrub cover was positively correlated with mean group size of Hinde’s Babbler in both seasons (dry, rs = 0.70, P=0.01; wet, rs = 0.80, P=0.02). The other variables of tree, herbaceous and grass cover (rs = -0.57, P= 0.03; rs = -0.83, P = 0.00, rs = - 0.54, P = 0.04) were negatively correlated during the dry season while no correlation was established between mean group size with bare and with crop cover. During the wet season, only tree cover was negatively correlated with mean group size. In terms of disturbance and threats to Hinde’s Babbler, only vegetation trampling in MNP was correlated with mean group size during the wet season (rs = - 0.26, P =0.03). These results imply that continuous monitoring of these three landscape and habitat is necessary to keep track of trends in population and the impact of disturbance on the conservation of the Hinde’s Babbler. The results are crucial in underscoring the importance of protected, partially protected and agricultural landscape as well as habitat structure and condition in the conservation of threatened avifauna population.
CHAPTER ONE
INTRODUCTION
Background Information
Habitat loss is the single threat to birds though other factors like alien species and hunting have been implicated in the decline of many bird populations (Njoroge & Bennun, 2000). According to BirdLife International (2011) human actions are putting pressure on species’ populations and their habitats thus contributing to a decline in population of birds globally. In an assessment of world avifauna 1,375 out of the 10,000-species listed on the IUCN Red List as threatened with extinction based on IUCN criteria and categories (IUCN, 2001). These comprise 217 species classified as Critically Endangered (meaning they are facing an extremely high risk of extinction), 419 species assessed as Endangered (very high risk of extinction) and 741 listed as Vulnerable (IUCN, 2006). An additional 959 species are listed as Near-Threatened because they are assessed as close to qualifying as globally threatened. In Africa, 245 species are threatened with extinction, 29 of which are Critically Endangered. For the Kenya case, 39 avifauna species are threatened, 6 species are Critically Endangered, 15 are Endangered and 18 are Vulnerable (BirdLife International, 2016a).
According to BirdLife International (2014a), of the 1,375 threatened bird species, 963 species of threatened birds have populations of fewer than 10,000 individuals, while 520 species have populations below 2,500 individuals. In total, 58 species of threatened birds have tiny populations that possibly number fewer than 50 individuals. For instance, there are 40–45 adult Tahiti Monarchs Pomarea nigra left on Tahiti, French Polynesia, and only 30–35 Puerto Rican Amazons Amazona vittata on Puerto Rico (BirdLife International, 2013). Thus, for most avifauna species with small populations, their numbers are also believed to be declining. Only 280 threatened species have populations that are estimated to exceed 10,000 individuals. Most of these species qualify as threatened because their populations are undergoing rapid declines (BirdLife International, 2011). In Kenya, the restricted range and critically Endangered Taita Apalis (Apalis fuscigularis) population has declined due to habitat fragmentation (Githiru, 2003). It is listed as Critically Endangered in the IUCN Red List because it has a tiny occupied range of 500 hectares with a population of not more than 150 individuals. It's montane forest habitat has become severely fragmented and continues to decline in both extent and quality.
Surveys by Githiru, et al. (2014) indicated that the very small population of the Taita Apalis has consequently been fragmented into extremely small sub-populations.
Habitat suitability influences species’ distribution in space (Moyle et al., 2012). Habitats that are better and attractive in terms of cover from predators, food availability and nesting sites influence species’ preference (Eddy et al., 2014). Avifauna species vigorous defend their territories with attractive resources to enhance their attractiveness in formation of breeding bonds. Thus, habitats with better resources are expensive to defend and some cost has to be foregone. Some have to expand their range to unoccupied sites with some resources or avoid forming bonds (Chalfoun & Martin, 2007). According to Plumb (1979), when species move to new environments they may take long to breed and thereby forego breeding. This is probably the case in Hinde’s Babbler range extension to Ngaya Forest, an area with high altitude in contrast to the former sites of lowland woodland and thickets (Njoroge & Bennun, 1998). Surveying new sites and comparing populations between different strongholds of the species becomes priority for conservation of these species at site level and landscape level.
The decline in populations is as a result of contracting ranges (Bonn et al., 2002). Habitat loss has been linked directly with bird population decline, with forestland being cleared and put under arable land (Njoroge et al., 1998). This has puts species under pressure to expand the range in order to seek refuge or try to co-exist with humans (Didham et al., 2007). Habitat condition directly and indirectly affect the population status of avian species, their traits and preferences which in turn determine their distribution (Both et al., 2006). Some birds have expanded their range depending on habitat suitability (Shaw et al., 2003). Though this might not be the case as surveys have not be carried out to prove whether they existed before (Njoroge & Bennun, 2000). Surveys in unsurveyed habitats can produce numbers necessary for conservation status of a species to be uplisted or downlisted in the IUCN RedList.
Hinde’s Babbler is a small bird measuring 23 cm from head to tail, sturdy and thrush-like in appearance (Plumb, 1979). It occurs in two forms; some are pale while others are dark. Pale form is mottled white-and-black on head, neck and breast, sometimes with asymmetrical blotching, belly and vent off-white (BirdLife International, 2015). Dark form has reduced white 'scaling' on head and breast, with rusty vent, but white belly (Plate 1). Orange-red eyes in adult, brown or dark grey in immature. Babblers within the range of this species have white or orange- yellow eyes and lack scaling on head and breast (Shaw et al., 2003). Hinde’s Babbler produces a chattering voice; it often stays silent for long periods. Good areas for this species are around
Mukurweini and Kianyaga (Bennun & Njoroge, 1999). It is highly sedentary and occurs in groups of individuals all year-round (Njoroge & Bennun, 2000).
Hinde’s Babbler is listed as Vulnerable on the IUCN RedList since it is known from a small number of locations within a small range, where its habitat is undergoing severe fragmentation (Collar et al., 2016). Its current population is believed to be between 1000-3700 mature individuals with a decreasing trend because of perceived habitat fragmentation within its range (BirdLife International, 2012). Its endemic to parts of ‘central and eastern Kenya’, thus it carries two tags that calls for conservation (Bennun et al., 1996). Its conservation within a severely modified agricultural landscape is a substantial challenge than it seems in to policy makers(Njoroge & Bennun, 2000).
Statement of the Problem
Hinde’s Babbler is endemic to Kenya, confined to central and eastern regions of Kenya. It is listed as Vulnerable in IUCN RedList and due to its small population is thought to be increasing but at a low rate. It is threatened since its habitat is undergoing continuous fragmentation and degradation due human population pressure and associated need for land for agricultural expansion within its range. By being listed as Vulnerable, it bears tags that make it a priority for conservation actions and critical efforts to prevent extinction. The Ngaya Forest population of Hinde’s Babbler remained largely unsurveyed and thus unknown. Effective conservation can only be undertaken if current information on conservation status of a species is known. Population trends of the species in protected sites such as Meru National Park, adjacent unprotected agricultural landscape remained unknown. Yet it is important to understand how the species is faring in protected and unprotected landscapes. Surveys at the Ngaya Forest Reserve, MNP and AS will fill existing gaps in biological knowledge of the distribution and population status of the Hinde’s Babbler. Threats as well as the habitat structure and variability in protected and unprotected sites are also undocumented. The process of downlisting and uplisting of species in IUCN Red List requires continuous up-to-date data on species population size, trends and distribution across its range. This information is not complete for this purpose when other sites within which a species is assumed to exist remains biologically unsurveyed. This study sought to provide information on the population status of Hinde’s Babbler, factors influencing its habitat preference and threats.
Objectives of the Study
Broad objective
To effectively improve the conservation status of the globally threatened Hinde’s Babbler through increased biological knowledge and targeted research and monitoring.
Specific objectives
i. To estimate the current population of Hinde’s Babbler and compare it between protected MNP, partially protected Ngaya Forest Reserve and unprotected agricultural landscape;
ii. To assess the influence of vegetation type on habitat preferences of Hinde’s Babbler in MNP, Ngaya Forest Reserve and agricultural landscape.
iii. To assess impacts of habitat disturbances on Hinde’s Babbler population size in MNP, partially protected Ngaya Forest Reserve and the agricultural landscape
Research hypotheses
H01 Population of Hinde’s Babbler does not differ between MNP, Ngaya Forest Reserve and agricultural landscape;
H02 Vegetation cover type does not influence Hinde’s Babbler habitat selection and use.
H03 The impacts of habitat disturbances do not affect the population size of Hinde’s Babbler across landscapes.
Justification
Evidence-based conservation concept requires continuous supply of vital data for use in setting priorities for species conservation, management and planning. For effective conservation of the globally threatened Hinde’s Babbler, up-to-date information on the species demography (population size and age composition), spatial distribution, habitat preference, threats and the its severity is vital. Shaw (2007) recommended the need to monitor abundance and habitat quality at managed sites (protected areas), and match these with unmanaged sites (unprotected). Most importantly, for the erstwhile unsurveyed Ngaya Forest information generated could be used in updating the conservation status of the species as well as in the development of the Species Action Plan as well as in the development of the Management Plan for the Ngaya Forest Reserve. This study provides the much-needed information to review the conservation status of on Hinde’s Babbler. Through the information, a species can be either downlisted or uplisted in the IUCN RedList. The study provides the much-needed data for a possible incorporation in site or to scale conservation action and policy-making process. This information is vital for institutions responsible for bird and ecosystem management such as the National Museums of Kenya, Kenya Forest Service, Kenya Wildlife Service, Nature Kenya and BirdLife International in conserving the respective sites. As part of extending protected area boundaries, this study is instrumental in determining areas that can be priority for protected area expansion such as the agricultural landscape around Meru National Park and Ngaya Forest Reserve. This information also forms a crucial baseline for future monitoring trends in species population and habitats at these sites in future.
Limitation of the Study
Some sites within the park were inaccessible on both foot and car patrol due to thick forest, and pricking thorn as well as rugged terrain. During wet season, it was difficult to access some sites due to flooding and poor weather. Getting off the car was unsecure due to dangerous wild animals. This study also faced management limitation such as finance and time constraints. A strict workplan was followed during the surveys besides incorporation of Meru National Park into the project to reduces the fuel cost. The research department provided a vehicle and a driver to curb on expenditure.
Assumptions of the study
In terms of the reaction of the focal species on the playback, the assumption was that the species would response to the playback. It was assumed that Hinde’s Babbler groups in Meru National Park did not move out into Ngaya Forest and agricultural landscape during the survey. Equally, the Hinde’s Babbler groups in Ngaya Forest and agricultural landscape didn’t mix with their counterparts in MNP during the survey. It was also assumed that there was no double counting of individuals along the transect and all Hinde’s Babbler groups were found along the transect and responded to the playback.
The Scope of the study
The study was confined to Meru National Park, Ngaya Forest and the adjacent agricultural landscape around Meru National Park. It focused on the Hinde’s Babbler the population size, structure, composition (i.e. the number of nestlings, fledglings, immatures and adult Hinde’s Babbler) and habitat preferences. The study also focused on the level of disturbance, seasonality and severity of threats in the two protected ecosystems and unprotected agricultural site.
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Item Type: Kenyan Topic | Size: 63 pages | Chapters: 1-5
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