Bird Community, Feeding Guilds and Habitat Associations Along the Proposed River Dibombe Hydropower and Transmission Line Project in Nkam and Moungo Divisions, Cameroon

Introduction

There is an ongoing challenge in balancing economic development and environmental protection. Environmental and Social Impact Assessment thus plays a crucial role in promoting a safe environment and ensuring sustainable development. Most international financial institutions have also embraced the ESIA to ensure that their projects contribute to ‘sustainable development’. In essence, for major projects above a certain funding threshold (currently US$10 million), Equator Principal finance institutions must ensure that an impact assessment appropriate to the scale and nature of the project is provided by the applicant [1].

Economic development in Cameroon is partly hindered by insufficient supply of electrical energy despite its rich biological and natural resources with significant ecological, economic and cultural values. Its water resource has a huge potential for hydropower generation, and the proposed Dibombe Hydropower project aims to add 64.2 MW of energy on the national grid contributing to the growth of the energy sector. Hydropower generation is a renewable energy which offers excellent merits against the negative factors of carbon dioxide and other flue gases which contaminate our environment. It’s the least costly way of storing large amounts of electricity, with low cost of operation as advantages. Nevertheless, hydropower implementation comes with social, economic and ecological impacts. From an ecological point of view, the construction and operation of hydro dams and transmission lines can affect avian biodiversity in many ways, among which are habitat degradation and fragmentation, changes in hydrology, introduced species, hunting and harvesting enabled by rights-of-ways (transmission line corridor) and construction of roads.

Overhead power lines are said to have negative impacts on bird populations, mainly through collision and electrocution [2, 3]. On the other hand, power lines may provide benefits for several bird species (e.g. storks, raptors, corvids), as wires and pylons may be used as perches, hunting, solitary resting and communal roosting and nesting sites [4, 5, 6, 7]. This creates a paradox for conservation, since positive and negative impacts on the use of power lines co-exists and the estimation of impacts of these structures at population level will have to take these trade-offs into account. Also, electromagnetic pollution related to power lines has been suggested to decrease reproductive success in several species, from small passerines to storks [8].

Hydroelectric dams can block non-Volant and aquatic animal migratory pathways, introduce alien species and flood surrounding lowland habitat [9, 10]. Furthermore, dam impoundments disrupt wildlife by altering the original environment, thereby hindering wild animals and plants from thriving due to the degradation or loss of habitat [11]

ESIA is a multidisciplinary study involving several taxa amongst which are birds. Birds are good indicator species because they are ecologically versatile and thrive in all kinds of habitat as herbivores, carnivores and omnivores. Their presence is an indication of healthy ecosystem or habitat. The diet of bird species represents a fundamental aspect of its ecological niche and dietary adaptations play an important role in understanding the ecology and evolution of communities [12]. Birds also play an important role in ecosystems as potential pollinators, scavengers and bio- monitors in controlling insect pests and also as excellent ecological indicators [13].

Cameroon like many other countries around the world has institutionalized the ESIA process. As part of the process, baseline data collection is crucial in understanding the existing environmental conditions before a project is implemented. This study was thus designed to establish a baseline of the avian community, their feeding guilds and habitat associations within the project sites and to highlight potential environmental effects of the proposed project on the avian communities which are vital at the outset, for potential impacts can be earmarked and mitigation measures considered.

**Results**

A total of 155 bird species belonging to 39 families were recorded during the survey; 104 species at the proposed hydropower construction site and 111 species along the proposed transmission line. Overall, the most dominant species were recorded from the family Pycnonotidae (17 species, 10%) while 11 families recorded just one species; Phalacrocoracidae, Scopidae, Threskiornithidae, Anatidae, Phasianidae, Rallidae, Burhinidae, Psittacidae, Collidae, Corvidae and Viduidae representing 0.6% each. Two globally threatened species were recorded: African Grey Parrot *Psittacus erithacus* (Endangered) and the Yellow-casqued Wattled Hornbill *Ceratogymna elata* (Vulnerable). Of these species, 140(90.3%) species where resident species, 12(7.7%) species where resident but partially migratory species, 2(1.3%) species where palearctic migrants and 1(0.65%) where vagrants.

Discussion

The checklists generated at the end of the study (Table 1) shows a great diversity in terms of bird communities as well as the species population assessed in the two sites. Generally, 170 species of birds where encountered belonging to 39 families among which 86 of them falls within the Guineo-Congolian forest biome (Lowland Forests: LF). Of the 32 globally threatened bird species listed in Cameroon according to the IUCN status 2018, only three where observed within the designated study area during this survey representing 9.4%, consequently, considering criterion A1, this area can be qualified as an Important Bird Area (IBA) as it does harbor three globally threatened bird species. The sites does not qualify according to criterion A2, as it does not hold any of the restricted range species, i.e. species with a total world range less than 50.000 km2. And again, No congregational species was recorded during this survey thus the sites do not qualify under category A4 as an IBA.

RpM= resident but partially migratory, PM= palearctic migrant, V= vagrant) Table 1: List of bird species, feeding guilds, distribution status and IUCN categorization along the proposed River Dibombe hydropower and transmission line project (LC= least concern, VU= vulnerable, EN= endangered, R=resident, While a total of 170 species of birds representing 17.6% of birds in Cameroon can be considered relatively low for a country like Cameroon with a bird species richness of 968, it should be noted that the area has no protected status and is heavily impacted by human activities thus the coming of the proposed hydropower project presents an additional cumulative impact of habitat loss for terrestrial bird and an additional habitat for aquatic birds after the construction of the dam, in a local area and within the lowland of Cameroon where avian species are unique but not particularly rich in diversity.

According to world commission on dams 2000, Hydropower is one of the most proficient technologies for energy generation, which is carbon free and produces energy continuously. Hydropower projects have impacts on the environment in general and birds in particular [21]. Change in water flow regimes, electrocution, collision, ecological differences, migratory barriers, fragmentation, degradation and loss of biodiversity are some of the identified potential ecological impacts of the proposed Dibombe HPP on bird communities within the sites while flow regulations, biotope amendment, noise reduction, use of bird friendly power lines, Flight diverters and construction of migration corridors are some of the alternative proposed actions for mitigating the negative impacts of the projects in the course of implementing Dibombe HPP. Therefore, to meet the increasing demands of energy and ensure sustainable development, the different mitigation and enhancement measures need to be incorporated at the early stage of the project lifecycle.

The effect of anthropogenic disturbance on avian communities has been highlighted in many studies [9]. From the assessment done in the project site and the transmission linecorridor on human activities, many bird species are of target to local hunters like Palm-nut Vulture (Gypohierax angolensis), African Fish Eagle (Haliaeetus vocifer), Great- blue turaco (Corythaeola cristata) and hornbills by villagers to supplement their protein source and the use of their body parts like feathers and bones for traditional purposes. Some of these species, especially hornbills, are frugivores, travelling long distances daily looking for fruiting trees, thus, placing them among the most important seed-dispersers of trees and lianas as confirmed by Holbrook, et al. [22]. This species rely heavily on intact tropical forest and large fruiting trees, their movements can expand significantly if this forest is fragmented with the transmission line corridor. Owing to the vulnerability of the hornbills to habitat fragmentation and occasional electrocution on power lines, we proposed that more fruiting trees should be planted dispersedly within the surrounding forest along the Dibombe River, and flight diverters installed all along the 10.8Km power line running from Sole village to the SONATREL substation in Njombe- penja. The loss of these species through over-hunting, bush fire, deforestation through logging, habitat fragmentation, through creation of access roads and habitat destruction for farm lands coupled with the coming of the proposed HPP and its transmission line corridor could have a significant effect on the regeneration of these sites. The direct threat to the communities of these birds is habitat degradation through farming, bush fire and logging. In areas where the degree of disturbance like the presence of plantations and farmlands was high, they were very poor in community composition of birds, A change in the vegetation on which these birds depends (that is from forest to plantations and farmlands) is been caused by clearing for agriculture and illegal logging, this is in line with Danjuma [23, 24, 25, 26, 27, 28, 29]. The neighboring villages to these sites like Sole, Mabombe, Lamba, Boneko, Njanga and Pendja depends on this forest for survival, they take advantage of the fertile soil for agriculture and also hunt some of these bird species and other animals therein for protein as well as cut down trees for building and energy. These first of all constitutes a threat for the bird communities within this area, thus the coming of the hydropower project and it’s transmission line is surfacing as a buster to further reduce this community of birds to their minimum. Insectivorous and nectarivorous birds that constitute 29% of birds on these sites decreases with an increase in the modification of their habita. This confirms that these groups of bird are vulnerable to deforestation and land use .This is the case under which the surrounding forest along the Dibombe River will be subjected tied with the coming of the hydropower project and its transmission line given that the area is already facing an enormous pressure as a result of farming and an additional pressure from poachers and loggers [30, 31, 32, 33, 34, 35].

The distribution of birds within these sites varies greatly between the project site and the transmission line corridor, just like the variation in terms of number of species and their composition, the transmission line is a linear infrastructure of 50m wide running for a distance of 10.8 Km from the intake to the SONATREL Substation in Njombe-Pendja, its cuts across so many habitats from forest to farmlands, grassland and plantations. The distribution of birds along this line is linear [36, 37, 38, 39, 40, 41]. An average of 20 bird species were recorded per station and a total number of 127 species were recorded all along the transmission line, thus as a result its implementation will warrant this birds to look for the next best available habitat along the line to ensure their continuity. With regard to the project site covering an area of almost 10.5Km², the distribution of birds within this zone is quite even and uniform holding to the fact of the uniform nature of the site too, from forest along the river back, to farm bushes, farmlands and finally to plantations. Birds within these zones have become adapted despite human disturbance in the said zone; a further disturbance by the project is simply coming as an addition to the already existing nuisance suffered by these birds and their habitats. A total of 154 resident bird species (R), 13 residents but partially migratory (RpM) species, 2 palearctic migrants (PM) and 1 vagrants (V) were recorded (Table 1). During the study period three species listed by IUCN Red List (2018) were recorded on the sites. Yellow-casqued Wattled Hornbill (Ceratogymna elata) under the ‘vulnerable’ category, Crowned Eagle (Stephanoaetus coronatus) under the “near threatened” category and Grey Parrot (Psittacus erithacus) under the ‘endengered’category, 167 of the remaining species where least concern (LC) [42, 43, 44, 45, 46, 47].

Conclusion

This study concludes that the present sites need more investigations and monitoring to bring out the complete biodiversity of birds in this area. The presence of endangered, near threatened and vulnerable birds species needs urgent monitoring to determine the trends. The findings of the present study indicate feeding guild pattern, diversity of avian fauna, their distribution status and IUCN categorization of birds within the sites. The results of this study showed that Dibombe river forest and the zone linking the forest to the SONATREL substation in Njombe-Penja is a highly productive habitat and harbors a wide range of bird species even though the area is not an intact forest crisscrossed by patches of cultivated lands at some areas by the local population for subsistence.

Acknowledgments

Authors are thankful to Pinnacle Group Cameroon for supporting the field work for this study. We are grateful to the local field guides for their collaboration and local knowledge of the site during the field work and lastly to the villagers at the site in Sole for their hospitality throughout the exercise.