AVIFAUNA SPECIES DIVERSITY IN TWO AGRO-ECOLOGICAL ZONES AND OKOMU NATIONAL PARK, EDO STATE, NIGERIA

Abstract

This project was carried out to investigate the abundance and diversity of avian species in two agro ecological zones in Edo state Nigeria. The investigation was carried out for a period of two years which covered two seasons in each year. Two methods; Line Transects Method and Point Count Methods were used to collect data on bird species composition, distribution and abundance in the study areas. The quadrant method was used to determine plant species composition in the habitats of the birds. This method involves total enumeration of all trees above 1m in height and basal area of not less than 10cm in 25×25m2 quadrant sample plot which were randomly selected through balloting from each sampling compartments. A total of 282 bird species belonging to 63 families and 20 orders inhabit the four study areas in two agro ecological zones. The order Passeriformes constituted the predominant group representing 51.3% of the bird species and 14.5% of the families in the three study areas. The result of bird species diversity index revealed significant difference in the Shannon diversity index (H) of bird species in ONP with 4.636c and NIFOR study 3.428a in 2012. Also, ONP with 4.68ᵇ of species shows significant difference in Shannon diversity index (H) than NIFOR with 3.52ᵃ.in 2013. However, there was no significant difference between the bird species in Leventis Foundation Conserved woodland (4.19 b) and Leventis Foundation Farmland, (3.86ᵇ) in 2012 and 2013 respectively. Results of the habitat structure revealed that in ONP, a total of 619 individual tree species in 104 taxa and 47families were enumerated. The highest occurring tree species are Myrianthus arboreus and Oxytenanthera abyssinica with 12 individuals sampled. The lowest occurring tree species is Allanblackia floribunda with only one (1) occurrence. The highest DBH of 5.82m was recorded in Ficus exasperata while the lowest DBH of 0.34m was recorded in Chrysophylum albidun. Also the highest mean height of 32m was recorded in Millicia excelsa and the lowest mean height of 11 m was in Polycerratocarpus parviflorus and Xylopia aethiopica. In NIFOR a total of 17 individual tree species in 13 taxa and 13families were enumerated. The highest occurring tree species is Alstonia boonei with 6 individuals sampled. The lowest occurring tree species is Cola acuminata with only one (1) occurrence. The highest DBH of 2.27m was recorded in Irvingia gabonensis while the lowest DBH of 0.28m were recorded in Hannoa klainenea and Tetrapleura tetaptera. Also the highest mean height of 28m was recorded in Antiaris africana and the lowest mean height was recorded in Monodora tenuifolia. In LFCW a total of 236 individual tree species in 50 taxa and 24 families were enumerated. The highest occurring tree species is Daniellia oliveri with 15 individuals sampled. The lowest occurring tree species is Anthoclestisa nobilis with only one (1) occurrence. The highest DBH of 6.21m was recorded in Daniellia oliveri while the lowest DBH of 0.22m was recorded in Funtumia elastica. Also the highest mean height of 23m was recorded in Ceiba pentandra and Millicia excelsa, while the lowest mean height of 10 m was in Prosopsis africana In LFFL a total of 48 individual tree species in 17 taxa and 12 families were enumerated. The highest occurring tree species is Daniellia oliveri with 5 individuals sampled. The lowest occurring tree species is Erythrophleum suaveolens with only one (1) occurrence. The highest DBH of 1.71m was recorded in Irvingia gabolensis while the lowest DBH of 0.37m was recorded in Vitex donania. Also the highest mean height of 23m was recorded in Vitex donania, while the lowest mean height of 10m was in Ficus thonningii. The habitat specialization revealed that 33 bird species were observed to utilize tall emergent layer, 60 bird species utilizes middle layer and 64 bird species utilizes understory layer while 7 bird species utilizes forest floor and wetland in ONP. At NIFOR study area, 12 bird species utilized tall emergent layer, 54 bird species utilized understory, 10 bird species utilize grassland and one bird species utilize forest floor. However, sixty bird species were observed to utilize tall emergent layer, 66 bird species utilize understory and grassland and 32 bird species utilize forest floor and wetland at LFCW, while Twenty nine (29) bird species were observed to utilize tall emergent layer, Fifty one (51) bird species were observed to utilize understory strata, Twenty two (22) bird species were observed to utilize grassland, and Eighteen (18) bird species were observed to utilize forest floor in LFFL. This study revealed that both conserved areas and mixed cropping system have been found to support bird communities than plantation agriculture. Therefore, the promotion of mixed cropping systems would aid in the protection of bird species. Several bird species observed in ONP simply do not occur within oil palm plantations in NIFOR and therefore the transformation of forest into plantations would be of limited value to birds. The discovery of some rare bird species in the ONP and LFCW is a sign of hope. However, their conservation must be guaranteed and that will only be achieved by the conservation of extensive areas of natural vegetation. The response to agricultural intensification factors is consistent with negative effects of landscape level of disturbance on farmland bird species found in previous studies highlighting the relevance of field and farm scale management. The management of these areas should design programme to discourage bush burning, deforestation and poaching by the local people. Leaving out strips of protected areas that link various ields that are swampy in addition to small patches of forest blocks within the oil palm plantation layout is important. The employment of eco-guards by the management of Leventis Foundation is highly recommended. A library with copies of field guide to mammals, birds, reptiles, butterflies, insects and plants of West Africa should be provided to stimulate and further widen horizon of the rangers and eco guards on issues of biodiversity conservation. The research strategy must integrate the physical, economic, social and cultural condition of the farmers so as to come up with innovations and technologies that conserve and sustain biodiversity