ASSESSMENT OF AVIAN SPECIES DIVERSITY AND RICHNESS IN SOME SELECTED DAMS IN OKE-OGUN, OYO STATE, NIGERIA

Abstract

Natural wetland degradation has significant effects on the biodiversity sustained therein and also the ecosystem services they provide. Hence, the conservation value of artificial wetlands needs to be explored to know if they could compensate for the natural wetlands. The present study was conducted to explore birds’ assemblage structure, anthropogenic activities and people’s perception of bird in three selected dams (Igboho, Okeho and Kishi dams) in Oke-ogun axis of Oyo state, Nigeria using point count method. Data was collected for six months (January to June) in 2019. Data were analysed using one-way ANOVA (Analysis of Variance). Birds’ diversity Indices was assessed using PAST (Paleontological Statistics software package for education and data analysis). The study recorded a total of 679 bird species (309, 160 and 210 at Igboho dam, Okeho dam and Kishi dam) belonging in 37 orders (14, 10 and 13orders), 84 families (35, 16 and 33 families) and 173 individual species (75, 32 and 66 species) in Igboho, Okeho and Kishi dam respectively. The order Passeriformes had the highest number of species in the 3 dams (31, 9 and 25) at Igboho, Okeho and Kishi dam respectively). Out of this, 22 water birds which was 29% of the total bird species, 16 water birds which was 24% of the total bird species and 13 water birds which was 40% of the total bird species were recorded in Igboho, Kishi and Okeho dam. There is no significant difference (P= 0.634) in the water bird species in the three selected dams but in contrast, there is a significant difference (P = 0.003) in the bird species across the dams at significance level (P ≤ 0.005). Also, 32 bird species (43%) were exclusive to Igboho dam, 3 bird species (9%) was exclusive to Okeho dam and 23 bird species (35%) were exclusive to Kishi dam while 20 bird species were common in all the dams. Birds relative abundance was highest in Igboho dam (198 and 111 bird species) and least at Okeho dam (102 and 58) during the dry and rainy season. Bird species Dominance Index was highest (0.5469 and 0.1027) in Okeho dam and lowest in Kishi dam (0.05407 and 0.07186) during the dry and rainy season. However, Kishi dam recorded the highest in the diversity indices (Simpson Index 1-D= 0.9459 and 0.9281, Shannon Weiner Index H= 3.296 and 3.24, Evenness= 0.6138 and 0.5937) during the dry and rainy season. Furthermore, the lowest Evenness index was recorded in Igboho Dam (0.1416 and 0.4872) during the dry and the rainy season. Birds were classified into 9 feeding guild and Insectivorous birds were the dominant species in Igboho and Kishi dam with 23 bird species (17%) and 17 bird species (11%) respectively while Nectarivore had the least record (1 bird species) in Kishi. Human activities/threat factor was categorized into 6 factors and Igboho dam experienced the highest severity of threat (fishing and farming) while cattle grazing was highly severe at Kishi dam. In addition, 78% of interviewed dam users had fundamental knowledge about birds and showed a favorable perception. Igboho dam houses the Purple swamp hen (Porphyrio porphyrio) which confirms the occurrence of the species in the southwestern part of Nigeria where the only previous records were seen in 1992 and 2014. In conclusion, the study revealed that Dams also has potential to support similarly diverse bird communities and they can have a valuable complementary role in conserving avifauna hence, there is a need for strict and immediate conservation attention in these dams and other dam sites.