Influence of Vegetation Cover Types on the Composition of Bird Foraging Guilds in the Agricultural Landscape of Muhoroni Sub-County

Abstract

Most wild biodiversity is found outside protected areas, in human-modified landscapes, it is therefore important to study the influence of human activities in these landscapes. Such studies guide how best to manage especially agricultural landscapes for the benefit of biodiversity and provision of ecosystem services. Many studies of this nature have been done in Africa. In Kenya, no study has been conducted in the sugarcane dominated agricultural landscapes. Muhoroni Sub-County (MSC) in Kenya provides a good case study and birds are recognized as good environmental indicators in such studies. The objective of this study was to determine the influence of vegetation types on the composition of birds of respective foraging guilds in study sites dominated by farmlands and sites dominated by natural shrubs in MSC. The bird counts were undertaken using standard-point-count method within 100 30-m radius plots set at intervals of 200 m along 10 transects measuring 2 km each. Percentage vegetation type within the same plots revealed that the farmland was more heterogenous than the natural shrubs. A total of 1450 birds representing 122 species from 46 families were recorded. Mann-Whitney U test revealed that there was significant difference in bird species abundance in the farmlands and natural shrubs (U = 2449, p < 0.05), while the magnitude in true diversity indicated that the farmland was 4 times more diverse than the indigenous shrubs. There was a significant association on how the farmers used their land (X2 = 977.96, p<0.05). Generalized Linear Models showed significant correlation between vegetation cover types and abundance of some foraging guilds. The higher bird species composition in the farmland dominated site could be explained by the Intermediate Disturbance Hypothesis and the high vegetation heterogeneity. This study recommends similar studies for other taxa, especially those that have economic importance for agriculture, for example invertebrates and small mammals, to elucidate general patterns that may guide management of vegetation covers in MSC and beyond.