Bird community response to landscape and foliage arthropod variables in sun coffee of central Kenyan highlands

Abstract

Land conversion represents a serious threat to terrestrial biodiversity and effective conservation in human-dominated landscapes requires an understanding of the relationship between spatial heterogeneity and biodiversity. Coffee is the most valuable tropical export in the world with the capacity to affect biodiversity on a large scale, and much of the world's coffee is grown in open plantations (sun coffee), where little research has documented how landscape structure or food availability affect bird diversity. We examined the effects of both landscape characteristics and foliage arthropod abundance on bird species richness, total bird abundance and the abundance of foraging guilds in sun coffee plantations of central Kenyan highlands. Variation in the local landscape appeared to have little effect on bird abundance, while the foliage arthropod community, particularly number of arthropod orders, may have a strong impact on omnivore and insectivore abundance in sun coffee. These results do not mean small scale fragments or landscape composition is unimportant to bird communities in our region for several reasons, including the high model uncertainty that may indicate an important missing variable, the habitat complexity and presence of large forest reserves around our study sites, and the single scale at which our variables were tested. Our results indicate that farm managers wanting to increase bird abundance, especially omnivores and insectivores, should consider balancing the need to eradicate coffee pests and leaving an intact arthropod community that likely increases these guilds. Further study is needed to validate these patterns, which may have strong implications for bird biodiversity in agricultural settings across other areas in eastern Africa. Keywords: Abundance, Species richness, Fragmentation, Landcover, Guild