Complementary seed dispersal by three avian frugivores in a fragmented Afromontane forest

Questions To what extent does species-specific variation in gut passage time (GPT), habitat use and mobility of three key avian frugivores synergistically affect the distribution of Xymalos monospora seeds within and among isolated forest fragments? Location Three fragments of a severely fragmented cloud forest, Taita Hills, southeast Kenya. Methods We experimentally determined GPTs of X. monospora seeds and recorded movements and habitat use by Turdus helleri, Andropadus milanjensis and Tauraco hartlaubi through radiotelemetry, and combined these data to generate species-specific seed dispersal patterns. Results Differences in mobility and habitat use among the three frugivores caused significant complementarity in seed dispersal, despite the fact that gut transit times were highly comparable. While the most sedentary and forest-dependent species mainly led to short-distance dispersal away from parent trees, two more mobile species dispersed seeds further away from the source trees, both within indigenous forest patches and towards exotic plantations and isolated fruiting trees in the landscape matrix. A. milanjensis inhabiting a very small forest fragment spent significantly more time in the landscape matrix than conspecifics residing in the two larger fragments. Conclusions By varying distances over which seeds are carried away from parent trees and the habitat types in which they are ultimately deposited, avian frugivores affect the spatial distribution of seeds and early plant recruits in a distinct and complementary manner. Because landscape properties are expected to lead to different constraints on avian mobility for habitat specialists and for generalists, ecosystem processes such as avian seed dispersal are shaped by complex interactions between disperser behaviour and the environment