Large‐scale features affect spatial variation in seed dispersal by birds in juniper woodlands

Abstract

AbstractFruit–frugivore interactions have received great attention from evolutionary, ecological and applied perspectives. However, despite the fact that large‐scale approaches may offer new insights on fruit–frugivore interactions, little work has been devoted to exploring the factors shaping large‐scale variation of seed dispersal. This paper studies the spatial variation in seeds regurgitated within pellets by wintering thrushes (genus Turdus) in a set of 26 Spanish juniper (Juniperus thurifera) woodlands scattered along a latitudinal gradient during two winters of contrasting cone and bird abundance. It explicitly explores whether pellet rain variation among woodlands was related to changes in vegetation cover, temperature, day length duration and bird abundance. Top regression models in the Akaike information criterion framework explained 34 % and 70 % of variance in pellet numbers in low and high crop and bird abundance years, respectively. In both winters, the spatial variation in pellets correlated to thrush abundance and day length duration. Pellet abundance linked to cone distribution only in the year of high crop, in which many migratory, extra‐Iberian thrushes arrived to exploit the resource. Strong dependence of seed dispersion on large‐scale features affecting bird numbers (e.g. the arrival of extra‐Iberian migratory birds) and feeding behaviour (e.g. latitudinal variation in day length duration) suggests a primary role for variables acting at large scale on this mutualistic interaction.