Plant traits that influence flower visits by birds in a montane forest

Abstract

In a bird-flowering plant network, birds select plants that present traits attractive to them. I studied plant characteristics that might predict flower visitation rate by the most common bird visitors in a bird-flowering plant network located in an elfin forest of the Andes. The nectarivorous birds which had the highest number of interactions with flowering plants in this network were the Coppery Metaltail (Metallura theresiae), the Great Sapphirewing (Pterophanes cyanopterus), and the Moustached Flowerpiercer (Diglossa mystacalis). I analyzed different flower traits (flower aggregation, nectar volume, nectar energy, color, orientation, and dimensions of the corolla) of the common plants that these birds visited with a principal component analysis. The plants most visited by birds were Brachyotum lutescens and Tristerix longebracteatus. While nectar traits of the plants seemed to be the best predictor for bird visitation, there was no statistical association between visitation and plant traits, except for Metallura theresiae in the dry season. I discuss the possible causes of resource partitioning for these nectarivorous birds.