Effects of the availability of floral resources and neighboring plants on nectar robbery in a specialized pollination system

Abstract

Many plants pollinated by nectar-foraging animals have to maintain a balance between legitimate visitor attraction strategies and mechanisms that minimize illegitimate visits. This study investigated how floral display and neighboring species composition influences nectar robbing in the tropical ornithophilous herb Heliconia spathocircinata. We tested the role of inflorescence display, flower abundance, and neighboring species in the reduction of nectar robbing in H. spathocircinata. Our results indicate that nectar robbing hummingbird activity was higher in moderately large inflorescence displays and that the frequency of nectar robbing in H. spathocircinata decreases with increased flower abundance and the presence of neighboring plant species. Neighboring non-ornithophilous plants decreased the frequency of nectar robbing in H. spathocircinata flowers to a greater extent than ornithophilous ones. These results suggest that nectar robbing hummingbirds are attracted to similar conditions that attract legitimate visitors, and that spatial aggregation and mixed-species displays may represent a mechanism to dilute nectar robbing effects at an individual level.

The Campsis-Icterus association as a model system for avian nectar-robbery studies

“…In the Neotropics, nectar-robbery is best documented among flowerpiercers ( Diglossa spp.) 14 – 16 , 19 – 25 , bananaquit ( Coereba flaveola ) 19 , 26 , 27 , and hummingbirds 17 , 22 , 23 , 27 – 36 , which use their bills to make holes or slits in corollas to obtain nectar. Less specialized nectar robbers may use cruder, less surgical techniques such as plucking, crushing, or tearing apart corollas 16 , 26 , 37 or mixed strategies that involves piercing and plucking 18 .…”