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

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 by hummingbirds 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.

Automated summary

This study investigated the influence of inflorescence display, flower abundance, and neighboring species on nectar robbing by hummingbirds in the tropical ornithophilous herb Heliconia spathocircinata. The results showed that moderate-sized inflorescence displays increased nectar robbing activity, while increased flower abundance and the presence of neighboring plant species reduced nectar robbing frequency. These findings suggest that nectar robbing hummingbirds are attracted to conditions that also attract legitimate visitors, and that spatial aggregation and mixed-species displays may help dilute the negative effects of nectar robbing.