“Optimal concentrations in nectar feeding” is an article by Wonjung Kim, Tristan Gilet, and John Bush. They are affiliated with the mathematical and engineering department at MIT.  The purpose of this study is to see at what concentration of sugar in nectar is ideal for the energy of nectar feeding species, such as hummingbirds. Although higher amounts of sugar offer more energy, the viscosity of the nectar could make it difficult for nectar feeders to carry. Due to nectar feeders needing to avoid predators, the energy levels are important. The study examines the optimal concentration based on the viscosity of the nectar for the performance of nectar feeders.

The sugar concentration of nectar in flowers is higher for the ones that are pollinated by bees (35%), while there is a lower concentration for those that are pollinated by hummingbirds (20-25%).  Because of the different feeding methods of bees and hummingbirds, the viscosity is important when determining the sugar concentration.

Due to the coevolution of flowers and their pollinators, the flowers have different concentrations that are optimal for its pollinators. Bees feed on nectar through a dipping method. Since less nectar is consumed, the flower produces a higher sugar concentration. Hummingbirds feed with a sucking method, consuming more nectar. These flowers that  are pollinated by hummingbirds produce a lower sugar concentration. The lower concentration also provides a lower viscosity, making it easier to fly. This shows that hummingbirds have a preference to lower concentrations. The flower also evolved to produce optimum concentrations. If the nectar was too sweet, it would reduce the amount of flowers that the hummingbirds visit, but too little would not attract them at all.

Works cited:

Kim, W., Gilet,T., Bush, J. 2001. Optimal concentrations in nectar feeding. Proceedings of the National Academy of Sciences. 108(40), 16618–16621, doi: 10.1073/pnas.1108642108
Retrieved from: http://www.pnas.org/content/108/40/16618.full