Staghorn sumac (Rhus typhina) is an early-successional shrub of old fields, hedgerows, and roadsides throughout the northeast and the upper mid-west United States and southeast Canada. Staghorn sumac contains many beneficial compounds, including phenolic compounds. These compounds are a defense mechanism to herbivory in plants and play a role in inhibiting seed germination. Specifically, when phenolic compounds decline, starches activate and respiratory activity increases, enabling seeds to germinate. It has been hypothesized that concentrations of phenolic compounds vary throughout the seasons, as an evolved mechanism to control the timing of seed dispersal by foragers and that freeze-thaw events transform and reduce phenolic compound concentrations. The focus of this project was to determine if variation in foraging on sumac by birds was influenced by concentrations of four phenolic compounds commonly occurring in berries of this plant through the winter months. A solvent extraction method for extracting the phenolic compounds from seeds and an HPLC method for separating and quantifying these compounds were developed. The phenolic compounds under investigation were gallic acid, tannic acid, ellagic acid, and caffeic acid. The sumac seed samples were picked every other week from Rice Creek, Oswego, New York, and analyzed for the concentrations of phenolic compounds. The results for the first year showed a decrease in the concentration from November to February and showed a slight increase during March. We are repeating the sampling and analysis two more years from October to April and from different regions in central New York to confirm the variation.

Effect of phenolic compound concentrations in staghorn sumac seeds on the winter foraging behaviors of birds

ACS Spring 2022

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