10. Influence of Container Color and Medium Depth on Avian Herbivory of Longleaf Pine Seed

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Survey results from nursery managers have indicated avian herbivory as the leading cause of seed loss and germinant mortality in forest tree seedling nurseries in the southern United States. Reports indicate over $150,000 in lost revenue with a 1% seed loss. Shade cloths are typically used to prevent herbivory but can often exacerbate losses when birds become trapped underneath the cloth. In a previous research trial that investigated longleaf pine sowing methods and subsequent seedling development, it was observed that birds exclusively foraged on seeds sown in cavities filled to depths of five inches (operational depth) compared to those sown at depths of three inches. The goal of this research was to determine if container color and medium depth affected the level of avian herbivory during the germination phase. Longleaf pine seeds were sown in either black or white container cells filled to either three or five inches of growing medium for a total of four treatments. There were three repetitions (trays of 49 cells) for each treatment. Birds consumed 74% of seeds sown in full cavities compared to 36% of seeds in cavities filled to three inches. Seed loss was 20 percentage points higher in black cavities compared to white cavities. Consumption occurred faster in cells filled to five inches (majority in first five days). Determining patterns in seed loss by avian species will assist nursery managers with decisions on sowing techniques and container selection and will help eliminate economic losses.