How the Presence of Feeders Affects the Use of Local Floral Resources by Hummingbirds: A Case Study from Southern Arizona

For hummingbirds, artificial feeders can serve as an alternative food source to nectar from flowering plants. The presence of feeders may lead to increases in local hummingbird populations and decreases in the use of native plants. We examined how the presence of feeders influenced the rate of hummingbird visits to a changing array of flowering plants in southeastern Arizona. Feeder visits represented approximately 59% of all visits during our yearlong study, but were less common in times of high floral abundance. The ratio of feeder visits to total visits was negatively related to overall floral abundance and to the abundance of the hummingbird-favored plant, Calliandra californica. The regular use of feeders by hummingbirds, which increases during periods of low floral availability, may have important implications for pollinator-plant relationships by reducing plant reproductive output. Additionally, this inverse relationship may affect estimates of hummingbird abundance and must be considered when analyzing data from studies that use feeders to attract hummingbirds.