Both frugivores and nectarivores are potentially exposed to dietary ethanol produced by fermentative yeasts which metabolize sugars. Some nectarivorous mammals exhibit preference for low-concentration ethanol solutions compared to controls of comparable caloric content, but behavioral responses to ethanol by nectar-feeding birds are unknown. We investigated dietary preference by Anna's Hummingbirds (Calypte anna) for ethanol-enhanced sucrose solutions. Via binary-choice experiments, three male hummingbirds were exposed to sucrose solutions containing 0%, 1%, or 2% ethanol; rates of volitional nectar consumption were measured over a 3-hour interval. Hummingbirds did not discriminate between 0% and 1% ethanol solutions but exhibited significantly reduced rates of consumption of a 2% ethanol solution. Opportunistic measurements of ethanol concentrations within hummingbird feeders registered values peaking at about 0.05%. Ethanol at low concentrations (i.e., around 1%) is not aversive to Anna's Hummingbirds and may be characteristic of both natural and anthropogenic nectars from which they feed. Given high daily amounts of nectar consumption by hummingbirds, chronic physiological exposure to ethanol may thus be substantial, although naturally occurring concentrations within floral nectar are unknown.

See the original publication in Proceedings of the Royal Society B titled "Hummingbird Ingestion of Low-concentration Ethanol within Artificial Nectar", to which these files are supplementary.

Three (3) data tables provided as separate sheets in spreadsheet format (.xlsx).