Research News: Hummingbirds don’t rely on taste when choosing food options
Hummingbirds need to consume a certain amount of sugar to provide energy to sustain themselves, but, as with many other birds, there is a delicate balance between eating enough food yet still being light enough to fly efficiently. So how do hummingbirds know how much to drink when they hover at your feeder or at a flower? Researchers Ida Bacon, T. Andrew Hurly, and Susan D. Healy looked into how hummingbirds decide how much nectar to sip at each sitting.*
Animals determine information about food in two ways: sensory input and physiological feedback. The sensory input in this context is taste. A hummingbird uses taste to immediately determine the caloric quality of a food. A food that contains more calories will taste more desirable. We humans do this too. Think of your morning coffee; you can tell when there is not enough sugar in it. This is also why we prefer a cheeseburger over a bland meal; it’s all about the calories!
Physiological feedback is a much slower process – this is the information about the actual value of the food as it is digested. A hummingbird will only know how much energy their food is actually providing as it digests and uses those calories.
The researchers in this study wanted to know whether hummingbirds relied more heavily on sensory input or physiological feedback. In order to test this, the researchers set up feeders with either low (14%) or high (25%) sucrose (sugar) concentrations and switched between low and high concentrations over periods of time. As they switched out from low to high or high to low, the researchers measured both how long hummingbirds (in this case male Rufous Hummingbirds) spent at the feeder during each visit and also how much nectar they drank during each visit. If the hummingbirds changed the amount they drank as soon as the researchers adjusted the sucrose concentration, the researchers could tell that the birds relied heavily on taste. If the hummingbirds only changed the amount they drank after several visits to the new concentration level, the researchers would know that the birds relied more heavily on physiological feedback
What the researchers found was that the hummingbirds did not change how much they drank at all during their first visit to a new concentration even though hummingbirds can detect small changes in concentration by taste. The birds did, however, change the amount they drank over several more visits to the same concentration. This suggests that hummingbirds don’t place as much value on the taste of the nectar as on the actual energetic value of the food. The researchers conclude that hummingbirds do use taste to determine changes in food quality, but wait for the more reliable physiological feedback to fine-tune how much they drink.
For more information on feeding hummingbirds in your backyard, see All About Birds.
*Bacon, I., Hurley, T.A., and Healy, S.D. 2011. Hummingbirds choose not to rely on good taste: information use during foraging. Behavioral Ecology 22(3):471-477