Frank B. Gill, author of Hummingbird Flight Speeds, describes in his introduction that little information is known about the hummingbird’s use of energy during flight. Gill introduces a few other studies that show different types of flying (hovering, forward, escape, etc.) either yield a net reward or produce results worth more than their energetic demands. There is not much information known about this concept and Gill states that his study will be one of the first of it’s kind. The research introduced by Gill suggests that there is a correlation between wing length and cost of flight, particularly hovering, for hummingbirds in general. In his experiment Gill plans to calculate forward flight speed of a 6-g hermit hummingbird. He hypothesizes that forward flight is the dominant and most energy consuming flight used by these birds.
The methods used in this experiment were fairly simple. Two artificial flowers were placed 40m from each other. An observer uses a stopwatch to time how long it takes the bird to get from one flower to the other. Wing lengths and body masses of each bird were also measured. A few possible areas of error include the observers delay with the stop watch and the idea that the birds will be flying slower when leaving and arriving at the flowers. Many log equations were used to calculated power and energy costs of the timed flights.
After a series of calculations two flight speeds were proposed for the hummingbirds. 10 and 11 m/s were the average commuting flight speeds for a 500m commute between feeding territories. The author describes that these are estimates subject to several errors including reaction time of observer, and larger variation of flight speeds among individual animals. The first graph in this paper is labeled as a theoretical flight power curve which describes the minimum and maximum power velocity associated with the Hermit hummingbird. This graph also contains the calculated cost of hovering as well as the average flight speed observed in the experiment. The second graph simply shows the weight (g) of each animal verses their wingspan (cm). This forms a linear regression line. These graphs are biologically relevant because they explain the differences observed between larger birds and smaller birds. They also explain how wing length plays a role in the flight speed of each individual.
In the discussion that author states that it still remains to be established if hummingbirds fly at speeds that minimize their power costs. Very little information has been published about this subject and the information that has is inconclusive. However, most research suggests that hummingbirds can easily justify spending more power in flying in order to again even a small amount of nectar from a plant. It is also suggested that wing length plays and very important role in flight speeds and energy costs. Hummingbirds are a species with a wide variety of wing lengths which has impacted not only their flight speeds, but their ability to hover and collect certain amounts of nectar. Gill suggests looking into these variations in body size and wing length of hummingbird species before coming to any conclusions about the energy costs of flying.
Citation: Frank B. Gill, Hummingbird Flight Speeds