Fly to Eat and Eat to Fly

By: Emma Woods

Most people know hummingbirds for their impeccable beauty but there is more then meets the eye when it comes to these little birds. These spectacular tiny birds are constantly flying to eat and eating to fly, in order to keep up with their massive appetites. In attempts to find a short reprieve from their constant search of food, hummingbirds are known to take long deep naps that drop their internal body temperature (~23-37⁰C) in order to save a substantial amount of energy. Unfortunately, these deeps naps can be quite dangerous for a hummingbird as they are at a higher risk of predation due to the fact that it takes them about 20 minutes to wake up. However, it seems as though hummingbirds may have developed a new strategy that saves a limited amount of energy but with fewer risks known as shallow torpor. Shallow torpor is the equivalent to a power nap that drops their internal temperature a fraction of that needed for a deep nap (3-10⁰C).

In order to evaluate the use of shallow torpor, researchers used a new and less invasive technique known as infrared heat imaging. First, establishing what a typical day to day body temperature is for several different hummingbird species (about 32⁰C). Shankar and her team found that infrared heat imaging of the eye provided the most accurate temperature readings, as the skin is unobstructed by feathers. Researchers were then able to compare their typical body temperature to the measured values throughout the night in order to asses and measure the hummingbirds use of torpor.

Shankar’s team of researchers discovered that shallow torpor was used by all the hummingbird species that were included in the study but for differing amounts of time. Some species use shallow torpor as a transitional stage to a deeper sleep. While other species use shallow torpor as their main source of rest. This chilling new information has scientists shivering with excitement, as this revelation indicates that hummingbirds not only use shallow torpor but its use varies by species. Researchers concluded that due to the high variability in shallow torpor use among species, hummingbirds have a far greater control of their body when it comes to energy management then originally thought.

Hummingbirds are remarkable creatures that have not been given all the recognition they deserve when it comes to their ability to satiate and manage their energy requirements. Through infrared heat imaging, Shankar and her team of researchers collected premium data, while having very little mal effects on the hummingbirds. Therefore, procuring the most accurate data possible with little to no human influence. The implication of the results found by these researchers could be eye opening for other species of birds or even small mammals who have been know to use shallow torpor, as they may also posses these fine energy management skills. The control demonstrated by this research indicates that hummingbirds may have superior energy management skills in comparison to humans. People will be flapping about this for generations to come! Shankar, A., Cisneros, N. H. I., Thompson, S., Graham, H. C., Powers, R. D. (2022) A heterothermic spectrum in hummingbirds. Journal of Experimental Biology. 225 (2), jeb243208.