The Impact of Exercise and High Ambient Temperature on Heat Dissipating Areas in Anna’s Hummingbirds (Calypte anna)
Author: Alexa Quintero
Faculty Supervisor: Derrick Groom
Department: Biology
Hummingbirds have unique physiological and morphological traits to fly at high speeds and hover in place. These adaptations require a high metabolism, which generates body heat as a byproduct that must be dissipated. Dissipating heat can become increasingly challenging when the thermal gradient between the bird and surrounding air becomes smaller. We aim to characterize body surface temperature patterns across the hummingbird under different temperatures and flight durations. Since the feet are relatively uninsulated, we hypothesize that the feet region is a site for efficient thermal regulation during high metabolic activity. Anna’s hummingbirds (Calypte anna) were placed under four temperatures (20℃, 25℃, 30℃, 35℃) and flew for a period of 30, 60, 90, and 120 seconds. Thermal imaging was used to record surface body temperatures prior to and immediately after each exercise bout. We find that the feet have the greatest change (10℃ rise) between the lowest and highest temperature treatments, compared to other heat-dissipating areas such as the eyes and axial region which rise by 3-5℃. Moreover, the feet showed a slight increase in surface temperature as the flight duration increased at 30℃ and 35℃, while other areas did not change. Our results demonstrate that the feet are highly flexible thermoregulatory areas during post-exercise heat dissipation. Our future work will examine the bill’s importance, another poorly insulated region of the body.