Flight Energetics of Anna’s Hummingbirds Using C-13 Labelled Bicarbonate
Mauricio Cruz
Department of Biology
Faculty Supervisor: Derrick JE Groom
The energetic costs are a major determinant of animal behavior; therefore, knowing the metabolic cost of an animal’s movement can help predict its behavior over a wide range of ecological contexts. However, one of the biggest obstacles ornithologists face is accurately measuring the energetic cost of flight in a way that represents natural conditions. Traditional methods require the attachment of equipment to the animal, which can disrupt normal flight behaviors or add additional energetic costs to flight. This project addresses this obstacle by using the labeled sodium bicarbonate method to measure the energetic cost of short flights for Anna’s hummingbirds in a wind tunnel across a range of speeds. The sodium bicarbonate method is a non-invasive stable isotope method in which 13C is incorporated into the animal’s bicarbonate pool and the extinction rate of the 13C during the period of exercise is then used to estimate metabolic rate. Given the curve of the mechanical cost of flight and flight speed is U-shaped, I expect the metabolic cost of flight to also be U-shaped and be least energetically costly at intermediate speeds. However, given that hummingbirds have adapted to hover, the curve may be more J-shaped than U-shaped.