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Hovering Energetics And Thermal Balance In Anna's Hummingbirds (Calypte Anna), Dennis Evangelista, Maria J. Fernandez, Madalyn S. Berns, Aaron M. Hoover, Robert Dudley

Aaron M. Hoover

We studied the energetics of hover-feeding Anna's hummingbirds, using three different simultaneous techniques: heat loss as estimated via thermal imaging, metabolic rate as measured at a feeder mask using flow-through respirometry, and aerodynamic power estimated from wingbeat kinematic data. These three methods yielded comparable estimates of power output at ambient air temperatures ranging from 18 degrees to 26 degrees C, whereas heat imbalance at higher air temperatures (up to 34 degrees C) suggested loss by mechanisms other than convection and radiation from the body, such as evaporative cooling and enthalpy rise associated with exhaled air and excreted water and convective …