As usual the lab’s field season starts with a trip the Flight Lab at the University of Montana to work with long time collaborator Dr. Bret Tobalske. The main goal of this trip was to continue our work on heat dissipation during hovering in calliope hummingbirds (Selasphorus calliope), and to begin looking to extend our work on heat dissipation during flight to other bird species.

University of Montana Flight Lab

We began our work by measuring total evaporative water loss during hovering in calliopes. We actually started this work two years ago, but needed to increase our sample size. There is no simple way to make this measurement beyond getting birds to hover continuously in a metabolism chamber.

Metabolism chamber used in our study.

Once the bird is hovering evaporative water loss is measured using open-flow respirometry. As you might imagine this also requires a high flow rate. In our case 8 L/min!

The Sable Systems Field Metabolic System used in this study and our trusty iMac Pro running Warthog Software.

Once these measurements were made we switched gears and began experiments designed to help us understand how hummingbirds might behaviorally thermoregulate to dissipate heat accumulated during hovering at high temperature. We were in luck because we were able to get some time in a temperature controlled room for a few days to do our work (thank you Dr. Zac Cheviron). Bret’s graduate student Tony Lapsansky collaborated with us on this project. Our experiment involved a large acrylic flight chamber, and we used two FLIR Infrared video cameras to track perching and hovering surface temperatures over a range of environmental temperatures. We also recorded each trial using GoPro Hero 6 cameras that will be used to assess kinematic changes in hovering flight that might occur across temperatures.

Short video of one of our temperature trials.

Overall the trip was quite productive and we were really pleased with the quality of our data. Next, in about a week, we will be off to Chiricahua Mountains in southeastern Arizona and the Southwestern Research Station!