Powers Research Lab

Lab fieldwork has shifted from the Flight Lab at the University of Montana to the Chiricahua Mountains, a “sky island” in southeastern Arizona. Here we will work at the Southwestern Research Station (SWRS), where the Lab has conducted hummingbird research for 35 years.

Our focus this year will be on how hummingbirds might use behavioral thermoregulation as a means of dissipating body heat accumulated during hovering bouts when environmental temperatures are warm. Motivation for this work came when our measurements of passive and evaporative heat dissipation during hovering appeared insufficient to deal with the extra heat projection that occurs due to the mechanical inefficiency of hummingbird flight muscles.

During this trip we will conduct two studies, one in the laboratory and one in the field. In the laboratory undergraduate researcher Elliot Shannon will offer hummingbirds a choice between a perch at ambient temperature and one that is artificially cooled to several degrees below ambient temperature. The experiment will be run across a range of environmental temperatures. The initial hypothesis is that when temperatures are warm (mid to upper 30’s °C) that the hummingbirds will choose the cooled perch to dissipate heat following hovering bouts. Normally ambient temperatures during the day are sufficiently warm that we can use naturally occurring temperatures cycles for such experiments. However, this year temperatures were unusually mild so we ended up using heat lamps to increase ambient temperature (yes, everyone laughed at us). Experimental trials were using the three common hummingbird species at SWRS: blue-throated mountain-gem (AOS just changed the common name from blue-throated hummingbird), Rivoli’s hummingbird, and black-chinned hummingbird.

The field experiment, conducted by undergraduate researcher Nathaniel Shiiki, tracked hummingbird use of perching locations around the station’s feeder patch throughout the day. Included in the protocol was placement of iButtons at typical hummingbird perches to measure perch-microclimate temperature cycles as well as trail cameras on feeders to monitor feeding frequency and duration across a range of daytime temperatures. The primary purpose of this work was to see if hummingbird perch selection throughout the day was consistent with the intentional selection of cool microclimates to dissipate heat accumulated during hovering bouts.

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.

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.

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!

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.

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!

The Powers Lab is pleased to welcome three new undergraduate researchers to the fold this Spring!

Elliot Shannon is a sophomore biology major from Ridgefield, WA. His core project for the next year will be a study of whether or not hummingbirds selectively choose cool microclimates to dissipate heat after hovering in high environmental temperatures. The work will be conducted in the Chiricahua Mountains of SE Arizona. Elliot will be funded by the Richter Scholar Program at George Fox University. Welcome Elliot!!

Nathaniel Shiiki is a junior biology major from West Linn, OR. Nathaniel’s core project will be a study of daytime temperature variation in natural perching microclimates used by hummingbirds throughout the day. This work will also be conducted in the Chiricahua Mountains of SE Arizona. Nathaniel will be funded by the Richter Scholar Program at George Fox University. Welcome Nathaniel!

Tiffany Regier is a freshman biology major who will be working on a variety of small projects including Arctic Tern energetics (collaboration with Dr. Hugh Ellis, University of San Diego) and validation of some changes to our open-flow respirometry protocol. Welcome Tiffany!!