Powers Research Lab

After a two-year, pandemic driven hiatus from our work in the Chiricahua Mountains in SE Arizona the lab returned in full force to the Southwestern Research Station this June! This was our largest crew ever with seven students (4 from George Fox University and 3 from my collaborator’s lab at Cornell University) plus me to tackle three projects.

We recently published a paper showing that the hummingbird species we work with in Arizona had the capacity to use a shallow form of torpor in addition to the deep torpor normally associated with hummingbirds. Our evidence for the use of shallow torpor came from continuous infrared thermography at night to track shanges in the surface temperature of the hummingbirds. One concern about this method is that we needed to make the assumption that changes in surface temperature correlated with changes in metabolic state. So, this year “Team Torpor” consisting of Emily, Sophia, Santi, and Shenni constructed a metabolic chamber with a thermal window that would allow us to simultaneously measure metabolic rate and surface temperature to test the validity of our assumption that surface temperature is indeed an index of metabolic state.

Last month we used thermal imaging and thermal PIT tags to track heat transfer from the body core to the exterior of the plumage surface in collared doves. This involved using thermal imaging to track the temperature of the external surface of the bird, a thermal PIT tag glued to the surface of the skin over the flight muscles to measure skin temperature, and a thermal PIT tag inserted into the abdominal cavity to measure core body temperature. We thought we could extend this study to a couple of our Arizona hummingbird species that are a bit larger in size. Whitney took charge of this study and has spent the last couple months designing and building what was needed. The abdominal PIT tag was omitted because of the bird’s small size but they were large enough to glue a PIT tag to the skin. We built a small flight arena that allowed us to collect data both during flight and perching. All this worked extremely well.

From the work we have done the past few years on body temperature managment during flight in hummingbirds it has become apparent that dumping extra heat accumulated during flight after landing on a perch is likely important. Most of what we have learned about this comes from our laboratory work. This year we wanted to take a crack at documenting whether or not free-living hummingbirds are using the sme post flight heat dissipation strategies that we have observed in the laboratory. To do this Kendra and Emma spent many hours documenting where hummingbirds were perching around our feeder patch then took thermal images of these locations to assess the thermal environment and also attempted to place protable thermal cameras at known perching locations to see if they could get thermal images of perching birds post flight. This was certainly in many ways the most challenging of our projects!

Overall our trip to SWRS was very successful! Now it is on to analyzing the mounds of data we collected and eventually writing the papers! Below is a selection of photos from the trip for you to enjoy.

Don traveled to the University of Montana to some quick experiments with friend and collaborator Dr. Bret Tobalske. For the first time they will be working solely with Eurasian collared doves to 1) begin expansion of their heat dissipation during flight work to non-hummingbirds, and 2) test whether or not gluing thermal pit tags to the skin over the flight muscles is an effective way to measure skin surface temperature beneth the breast plumage. The doves were also large enough that they could insert a thermal pit tag into the dove’s abdominal cavity to measure core body temperature. The goal will be to simultaneously measure core body temperature and skin surface temperature above the flight muscles using the thermal pit tags, and breast plumage surface temperature over the flight muscles using infrared thermography. Measurements were made both for flight and perching. The goal is to gain a better understanding of how rapidly core body heat moves across the plumage for dissipation into the environment.

The entire lab traveled to Phoenix, AZ for the Society for Integrative and Comparative Biology meeting January 3-7. This was an exciting time for all of us not having attended an in-person meeting in two years. Audrey, Tiffany, Whitney, and Emily all presented posters on their Anna’s hummingbird projects attracting a wonderfully high level of interest. Don gave an oral presentation on some of the lab’s more recent work on post-flight dissipation of heat accumulated during hovering drawing on data from both our calliope hummingbird work in Montana and Audrey’s work on Anna’s this past Summer. All-in-all it was a great week of immersion in comparative physiology. Looking forward to next year in Austin, TX!!

Today and tomorrow Audrey Smith and I will be attending the Murdock Collaborative Research Conference. This conference is specifically for undergraduate researchers at small liberal arts universities and is sponsored by the Murdock Charitable Trust. This is a pretty amazing meeting that gives undergraduates doing research the chance to shine. Pre-Covid there would be more than 500 attendees from 36 institutions in the the northwest. Attendance was intentionally reduced this year because of Covid (it was totally virtual last year), but the fact that it is live and in person this year is a win.

Audrey Smith kicked off the program this year with her talk on “Use of the Bill as a Heat Radiator by Anna’s Hummingbird, Calypte Anna.” She did an amazing job making all of us in the lab proud! Sadly Audrey was the only student from the Powers Lab to get to attend the meeting as they limited us to 10 attendees thanks to Covid. It would have been great to have Tiffany, Whitney, and Emily here as well. Regardless, all the George Fox students who did make it to the meeting did extremely well which is a testament to the quality of our program and the scholars that mentor our undergraduates in research.

Well, this past summer did not go as planned. While we did have a couple projects planned for the George Fox University campus much of what we intended to do would be in the Chiricahua Mts in SE Arizona. You know what they say about the best laid plans. When the American Museum of Natural History decided to close the Southwestern Research Station for the year it sent labs across the country scrambling….including ours. Now, our field season had to shift focus to our small population of Anna’s hummingbirds on the GFU campus and my backyard.

What was intended to be two projects on the GFU campus turned in to five. Our biggest challenge was figuring out how to share a limited number of birds, and to pivot a bit on a couple of the projects so everyone could get their work done. Dr. Anusha Shankar, a Rose Postdoctoral Fellow in the Laboratory of Ornithology at Cornell spent the entire summer with us shifting her torpor genomics project to Anna’s. She and Emily Blackwell teamed for the summer building a lab for nighttime torpor work in the shed outside the Powers home. This allowed all the equipment to be under a roof while the bird was outside subject to natural light and temperature. Emily had to change her protocol substantially in order to share birds with Anusha, but when all was said and done both got great results. One highlight of Anusha and Emily’s work was our first use of thermal windows built in to a metabolism chamber that allowed concurrent measurement of surface temperature and metabolic rate. Data from the work will allow us to show that hummingbird surface temperature during the night is a reliable indicator of metabolic state.

Tiffany Regier and Whitney Dobbyn spent the summer tracking thermoregulatory strategies in free-living Anna’s hummingbirds both on the GFU campus and at the Powers home. Tiffany was originally going to do her work in Arizona, but for the second straight year got bit by Covid restrictions and had to settle for work at home. One nice thing about doing the work at GFU is that we had some remarkably hot days allowing us to see if what we were seeing in the laboratory applied to free living birds as well. On key thing that came out of Tiffany and Whitney’s work was how complex and difficult it is to measure radiative heat gains and losses in birds. This is particularly true for flying birds where radiative heat simply does not appear to move quickly across the plumage. We have designed experiments for next summer that will hopefully help us to get a handle these measurements.

Last but not least Audrey Smith was also bitten by Covid restrictions for the second straight year. For the past two years she had intended to repeat studies we have done on cool-climate calliope hummingbird on warm-climate species in Arizona. However, like the rest of us she had to pivot to working with Anna’s hummingbirds. The silver lining to this shift in focus is the Anna’s is a non-migratory species that must tolerate a wide range of climatic conditions being around for both cold winters and warm summers (particularly this summer). In addition, Anna’s is also a winter breeder making them a somewhat unique species that likely have a number of thermoregulatory tools in the box.

The first thing Audrey needed to do was build a flight chamber that would fit inside our Percival environmental chamber. This gave us a chance to learn to use the laser cutters over in our Maker Hub to precisely cut the pieces which we glued together. Because we needed to image the birds with our IR camera we could not close the Percival door so instead sealed if off with plastic to allow for temperature regulation. Our initial plans were to complete trials at 5, 20, and 35 °C. However, the refrigeration unit went out so we could only do 20 and 35 °C.

Two things that had to happen prior to collecting data on a bird was that they had to be trained to 1) feed from the respiratory mask and 2) use the provided perch so that we could get post-flight perching data. Audrey discovered quickly that each bird had their own personality. Some took to the mask and perch easily and others not so much. Eventually Audrey developed some training strategies that worked for most birds. In the end Audrey got some really interesting results that now has us thinking that heat dissipation post-flight from the perch is a critical part of the body-temperature management for flight at warm temperatures. In the video below note how the bird not only heats its bill and feet, but also the leading edge of its shoulder!

While we were disappointed to not be able to travel this summer there were some really good things that came out of Project Anna’s Hummingbird. The teamwork and relationships that were established in many ways was far superior to any previous year. The entire lab functioned as a big family which was truly fun. Things appear as if they will be sort of back to normal this coming year, but even so this past summer was fun. Go Team Project Anna’s Hummingbird!!