Another Study Supports the Relevance of this Project!

As I write this note we have thus far achieved only 45% of out funding goal with 9 days to go. Even so, now that Nathaniel is back from Europe we hope getting the word out to his networks will allow us to make rapid progress over the next few days.

In this lab note I wanted to share some data just collected by the Powers Lab during a recent research trip to the University of Montana where we collaborate with Dr. Bret Tobalske. While there we conducted an experiment where we placed hummingbirds in a temperature controlled room and studied heat dissipation and activity at 5, 22, and 32 °C. Sharing this here is relevant because the results illustrate the different strategies used by hummingbirds to manage their body temperature at cold vs. warm temperatures.

In our study we placed hummingbirds in a large flight chamber and recorded infrared images both while the birds were feeding and while they were perched. We also recorded their activity with GoPro Hero 6 cameras. The activity videos will be used to not only quantify activity levels, but also to measure flight speed and acceleration.

 

Flight chamber we used at the University of Montana.

A couple of things that really stood out from our data was that when cold the hummingbird remained "fluffed up" even during hovering. This was totally unexpected as it suggests the possibility that the hummingbirds were trading a decrease in aerodynamics for increased insulation. It also suggests that this "fluffing up" of the feathers is different from the feather erection that is used to expose skin for heat dissipation. More relevant to this study is that when the birds were warm (32 °C) they fully extended their feet and heated them up (likely with increased blood flow) to near 40 °C! This supports our earlier work that suggests hummingbirds start needing to dump heat quickly while hovering at even moderately warm temperatures.

 

Thermal images of hummingbirds over a range of ambient temperatures.

Note how much more extensive the eye heat dissipation area (warm area around the eye) is at 32 °C. In this project we hope to elucidate further warm temperature body-temperature regulation strategies in hummingbirds.