New research is being conducted to understand how hummingbirds balance their daily energy needs in the face of a changing climate and other stressors. Results point towards the duration of torpor as well as the depth of torpor being important to a hummingbird’s energy balance.

METHODS: Researchers injected stable double isotopes of water into chest muscle. Shortly afterward, urine samples were collected, then twenty-four hours later, birds were recaptured and another urine sample was collected. From such data, the researchers extrapolated energy usage over time, as well as how different environmental variables, such as temperature and altitude, affect that. To understand how hummingbirds use energy at night, researchers analyzed torpor. Individual birds were placed in respirometry chambers to measure the oxygen in their breath, essentially how much energy they expend every second. They also used infrared cameras to show the pattern of a hummingbird’s skin temperature warming and dropping as it slept.