ABQ Times

Hummingbirds, known for their resilience and long migrations, face increasing challenges due to climate change and land-use changes that affect the availability of nectar from wildflowers. To cope with these uncertainties, they employ a process called torpor—a brief state of reduced metabolic activity akin to hibernation. New research by Shayne R. Halter, a Ph.D. candidate at The University of New Mexico Department of Biology, explores how hummingbirds manage fat reserves during their fall migration through New Mexico.

The study titled "The hummingbird’s adipostat: can a simple rule explain torpor frequency and duration in hummingbirds?" has been published in Proceedings of The Royal Society B. Halter conducted this research with UNM Professor Blair Wolf and Professor Emeritus Carlos Martinez del Rio from the University of Wyoming.

According to Halter, the unpredictable distribution of wildflowers in the southwestern U.S., exacerbated by climate change and land-use alterations, poses significant energy maintenance challenges for migrating hummingbirds. Torpor involves a marked decrease in metabolic rate and body temperature over several hours. This state is crucial when energy levels are low but also increases vulnerability to predators.

Halter's research focused on Calliope (Selasphorus calliope) and Rufous hummingbirds (Selasphorus rufus) along the Mimbres River in New Mexico. He explained, “During torpor, hummingbirds are unaware of their surroundings... I use a combination of body fat and overnight metabolic measurements to determine whether hummingbirds are low on energy.” His findings indicate that if evening body fat drops below a certain threshold—specifically 500 milligrams—hummingbirds will enter torpor to conserve energy for survival until they find food.

In discussing his findings on Rufous and Calliope hummingbirds, Halter noted that minimum morning fat reserves were approximately 180 milligrams: “Birds will only use torpor if needed...”

This research offers insights into how annual migrations impact hummingbird survival rates amid changing environmental conditions. It provides models predicting torpor patterns which can help assess ecological health and inform conservation strategies.

Halter's journey into biology followed an extensive career in the U.S. Air Force as a navigator and flight examiner before retiring in 2013. Afterward, he pursued studies at UNM where he developed an interest in biology while earning his B.S. in Anthropology.

Encouraged by Dr. Wolf to pursue research on hummingbird physiology starting from 2021, Halter dedicated himself fully to understanding these birds' biological mechanisms throughout his master's program at UNM.