Using airborne thermal imaging to understand American Coot movement patterns in a hot spring refugium during winter

We examined the movement patterns of American Coots relative to water temperature and heat index where a geothermally heated stream enters Utah Lake, UT, USA during winter using a thermal imager onboard an Unmanned Aerial System (UAS). Observations of Coots in different water temperatures (n = 2354) were compiled during 31 flights in January-March, 2020. Coots were actively swimming during 82.3% of the observations, fleeing during 8.1%, and sedentary in water during 9.6%. The population spent more time swimming in cooler water and were sedentary for longer in warmer water. The only instance of uniform behavior occurred during an anomalously cold period in which Coots stood huddled in the warmest available water. Using a linear model framework, we found that Coot time spent increased with water temperature when heat index decreased. Coots' swim paths deviated away from warmer water more than cooler water and more so as heat index increased. We suggest that Coots use the spring water primarily for ice-free habitat and maintain metabolic rates via a combination of thermal conductance, caloric ingestion, and exercise, but only exploit the heated water strictly for thermoregulation during anomalously cold periods. We discuss the benefits and hindrances of using UASs amidst a rapidly expanding assortment of sensors and aircraft available to researchers. Given wetlands' immediate conservation concern, ecosystem services they provide, and support of unique species assemblages, our research provides valuable insight into documenting wildlife's use of wetlands with relatively low scientific take and human interference.

Automated summary

This study examined the movement patterns of American Coots relative to water temperature and heat index in Utah Lake during winter. The results showed that Coots spent more time swimming in cooler water and were sedentary for longer in warmer water. It was also found that Coots' swim paths deviated away from warmer water as heat index increased.