Radar Indications of Altered Foraging Behavior during the February 2021 Severe North American Cold Wave

Total radar cross-section of birds was quantified in observations of four large bird assemblages with daily sunrise foraging flights for January and February 2021, including the severe February 2021 cold wave. Reduced foraging behavior during the cold wave was expected as birds reduced energy expenditure during the extreme cold. While this was observed with two assemblages in Oklahoma where the cold was most severe, a site in central Texas showed the opposite response, indicating increased foraging to meet increased energy demands. Foraging behavior was influenced by temperature and windspeed, but the direction of this influence differed across sites. This difference seemed partially driven by cold wave severity at individual sites, and may have also been influenced by differing species composition. At the site where waterbirds were the primary contributors, these larger and more cold-tolerant species showed less of a wind/temperature dependence.