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Dryad

Caught out in the cold: Mallard survival decreased during an extreme climatic event

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Jun 06, 2024 version files 3.36 MB

Abstract

Extreme climatic events (ECEs) can have profound impacts on individual fitness, affecting survival directly or indirectly. Late winter ECEs may be especially detrimental to fitness due to limited food resources and increased energetic requirements during this time. A polar vortex disruption ECE descended upon the mid-continental United States during 7–20 February 2021 with temperatures as low as −29ºC in areas concurrent with ongoing research on mallard (Anas platyrhynchos) movement ecology and survival in Arkansas, Louisiana, and Tennessee, USA spanning winters 2019–2022. Therefore, we opportunistically evaluated the effects of individual characteristics and latitude on daily survival during the ECE. We extended the survival analysis into March to test for lasting effects of the ECE on survival. We tracked 181 GPS-marked mallards during February 2020, 256 in February 2021, and 324 in February 2022. We documented 22 mortalities during the February 2021 ECE (i.e., 9%), but only 6 mortalities during February 2020 (i.e., 2%) and 2022 (i.e., 1%) when conditions were average. February survival (e.g., 28-day survival) during the ECE was 0.908 (85% CI = 0.879–0.937) but was 0.982 (85% CI = 0.973 – 0.991) during the two non-ECE Februaries. The ECE effect on survival was isolated to February and did not affect March survival. Mallards were 5.4 times more likely to die during the ECE in 2021 compared to non-ECE Februaries. Although large-bodied waterfowl appear cold-tolerant and less sensitive to polar vortex disruptions compared to smaller-bodied passerines, direct mortalities can occur if conditions are severe enough and persist, highlighting the need to consider the influence of ECEs on common, seemingly robust species in future global climate change scenarios.