RAPID: Impact of extreme heat-induced mortality on avian cooperative social systems

University Of Nebraska-Lincoln, Lincoln NE

Investigators

Abstract

Extreme weather events such as heatwaves, droughts, and storms can have dire consequences for local ecosystems, sparking population decline or range shifts. While physiological and morphological adaptations may help buffer animals against ecological shifts, little is known about how sociality—a trait which can help animals cope with unpredictable or harsh environments—might mitigate (or exacerbate) the consequences of abrupt, prolonged climatic events. This year, wildlife in South Australia were subject to extended heatwaves which resulted in mortality in nearby animal communities. This project will take advantage of long-term data collected on social behavior of two social species of birds - splendid and purple-backed fairywrens - to ask whether social group membership can improve survival outcomes following extreme environmental stressors. This work will help elucidate how different social systems and communities will respond to climatic events in the future by capturing both the population-wide and individual level response to this weather event in two social species with varying degrees of social participation. Broader impacts will include training of students and a post-doctoral researcher and dissemination of findings to the broader non-scientific community to help general audiences understand how extreme weather events impact natural populations of animals. Australia has recently experienced numerous catastrophic droughts, heat waves, and fires that have led to heat-induced avian mortality events where assessment of population responses could provide insight on the impact of increasingly common extreme climatic events on populations. Previous work has focused on critical temperature, demography, and morphological changes; no work has addressed cooperative breeding — a behavior linked to environmental variability. This project will address two research aims: 1) Determine whether differential survival occurred with respect to group size and 2) Determine the impact of catastrophic mortality on subsequent social structure and dynamics in two different cooperatively breeding systems. Group composition and reproductive success of both splendid and purple-backed fairywrens were last monitored in the days immediately prior to the December 2019 heatwave. This project will consist of a survey in autumn to assess survival and population composition, and a second trip spanning the pre-breeding and breeding seasons to assess the impact of demographic changes on the strength and structure of social groups. During each trip social associations and individual presence will be assessed through re-sighting of individually unique color bands. Unbanded individuals will be captured and banded, and their social status within the population assessed. These methods will allow 2019 social behavior to be linked to survival of the heat event, and allow team members to subsequently assess how dispersal behavior, group structure, and reproductive success in the 2020 breeding season is impacted by demographic changes. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.