Hot Birds Research Project

Climate change and urbanization are notably the most important human-induced environmental changes threatening biodiversity today. However, the majority of literature focus solely on discussing their effects singly limiting the ability to predict how urban species will respond to climate change. During hot weather events, individuals reduce foraging activity to lessen heat gain and control body temperature within narrow ranges. However, such behavioural adjustments can result in costly trade-offs, particularly the inability to maintain daily body mass. This can have potentially far-reaching implications for body condition and thus individual fitness. Abundant anthropogenic food availability in urban systems allows many ‘urban exploiter’ species to reach their metabolic demands with less time being devoted to foraging. Therefore, some urban species may be buffered from the potential costs of climate change on body condition. Consequently, we explore the impacts of daily maximum air temperatures during summer on the foraging behaviour and body mass of an urban-exploiting passerine, the Red-winged starling, Onychognathus morio resident to the University of Cape Town, South Africa. Anthropogenic food abundance fluctuates in relation to the student activity on campus with food being more abundant on workweek days and less abundant on weekends. Using focal observations, we explore (1) whether foraging effort and (2) foraging efficiency differs on hot and cool days and (3) whether this is influenced by heat-dissipation behaviour. We also explore (4) whether this differs in relation to anthropogenic food availability between workweek and weekend days and (5) whether this interaction has an impact on daily body mass.