Fluctuating human activity and associated anthropogenic food availability affect behaviour and parental care of Red-winged Starlings

• Main Author: Catto, Sarah
• Other Authors: Cunningham, Susan
• Format: Dissertation
• Language: English
• Published: University of Cape Town 2019
• Subjects: biological sciences
• Online Access: http://hdl.handle.net/11427/29429

Increased food availability associated with urbanisation is widely recognised as one of the key factors influencing avian demography. Temporal fluctuations in food availability, tied to variation in human presence, are of particular interest as they occur frequently in urban environments, but their impacts on the survival and reproduction of birds have not been particularly well-studied. In this study, I explored whether breeding Red-winged Starlings at a university campus in Cape Town, South Africa alter their behaviour and parental care of nestlings in response to fluctuating numbers of people and associated food over a relatively short timescale. I used data from nest watches and behavioural observations collected during both incubation and nestling periods to test whether differences in food availability due to day status (week days with thousands of students present versus weekends with substantially fewer students) affected a number of behaviours related to parental care. I found that, with less available food on weekends, parent birds appeared to trade off feeding their offspring for maintaining their own energetic requirements, meaning that nestlings received less food on weekends. I also found that parents preferentially fed their nestlings natural food on week days, despite an increased availability of anthropogenic food. This suggests that, with increased food availability, birds in this system may use anthropogenic food to supplement their own diets, allowing them to prioritise the feeding of natural food to their chicks. These results provide evidence that fluctuating food resources impact the behaviour and parental care of starlings, but it is still unclear what effect they have on the individual health of adult birds and their developing young. To further enhance our understanding of some of the ecological implications of urbanisation, future research should prioritise understanding the potential health impacts such a variable urban diet may have on the birds exploiting it.