Juggling a "junk-food' diet
The resident population of Red-winged Starlings, Onychognathus morio at the University of Cape Town are often seen scavenging anthropogenic food around students, kiosks and in rubbish bins. Anthropogenic foods are a major driver facilitating the colonization of cities by animals and can allow animals living in human proximity to devote less time and less effort into foraging. However, one aspect of urban ecology that has received little attention is how urban animals cope with high fluctuations in human activity that greatly affect the availability of anthropogenic food resources. For example, at educational institutions like UCT the relative abundance of anthropogenic food at is likely to fluctuate according to the academic calendar and weekly cycles.
Using the University of Cape Town as our study system, we investigate whether Red-winged Starlings are “junk-food dependent” by comparing the daily diet composition, activity budget and body mass gain of starlings on weekdays; when there are high numbers of students present on campus versus weekends; when students are largely absent and food kiosks closed.
Our results suggest that starlings are not junk-food dependent and have the behavioural flexibility to cope with dramatic fluctuations in anthropogenic food availability over short time scales. Although the proportion of junk food and natural food in the starlings’ diet differs, the overall amount of food consumed by starlings was similar between weekends and weekdays. Likewise, starlings devoted similar amounts of time foraging on weekends and weekdays. Finally, starlings appeared to gain greater mass on weekdays possibly due to the greater consumption of calorie-rich or carbohydrates-rich anthropogenic foods.