Poster: Native vs Introduced: Does feeding of urban waterfowl by the public disproportionately favour one over the other?
Christopher Dawson1
1School of Biological Sciences, University of Canterbury, Christchurch, New Zealand. christopher.dawson@pg.canterbury.ac.nz
Public feeding of birds adds a large amount of energy to avian systems every year, potentially altering community structure. Introduced waterfowl are common throughout New Zealand, but could this be due to introduced species being favoured when members of the public feed waterfowl? To determine whether introduced waterfowl disproportionately attend public feeding, I set up a series of feeding experiments around Christchurch and recorded all aggressive interactions among native and introduced species of waterfowl. I found that numbers of native waterfowl were less than number of introduced waterfowl across most of my 19 study sites, but native species were more common in larger waterways. Introduced species were more likely to attend my feeding experiments. The rate of aggressive behaviours was significantly different between native and introduced species, with natives more likely being the recipients of aggressive acts from introduced waterfowl. This was likely due to the larger body size of introduced waterfowl, allowing them to dominate a feeding event. There were low numbers of native waterfowl in the smaller waterbodies in Christchurch, and given the levels of aggression by introduced species, I suggest native waterfowl may over time become excluded from small lakes in part due to their inability to compete. Restricting public feeding to waterways where introduced species are already common may save native waterfowl being outcompeted in lakes where both co-exist. Alternatively, development of duck feed that is specific to native species may allow feeding without inadvertently assisting introduced species.