Flamingo predation impacts on benthic communities: effects of spatial gradients

Abstract

Biological disturbances on marine soft sediment ecosystems have been well researched. However, little attention has been paid to the potential ecological role that iconic shore bird predators may have on marine ecosystems. This paper tests the effects of spatial gradients on Greater Flamingo (Phoenicopterus ruber) predation impacts on the benthic macrofaunal community structure in an intertidal sandflat ecosystem in South Africa. P. ruber is a benthic filter-feeder known to feed on benthic dwelling invertebrates through pit formation, where deep sediments are stirred up by trampling their feet. Macrofaunal community structure between flamingo pit foraging structures and adjacent non-foraged sediments (controls) yielded insignificant spatial differences. However, subtle positive and negative effects of flamingo predation on macrofaunal abundance were noted at specific sites. Flamingos in this study were not targeting a specific prey group. Thus of the 19 macrofaunal prey items identified, none were significantly impacted across treatments, except for an unidentified polychaete. However, this was once again site specific. The results suggested this polychaete is generally abundant within the area sampled. Furthermore, its distribution is perhaps affected by the level of intensity employed in pit-foraging, rather than being preyed upon. Greater polychaete abundance in pits relative to controls may be attributed to vigorous flamingo feeding efforts. Pit foraging appears to be an expensive strategy to employ, but the energy investment may be reduced through the use of sophisticated sensory organs to detect accessible prey deep within the sediment. Overall, the study has shown that the impact of flamingo predation on a spatial gradient is small and site specific. However, the study highlights the need for further research on quantifying the ecological role flamingos play as predators on marine ecosystems.