Fowl, not foul
Last updated 05:00 14/04/2011
Birds in the Avon-Heathcote Estuary appear to be healthy despite raw sewage being pumped into Christchurch waterways.
University of Canterbury associate professor of biological sciences Jim Briskie said a degree of contamination – as had happened when treated sewage was discharged into the Estuary – was actually beneficial to birds.
"It sounds a bit perverse, but by making the water cleaner it takes away some of the food's nutrients," he said.
However, too much sewage could be a problem.
"Dumping raw sewage is different. There is the potential for disease outbreaks."
Intestinal complaints would be the most likely problem, Briskie said, but there had been no "major catastrophes" so far.
An ongoing study of the Estuary, measuring any change in its ecology as the ocean outfall pipe off New Brighton came into use, could also reveal the impact of the raw sewage, Briskie said.
Raw sewage had been put in waterways to ease pressure on the city's battered sewerage system after February's quake.
Oystercatchers and pied stilts were the most common birds in the Estuary at this time of year, Briskie said.
The godwits had migrated to Siberia and Alaska for the northern summer, with only a few young, non-breeding birds staying behind.