Why sewage plants are great for birds
BIRD WATCHERS KNOW THAT bad smells and good birds go together. Many of Australia’s best locations for waterbirds are sewage plants, where waste water is treated in a series of ponds. Victoria’s waste stabilisation ponds support more birds and more bird species than any natural pools in the state.
The Western Treatment Plant at Werribee, west of Melbourne, is one of Australia’s premier birding sites, described as a ‘Disneyland for birdwatchers’, with 284 species recorded. Melbourne Water, which runs the plant, boasts about the rarer species on its website.
Other outstanding sewage plants include Leanyer at Darwin, where I saw a crocodile plump from feasting on birds, and Alice Springs, which had many more birds than any other outback wetland I’ve visited. The Alice Springs plant has information posted about its bird life. Leanyer is currently closed because of dangerous crocs, which enter the fenced ponds by crawling up the outlet pipe.
Alice Springs sewage farm attracts many birds, such as teal, avocets, stilts and gulls. (Image: Christopher Watson / Wikimieda)
Studies by ornithologists show why sewage matters. The most polluted pools aren’t favoured, but in those at the end of the treatment sequence rich nutrients generate many invertebrates to eat. The zooplankton suits filter-feeders such as pink-eared ducks and shovellers, the insects feed grebes, and waders nab items in mud along the edges. Where treated effluent irrigates nearby pastures this benefits soil-dwelling insects and the ibises that eat these. Some plants pipe treated effluent onto intertidal mudflats, where thriving invertebrates sustain crowds of waders. The foreshore at Werribee attracts 16,000 shorebirds.
Sewage plants are never dry during droughts, and another plus is safety from duck hunters. Shooting is not allowed, and in any event no one wants to retrieve and eat a duck shot in a stinking pond.
With ever more natural wetlands succumbing to development, sewage plants can only assume more importance for birds. But this situation is not ideal. Outbreaks of botulism sometimes kill birds. Of more concern are policy shifts towards smaller sewage plants and cleaner discharges. In Europe the downsizing of plants is a serious conservation concern, and in Victoria tighter government regulations have seen less nitrogen reaching mudflats, to the detriment of shorebirds.