Avian botulism has been confirmed as the cause of the deaths of more than 700 birds at Bells Swamp, south-west of Bendigo in Victoria.

Testing and monitoring by Parks Victoria confirmed the bird deaths were due to ingestion of the deadly toxin produced by the bacterium Clostridium botulinum – found naturally in various environments when conditions are favourable for its growth. The illness has been known as a major contributor to mortality in wild birds since the 1900s, and often reoccurs in wetlands that have suffered infections in the past.

Botulism spores (which are the harmless resting stage of the bacterium Clostridium botulinum) are commonly found in habitats where oxygen levels are low, including the aquatic sediments of wetlands and lakes. When the correct conditions occur concurrently – such as warm water temperatures, an oxygen-deprived environment, and a bacterial substrate rich in nutrients such as those found in bird droppings – these spores germinate, and the growth of the toxin-producing bacterial cells which cause avian botulism begins.

Given the current conditions around the state with respect to warm weather, receding water levels and large concentrations of birds adding extra nutrients to the water, we expect the incident at Bells Swamp will not be an isolated occurrence.

Claims from those against hunting that the slight impact on the duck population due to such outbreaks is a reason to ban duck hunting are baseless – indeed, sustainable, ethical and responsible harvesting will reduce the pressure on wetlands that may be susceptible to an avian botulism outbreak due to the large numbers of birds present, thus preventing the sustained suffering that will result should an outbreak occur.

Avian botulism typically results in paralysis of infected birds; they may not be able to fly or walk and may not be able to hold their heads up – and as a result, they often drown.

Hunters should never harvest birds that are sick or dying but should instead report the occurrence of sick or dead birds to the authorities as a matter of urgency.

More information is available here: https://www.gma.vic.gov.au/__data/assets/pdf_file/0005/481523/What-duck-hunters-need-to-know-about-avian-botulism.pdf