Bittern with its bell frog prey (Photo: Peter Menkhorst)
The Southern Bell Frog (Litoria raniformis), also widely known as the Growling Grass Frog, is a nationally and globally threatened species too. And it seems bitterns find them very tasty. They are the only large frogs commonly found in rice crops of the Riverina, where they breed. Pictured below is a tadpole from Coleambally during the 2014-2015 season.
Interestingly, bell frogs are found in rice in the Coleambally and western Murray Valley regions (e.g. Caldwell, Wakool, Moulamein and Swan Hill), but are absent in the Murrumbidgee Irrigation Area (e.g. around Leeton and Griffith) and east of Deniliquin (e.g. Finley, Jerilderie, Mulwala).
In 2012, at Werribee near Melbourne, Peter Menkhorst watched an Australasian Bittern eat 17 of them (Menkhorst 2012) so it’s a fair assumption that they might be an important food source in the rice fields as well, at least in the Coleambally and western Murray Valley regions.