The deaths of around 160 birds in the southern suburbs of Perth are being investigated by the Western Australian Department for Environment & Conservation.
The birds are a variety of species including ibis, silver gulls and ravens. They were found dead within a 1km radius of a landfill site.
The agency says it's likely they died from something they ate.
Some sick birds are been taken for monitoring. Samples of their blood and stomach contents are being analysed.
The ABC reports the landfill has been covered to prevent further deaths.