Australia's millennium drought may still be impacting penguin populations in South Australia, more than 10 years after it broke, a new study has found.
Flinders University researchers have identified a strong link between the drought, which stretched from 2001 and 2010, and remaining little penguin numbers in colonies south of Adelaide including one on the edge of survival.
The current Granite Island population has fallen to 20 adults while all other populations in nearby Encounter Bay are extinct.
"The fact that the Granite Island little penguin population still had not recovered suggests ... the population may have reached some critical reduction in the number of breeding birds during the drought period," researchers said.
The study also found a strong association between little penguin numbers, river outflows and one of their main local food sources - southern garfish.
It suggested ocean warming and other factors such as predation and low juvenile survival rates could have contributed to the colony's issues.
Little penguins are seabirds that become central-place foragers during breeding, with most of their prey captured within 60 kilometres of the colony.
The coastal and estuarine environment at Victor Harbor's Encounter Bay, the Lower Lakes and Coorong depends on regular outflows from the mouth of the River Murray, which regularly closes during periods of drought.
"Given droughts are becoming more and more frequent, future studies are needed both within Australia and elsewhere to identify which species may be affected for seabird conservation and river management," the study said.