The season will start on March 20 and run to May 30. And shooters will be allowed to kill more birds.

The State Government said expansion of the season was possible because of increased bird numbers, but stressed that the season would still be shorter - and have lower bag limits - than seasons before the recent years of drought.

But the expert whose bird surveys helped inform the decision said it was unclear whether there had been any rise in bird numbers in Victoria during the past year.

Surveys are typically done across eastern Australia, meaning that bird populations in Victoria, Queensland, NSW and South Australia are combined into one survey.

Surveys led by University of NSW professor Richard Kingsford are widely accepted as the best guide to bird numbers, and one of his reports from October was used by the State Government to guide yesterday's decision.

Professor Kingsford said that although his survey found a slight increase in bird numbers in eastern Australia, that result was largely due to a single breeding event near the Coorong in South Australia.

''It's very unlikely bird numbers in Victoria have increased more than last year's numbers; they're more than likely on par with last year,'' he said. ''This is now a string of really dry years in Victoria, so the birds are unlikely to be breeding there.''

He said combining survey information from across the states meant the localised picture could be overlooked.

''It hides the patchy nature of the numbers,'' he said.

Anti-duck-hunting campaigner Laurie Levy said surveys in the states were important, but Victoria needed to conduct more localised surveys.

''Victoria needs its own waterbird count,'' he said. ''With climate change, native waterbirds are going to be struggling in the years to come, so it seems amazing the Brumby Government is allowing the recreational shooting of birds just as a fun thing.''