Thousands of mallards have flocked to rivers in Otago and Southland only weeks before opening weekend of the 2022 game bird season.

It comes as many parts of Otago and Southland endure a dry autumn following a good duck-breeding season in the wet spring.

Otago and Southland Fish & Game have recently finished their aerial mallard trend counts on selected ponds, river reaches and land transects across both regions.

"The counts this year have been a standout," Otago Fish & Game officer Paul van Klink said.

The total mallard count in Otago skyrocketed to more than 10,400 birds, the highest since aerial monitoring began in 2015. This compared with last year’s trend count of 5600 mallards.

In Southland, the mallard monitoring data is still being processed but everything is pointing towards a larger than usual population.

Large rafts of mallards were concentrated on rivers, especially the Taieri, Pomahaka and Clutha in Otago and the lower Aparima, Mataura and Waiau in Southland.

Some ponds also supported high numbers. One pond near Ashley Downs had more than 900 mallards and a pond in Balfour had over 2000 mallards. Several ponds had no ducks or were dry.

"We can’t categorically say there are more ducks in South Otago but the trend is higher than previous years for sure," Mr van Klink said.

"Given the number of variables like dry weather and food availability such as grain crop paddocks, it may just be because the birds were all grouped rather than spread out over larger areas."

However, higher numbers are likely due to favourable spring breeding conditions.

Both regions experienced a wet spring. Fish & Game research has shown that puddles in paddocks significantly improve duckling survival by providing more food for the growing birds.

More rain is expected before opening weekend and will change food availability, dispersing mallards across Otago and Southland.

Otago’s paradise shelduck population in February also recorded its highest trend count in 31 years.

The game bird season opens on Saturday, May 7.