Copenhagen - An increase in bird flocks in Denmark due to mild winters pose a threat to farmers' crops, reports said Friday.

Mild winters in recent years have contributed to an increase in bird flocks, and the regional farmers union in Denmarks's northern Zealand region say they want to be able to cull the flocks that feed on their crops, the regional paper Frederiksborg Amts Avis reported.

"This is a vicious circle," farmers union leader Herdis Dam told the newspaper.

"The mild winters mean that more birds breed the year round, and since one doesn't want to hunt the birds when they have young the hunting season is reduced," he added.

Dam said he could not give an exact estimate of the damage, but said he knew of farmers who had lost up to 30 per cent of their rapeseed crop due to wood pigeons.

Farmers are also burdened by extra costs for fuel and fertilizer.

The farmers union plans to raise their concerns with the Danish Forest and Nature Agency that is in charge of management of flora and fauna. (dpa)