Since the virus was first confirmed in the county last month, there have been 12 outbreaks confirmed, according to the BBC.
Exclusion zones were put in place around Lincolnshire sites - including near Mablethorpe, Alford and South Elkington - to prevent the spread.
Hens were also placed into their houses and high levels of biosecurity introduced on farms, Lincolnshire World has been told.
The Department for Environment, Food & Rural Affairs (Defra) has not confirmed the number of culled birds.
Professor Ian Brown, of the Animal and Plant Health Agency, told the BBC: "There is a high density of poultry farms in Lincolnshire and the virus has found its way in because it has been able to breach the biosecurity barrier of the farms."
The estimated number of birds culled at each farm is based on the unit size multiplied by the number of birds allowed per square metre, the BBC said.
UK's chief veterinary officer Dr Christine Middlemiss said: "We are seeing a growing number of bird flu cases both on commercial farms and in backyard birds right across the country, with a high number of cases in Lincolnshire."
Wild birds migrate to the UK from mainland Europe during the winter so it is vital to not allow wild birds to mix with chickens, ducks, geese or other birds, she said.
However, the UK Health Security Agency (UKHSA) has said avian flu is primarily a bird disease and the risk to human health is very low.