Researchers at Kadoorie Farm on Wednesday called on the authorities to conserve farmland in the future Northern Metropolis, saying sites there are the habitat of over a quarter of Hong Kong's bird species.

The farm said it spotted 154 species of birds during a year-long survey from late 2021 at nine farmland areas in the northern New Territories.

The researchers said four out of 10 species were of conservation concern, including endangered birds like the Yellow-breasted Bunting and the Greater Painted-snipe.

Philip Lo, a senior conservation officer with the farm, said they spotted the greatest number of species at three farmland sites totalling 121 hectares near Lo Wu and in Ta Kwu Ling.

But Lo said he is concerned the birds may lose a vital foraging and breeding ground if the government turns the sites into residential or business areas.

"People pay quite a lot of attention to wetland and fish pond conservation, but farmland is a bit overlooked. People see farmland as a land reserve for development, but they don't see the conservation value," he said.

Lo said the government needs to come up with a comprehensive conservation strategy which includes designating farmland sites of higher ecological value as agricultural priority areas and conducting research on the bird species there.