Small birds are struggling to survive in freezing temperatures and heavy snow, a charity has warned.
The Royal Society for the Protection of Birds said some birds were dying because they could not find food.
They urged people to leave food and water out for the birds.
The extreme weather is also changing the behaviour of some species with reports of arctic birds, normally seen in Greenland, visiting NI shores.
Birds like redwings and snipe which normally dwell in the countryside are coming into the city for food.
RSPB manager Anne Marie McDevitt said people really need to look after the bird population.
"Their fat reserves are basically running down and they are not able to keep warm," she said.
"They are not taking in enough calories to keep themselves warm and alive.
"They can just simply die at this time of year if they don't get enough food. They are not able to replenish their energy reserves."