The extremely cold weather that’s blanketed southern Ontario for nearly a month is wreaking havoc on birds that aren’t used to the cold.

“With all these mild winters over the last 10 or 20 years, there are some birds that used to be more southern and have moved into Ontario and become more common,” said Paul Pratt, head naturalist at the Ojibway Nature Centre in Windsor, Ont.

For example, the Carolina wren is most common in the southeastern U.S. but has recently making its way north.

“They used to be quite rare in Ontario,” Pratt said. “They’re now established in the milder parts of Ontario.

“They’re not cold, hardy birds. I haven’t heard any lately. I’m a little more concerned.”

Pratt said red bellied woodpeckers and the tufted titmouse have also been creeping north for years.

“These are species more typical found further south,” Pratt said. “It’s hard for them to find food when a lot of the ground is covered in deep snow.

“When it’s cold they require a lot more energy just to keep warm.”

Kevin Money of the Essex Region Conservation Area also said “some birds species are migrating farther south than they normally would” because of the cold.

Pratt said even some trees are being damaged by the extreme cold.

“When you get very, very cold nights, down to - 15 C or - 20 C, it can be very hard on them. A lot of trees, once you get down around - 20 C it can kill them,” he said.

Pratt said persimmons trees are a species normally found south of the Great Lakes, so they’re at risk.

“They may struggle through cold winters like the one we’re having now,” Pratt said.

The paw paw tree, which has made a comeback in southern Ontario, is also struggling this year, Pratt said.

“They’ve developed big cracks up the length of the trunk from the sap expanding and freezing inside the wood and splitting the trunk,” Pratt said. “We expect some of our paw paw aren’t going to survive the winter.”

Money said the cold does have its upside.

“Because things have become so cold, the level of ice is thicker than normal. Because of that, it’s getting into the muck where mosquitoes live in the winter,” he said. “Some of the mosquito larvae that lives under that ice, they may be dying off. “