Carolina wren

The Carolina Wren is sensitive to cold weather. Since they do not migrate and stay in one territory the northern populations of Carolina wrens decrease markedly after severe winters. Because of this sensitivity to weather, gradually increasing temperatures over the last century may have been responsible for the northward range expansion seen in the mid-1900s.
Populations in Canada and the northern half of the US experience regular crashes following severe winters, but their high breeding productivity soon results in a return to higher numbers. These birds are generally permanent residents throughout their range and defend territory year round; some birds may wander north after the breeding season.
They eat insects, found in leaf litter or on tree trunks; they may also eat small lizards or tree frogs. In winter, they occasionally eat seeds, berries, and other small fruits.