Winter Wren

The adjective “diminutive” is overused when describing the Winter Wren, but it is certainly apt. Weighing in at only 9 grams (a third of an ounce), this is one of the smallest species that breed in New Hampshire. Unlike most wrens, Winter Wrens are birds of the forest, and in New Hampshire are found at their highest densities in the conifer forest of the north and west, but also use hardwood and mixed stands as long as there are areas of dense shrubs or downed wood where the wrens can hide. Far more often heard than seen, listen for their long bubbly song coming from deep in the woods starting as early as April.

Most Winter Wrens migrate to the southeastern United States, and it is probably from this that they got their common name. However, perhaps because of a warming climate, the species is increasing as a winter bird in southern New England as far north as parts of New Hampshire. The best way to find a Winter Wren in winter is to find an area of dense vegetation near running water and listen for their sharp chip notes. But not all winters are equal, and particularly cold ones can be hard for this species, even well to the south. In the New Hampshire population graph shown here, you can see a dramatic decline in the 1970s. This is believed to be related to several unusually cold winters in the southern United States that resulted in high mortality – a population-level blow that Winter Wrens took roughly a decade to recover from. The ups and downs in the 1990s and 2000s are likely related to the same phenomenon, making it hard to ascribe a trend to this half century of data.

While erratic weather may pose a short-term threat to Winter Wrens, it’s not likely to be the sort of thing that leads to consistent changes in populations. On this front, it might be more appropriate to think about changes to the forests where the species nests. In the Pacific Northwest, the closely-related Pacific Wren (the two used to be considered the same species) is known to prefer older and less fragmented forests. It’s certainly possible that our own Winter Wren has similar proclivities, although in general it seems less specialized, and we don’t have a lot of data from the boreal forests of Canada where most of them breed. For all we know, climate change is having negative effects on those forests at the same time as it’s allowing wrens to winter farther and farther north.