Adorned with a black necklace of spots on its chest, this warbler resembles the magnolia for its intricate jewelry. A curious white eye-ring resembles a Connecticut warbler without the temperamental dark grey head. Cheeky black markings resemble a Kentucky warbler or even a hooded warbler. Together these markings, with the addition of a wondrous blue-gray back, provide evidence of a Canada warbler.
Canada warbler peeks out behind a tree. Photo by Drew Harry
This bird mostly migrates through southern Wisconsin, preferring the boreal forest elements of northern Wisconsin. Its continental range extends well into Canada and includes the northern tier of most Midwestern and eastern states, extending down into the Appalachian range. These warblers breed preferentially in wet areas like spruce and tamarack swamps, and are thus a difficult bird to monitor and document breeding. The Canada warbler’s range does reach into southern Wisconsin; in areas with extensive forest cover like the Baraboo Hills and areas with large undisturbed blocks of tamarack swamp like Cedarburg Bog, the Canada warbler can be a surprising summer find.
As a member of the boreal forest birds, the Canada warbler may be especially susceptible to a warming climate. According to Audubon’s climate scenarios, under warming of three degrees Celsius, the Canada warbler will lose 95% of its current range. Range expansion north could result in a 63% gain in habitat, but overall a net loss of a huge amount of habitat and birds is possible. Boreal forest birds are especially susceptible to a changing climate because they are at the northern reaches of forested cover in North America. If the climate of these forests becomes uninhabitable, there is a lack of forest cover to the north for them to inhabit. Of the 48 boreal forest species identified by Audubon, 47 face moderate to high vulnerability.
Photo by John Sutton
While the long-term prognosis may be grim, Canada warblers have seen small population increases in Wisconsin over the last few decades, according to breeding bird survey data. Finding suitable habitat in southern tamarack swamps, the birds will build a nest on or near the ground in dense shrub thickets, producing 2-6 eggs.
Fall migration begins in August and stretches into September, and the birds will make a long flight to the Colombian Andes, where over 50% of the over-wintering population resides. On these slopes, the birds prefer elevation between 3,200 and 6,000 feet and also prefer mature and large forest blocks. Research from Laura Céspedes and Nicholas Bayly indicates that 14% of overwintering range in the Colombian Andes is currently protected, and these unprotected areas could be prime for conservation and restoration.
Your best bet for finding Canada warbler at Faville Grove Sanctuary is during spring of fall migration. In the middle of May, areas along the Crawfish River may be an excellent spot for finding mixed flocks of warblers, including the Canada. The foraging behavior of Canada warblers is unique, and you can find the birds low in the understory, moving quickly, often with its head cocked.
Written by Drew Harry, Faville Grove Sanctuary land steward
