Canada Warbler

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

Northern Goshawk

The northern goshawk is a fierce bird, the largest of the Accipiter genus in Wisconsin. With a Holarctic distribution, the goshawk glides through coniferous and hardwood forests of boreal and northern temperate regions across the world. The face of northern goshawks is dark grey, with a white eyebrow slashing across its side, contrasting its red eyes. The belly is finely barred grey in adults.

Juvenile goshawk in the nest, photo by Andrey Gulivanov

Goshawks in Wisconsin prefer mature forest, and will often find the largest tree in a tract to place their nest. Hunters of the forest, these birds tend to prefer open understories free of brush where they can hunt with more airspace. For Wisconsin birds, diet includes ruffed grouse, red squirrel, blue jay, crow, and eastern chipmunk. A majority of the North American breeding population of goshawks resides in Canada, but most northern Wisconsin counties have nesting pairs, and the birds will migrate into Wisconsin in great numbers every 8-10 years when the abundance of ruffed grouse and snowshoe hare declines in the Canadian boreal forest.

Nesting pairs will produce 2 to 4 eggs, though research from northern Wisconsin suggests that the fisher (a small carnivore of the weasel family) will prey upon goshawk eggs and reduce reproductive potential. Nests in northeastern Wisconsin that produced 2.3 fledged young per nest from 1971-1981 only produced 1.3 fledged young per nest from 1982 to 1992 as fisher populations increased. Goshawks are known to fiercely defend nests, but fishers ambush the nest as can humans. Goshawks are valuable in falconry, and multiple nests in Wisconsin were found to be illegally captured for this purpose. For an excellent read about a singular goshawk, you might check out H is for Hawk, Helen Macdonald’s memoir about raising her goshawk Mabel.

The fierce look of a northern goshawk, photo by Zweer de Bruin

There remains some concern about the future of the goshawk in Wisconsin. As a northern bird, climate change may push this species to the brink. Even under the most conservative estimate of 1.5 degrees Celsius warming, the goshawk is projected to lose its entire breeding range in northern Wisconsin and most of the eastern United States, according to Audubon’s “Survival by Degrees: 389 Bird Species on the Brink.” The northern goshawk ranks as one of 44 high vulnerability species in Wisconsin.

These fierce accipiters should be enjoyed while they still inhabit Wisconsin. A quick look at current sightings on eBird reveals birds at Wehr Nature Center near Milwaukee and at UW-Madison’s Arboretum.

Written by Drew Harry, Faville Grove Sanctuary land steward

Cover photo by Martha de Jong-Lantink

Northern Parula

The northern parula is a delightful spring treat in Wisconsin, as it skips along the canopy, headed to northern boreal and coniferous forests. This blue-gray bird, with a yellow belly and throat and a bejeweled necklace of blue gray and copper, looks to have arisen from the tropical forests of Central America, and does return to those forests to overwinter for over almost 8 months of the year.

Photo by Steve Guttman

Recent research indicates that northern parulas may not be keeping up with a changing climate. On their spring flights from Central America and the West Indies, the birds are falling behind leaf-out dates in North America. This asynchrony can have cascading impacts on the birds and their overall populations. A key to the migratory ecology of neotropical migrants is the correct timing of migration, yet as these birds follow the day length, northern climates are rapidly greening, and this leafing out of trees and shrubs brings a pulse of insects, including many caterpillar species. Missing this important pulse of resources could have significant implications for the conservation of the northern parulas.

Range maps of northern parulas show a distinctive gap roughly through the Midwest and portions of the Northeast. There are a number of possible explanations for this, though none very satisfying.

One possibility is habitat loss in these areas; the northern parula needs rather extensive blocks of forest, and remaining forest tracts in southern Wisconsin are relatively small. Yet, the parula makes it into areas of northern Illinois and Indiana, which are intensively agricultural and only have small forest fragments.

Old Man’s Beard lichen, photo by Bob the Lomond

Another possibility is that parulas have some ecological requirement that is unfulfilled in the upper Midwest. In many observed cases of nest building, northern parulas use Spanish moss in the south (actually a bromeliad) and old man’s beard lichen in northern Minnesota, Wisconsin, and Michigan. These wispy materials are ideal for constructing nests. It is possible that a decline of the old man’s beard lichen (an Usnea species) due to air pollution has also caused a decline in northern parulas.

Lichens offer astounding insights into the overall quality of an ecosystem. Research in the Pacific Northwest has shown lichens to be reliable bioindicators, or representative of ecosystem health. Lichens accrue pollutants throughout the year, showing no seasonality, and they are long-lived. Lacking roots, lichens depend on atmospheric and water sources for nutrients, which also contain contaminants. Dynamic cycles of moisture and drying can concentrate pollutants over the lichen tissues, cell walls, and organelles. These features make lichens sensitive to pollution. In addition, widespread ranges offer clues as to where more severe pollution may have reduced or eliminated populations of lichens.

Above, a density map of native epiphytic (plant growing on another plant, obtaining nutrients from air, rain, water, or debris) species in the United States roughly corresponds with the range of the northern parula.

All of this is to say, the northern parula has an interesting range map; a curious gap in the central United States likely has no clear explanation, but a number of theories take aim at reasons why.

While northern parulas do not breed in most of southern Wisconsin, you can find them right now and in the next few weeks as they move through woodlands where the oaks are just starting to leaf out. Just the other day I was watching a group of parulas flitting through a stand of aspen. I got an excellent look at one of the birds as it dropped down onto a shrub and swallowed a massive caterpillar. The bird sat still for a few seconds—an eternity for a parula—and then flew off again, likely on its way to a spruce or tamarack forest in northern Wisconsin.

Written by Drew Harry, Faville Grove Sanctuary land steward

Header photo by Dan Pancamo