by Marshall Helmberger
I learned the ways of warblers on my long walks each morning to the north end of Kent Island.
It was 1981, and I was a college sophomore with a summer job as a research assistant for a University of Minnesota doctoral candidate. We were studying blackpoll warblers on a small island in the Bay of Fundy, off New Brunswick, Canada. The territory I covered for the study was located in an area of dense spruce.
See 10 warblers that make Minnesota their summer home and read about what habitat they are commonly found in.
I'd been an avid Minnesota birder for several years by that time, but this was the first time that I lived and breathed warblers seven days a week, giving me the opportunity to learn much more about this fascinating family of birds beyond their basic field marks and songs. I learned their unique behaviors and fidelity to seemingly subtle differences in habitat. I've been smitten by warblers ever since.
In that, I am hardly alone. No family of birds generates more excitement among birders in Minnesota than warblers. Before my summer on Kent Island, I had struggled, as many birders do, to separate the roughly two dozen species of warblers that make northern Minnesota their summer home. While each warbler species has telltale field marks, pinpointing those marks on a 4-inch bird as it moves quickly through dense understory or tree canopy can be challenging.
The good news is, it doesn't have to be that way. Context is everything when it comes to identifying most warblers. If it's June in northern Minnesota and you're in a black spruce bog among tall, dense trees, you can bet that colorful bird with the yellowish-orange face is a Cape May warbler. Farther out in the bog, where the spruce are stunted and scattered, that flash of yellow is paler, but the identification is no less sure—it means you've found the tail-wagging, rusty-capped palm warbler. In between, where the tall black spruce begins to dwindle to its stunted version, you'll find the habitat of the Connecticut warbler, one of the largest of the warblers, with solid yellow breast, gray head, and prominent eye rings.
You can easily classify most north woods warblers into three broad groups, based on their habitat preferences. Within each broad group, you'll find that each individual species has even more precise habitat preferences that separate it from others in the group.
Cape May warbler, yellow-rumped warbler, common yellowthroat, northern waterthrush, Connecticut warbler, golden-winged warbler, palm warbler
Both the Cape May warbler and the yellow-rumped warbler typically spend their summers in dense, mature spruce woods. In Minnesota that forest type is usually found in mature bogs, which is why I place these two species with the other swamp warblers. In the right habitat, the yellow-rumped warbler is easy to find during the breeding season. While the Cape May has long had a reputation as a tougher target, that's mostly because their preferred habitat is somewhat limited in the northern Minnesota landscape. But visit a mature black spruce stand, and you're likely to be amply rewarded.
As for the others in this group, none is more predictable than the common yellowthroat. This noisy, high-spirited little bird can be found in a variety of shrub habitats, particularly alder and willow thickets, usually in or along the edges of wetlands. By early June, when the summer breeding season is in full swing, it's unusual to pass a decent patch of alder without hearing the "witchety-witchety" song of a male yellowthroat. With its bright yellow breast and throat, black bandit's mask, and up-tilted tail, the male yellowthroat is easy to identify. The female is paler and lacks the black mask. And like many female warblers, she is also quite retiring, at least in contrast to the noisy and aggressive male. So if you're in yellowthroat habitat, it's the male you're likely to see.
As for the northern waterthrush, this is a bird more often heard than seen. Actually, it's quite common in swamps of black ash and white cedar, but for birders who don't recognize its loud and jerky song, it can be a tough one to find. If you learn to recognize its song, you'll discover this species is far more common than you probably ever realized.
The golden-winged warbler is a species that's declining in many parts of the United States, but it is still doing pretty well here in Minnesota. John James Audubon originally named this species the "golden-winged swamp warbler," because of its preference for brushy swamp edges. Unlike the yellowthroat, however, it's less common in pure alder and more attracted to the grassy and brushy transition between alder or tamarack swamps and nearby uplands. It can also make use of overgrown fields or recent cutovers on uplands, where fresh growth resembles the swamp edges it most prefers.
Chestnut-sided warbler, mourning warbler, American redstart, Canada warbler
My favorite presidential anecdote involves Teddy Roosevelt, who reportedly burst excitedly into a meeting of his cabinet and breathlessly exclaimed to the suddenly alarmed top officials: "Gentleman, do you know what has happened this morning? Just now I saw a chestnut-sided warbler—and this is only February!"
To this day, I can't help but think fondly of the former president every time I see a chestnut-sided warbler, nor can I help but sense a bit of Roosevelt's famous pugnacity in the attitude of this little bird. There's nothing shy about its loud and frequent "pleased, pleased to meetcha!" song and its preference for the outer tips of branches. Chestnut-sided warblers are usually easy to spot in young, deciduous woods in northern Minnesota. Ten-to 15-year-old aspen or birch cutovers make ideal habitat, although this warbler can be found in a variety of young forest types. Look first for its white breast, black sideburns, and yellow cap. The chestnut racing stripe on its flank is a bit tougher to spot unless you have a clear view.
The American redstart turns up in similar habitat, but it behaves differently. While most warblers feed primarily by gleaning caterpillars and other insects from tree branches and leaves, the redstart spends much of its time fly-catching, snatching insects in midair. If their aerial acrobatics aren't enough of a clue, a redstart's striking black-and-orange color pattern should make this bird an easy add to your trip list.
A few warblers are a bit more down to earth, and that's another valuable behavioral clue. The mourning warbler is a ground-nesting bird that spends its summer days in dense brush. In northern Minnesota, thickets of raspberries, dogwood, hazel, and bush honeysuckle all make good habitat for this songster, well known for its bubbly, full-throated song. It's also fond of forest edges, where brush tends to be the thickest.
Try pishing to coax this species into view. If you haven't pished before, it's easy. It's like shushing somebody, only with a "p" sound in front. You can also make a squeaky kissing sound on the back of your hand. Pishing is like telling birds "Hey, come here, look at this!" For some species, it's practically irresistible.
The Canada warbler, a bird of dense thickets and brush, has a noticeable preference for sloping terrain. It spends its time close to the ground, which makes it easy to watch if you can coax it out of heavy cover. Its remarkable black necklace contrasts dramatically with its bright yellow breast and makes this species a favorite of birders.
Black-throated green warbler, Blackburnian warbler, pine warbler, northern parula, ovenbird
Warbler watchers frequently complain of stiff necks, and it's older-forest species, which tend to fly high in the treetops, that usually cause such complaints. But their bold, colorful plumage makes them worth the neck strain.
The male Blackburnian warbler, with its fiery orange face and throat, is probably the most dramatic of Minnesota's warblers. This species favors the high branches of mature white pine, spruce, and fir, so you're going to want a decent set of binoculars, at least 7 x 35, in order to get a good look. The good news is that Blackburnians are usually responsive to pishing or recorded bird song (yes, there's an app for that), so you can often coax them down a bit closer to earth.
You could try the same technique to see another treetop denizen, the pine warbler. This species is heavily dependent on mature red pine forests in Minnesota for its breeding habitat. Find a red-pine stand at least several acres in size and listen for a chipping-sparrow-like trill up in the treetops. As with the Blackburnian warbler, bring your best binoculars to get a decent look.
You'll want to keep them handy to spot two other spectacular warblers, the black-throated green warbler and the northern parula, both found in mature woods dominated by conifers. The black-throated green is particularly fond of large spruce or balsam fir.
The ovenbird, on the other hand, is an older-forest warbler that prefers the understory. This good-sized warbler has an explosive "teacher-teacher-teacher" song, but it can be tough to spot because its olive-brown back and streaked breast are excellent camouflage; and unlike other warblers, it tends to sit still when it sings.
Fortunately, if you do spot one, you can usually watch it for a while.
No matter where you are in the forests of Minnesota, you can find warbler habitat nearby. And by understanding which habitats attract which warbler species, you'll be able to narrow the possibilities to just three or four likely species in most circumstances, making identification much easier.
So spend a little time studying the habitat keys in your birding books before you head out to the field. Books are devoted to bird habitat, such as The Sibley Guide to Bird Life and Behavior. Knowing not just what to look for, but where to look, will make you a faster, more successful birder.