Agate is pleased to share this excerpt from Duluth-based expert birder Kim Eckert’s book, Birding by Hindsight, published by Stone Ridge Press. Seasoned and aspiring birders alike will appreciate his foray into the finer points of warblers in their fall plumage. Artist Lou Ferreri’s wonderfully wild depiction of birders, above, is part of Ferreri’s series, The Internal Affairs of Mr. Invincible. “Birders” is one of 25 mixed-media drawings published and available as archival prints via his website .
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You’re probably looking at the title of this article and feel that something is missing. You may be thinking, “I’ve heard of confusing fall warblers, but never just fall warblers.” After all, that three-word group of birds is an ornithological institution, something birders have been whining about for decades ever since the earlier editions of Peterson came out in print. The words “confusing fall warblers” just naturally roll off the tongue as smoothly as, well, the words “Roger Tory Peterson”. To say merely “fall warblers” almost leaves one with a vague empty feeling. Why, it’s practically blasphemous — almost as bad as saying just “Roger Peterson!” Well, Roger Peterson is a friend of mine, a Duluth birder, and Certified Public Accountant, his middle initial is “A”, and to call him anything more than just plain ol’ Rog is overdoing it and leaves him embarrassed. Similarly, now that fall migration is getting underway, it’s high time birders learn to relax and get over their Confusing Fall Warblers phobia. If you take another look at these warblers, you’ll find they’re not all that confusing — most are actually as straightforward and as easy to get along with as my friend Rog. Honest! Sure, many of the ones you see in late summer and fall as they head south are not as colorful as most of the warblers you see during spring or on their breeding grounds, but the identification difficulties of fall warblers have long been overrated.
To begin with, and to keep this all in perspective, keep in mind the following:
• While many fall warblers are not all that colorful, virtually all of them are at least in fresh plumage, having molted on their breeding grounds before heading south. (About the only exception to this in Minnesota that comes to mind would be all those ratty and ragged juvenile Yellow-rumped Warblers still in molt one sees in Duluth in August and early September.) Therefore, when looking at fall warblers, birders generally do not have to deal with birds in molt or worn plumage.
• A common misconception is that all adult male warblers change into drab plumage before their fall migration. Yes, they do molt, but most adult warblers actually look about the same all year and are just as recognizable in fall as they are in spring. True, adult male Chestnut-sideds, Bay-breasteds, and Blackpolls in fall do look entirely different and are much duller than in spring. But that’s about it: these are the exceptions, not the rule. Just about all the other adult males look essentially the same as they do in spring; or, if duller like the Magnolia and Yellow-rumped, they still are distinctive enough to be recognized with little difficulty. And there is even one adult male (the Tennessee) that actually looks brighter in fall than in spring!
• Most of the truly “confusing” warblers you encounter in fall are immatures, especially immature females. Immature males of most species resemble — and are often almost indistinguishable from — adult females. Since you never hear much about a “Confusing Spring Female Warblers Complex”, these should not be especially daunting.
In sum, just be prepared for encountering three general plumage types this fall: adult males (almost all of which are relatively easy to identify), adult females/immature males (which are no more difficult than females in spring), and immature females (OK, I admit it, some of these are hard). Not including the rarities and local species, there are perhaps 25 warbler species an active birder could potentially encounter in Minnesota in fall. But among these, I would say there are really only nine difficult identification groups, which are briefly discussed below. (Just nine? So what’s all this Confusing Fall Warbler fuss about?!)
Tennessee vs. Orange-crowned vs. Philadelphia Vireo
One of the more common warblers you see in fall may not have any obvious streaking or wing bars or face pattern, but it is colorful: generally bright greenish above and mostly clear yellow below. While the others are fumbling with their field guides, you can just confidently say: “It’s a Tennessee.” Not only will you usually be right, but after a few days you’ll find yourself saying, even more confidently, “It’s just another Tennessee.” The most confusing thing about a fall Tennessee Warbler for novice warbler watchers is how bright and yellow they are — so much so, that it’s one warbler that usually looks brighter in fall than in spring. Once the birder realizes this, and that Tennessees are relatively common, the identification of many of those formerly confusing green-and-yellow things is solved.
So far so good, but what about the similar Orange-crowned Warbler and Philadelphia Vireo? As far as the Orange-crowned goes, if your bird has white under tail coverts which contrast with the yellow of the belly and breast, it’s a Tennessee (Orange-crowneds are always yellowish under the tail). The only problem is that a few Tennessees have a yellow tinge under the tail: however, they have brighter yellow underparts which contrast more with their greenish upperparts. An Orange-crowned’s underparts are duller greenish yellow, usually faintly streaked, and this color contrasts little with its similar upperparts color. Both adult and immature Philadelphia Vireos, like the Tennessee Warbler, also tend to look more colorful in fall than in spring with brighter and more extensive yellow on the underparts. With practice, however, you will be able to notice this vireo’s thicker bill with its hooked tip and its higher, rounder crown profile. These combine to give the Philadelphia Vireo a much different head shape than the thinner-billed, flatter-crowned Tennessee Warbler. And, as is the case with most vireos, the Philadelphia tends to move around more slowly and deliberately than a warbler.
Orange-crowned vs. Yellow vs. Wilson’s
If it’s August or early September and you see a nondescript warbler which is dull greenish yellow overall, don’t assume it’s an Orange-crowned. For one thing, Orange-crowneds don’t usually arrive in Minnesota until late September. Consider the probability of it being a Yellow Warbler, probably an immature female, which can appear surprisingly dull and not very yellow. Look carefully to see if the bird has a “beady” black eye surrounded by the suggestion of a vague yellowish eye ring — a characteristic mark of the Yellow Warbler. On the other hand, if it’s October or even late September, and you think you see a Yellow Warbler, take another look. Most Yellow Warblers have left Minnesota by the first of October. Now is the time when Orange-crowneds are passing through. If it’s not an Orange-crowned, consider a female Wilson’s. Many birders have trouble telling female/immature Yellows from Wilson’s, but, again, look for the Yellow Warbler’s beady black eye. Or, if it’s a Wilson’s Warbler, look for its grayer crown which is darker than on a Yellow.
There’s another fall warbler out there that’s about as common as the Tennessee — and more confusing to novices than it ought to be. This bird is even more distinctively plumaged than a Tennessee: uniformly whitish or pale grayish below, bright lime green above, with a bold white eye ring and thick yellowish wing bars. It sort of looks like the picture of a Chestnut-sided in the Geographic field guide, except the eye ring and wing bars are bolder than in the book. The Chestnut-sided picture in the Robbins guide also fails to portray a bold enough eye ring, and the painting in Peterson shows a Chestnut-sided with drab greenish upperparts. So what is it? Indeed it is a Chestnut-sided, after all. Despite its lack of yellow cap and chestnut sides, a fall Chestnut-sided is still patterned distinctively enough that it should be relatively easy to identify. The next time you see one (and they’re common enough), put the field guide aside and take a good look at the bird itself. It’s not only a nice looking bird, but it will restore your faith in your fall warbler identification skills.
Cape May vs. Yellow-rumped
The Cape May is one fall warbler that varies widely in plumage. Some (usually adult males) have obviously yellowish underparts with dark streaking, bold wing bars, and the clear remains of chestnut color on the face. Others (usually immature females) have no color and little pattern on the face, only indistinct wing bars, and little or no streaking or yellow on the underparts. The plumage of most fall Cape Mays falls somewhere in between these two extremes, and such birds bear a strong resemblance to fall Yellow-rumpeds, especially since Cape Mays also have yellow rumps. When looking at one of those dull or average Cape Mays, you should see a paler mark on the side of the neck, which hints at this species’ distinctive facial pattern (also see Pine Warbler below). Note as well how the streaking and any yellowish color on the underparts extends uniformly across the breast. A Yellow-rumped Warbler lacks that mark on the side of the neck, and its streaking and yellow on the underparts are more limited to the sides of the breast. One additional hint. If you see a warbler up in a spruce tree that has the general appearance of being just another one of those ubiquitous Yellow-rumpeds, take a second look. While lots of warblers will forage in spruce trees, migrating Cape Mays tend to be in a spruce more often than not. Be aware of this especially along the North Shore of Lake Superior, and you might be surprised at how relatively common the Cape May Warbler is during fall migration.
Other “yellow-rumped” warblers
So, you had never really thought about Cape May Warblers having yellow rumps before, did you? So do Magnolias, by the way. And there is yet another species, about as nondescript and as widespread as a Yellow-rumped Warbler, which often shows yellowish color on the rump. Of course, the Palm Warbler is brightest yellow under the tail, but when one flushes up and flies away from you the under tail coverts are not visible. What is visible then on many Palm Warblers, however, is the yellowish color on the rump — enough so that more than once I have found myself assuming the warbler flying off was just another Yellow-rumped until it landed to provide a second look.
Just as the Cape May Warbler has a tendency to spend its time in spruce trees, the Pine Warbler has even a stronger preference for pines. This association is strong enough that only rarely have I found a Pine Warbler singing or foraging in anything other than a stand of pines (or some adjacent non-conifers). And it’s reassuring for a change to have a bird’s name that actually describes something useful about the bird. Less reassuring, however, is how often other things are misidentified as Pine Warblers. Too many birders assume this warbler is just another species one would routinely encounter when out looking for migrants. In reality, the Pine is quite uncommon in Minnesota as a migrant, since it has a tendency to arrive on and depart from its breeding grounds without making many stops in Minnesota in transit. Many birders are also unaware how early this species migrates in spring and how late it moves in fall, and it is not likely to be seen in mid-May or September during peak warbler-watching time. Some fall Pine Warblers (again, probably adult males) are colorful enough to be relatively easy to tell. But others (probably immature females) can be quite nondescript, lacking any evidence of greenish color above or yellowish below. But even the dullest Pine Warbler should show obvious wing bars — and about the only other warblers with no obvious markings other than wing bars would be the Bay-breasted and Blackpoll. Look for the Pine’s lack of back streaking (which is often hard to see), its somewhat vireo-like (i.e., slower and more deliberate) movements, and its distinctive face pattern which features a vaguely Peregrine Falcon-like darker wash on the ear coverts. Note, however, this wash may be set off by a paler area on the side of the neck, which may then suggest a Cape May Warbler.
Bay-breasted vs. Blackpoll
This pair of warblers has long been considered part of the quintessential confusing fall warbler problem, although usually the Pine Warbler is also included in the mix. However, as indicated above, I have never considered the Pine Warbler to resemble the other two – the Pine’s face pattern in combination with other things always seems to give it away. Of course, some Bay-breasted Warblers still retain enough of a buff or even chestnut tinge on the flanks to be easily recognized. Conversely, though, there have been a few Blackpoll/Bay-breasted types I have seen over the years which I was uncomfortable identifying. The identification of most of them, however, is straightforward, as follows:
- streaked underparts = Blackpoll
- unstreaked underparts = Bay-breasted
- short or faint smudges on underparts = either species
- pale legs and feet = Blackpoll
- dark legs and feet = either species
- yellowish wash on breast = Blackpoll
- buffy flanks = Bay-breasted
- no color on underparts = either species
Time and space considerations preclude a complete analysis of the identification of those questionable “either species” individuals, and it’s safe to say that a few of those Blackpoll/Bay-breasteds you see may have to be left as unidentified. But for further information on this ID problem, consult “The Blackpoll Trio” chapter in Kenn Kaufman’s A Field Guide to Advanced Birding, or the Birding article “Bay-breasted, Blackpoll, and Pine Warblers in Fall Plumage” (15:219–222).
And while you’re looking up Bay-breasteds and Blackpolls in Kaufman’s Advanced Birding guide, you may as well continue on to the next chapter on waterthrush identification. Actually, I could have almost left waterthrushes out of this article, since that chapter covers it well, and since migrant Louisianas are only infrequently encountered in Minnesota. Besides, this ID is not really a confusing-fall-warbler problem – after all, it’s hard to tell a Northern Waterthrush from a Louisiana at any time of year. Briefly, however, one feature to consider is the bird’s supercilium (i.e., the line over the eye). The Louisiana’s tends to be whiter, bolder, and typically wider behind the eye; the Northern’s supercilium is usually buff (but sometimes white) and narrows more behind the eye. Another good mark is the Louisiana’s buff flank patch which contrasts with the rest of the white underparts; the Northern’s underparts are uniform in color overall, either white or buff. Finally, try to see the leg color: typically (but not always) brighter pink on a Louisiana, usually duller grayish pink on a Northern.
Connecticut vs. Mourning
Because of the sought-after nature of the species, it is perhaps understandable how easily other things are mistaken for a Connecticut Warbler. After all, few other warblers in the U. S. rival the Connecticut in being so highly sought. Perhaps the most obvious error that novice warbler watchers make is to get excited over a Nashville Warbler. While its plumage may superficially resemble the Connecticut’s, a Nashville’s behavior up in the shrubs and trees is typically “warbler-like” – unlike anything a secretive, slower-moving, ground-walking Connecticut would normally do. I have also seen birders puzzle over a female or immature Common Yellowthroat, wondering if it might be a Connecticut, and I have been told of Yellow Warblers also being misidentified as Connecticuts (although I’m not quite sure how). In fall, however, the biggest source of confusion is with the Mourning Warbler, a highly sought warbler in its own right which acts just as secretively as the Connecticut. The problem is that many Mournings show an obvious and essentially complete eye ring in fall. While it may not be as thick as on a Connecticut, this ring can look bold enough to mislead even the experienced birder. If possible, concentrate on the hood and throat colors: most Mournings have grayer hoods and yellower throats, while Connecticuts tend to have browner hoods and buffier throats. Of course, given the secretive nature of both these warblers, it can be impossible to get a clear view of the eye ring, hood color, or throat. They do have different call notes, although a migrant Connecticut only rarely has anything to say, and the notes of both species are difficult to describe in words in any useful way. Just be thankful the MacGillivray’s Warbler does not migrate through Minnesota (or does it?), and for more information on this ID problem two helpful articles in Birding (20:96–99 and 22:222–229) have been published.
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Dunn and Garret’s book A Field Guide to Warblers of North America is a good resource, especially if you still have a vague and nagging fear of fall warblers. But, not to worry: there are still Confusing Fall Shorebirds and Confusing Immature Gulls on which to vent your frustrations.
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Kim Eckert’s interest in birding was sparked in the Chicago area during a 10th-grade biology class. It was the only biology course he would ever take, as he became an English major at St. John’s University in Minnesota and then taught English (with some first-year French on the side) during the 1970s. But he turned to a career in birding after moving to Duluth, Minnesota in 1977 where he served as Naturalist at Hawk Ridge Nature Reserve (for a total of 20 years), taught bird identification classes for a decade, and started leading birding tours (including 30 years with Victor Emanuel Nature Tours). In 1986, he began the Minnesota Birding Weekends & Weeks program of tours throughout Minnesota and elsewhere in the U.S. and Canada, which is now completing its 32nd season. Kim has written numerous articles for The Loon and other publications, and he authored four editions of A Birder’s Guide to Minnesota.
Thanks to Sparky Stensaas for providing the photographs for this story. Find more of his photography, videography, and a wealth of great natural history writing on his website. (In birding news, according to Sparky, exciting recent sightings have included a Lewis’s Woodpecker in western Minnesota, a Wood Stork in far northwestern Minnesota, and a first state record Roseate Spoonbill about a month ago in Minneapolis.)