The following article was written by Mark A. Smith, an English Professor at Lock Haven University and appeared in their online newsletter, The Hemlock. Professor Smith kindly allowed us to reprint it here.

Wood-Warblers 
     --Mark A. Smith (LHU English Professor)

"How they filled the oriole’s elm, a twittering restless cloud, all one morning, 
And I watched and watched till my eyes blurred from the bird shapes,
—Cape May , Blackburnian, Cerulean,—"  
Theodore Roethke “The Far Field”

I suppose many non-birders know, in some nearly abstract way, that such things as warblers exist, but I doubt many have a good idea what one actually looks like, and I’ll wager most have never seen one in the wild and known it for what it was. That’s perfectly understandable, for reasons I’ll get to shortly, but it’s also sad because the warblers—or wood-warblers as they are more properly called—are simply some of the most beautiful, colorful birds you’ll ever get to see.

I look forward to their return every April and make sure to devote a day for “warbling” as I like to call it (some prefer “warblering”), which for me is an all-day, leisurely stroll through the woods with a sandwich and binoculars, just gazing up at these stunning gems of the bird world. After six or eight hours of craning, my neck gets pretty stiff—birders call it “warbler neck”—but it’s definitely worth it.

So why do so few of us know about them? They are very small, for one thing, somewhere in the range of 4½-6” long and weighing half an ounce or less. They are also very active, tirelessly darting after the insects that make up the bulk of their diet. They generally won’t sit still for a good look. In addition, many of them spend their days either high up in the forest canopy or deep in thickets, so that once the leaves are fully out it’s almost impossible to find them unless you know their songs. As you might surmise, a good pair of binoculars is pretty much required, and that means even fewer of us have a chance to see them. So warblers aren’t the easiest birds to get to know, but they are definitely some of the most amazing.

There are about 112 species of warblers in the Americas, about 57 of which spend time in North America above Mexico. A couple dozen of them are quite common in Pennsylvania. Warblers have been studied extensively by ornithologists, which is nice because there’s no shortage of information if you want to learn about them. One of my warbler guides runs to 650 pages, and yes, I like warblers enough to sit down and read it for pleasure, especially at this time of year when I’m gearing up for warbler season. I also refresh my memory of their songs by listening to recordings. What can I say? Warblers are a big deal for birders.

In fact, twelve years ago when I actually started looking warblers were a kind of revelation for me. Suddenly, I saw them everywhere: the shocking black and orange of the Blackburnian male, the vibrant lemon-yellow and coal-black bill of the Prothonotary, the bold stripes of the Black-and-White—they all just took my breath away. I remember thinking: Where have these birds been all my life? Why haven’t I noticed them before?

Although many of the warblers aren’t great singers (by human standards anyway), I love their songs as well. My wife and I both get a big kick out of the “zoo zee zoo-zoo zee” of the Black-throated Green. It sounds like a bird with confidence and a swagger. And of course there’s the “teacher, teacher, teacher, TEACHER,” of the Ovenbird, each iteration getting louder and more adamant until, at close range, you’d swear the thing was about to smack you. Anyone who has spent time in Pennsylvania’s springtime woods has heard that one, by the way, whether they recognized it or not. Or how about the sweet, drawling whistle of the Common Yellowthroat: “wichity, wichity, wichity, wich,” the three syllables rising like the summer heat. In January I can close my eyes while listening to a recording of that one and be transported to the humid heat of the wet thickets the Yellowthroat prefers. Male warblers use all these songs to attract mates, of course, but also to stake out and defend their territories (imagine if humans had the wisdom to defend their borders by whistling tunes).

On top of their intricate beauties they are simply astonishing when it comes to their lifestyle. Those that breed in North America generally winter in Mexico, Central and South America, and the Caribbean, so the migrations are epic for these tiny birds. In spring, many fly straight north across the Gulf of Mexico in an exhausting twelve-hour, nighttime flight. When they reach the Gulf coast they often “fallout” by the millions. Not surprisingly, birders come from everywhere to witness the spring migration.

After breeding they head south again, and the champion fall migrant is the Blackpoll, which may take a 2500 mile nonstop flight across the Atlantic to reach South America. But many warblers head south at a more leisurely pace, tripping down the latitudes and island-hopping to reach their winter homes. Nonetheless, there are still many challenges. One September morning while my wife and I were visiting downtown Chicago, we found an exhausted warbler at the foot of a skyscraper. It might have been a female Pine Warbler or maybe a first-year Blackpoll (because of a change in plumage, many warblers are hard to tell apart in the fall). Perhaps it spent the night crossing Lake Michigan and then happened upon the city, instead of some trees. Or maybe it hit a building in the darkness (this happens all the time—buildings, towers, and windmills all take a heavy toll on birds migrating at night). But the bird appeared unharmed. I think it was simply spent, and wouldn’t last the day without food. I picked it up and held it, a tiny, taut bird of the softest olive tones. It looked at me briefly, then closed its eyes. My wife and I discussed going back for the car and driving it out to the countryside, or at least a big city park, but I’m ashamed to report that I put it down again in a square yard of dirt at the base of a spindly locust tree. It was a goner.

Around here, one of my favorite warblers is the Ovenbird I mentioned earlier, which is very common and generally stays low to the ground in an open understory so it’s easy to see. It’s named for the nest it makes, built right on the ground and shaped like a little domed Dutch oven with a side entrance. A nest on the ground you say? What about predators? Well I have tried to find that nest a few times and have yet to succeed. There must be some trick to it.

Speaking of nests, most of the warblers are victims of nest parasitism by the Brown-headed Cowbird. The Cowbird lives in open country and builds no nest of its own, so it flies a short distance into the nearest woods until it finds a likely nest, then lays its egg there. The warblers, who never dealt with Cowbirds in centuries past, haven’t evolved defenses against the parasitism (some birds toss the Cowbird egg; others rebuild the nest on top of it) so they end up raising Cowbirds instead of Warblers. Forest fragmentation is the culprit here. When a big tract of woods is opened in some way, the Cowbirds gain access to the interior. All the songbirds fall victim, none moreso than the warblers.

Another favorite of mine is the Canada warbler, aka the “necklaced” warbler, which frequents rhododendron thickets alongside our streams. It’s a soft gray above, with a bright yellow breast across which dances a stark black necklace. Quite a stunner, and a pretty good singer as well, though I won’t try putting it into words. One of my guidebooks describes the song this way: “a sputtery descending jumble of high, clear, liquid notes mixed with sharp chips.” You’re better off just listening to that one. It sparkles like sunshine falling on the nearby streams, and I can’t wait to hear it again.

Tips for watching springtime warblers:

• The best time is mid-April to mid-May.
• It helps to watch on a calm day so the movement of the birds can be picked out from the leaves. On a breezy day, your eyes dart all over chasing every fluttering leaf.
• Binoculars.  Pretty good ones can be had for $100-200. Unless you really want something small, a bigger pair generally works better.  8x42mm is the most popular format.
• Field guides. The Sibley and Peterson field guides to eastern birds are both excellent and small enough to carry easily in the field, but there are many others to choose from.
• Patience is definitely a virtue when looking for warblers, not so much for finding them (really, they’re everywhere!) but for getting good views of them.
• Some common warbler species around here include: Northern Parula, Yellow Warbler, Magnolia Warbler, Blackburnian Warbler, Black-throated Blue Warbler, Black-throated Green Warbler, Yellow-rumped Warbler, Pine Warbler, Blackpoll, Black-and-white Warbler, American Redstart, Common Yellowthroat, Ovenbird, Louisiana Waterthrush, Canada Warbler, Cerulean Warbler, and maybe a Worm-eating Warbler if you’re lucky. There are others, but as a casual birder, these are the ones I can generally count on every year.
• Finally, be prepared to be dazzled by all the rest of the birds as well—the Tanagers, Grosbeaks, Vireos, Orioles, etc.—that will be returning at the same time. And be forewarned: watching birds is addictive and can turn you into a birder in no time. Once you’re hooked, you’re hooked for life.

At the Cornell Lab of Ornithology website you can see pictures, hear songs, and find out more information about warblers.