Warblers: A Storm of Angels

In Headwaters country eighteen species of warblers flourish among the trees of the Niagara Escarpment and the Oak Ridges Moraine.

March 21, 2009 | | Back Issues | Environment | Spring 2009

fell in love with warblers one foggy May morning as a young child. Home with the mumps I convinced my mother that fresh air would do me well, so I headed for the woods. Hiking alone in the fog-shrouded woods I felt a delicious sense of privacy. Soon, however, I discovered that I wasn’t alone at all. The trees were alive with tiny feathered acrobats garbed in yellow, orange, navy and olive. They would pause among fresh emerald leaves, creating fleeting vignettes of aching beauty, and then they would be gone, exiting my fog-bound world, to light up another.

American Redstart. Photo by Robert McCaw.

American Redstart. Photo by Robert McCaw.

I had known about warblers before this. I had gazed with interest at their images in Peterson’s Field Guide to the Birds, but these warblers were real and bursting with energetic, vibrant life. I was smitten.

It is not hyperbole to claim a love for warblers. These are the birds that lure tens of thousands of people to Point Pelee on Lake Erie every spring. Sure, fabled Point Pelee brims with a diversity of other beautiful migrating birds, but it is the warblers that evoke the most slavish devotion. Arriving with the first flush of new leaves and warm spring breezes they stir the winter-weary soul like no other.

In 1900, Katherine Bates captured the bliss of warblers returning to her yard in her poem “Yellow Warblers”:

And lo! With golden buds the twigs were set,

Live buds that warbled like a rivulet

Beneath a veil of willows. Then I knew

Those tiny voices, clear as drops of dew,

Those flying daffodils that fleck the blue,

 

Those sparkling visitants from myrtle isles,

Wee pilgrims of the sun, that measure miles

Innumerable over land and sea

With wings of shining inches. Flakes of glee,

They filled that dark old oak with jubilee.

 

Warblers may be “wee pilgrims of the sun,” but they move northward by night during spring migration. Sometimes, with other migrants, they assemble into bird “super cells” that mimic storm systems on weather radar. Bridget Stutchbury, a York University professor and author of Silence of the Songbirds, wrote that early radar operators, mystified by the multitudinous blips on their radar screens, referred to them as “angels.”

These storms of angels descend from the sky after their arduous night flights to feed and build energy for the next leg of their northward journey. It was one of these warbler refuelling stops that my hike of forty years ago serendipitously intersected.

That transforming hike in a local woodlot testifies to the fact that people need not make a 300-kilometre trip to Point Pelee to experience the magic of migrating warblers. Even urban backyards host warblers during spring migration, but local river valleys with their abundant food, water and shelter, are better places to find them. Here, in constant motion, warblers gorge on the insect buffet that streamside trees and shrubs offer. Willow trees in particular seem to draw the attentions of the famished birds.

After spring migration warblers settle down to raise families. This is a frenetic time for them. Nest building, egg laying and the feeding of young takes place over a mere two months or so. The yellow warblers celebrated by an enraptured Katherine Bates, arrive in May and often begin their southward return journey in early July.

This speaks to a truism that “our” warblers are not really ours at all, but are merely on loan from the tropics. All but one or two of the warbler species that breed in Ontario spend most of the year in the Caribbean and Latin America, finding food and shelter among tropical hardwoods and seaside mangroves.

This yellow warbler enjoys a bird’s eye view through a rearview mirror. Photo by Robert McCaw.

This yellow warbler enjoys a bird’s eye view through a rearview mirror. Photo by Robert McCaw.

Warblers are often referred to as “wood warblers” with good reason – trees are to warblers as binoculars are to birders, generally inseparable. (Only one species of warbler in Ontario, the common yellowthroat, can thrive in a treeless environment. It has learned to find food and shelter among marshland cattails.) And though small copses of trees can serve warbler needs on migration, nesting warblers need trees aplenty. This puts most urban and agricultural land off limits to them. In Headwaters country it is among the trees of the Niagara Escarpment and Oak Ridges Moraine that our warblers flourish. Eighteen species commonly breed in these tree-rich environments and a few others do on occasion.

This region’s woodlands can support so many warbler species because the different species catch their staple food – insects and other arthropods – in different ways. The black and white warbler creeps along trunks like a nuthatch, and the northern waterthrush (a warbler despite its common name) dips its bill in ponds to capture aquatic insects. The northern redstart imitates a flycatcher, sallying forth from perches to snag flies, and the ovenbird, a warbler that has adopted a thrush-like lifestyle, flips leaves on the forest floor to look for spiders. The pine warbler forages high in its namesake trees, the black-throated green warbler favours hemlocks, and the blue-winged warbler seeks bugs in sun-soaked hawthorn and feral apple trees.

The appetites of warbler young are all but insatiable, so it is important that food be in abundant supply. One very patient observer sat beside a yellow warbler nest for ninety-six hours during the nesting period and counted as the parent birds dropped 2,373 beaksfull of squirming caterpillars and hirsute spiders into the gaping mouths of their brood! This works out to a feeding every four minutes or so.

It’s not surprising then that the food requirements of growing warblers help keep our forests healthy. Bridget Stutchbury cites New Hampshire research that revealed that warbler and thrush species eliminated 50 per cent of the tree-feeding caterpillars in the study area.

Nashville Warbler. Photo by Robert McCaw.

Nashville Warbler. Photo by Robert McCaw.

Warblers are one of the few varieties of birds that will feed on gypsy moth caterpillars, an invasive, introduced insect that has caused extensive damage to woodlands in southern Ontario. A Nashville warbler was observed devouring forty-two gypsy moth caterpillars in half an hour. Both Nashville and yellow warblers also dine on the tent caterpillars that sometimes defoliate our cherry and apple trees.

The caterpillar-chomping propensity of the Nashville warbler is notable, but its true claim to fame is its sheer numbers. A surprise revealed by data collected for the recent Breeding Bird Atlas Project found that this warbler, a bird which most Ontarians have never heard of, in fact outnumbers the people of the province by two million or so.

An estimated 15 million Nashville warblers inhabit Ontario in spring and summer, making it the most populous of Ontario’s birds. Most live within the vast expanse of the northern boreal forest, but we have our share here, where they are common in forests with a northern flavour containing spruce, tamarack and balsam fir.

Nashville warblers are pretty birds with lemon-yellow breasts and grey caps, but other local species are truly striking. Redstarts, adorned with brilliant orange and yellow, contrasting with sharply delineated black, are common. They are typically found in brushy growth along streams and other wetlands and often nest in grapevine tangles. This is how Hal H. Harrison, author of Wood Warblers World, described his first sighting of this species: “A flaming black and orange torch [that] came flickering through the leaves on a shaft of sunlight.” The Cubans have a delightful name for the redstart – Candelita or “little candle.”

Another warbler that causes writers to wax poetic is the Blackburnian. Hal Harrison again: “One of the most delightful experiences in bird watching is to see the first male Blackburnian warbler each spring, with his flaming orange head and throat accentuated brilliantly against the deep green of a coniferous forest.” Unfortunately here in the hills, Blackburnian warblers are thinly distributed. But even where they are common they can be hard to find because they spend most of their time high in conifer trees and their thin high-pitched voices are easy to miss.

Though finding an uncommon species like the Blackburnian warbler is challenging, others are easier to locate. It helps to learn warbler calls.

In the past, bird watchers had to be satisfied with written interpretations of these calls. Some truly did help. The ovenbird does have a call that sounds like “teacher-teacher-teacher.” And “witchity-witchity-witchity-witch” does aptly describe the call of the common yellowthroat. Other more fanciful renditions were not very helpful though. These included “trees, trees, murmuring trees” for the black-throated green warbler and the magnolia warbler’s affirmation of a woman’s intuition: “she knew she was right, yes she knew she was right.” Thankfully there are now excellent audio recordings of bird songs that eliminate the guesswork.

Before we leave bird calls, be cautioned that warblers don’t warble. They trill, they whistle, they buzz, but they don’t warble. Some are truly musically challenged and sound more like insects than birds. One of these is the blue-winged warbler, a fairly common inhabitant of scrubby fields in this area. I’m sure when I was a novice birder I ignored singing blue-winged warblers, ascribing their buzzy calls to grasshopper conversation.

So to find breeding warblers, learn their calls, read about their habitat preferences and … learn how to “pish.” Pishing is not rude. Rather it is a time-honoured method of luring warblers into the open by making a noise that sounds, well, like “pish.”

As with warblers, there are a diversity of “pishers” in the birding fraternity. With subtly different manipulations of tongue and lips, birders pish in different ways, and each birder of course, believes his or her “pish” to be the most effective. Regardless, this technique does summon warblers into view, especially during the breeding season. Redstarts, yellowthroats and many other warbler species can’t resist a good “pish.” The theory is that this high-pitched sound mimics the calls that songbirds use to “out” a predator. When a predator is discovered – an owl or a weasel perhaps – small birds gather round to show that it has lost the element of surprise.

Magnolia Warbler. Photo by Robert McCaw.

Magnolia Warbler. Photo by Robert McCaw.

While warblers are wise to the ways of natural predators, they are ill-equipped to deal with a variety of human-generated perils. Bridget Stutchbury imagines “that in forty years, I’ll be sitting on the back porch in my rocking chair, clutching my old pair of Leica binoculars, telling stories about our woods once being full of tanagers, thrush and warblers as my teenage grandchildren listen politely though not really believing a word the old lady says.”

My own imagining of another time hearkens back to a 1960s’ camping adventure on the Niagara Escarpment. The dawn songbird chorus was deafening. Memory is fallible, but the woods do seem quieter now.

Enemy number one for warblers is the bogey behind the decline of most animal species – habitat loss. When trees are cut, or wetlands filled in, the resident warblers cannot simply relocate to the woodlot on the next concession – that woodlot is likely already claimed by others of their kind.

The loss of woodlands along migration routes is also a problem. Stutchbury likens the fragmented woodlots that now prevail in eastern North America to “gas stations.” If these stations become too widely separated, warblers and other migrants will simply run out of energy before reaching their breeding territories.

While habitat loss is of concern here, it is also a big concern in the tropics where our warblers spend most of the year. Primary forest in Central and South America is being cut and large tracts of land are being transformed into fruit and coffee plantations.

Surprisingly, these coffee plantations can be a boon to warblers, if the coffee is grown under the shade of native trees. These trees, shading the coffee shrubs, provide food and shelter for at least twenty-two species of warblers. Alarming then, is the preference of most large corporate growers for more productive (albeit more chemically dependent and environmentally damaging) “sun” coffee. A monoculture of sun-grown coffee supports a fraction of the songbirds that a shade-grown coffee plantation does.

Many coffee drinkers are already aware of many compelling socio-economic and environmental reasons for purchasing shade-grown coffee. The resolve to avoid sun-grown coffee may be strengthened by Stutchbury’s observation that: “In the swirling steam that rises from your coffee cup could be the ghosts of warblers.”

Chestnut Warbler. Photo by Robert McCaw.

Chestnut Warbler. Photo by Robert McCaw.

If warblers find enough “refuelling” habitat to power their northward migration, if they manage to avoid colliding with buildings, communication towers and picture windows (see “flap,” Did you know sidebar), they face further perils when they arrive at their breeding destinations. Woodlots near human habitation have been infiltrated by a killer that dispatches warblers and other birds with cool efficiency – the house cat. Millions of birds are killed by cats every year in Canada. Ground-nesting birds, which include many of our warbler species, are particularly vulnerable.

Losing warblers compromises the vitality of our woodlands, in part by granting leaf-munching insects greater licence to destroy our trees. On a more emotional level, warbler decline makes our woodlands lonelier, quieter places. We can help warblers and other birds through thoughtful personal practices and by supporting habitat conservation efforts.

The arrival of warblers in spring heralds the resurgence of warmth and sunlight. They enliven our world with joyful exuberance and glorious colour. May boys and girls on future woodland rambles always be able to experience the joy of their discovery.

A warbler walk in the hills

Forks of the Credit Provincial Park has been one of my favourite warbler-viewing destinations for many years. Several of our local species are found there.

Look for yellow warblers in trees and shrubbery surrounding the kettle lakes. Buzzy-voiced blue-winged warblers sometimes nest in the scrubby growth on the south side of the largest kettle lake. I’ve found Nashville warblers along the crest of the valley where forest meets meadow. And the deciduous forest itself is home to ovenbirds. Listen for their signature “teacher-teacher-teacher.”

The trail from Cataract to Brimstone often runs through cedar woods clinging to the slopes of the Credit River valley. These cedars are favourite haunts of black and white warblers. Experiment with the “pish” to call these birds forth. It’s also possible to find a variety of warblers along the riverside.

Redstarts and mourning warblers can sometimes be found in shrubby second-growth woodland near the washroom facilities at the bottom of the valley. And you may be able to hear the “witchity-witchity-witchity-witch” of the common yellowthroat in this area as well. Listen for the exuberant calls of northern waterthrush along the trail from the washrooms to Brimstone. These water-loving warblers are reliably there in May and June. Black-throated green warblers are also very dependable along this stretch of trail in hemlock trees, though they are much easier seen than heard as they forage high in the foliage.

Beyond Forks of the Credit, visit pine plantations to find pine and yellow-rumped warblers and visit moist areas containing tamarack, spruce, aspen and alder to look for Nashville, Canada and chestnut-sided warblers.

Good luck!

About the Author More by Don Scallen

Don Scallen enjoys sharing his love of nature through his writing and presentations. Check out his blog "Notes from the Wild".

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