Prince Edward County, Ontario, Canada
ONE FLEW OVER THE CUCKOO'S NEST August/September, 2014 issue The tropical groove-billed ani is one, and also the couas and coucals of Madagascar. Even that star of cartoons, the famous roadrunner who is relentlessly pursued by Wiley Coyote, is also a member of the same family. In total, this large family comprises some 130 species. Here, in our area though, we have only two species in this diverse family known collectively as cuckoos. By the way, contrary to the famous cartoon, real roadrunners don’t “beep, beep”, but produce a series of low dovelike coos dropping in pitch. It was hard to miss the forest tent caterpillars four summers ago in the Deroche Lake area just north of Moneymore Road. The forest tent caterpillar invasion and the damage they had done was actually the first I had ever witnessed. It is not a common occurrence, and cycles about every 15 years. Their name is a misnomer for they really don’t build a tent, like our better known eastern tent caterpillar, although we did come across a few caterpillars intertwined with some sort of silky webbing on a lower branch, the leaf curled, perhaps harbouring a cocoon. In some areas we walked, the defoliation was close to 90 per cent while other trees fared better. There was concern from the woodlot owner about the future of his bush that summer near Marlbank; however, Nature is very resilient, and it was early enough in the season for the trees to generate new leaves. In fact, this type of defoliation can probably take place for two years, even three, without weakening the tree substantially. Like crossbills that follow pine cone harvests around in the boreal forests, forest tent caterpillars are very nomadic, and the adults might not be present the following year to attack again. Already there was evidence that the outbreak was weakening when we walked his trail, and we came across one caterpillar displaying classic signs of a virus that usually breaks out in massive invasions like this. We seldom have to worry about predation as Nature always has back up controls. It was also hard that summer to miss at least one member of this family nearby, the black-billed cuckoo, for it is an energetic connoisseur of these hairy caterpillars. If you listen right now, you can hear cuckoos calling this month. I have yet to understand why this species becomes more vocal in the late summer, when the oppressive heat and humidity keep most other birds rather quiet. But I’m working on it. Don’t expect the same explosive outburst that we associate with cuckoo clocks though. Rather, listen for a very soft, but rhythmic “cucucu”, delivered in groups of three or four. That they call before a rain is a persistent myth. Their happy calls have more to do with the abundance of tent caterpillars, both the forest tent species that defoliate large trees, and our more familiar eastern tent caterpillar that builds the familiar webbed tents we see in bushes and on trees each year. A long tail contributes to its large size, much longer than a blue jay, but decidedly thinner, and certainly shyer, rarely being seen, despite its size. During a series of guided bird walks I conducted one spring, a hidden cuckoo called tantalizingly from the thickets in the same location almost daily. On one of those hikes, the cuckoo thoughtfully remained perched for at least 10 minutes on an exposed dead limb at almost eye level, only a few metres away. Everyone commented on the experience of seeing one so clearly and thanked me profusely. I saw no reason to let on that it was one of few times that I had experienced such a good view myself! The almost identical yellow-billed cuckoo is more southern in its distribution, but is becoming established in our area. One called almost daily for a week along a road I walk near our home. Unlike the low song of the black-billed cuckoo, this was a more robust call, a rapid, rattling clatter slowing down at the end. As the names indicate, their beak colour is a diagnostic feature of both species. While both species occasionally occur in Europe as very rare North American vagrants, displaced on migration during prolonged winds, the image that comes to mind of most European cuckoos is much different. We have all heard of European cuckoos who spend their time there, as cowbirds do here, searching out other species of birds in whose nests they will deposit their eggs. Like our cowbirds, European cuckoos have no interest in raising their own offspring, but leave the job instead, to foster parents. The cuckoos here in our area are less inclined to leave the worry of their young to another species, but raise their own young responsibly. During July and August we often hear the low rhythmic cooing of the black-billed species floating gently through the dense foliage, though few may realize what it is they are hearing. However the most amazing thing about cuckoos is their obsession with tent caterpillars. They are one of few species that have evolved the skill of consuming tent caterpillars in their entirety. Most birds avoid tent caterpillars as the hairs and spines will puncture the stomachs of birds. When they do eat tent caterpillars, they open up the soft skin and devour the contents, leaving the hairy, dehydrated carcass behind. Not so with cuckoos. Both species have evolved the ability to swallow entire tent caterpillars. With great dexterity, the cuckoo rips apart the tented nests of the caterpillars, and consumes the hairy creatures as though they were fine caviar. When its stomach becomes so congested with indigestible spines and hairs that it cannot hold one more caterpillar, the bird throws up, disgorging the entire contents, stomach lining and all. The regurgitated sack probably resembles a miniature Glad Kitchen Catcher. Immediately, the cuckoo grows a new stomach lining, and off he goes again to feast on more tent caterpillars. And when tent caterpillars experience a population explosion as they do every 10 years or so, there is a correspondingly higher number of cuckoos to eat them. In less than a month, both species of cuckoos will commence working their way south. Nature is forever evolving, devising new and intriguing ways to preserve the fittest. If we stick around another thousand years or so, likely the tent caterpillar will have devised a way to once again outwit the hungry cuckoo. For now though, hairs and spines are no problem for these birds with their disposable stomachs. For more information on birding and nature and guided hikes, check out the NatureStuff website at www.naturestuff.net . Terry Sprague lives in Prince Edward County and is self-employed as a professional interpretive naturalist.