One Flew Over the Cuckoo’s Nest

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.