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Door to Nature: Our Two Cuckoo Species

A bird that is usually heard more than it is seen thrilled us on a Saturday early morning Ridges bird outing many years ago, first with its song and then with its shy appearance in a small tree. It was the black-billed cuckoo, referred to for many years in some parts of the country as the rain crow. Rain was sure to follow the bird’s singing. What most of those folks didn’t know was here was a “crow” with a white belly!

The black-billed cuckoo has appeared to be the most abundant of the two species of cuckoos in this part of the state in recent years. “Kloo-koo-koo-koo, kloo-koo-koo,” it sings, over and over, quite musical and pleasant to the ear.

Its cousin, the yellow-billed cuckoo, is harsher and louder, singing a rapid “kuk kuk kuk kuk-kowp kowp kowp” (or kloop kloop kloop). The wings of this bird have a definite rusty-brown appearance and its lower mandible is yellow.

Experts tell us that the first cuckoos made their way from Eurasia into North America via the Bering Strait. It is the common cuckoo of Europe that possesses the real cuckoo clock-like song. In fact, it says its name with remarkable clarity. Beethoven beautifully set its song to music and included it in his Sixth Symphony, the Pastoral.

The eastern tent caterpillar forms this strong filmy tent in the branches of young trees.

The generic name for cuckoos is Coccyzus. This alludes to the similarity of the shape of its bill to that of the coccyx (tailbone) of the human skeleton. The black-billed species name is erythropthalmus in reference to its red eye. The yellow-billed, C. americanus, can be told, if seeing it from below, by its large white tail spots.

To realize how valuable the cuckoo is to man, one needs only to catalog the bird’s favorite foods. Among them are tent caterpillars, fall webworms, cankerworms, tussock moths and many other hairy and spiny caterpillars consumed by very few other animals.

One cuckoo’s stomach was found to contain 325 fall webworms. The fall webworm, quite prevalent in this area during late August, covers branches of wild cherry leaves especially as well as other plants, whereas the tent caterpillar is more common in spring and is usually found in the crotches of branches. Some of the cuckoos’ stomachs that were examined were found to be completely lined with the fur-like hairs of spiny caterpillars. Cuckoos are capable of regurgitating this unusual stomach lining.

Upon checking the spring dates for the black-billed cuckoo I found that it was seen, or heard, every year between 2002 and 2016 except 2004. Last year the black-billed was first reported on June 2. The earlier arrival dates during those 15 years ranged from May 10 to May 31.

On the other hand, the yellow-billed cuckoo was seen only seven of the last 15 years, in 2005, 2006, 2007, 2010, 2012 and 2013. The first dates for this species are much later in the month, from May 22 to May 30. Last year it was not reported until June 18.

The cuckoo has a very pretty flight enhanced by its rather long tail. It’s a streamlined bird adding to its beauty and, with its somewhat slow flying, presents a beautiful picture of gracefulness.

You can imagine my surprise one morning when I walked up to photograph a small black cherry tree quite covered in fall webworms only to have a black-billed cuckoo fly out from the rear of the tree. I had unexpectedly interrupted its breakfast.

Just as so many caterpillars have their unusual little defense mechanisms, so do these webworms. At the slightest touch to their filmy, silky tent the caterpillars (not really worms) would swing their bodies rapidly from side to side. Perhaps this action makes them more difficult targets for the cuckoos to snatch them.

Roy holds a black-billed cuckoo during a federal bird banding session.

The fall webworm, Hyphantria cunea, matures in its caterpillar or larva stage, makes a loose cocoon, and eventually emerges as an adult creature, a small white moth with lightly speckled forewings. The eastern tent caterpillars of spring, Malacosoma americanum, are larvae of the lappet moth.

After examining one of the tent caterpillars, covered along its flanks with what look like thin spines of fiberglass, I couldn’t help but think that you’d have to be a little cuckoo to want to eat them.

 

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