Cuckoos

(This 797th Buffalo Sunday News column was first published on July 9, 2006.)

You may have noticed as I have that tent caterpillars are especially active this year.

These caterpillars are the larva of a small moth that is of such minimal importance that, unlike most other species, it gets its name from its own young. It is called the eastern tent caterpillar moth. (There is a related species, the forest tent caterpillar which, despite its name, does not erect a tent.)

These colonial caterpillars hatched back in early March when they spun their silken tent usually in a tree crotch. They are crepuscular, that is most active during early morning or evening twilight when they leave the tent to feed on leaves. They also feed at night when it isn't too cool. They remain in the tent during the heat of the day or rainy weather.

When they emerged from their eggs back in March, those tent caterpillars were small and their tent was an attractive white. Now the caterpillars are large and their tent is soiled with caterpillar feces.

Photograph of a Yellow-billed Cuckoo taken by Carl Carbone

Enter the hero of this column, the cuckoo, the deadly enemy of the tent caterpillar.

Two species, yellow-billed and black-billed cuckoos, are found here in western New York. They are members of an international family that includes roadrunners, anis and the European cuckoo. That European cuckoo is the bird of the cuckoo clock with its "kuck'-oo" call. It is also the bird from which the word cuckold is derived for it is parasitic, like our cowbird laying its eggs in other birds' nests. Our cuckoos are rarely parasitic, although a few nest invasions were identified by early ornithologists. Instead they build their own flimsy nests - not much better than those of mourning doves.

Cuckoos normally remain hidden in foliage. I rarely see them and, when I do, my view is usually a brief glimpse of a blue jay-sized bird flying arrow-like through the forest, its flight somewhat like that of a mourning dove. They are brown backed and white bellied, the two species with only minor differences in markings.

More often I hear them. The yellow-billed cuckoo's call is described by Peterson as "a rapid throaty ka-ka-ka-ka-ka-ka-ka-ka-ka-ka-ka-ka-kow-kow-kow-kowp-kowlp-kowlp-kowlp-kowlp (retarded toward end)". He describes the black-billed cuckoo's call as "a fast rhythmic cucucu, cucucu, cucucu, etc." I enjoy listening to these unique sounds just as much as I did listening to their cousins calling in England years ago.

Now back to the caterpillars. Tent caterpillars have hairy bodies and for this reason are not attractive as food for many birds. But cuckoos feed on them regularly. As Arthur Cleveland Bent points out, "An abundance of caterpillars in a locality is very likely to bring with it an invasion of cuckoos." Back when ornithologists analyzed such things, one report told of an average of almost 23 caterpillars in each of 121 cuckoo stomachs, a total of 2771 larvae.

Tent caterpillars are not the only species eaten. Bugs, beetles and grasshoppers are consumed as well and cuckoos even devour the poisonous caterpillars of the Io moth. But they are best known for their attacks on tent caterpillars. In 1897, Amos Butler reported that "he has known these cuckoos to destroy every tent caterpillar in a badly infested orchard and tear up all the nests in half a day."

Fall webworms, often mistaken for tent caterpillars, are also taken. In a single stomach 325 of these larvae were found.

Sometimes cuckoos have been observed stripping the hair from caterpillars before eating them but most often they merely eat the entire insect, later disgorging pellets of hair in a manner similar to that of owls.

Most observers rate these birds very positively but they do have a down side. They eat grapes, elderberries and mulberries and one early ornithologist indicted them as nest robbers. In 1896, C. J. Maynard claimed this and added that other species defending their nests would follow the intruding cuckoo, pecking at its tail, so that "by the middle of summer, it is difficult to find a cuckoo which has a full complement of tail feathers." Since then, however, other ornithologists have disputed Maynard's claims.

On balance, I'll take cuckoos.-- Gerry Rising