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Blane Klemek: The curious call of the cuckoo

It wasn’t long ago when I heard the telltale call of a black-billed cuckoo coming from the top of one of my backyard bur oak trees. The cuckoo’s call is a curiously monotonous series of whistled notes, “po po po po . . . po po po po . . . po po po po”, which is not unlike the song of the little toy bird of cuckoo clocks. Other variations of this common cuckoo-call are also delivered by these elegant looking birds.

Cuckoos belong to an interesting avian family comprised of only a handful of members. Three different species of cuckoos — the mangrove cuckoo, yellow-billed cuckoo, and the black-billed cuckoo — and two species of anis, the groove-billed anis and smooth-billed anis, along with the greater roadrunner, all belong to the family Cuculidae.

Preferred habitats for black-billed cuckoos are forests of dense deciduous trees and shrubs where they actively hunt for their favorite food — caterpillars. And while the range of yellow-billed cuckoo includes southern Minnesota with records in the north too, chances are that any cuckoo observed here in the Northland will be the black-billed cuckoo.

Black-billed cuckoos are slender, long-tailed, rarely seen birds. About 12 inches long, their off-white under-parts, brownish upper-parts, white tail spots, and their black de-curved beak, sets this bird apart from many other birds — that is, if you ever see them.

As already mentioned, their distinctive call, which is unique in its own right, is often all we get to “see” of the cuckoo.

Cuckoos are somewhat reclusive during most of their summer stay here in Minnesota, but in years when caterpillar populations are especially high, such as during forest tent caterpillar infestations, you may also notice an abundance of cuckoos. During years when hoards of forest tent caterpillars defoliate aspen woodlands, cuckoos will be there as well as they hungrily forage on the nutritious insects. Indeed, this year is one such year, although not as severe as several years ago, forest tent caterpillars are abundant enough that some people are observing — including yours truly — an increase in cuckoos.

Black-billed cuckoos consume many different species of caterpillars, as well as other insects, but are particularly fond of caterpillars. In fact, cuckoos are especially adapted to eating spiny caterpillars. Not surprisingly, the spines of these insects evolved to deter predators, but this doesn’t seem to bother cuckoos. Even though the spines tend to stick to the lining of a cuckoo’s stomach, black-billed cuckoos have the astonishing ability to shed their stomach lining every so often in order to rid themselves of any accumulating spines.

Although not as frequently as do some of its cousins and Old World relatives, black-billed cuckoos occasionally lay their eggs in other birds’ nests, thus leaving the chores of incubating and caring for young to “foster” birds. Other species, such as wood ducks and hooded mergansers, not to mention brown-headed cowbirds, do this as well.

The black-billed cuckoo nest is normally built of twigs in the lower parts of deciduous or coniferous trees and shrubs. Apparently because of their irregular nesting habits, some eggs tend to become partially incubated during the egg laying process before the entire clutch is deposited. This sometimes results asynchronous hatching.

I recall several years ago when I had the pleasure of observing my first cuckoo nest and nestling. Just as the literature states, the nest consisted of just twigs within the branches of a small tree (in this case a balsam fir) close to the ground. It was a rather haphazard looking nest; not very well built at all. In fact, it appeared only half-built, and barely holding together. The nest reminded me of the kind mourning doves often construct. And I’m certain that if not for the sight of a half-grown cuckoo chick sitting precariously inside the makeshift affair, lesser trained eyes would’ve simply passed it off as merely a collection of woody debris.

Nevertheless, a lone and homely cuckoo nestling sat nearly motionless while I slowly examined the odd looking bird up close. Its oversized head was adorned with a few tufts of down that stuck up here and there, giving the bird a disheveled, almost laughable appearance. I was surprised, however, at how alert the little fellow was — it never took its dark eyes off of me as I circled around the entire nest.

According to the literature, the black-billed cuckoo is known to have one of the shortest nesting periods of any bird known. Amazingly, the time it takes for a black-billed cuckoo to lay its eggs, through incubation, to hatching, and to the time that the chick or chicks fledge is a mere 17 days. Despite this remarkable short timeframe, cuckoos typically raise only one clutch per nesting season.

To compare, birds such as eastern phoebes and eastern bluebirds usually raise two clutches per season.

The fascinating black-billed cuckoo is one of those birds that capture people’s imagination. Cuckoos are not well known, yet are common; they’re vocal, yet the calls are unfamiliar; and they’re beautiful, yet we rarely see them. When they call from the tops of trees, they pump their long tails. And they fly gracefully wherever they go and they feed voraciously upon caterpillars wherever they are.

For sure, the cuckoo bird, while still here in the Northland raising young and calling their “cuckoo coos”, will soon enough be migrating southward and won’t be back until late next spring. Even so, there’s still time to listen to and observe the black-billed cuckoo as we get out and enjoy the great outdoors.

BLANE KLEMEK is a Minnesota DNR wildlife manager. He can be reached at bklemek@