While searching the forest canopy for the male scarlet tanager I had just heard (its raspy voice sounds like a robin with a sore throat), another bird sailed through my field of view. It disappeared into a dense thicket so quickly I saw it for only a moment.
I mentally reviewed the general impressions the bird had left on me. It was blue jay sized. Slender. White below and dark above. But most importantly, the tail, which fanned as the bird pulled up to enter the thicket, consisted of white-tipped feathers that shortened abruptly from the center to the outer edge. This combination of characteristics convinced me I had seen a cuckoo.
But which one?
Both black-billed and yellow-billed cuckoos inhabit wooded areas throughout the eastern U.S. Farmers call them rain crows because of their habit of singing before thunderstorms. Their “songs” (black-bills say, “Cu-cu-cu, cu-cu-cu;” yellow-bills, “Kow, kow, kow, kowlp, kowlp.”) are simple and not at all musical.
Black-bills sometimes sing at night. The bird remained quiet so I had to find it again to identify it. I sat down and watched the thicket the bird had entered. After a few minutes, some leaves moved.
Looking closely
I scanned the area with my binoculars. I made a “pishing” sound, a universal bird call many birds find irresistible. Suddenly, the bird appeared on an open branch. As it perched, I could discern the distinctive two forward, two backward toe arrangement shared by all cuckoos. The red eye ring, the all black bill, and small white tail spots made it a black-billed cuckoo. Had it been a yellow-bill, the lower half of the bill would have been bright yellow, the eye ring paler, and the white tail spots much larger. Cuckoos eat everything from insects to bird eggs, frogs, and berries.
And after returning from a winter in South America, they are no doubt hungry. A favorite food is hairy caterpillars. In the spring that means eastern tent caterpillars — the ones that hatch in the tent-like webs so common this time of year. They also eat gypsy moth caterpillars. And while there is no way cuckoos can begin to control an outbreak of gypsy moths, it’s reassuring to know gypsy moths have at least a few natural predators.
Tanagers, orioles, and vireos are also among the relatively few birds that eat hairy caterpillars. Thanks to protection provided by a coat of irritating hairs, hairy caterpillars are safe from many predators. Cuckoos and other birds that eat them remove most of the hairs by whacking them on branches to remove the hairs.
Important foods
Because these caterpillars are such important foods, cuckoo breeding cycles coincide with caterpillar infestations. They even lay more eggs when caterpillars are abundant. When hairy caterpillar populations are low, they may lay only two eggs. But when caterpillar populations soar, cuckoos raise as many as five young. The pale blue-green eggs are laid at one to three day intervals, and incubation begins with the laying of the first egg.
This leads to asynchronous hatching — each egg hatches about 14 days after it’s laid. Consequently, a cuckoo nest can have as many as five different sized chicks, each a day or two older than the next. This gives the older chicks an advantage. If food gets scarce, the larger chicks out-compete their nest mates for parental attention at meal time, and the younger siblings starve. A cuckoo nest is a rickety affair, not much more substantial than a morning dove nest, and often not more than 12 feet above the ground.
Cuckoo home
Viewed from below, light often passes through the maze of twigs cuckoos call home. Perhaps this is why cuckoos keep nest time to a bare minimum. A week after hatching, young cuckoos climb around the branches near the nest, and they can fly at three weeks of age.
Both parents share the incubation duties, and they also share the responsibilities of tending to nestlings. When it’s time to leave the nest, the male tends to the first fledglings, and the female takes care of the younger half of the brood.
Compared to the more familiar forest birds we see every day, cuckoos differ in voice, behavior, and even toe arrangement. Maybe that’s why we call them cuckoo.
Send questions and comments to Dr. Scott Shalaway, RD 5, Cameron, WV 26033 or by email via my web site, http://scottshalaway.googlepages.com
