Birds, raccoons, rodents and many other small mammals feasted on the billions of periodical cicadas that emerged this spring.
And experts say that, next year, these populations are likely to exhibit a baby boom, thanks to the additional food source.
“These predators go crazy when the big (cicada) populations come out,” said Michael Valenti, forestry administrator for the Delaware Forest Service. “(The cicadas) come out as a nymph, … and to turn into an adult with fully formed wings, they have to pump up those wings with their blood, which takes an hour or even more. So they’re basically sitting ducks, and they’re very vulnerable to predation.”
In a 2005 study by the Ecological Society of America, written by Walter Koenig and Andrew Liebhold, the year after the last Brood X cicada emergence, researchers predicted that the extremely long life cycle of periodical cicadas has evolved to escape the overwhelming response of predators.
“This combination of abundance, lack of natural defenses, and extraordinary synchrony within a region can result in periodical cicadas being consumed in large numbers during emergences; predators, in turn, have been observed to annihilate small populations of periodical cicadas,” the study said. “In contrast, predators are generally unable to consume more than a fraction of the periodical cicadas during emergences when cicadas are abundant.”
Mr. Valenti said that in Delaware, wild turkeys are cicada predators that may exhibit a significant population increase. He added that reptiles and fish feed on them, as well.
Additionally, “It’s known that copperhead snakes will set up shop at the base of a tree and wait for these things to come out, and they just gorge themselves,” he said.
The Ecological Society of America affirmed from the study in 2005 that several bird species also exhibited a boost following emergences. Eight of 10 species for which significant differences were detected within the span of one year indicated increases.
“(The increase is) presumably attributable to high survivorship or reproductive success enjoyed during emergence years,” the study read.
Some reports show that many songbirds will exhibit larger populations during emergence years, as well. One conducted in southern Indiana observed this in yellow-billed cuckoos.
“When there was a vast emergence of periodical cicadas: the Yellow-billed Cuckoo advanced its normal schedule and bred during peak cicada abundance, laid unusually large clutches, and parasitized Black-billed Cuckoo nests,” the report said.
Another investigation in Indiana reported that 51% of raccoons’ diets consisted of cicadas during emergence years.
Mr. Valenti added that only certain parts of Delaware had high populations of Brood X, primarily in the Piedmont regions in the northern portion of the state. He said there was some significant damage to trees but no lasting effects.
“Females lay eggs in terminal tree branches, and the dead or dying branch tips were quite noticeable in areas of high populations, especially on mature oak trees,” he said. “But eventually, the tips fall to the ground, the eggs hatch, and the nymphs burrow into the ground for another 17 years. Trees respond by simply pushing out more branches the following year. From a timber-quality point of view, the damage does not affect timber quality.”