When trillions of periodical cicadas emerge in a rare double event, they create disruption in the food chain.
In April, trillions of periodical cicadas began swarming the midwest and southeast of the United States, causing such a racket that local residents called the police to complain. However, the cicadas’ impact goes beyond just generating noise—they also throw food chains into disarray.
Having spent over a decade underground, feeding on tree root juices, two broods—Brood XIII and Brood XIX—are emerging simultaneously in 2024, the first time this has happened since 1803.
The mass emergence of these insects disrupts ecological food systems, according to Grace Soltis, a PhD student studying evolutionary biology at Florida State University.
While the cicadas’ emergence doesn’t directly affect the human food system, it poses challenges for various species. Thus, scientists are seizing the opportunity presented by the dual emergence in 2024 to investigate the ripple effects of cicadas on other species, both in the animal kingdom and among plants.
Brood XIII, a 17-year brood that hatched in 2007, is expected to emerge in Northern Illinois, while Brood XIX, a 13-year brood, will emerge in parts of the southeastern US. Both events commenced as predicted in late April 2024.
These insects offer a feast for a wide range of wildlife. Birds of all kinds—such as sparrows, crows, and swallows—adjust their diets to capitalize on the cicada abundance. A study published in 2023 revealed that the emergence of periodical cicadas alters the diets of entire bird communities.
Mass cicada emergences can span up to 190,000 square miles (500,000 square kilometers), notes John Lill, a professor of biology at George Washington University’s Department of Biological Sciences and another co-author on the study.
Consequently, this dietary shift creates a ripple effect throughout the food chain: “It’s a significant disruption across an entire landscape,” he remarks. “Generalist predators shift their focus to feeding on this abundant food source.”
Wild turkeys, for instance, take advantage of the bounty, resulting in a surge in wild turkey populations. Shrews, bats, spiders, wasps, and even snakes also feast on cicadas, according to Lill.
However, birds are the most visibly affected by these disruptions. Soltis and Lill’s study found that over 80 species of birds switched to cicadas as their primary food source during the 2021 emergence.
The scientists realized that what the birds weren’t consuming was just as crucial as what they were. This led to a ripple effect; caterpillars, usually preyed upon by birds, saw their populations double. Consequently, unchecked caterpillar numbers led to tree damage.
