Welcome to the Protein Bar

Common Grackle eating a dog-day cicada. Photo by Dan Gruner, PhD., professor of entomology at the University of Maryland.

by Kris Hansen

I scream, you scream, we all scream for … cicadas?

You do if you’re a bird in Chicagoland this summer. The bumper crop of 13-year, 17-year, and dog-day cicadas will provide a protein bonanza for area birds, says Allen Lawrance, associate curator of entomology for the Peggy Notebaert Nature Museum in Chicago.

And which birds are eating those cicadas? Pretty much all of them, says Zoe Getman-Pickering, Ph.D., an ecologist and program coordinator for the Energy Transition Institute at UMass Amherst.

In 2021, she and other researchers from the University of Maryland and Georgetown University studied which birds feasted on the periodical cicadas that emerged at the Izaak Walton League Conservation Farm in Poolesville, MD. The site offers multiple habitats, including fields, ponds and woods. Members of the Montgomery Birding Club, which regularly birds the location, and other area birders added their observations to those of the scientists.

Together, they observed nearly 1,000 separate birds representing 82 species feasting on cicadas during the six-week emergence, ranging from tiny Blue-gray Gnatcatchers to Trumpeter Swans, Mississippi Kites to Tufted Titmice, and Fish Crows to House Finches. The researchers were amazed.

The 82 species of birds that were observed eating cicadas. Image originally published in the Oct. 20, 2023, issue of Science and reproduced here with permission of the authors.

“We were shocked that just about every bird we saw was eating cicadas,” Getman-Pickering recalls. “Even birds that normally focus on seeds and grains were giving cicadas a shot.”

They even changed their minds, she says. “When the cicadas first came out, we saw a whole flock of Cedar Waxwings foraging on old fruit. The trees that they were foraging on were absolutely crawling with newly emerged cicadas, but the waxwings completely ignored them. Two weeks later, in that same spot, we saw Cedar Waxwings stuffing themselves with cicadas. There is a lot to learn about how and how quickly birds adapt their behavior to handle cicadas.”

The birds used a variety of methods to capture and consume the bugs. Spotted Sandpipers repeatedly dunked bugs in water until they stopped struggling. Chipping Sparrows and Carolina Chickadees dragged cicadas to the ground before picking off their legs. Purple Martins simply devoured them whole.

That came as a surprise to an ornithologist from Georgetown University. He led the researchers, who are primarily entomologists and ecologists, on a preparatory bird walk.

“He was giving us all these theories of which birds were likely to eat cicadas,” Getman-Pickering said. He also listed birds he did not think would eat them, including Purple Martins. Not so, she said with a laugh. “We saw a pair of Purple Martins feed 23 cicadas to their nestlings in one day.”

Purple Martin. Photo by Alex Muench.

Depending on the bird species, that might not be such a good thing. Cicada nymphs feed solely on xylem, a nutrient-poor portion of the circulatory system of a tree. Scientists from several other institutions are exploring whether a diet of only cicadas might not be healthy for chicks, which usually get a wider range of vitamins and minerals from caterpillars and insects.

Still, “there is some evidence that many bird populations spike (increase) during and in the years after emergences,” Getman-Pickering says. “I think that even if there were a surprising number of bird deaths, that might be overshadowed by how many birds survived and had successful nests.”

It’s not just birds that will see a population increase, says Lawrance: “Everything will eat cicadas. Bigger birds for sure, but also foxes, coyotes, squirrels, snakes, skunks—even deer.”

Squirrel eating cicadas. Photo by Dan Gruner, PhD., professor of entomology at the University of Maryland.

Because of the ample food supply, he says, “There will be a bump in the predator populations for the next couple of years, and then they'll wind back down because there aren't more periodical cicadas out there to sustain them.”

Meanwhile, the plants, fruits, seeds, and insects that the birds and other animals would usually eat are left to flourish in greater numbers, he adds.

“They call it a nutrient pulse. It's free fertilizer, is what it is. These cicadas have spent 13 or 17 years concentrating nutrients, and now they're returning it back to the soil all at one time. So, growth rates of plants or the establishment of forests in open areas have been documented to increase,” he says. “Oak trees might produce more acorns, which has downstream effects such as more squirrels.”

Acronicta caterpillar, which birds normally eat in large numbers but which did extensive damage to oak trees during the cicada emergence in Maryland. Photo by John Lill, Ph.D., professor of biology at Georgetown University.

Not all those changes are positive, says Getman-Pickering. “We saw that, with the birds turning their attention elsewhere, caterpillar populations doubled in number and doubled the amount of damage.”

“That really highlights how vital birds are in the ecosystem as predators controlling these insect populations on absolutely vast ecosystem scales,” she continued.

“Everything is interwoven, and when the birds aren't doing their job, then it dramatically changes what the insects and plants experience. And that's definitely something to keep in mind as we look towards bird conservation.”

If you observe birds eating cicadas, you are invited to share your observations with the research team.

Read the scientific paper.